The instability of enzymatic glucose sensors has prevented the development of a practical artificial pancreas for diabetic patients. We therefore developed an enzyme-free glucose sensor using the gate effect of a molecularly imprinted polymer (MIP). This sensor has the advantages of improved stability and a simplified manufacturing procedure. An adduct of glucose and 4-vinylphenylboronic acid (VPBA) was synthesized by esterification and was then purified. The copolymer of the glucose/VPBA adduct and methylene bisacrylamide was grafted onto an indium tin oxide electrode surface. Glucose was washed out from the copolymer to obtain an MIP layer. Cyclic voltammetry of ferrocyanide in aqueous solution was performed using an MIP-grafted electrode, and the effect of glucose on the anodic current intensity was evaluated. The anodic current intensity was sensitive to the glucose concentration, and the dynamic range (0-900 mg/dl) covered the typical range of diabetic blood glucose levels. The response time of the MIP-grafted electrode to a stepwise change in the glucose concentration was approximately 3-5 min. Thus, we can conclude that, by taking advantage of its gate effect, it is feasible to use an MIP-grafted electrode as a glucose sensor for monitoring blood sugar in diabetic patients.

Fluorescence enhancement of fluorescein isothiocyanate-labeled protein A (FITC-protein A) caused by the binding with immunoglobulin G (IgG) in bovine plasma was studied. FITC-protein A was immobilized onto a glass surface by covalent bonds. An increase in fluorescence intensity was dependent on IgG concentration ranging from 20 to 78 mu g/mL in both phosphate buffer saline and bovine plasma. This method requires no separation procedure, and the reaction time is less than 15 min. A fluorescence enhancement assay by the affinity binding of fluorescence-labeled reagent is thus available for the rapid determination of biomolecules in plasma.

Well-defined diblock copolymers comprising thermoresponsive segments of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (P(IPAAm-co-DMAAm)) and hydrophobic segments of poly(D,L-lactide) were synthesized by combination of RAFT and ring-opening polymerization methods. Terminal conversion of thermoresponsive segments was achieved through reactions of maleimide or its Oregon Green 488 (OG) derivative with thiol groups exposed by cleavage of polymer terminal dithiobenzoate groups. Thermoresponsive micelles obtained from these polymers were approximately 25 nm when below the lower critical solution temperature (LCST) of 40 degrees C, and their sizes increased to an average of approximately 600 nm above the LCST due to aggregation of the micelles. Interestingly, the OG-labeled thermoresponsive micelles showed thermally regulated internalization to cultured endothelial cells, unlike linear thermoresponsive P(IPAAm-co-DMAAm) chains. While intracellular uptake of P(IPAAm-co-DMAAm) was extremely low at temperatures both below and above the micellar LCST, the thermoresponsive micelles showed time-dependent intracellular uptake above the LCST without exhibiting cytotoxicity. These results indicate that the new thermoresponsive micelle system may be a greatly promising intracellular drug delivery tool.

Dialyzer performance strongly depends on the flow of blood and dialysis fluid as well as membrane performance. It is necessary, particularly to optimize dialysis fluid flow, to develop a highly efficient dialyzer. The objective of the present study is to evaluate by computational analysis the effects of dialyzer jacket baffle structure, taper angle, and taper length on dialysis fluid flow. We modeled 10 dialyzers of varying baffle angles (0, 30, 120, 240, and 360 degrees) with and without tapers. We also modeled 30 dialyzers of varying taper lengths (0, 12.5, 25.0, and 50.0 mm) and angles (0, 2, 4, and 6 degrees) based on technical data of APS-SA dialyzers having varying surface areas of 0.8, 1.5, and 2.5 m(2) (Rexeed). Dialysis fluid flow velocity was calculated by the finite element method. The taper part was divided into 10 sections of varying fluid resistances. A pressure of 0 Pa was set at the dialysis fluid outlet, and a dialysis fluid flow rate of 500 mL/min at the dialysis fluid inlet. Water was used as the dialysis fluid in the computational analysis. Results for dialysis fluid flow velocity of the modeled dialyzers indicate that taper design and a fully surrounded baffle are important in making the dialysis fluid flow into a hollow-fiber bundle easily and uniformly. However, dialysis fluid flow channeling occurred particularly at the outflowing part with dialyzers having larger taper lengths and angles. Optimum design of dialysis jacket structure is essential to optimizing dialysis fluid flow and to increasing dialyzer performance.

This study reports on evaluation of the optimum design of a blood outlet port structure for providing uniform flow by visualizing the blood flow in an extracapillary membrane oxygenator. We tested a cylindrical type extracapillary membrane oxygenator, HPO-20. The HPO-20 has a tangential blood outlet port and is thus referred to as "Tangential HPO20." We engineered "Vertical HPO-20" with a vertical blood outlet port by modifying the Tangential HPO-20. To visualize the blood-side flow, a total of 120 insulated copper-wire electrodes were placed in the "Tangential" and the Vertical HPO-20s. The test solution flow was visualized by the dimensionless fluid arrival time reaching each electrode. The test solution flow in the Tangential HPO-20 was not uniform, particularly at the outside blood channel. The flow was more uniform in the Vertical HPO-20. The blood flow in an extracapillary membrane oxygenator with a vertical blood outlet port is well distributed so that it produces more uniform blood flow than that with a tangential outlet port because of the small stagnation and reduced channeling. ASAIO Joumal 2009; 55:209-212.

Dialysis fluid flow and mass transfer rate of newly developed dialyzers were evaluated using mass transfer correlation equations of dialysis fluid-side film coefficient. Aqueous creatinine clearance and overall mass transfer coefficient for APS-15S (Asahi Kasei Kuraray) as a conventional dialyzer, and APS-15SA (Asahi Kasei Kuraray), PES-150S alpha (Nipro), FPX140 (Fresenius), and CS-1.61U (Toray) as newly developed dialyzers were obtained at a blood-side flow rate (Q,) of 200 ml/min, dialysis fluid-side flow rates (Q(D)) of 200-800 ml/min and a net filtration rate (Q,) of 0 ml/min. Mass transfer correlation equations between Sherwood number (Sh) containing dialysis fluid-side mass transfer film coefficient and Reynolds number (Re) were formed for each dialyzer. The exponents of Re were 0.62 for APS-15S whereas approximately 0.5 for the newly developed dialyzers. The dialysis fluid-side mass transfer film coefficients of the newly developed dialyzers were higher than those of the conventional dialyzer. Based on the mass transfer correlation equations, introduction of short taper, full baffle of dialyzer jacket and further wave-shaped hollow fiber improves the dialysis fluid flow of the newly developed dialyzers. ASAIO journal 2009; 55:231-235.

The objective of the present study was to evaluate the characteristics of protein adsorption on the inner surface of various dialysis membranes, to develop protein adsorption-resistant biocompatible dialysis membranes. The adsorption force of human serum albumin (HSA) on the inner surface of a dialysis membrane and the smoothness of the membrane were evaluated from a nanoscale perspective by atomic force microscopy. The content ratio of the hydrophilic polymer, polyvinylpyrrolidone (PVP), was determined by attenuated total reflection Fourier transform infrared spectroscopy. Nine synthetic-polymer dialysis membranes on the market made of polysulfone (PSF), polyethersulfone (PES), polyester polymer-alloy (PEPA), and ethylene vinylalcohol (EVAL) were used in the present study. The HSA adsorption force on the surface of the hydrophobic polymer PEPA membrane was higher than that on the hydrophilic polymer EVAL membrane surface. It has been considered beneficial, for decreasing the HSA adsorption force, to cover a hydrophobic polymer membrane surface with PVP. However, there were some areas on PVP-containing membrane surfaces at which much higher HSA adsorption forces were observed. The HSA adsorption force gave a nearly linear correlation with the surface roughness on the PSF membrane surface. However, the HSA adsorption force was uncorrelated with the PVP content ratio for any of the PSF membrane surfaces tested. in conclusion, protein adsorption can be minimized by the use of dialysis membranes made of hydrophobic polymers containing PVP with a smooth surface. ASAIO journal 2009; 55:236-242.

The control of protein adsorption on microchannel Surfaces is important for biosensors. In this Study, we demonstrated protein adsorption method that is controlled through temperature change, i.e., thermoresponsive protein adsorption, on polydimethylsiloxane (PDMS) microchannel surfaces using a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAAm). To provide general protein adsorption control method, we adopted biotin-streptavidin chemistry and synthesized streptavidin covalently modified with PNIPAAm (PNIPAAm-StAv). Modification of streptavidin, a hydrophilic protein, with PNIPAAm induced successful thermoresponsive adsorption on a PDMS microchannel Surfaces: PNIPAAm-StAv adsorbed at 37 degrees C and desorbed at 10 degrees C on the surfaces. We also demonstrated the thermoresponsive adsorption of biotinylated immunoglobulin G (IgG-b) using PNIPAAm-StAv. Conjugation of IgG-b with PNIPAAm-StAv induced successful thermoresponsive IgG-b adsorption on PDMS. Modification of PDMS surfaces with PNIPAAm reduced physical adsorption of the partially hydrophobic IgG-b on the surface and contributed to the high-contrast thermoresponsive adsorption of IgG-b: less than 1% of the IgG-b adsorbed at 37,C was detected after the PNIPAAm-PDMS surface was washed at 10 degrees C. The controllable adsorption of this system is expected to be applied to the regeneration of biosensor chips and to on-chip protein manipulation. (c) 2008 Elsevier B.V. All rights reserved.

We prepared well-defined diblock copolymers of thermoresponsive poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) blocks and biodegradable poly(D,L-lactide) blocks by combination of reversible addition-fragmentation chain transfer radical (RAFT) polymerization and ring-opening polymerization. alpha-Hydroxyl, omega-dithiobenzoate thermoresponsive polymers were synthesized by RAFT polymerization using hydroxyl RAFT agents. Biodegradable blocks were prepared by ring-opening polymerization Of D,L-lactide initiated by a-hydroxyl groups of thermoresponsive polymers, which inhibit the thermal decomposition of omega-dithioester groups. Terminal dithiobenzoate (DTBz) groups of thermoresponsive blocks were easily reduced to thiol groups and reacted with maleimide (Mal). In aqueous media, diblock copolymer products formed surface-functionalized thermoresponsive micelles. These polymeric micelles had a low critical micelle concentration of 22 mu g/L. In thermoresponsive studies of the micelles, hydrophobic DTBz-surface micelles demonstrated a significant shift in lower critical solution temperature (LCST) to a lower temperature of 30.7 degrees C than that for Mal-surface micelles (40.0 degrees C). In addition, micellar LCST was controlled by changing bulk mixture ratios of respective heterogeneous end-functional diblock copolymers. Micellar disruption at acidic condition (pH 5.0) was completed within 5 days due to hydrolytic degradation of PLA cores, regardless of showing a slow disruption rate at physiological condition. Furthermore, we successfully improved water-solubility of hydrophobic drug, paclitaxel by incorporating into the micellar cores. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7127-7137, 2008

When uremic blood flows through dialyzers during hemodialysis, dialysis membrane surfaces are exposed to shear stress and internal filtration, which may affect the surface characteristics of the dialysis membranes. In the present study, we evaluated changes in the characteristics of membrane surfaces caused by shear stress and internal filtration using blood substitutes: water purified by reverse osmosis and 6.7 wt% dextran70 solution. We focused on the levels of a hydrophilic modifier, polyvinylpyrrolidone (PVP), on the membrane surface measured by attenuated total reflectance Fourier transform infrared spectroscopy. Experiments involving 4 h dialysis, 0-144 h shear-stress loading, and 4 h dead-end filtration were performed using polyester-polymer alloy (PEPA) and polysulfone (PS) membranes. After the dialysis experiments with accompanying internal filtration, average PVP retention on the PEPA membrane surface was 93.7% in all areas, whereas that on the PS membrane surface was 98.9% in all areas. After the shear-stress loading experiments, PVP retention on the PEPA membrane surface decreased as shear-stress loading time and the magnitude of shear stress increased. However, with the PS membrane, PVP retention scarcely changed. After the dead-end filtration experiments, PVP retention decreased in all areas for both PEPA and PS membranes, but PVP retention on the PEPA membrane surface was lower than that on the PS membrane surface. PVP on the PEPA membrane surface was eluted by both shear stress and internal filtration, while that on the PS membrane surface was eluted only by internal filtration.

The affinity control of integrin-RGD (Arg-Gly-Asp) binding by a thermal "on-off' switch has been achieved using newly designed surfaces presenting grafted temperature-responsive poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) copolymers functionalized with synthetic peptides. The prepared surface was designed to expose the tethered peptides available for cell binding at active "on" state above the lower critical solution temperature (LCST). The fully extended chains, on the other hand, masked the peptides completely and the cells started to detach from the surfaces at inactive "off' sate below the LCST. This paper elucidates the shielding effect of the grafted polymer chains on the dissociation of integrin-RGD binding below the LCST. To assess the ability of the polymer-shielding, extensible poly(ethylene glycol) (PEG) tethers were introduced between peptides and the grafted polymers. PEG chains allow peptides to be tethered to surfaces via functional PEG end-groups, leading to active "on" state even below the LCST. The time required to release cells from the surface was found to be longer when peptides were coupled to an extensible tether ends, suggesting that the surfaces can engender cell attachment through adhesive moieties covalently bound to the free ends of PEG chains. These results indicate that architectural changes on the nanometer length scale are crucial for controlling integrin-RGD binding and one of the main factors causing cell detachment is the shielding effect of the grafted polymer chains. (C) 2008 Elsevier Ltd. All rights reserved.

A novel assay for measuring time-dependant ligand-receptor affinity changes is developed based on a peptide-immobilized temperature-responsive surface, as schematically illustrated in the figure. The grafted thermoresponsive polymer acts as an "on-off" switch for mediating integrin-peptide bonding. At temperatures above and below the lower critical solution temperature (LCST), the peptides are accessible and shielded from integrin access, respectively.

Hydrophilizing synthetic polymer dialysis membranes with polyvinylpyrrolidone (PVP) play an important role for inhibition of protein adsorption on membrane surface. In the present study, the effect of PVP on protein adsorption was evaluated from a nano-scale perspective. Swelling behavior of PVP present on wet polysulfone (PS)/PVP film surfaces was observed by atomic force microscopy (AFM). Fibrinogen and human serum albumin (HSA) were immobilized on the tip of AFM probes, with which a force-curve between protein and wet PS/PVP film surface was measured by AFM while scanning in order to visualize two-dimensional protein adsorbability on film surfaces. Furthermore, HSA adsorbability on non-PVP containing PEPA dialysis membrane (FLX-15GW) and PVP containing PEPA dialysis membrane (FDX-150GW) was evaluated by the AFM force-curve method. As a result, PS/PVP film surface was completely covered with hydrated and swollen PVP at 5 wt% or more PVP content. Protein adsorbability on PS/PVP film surfaces decreased greatly with increasing content of PVP. The adsorption of HSA was inhibited by the presence of PVP on film surfaces more significantly than that of more hydrophobic fibrinogen. HSA adsorbability on wet FLX-15GW dialysis membrane surface was 428+/-174 pN whereas that on wet FDX-150GW dialysis membrane surface was 42+/-29 pN. (C) 2007 Elsevier B.V. All rights reserved.

透析で用いられている合成高分子膜のうち、ポリスルホン(PS)とポリエステル系ポリマアロイ(PEPA)は、親水化剤であるポリビニルピロリドン(PVP)を添加することによって膜表面を親水化し、生体適合性の向上を図っている。しかし、透析により生じる中空糸膜表面のPVP分布の変化を定量的に検討した例はない。そこで、本研究では、透析器内の中空糸膜を軸方向および断面方向のいくつかのエリアに分け、各エリアにおける膜表面PVP残存率を測定し、PVPの溶出性を評価した。APS-15EX(試作品:PS膜、旭化成メディカル)およびFDX-15GW(PEPA膜、日機装)の透析器を用いて、血液側流量200mL/min、透析液側流量500mL/minで4時間透析を行った。このとき、血液側には血液と同粘度を有する6.7wt%デキストラン70水溶液、透析液側には逆浸透水を用いた。透析終了後に透析器ジャケットを取り外し、各エリア(透析器軸方向に3分割、断面方向に12分割、合計36エリア)から中空糸を取り出した。全反射減衰フーリエ変換赤外分光法(FTIR/ATR)で透析前後の中空糸膜内表面におけるPVP残存率を測定した。APS-15EXおよびFDX-15GWのいずれの透析器も、透析によって膜表面PVP残存率はすべてのエリアで減少しており、すべてのエリアでPVPが溶出したことがわかった。なお、APS-15EXとFDX-15GWの平均PVP残存率は、それぞれ94.1%、90.8%となり、APS-15EXの方が若干高いPVP残存率を示した。さらに、断面方向と軸方向で比較したところ、いずれの透析器も次のように同様の傾向を示した。断面方向では各断面にPVP残存率の偏りがみられた。軸方向では、中空糸束中央部に比較して、内部濾過量の多い中空糸束両端部においてPVP残存率が著しく低下した。特に、濾過が生じている血液出口部において、この傾向は顕著であった。(著者抄録)

This paper discusses the chiral discriminative gate effect of molecularly imprinted polymer (MIP) in organic solvents. We grafted L- (or D-) phenylalanine anilide (PAA) imprinted poly(ethylene glycol dimethacrylate-co-methacrylic acid) on an indium-tin oxide (ITO) in a number of organic solvents. Cyclic voltammetry of ferrocene with the grafted ITO electrode was carried out in several organic solvents and the effect Of L-(or D-) PAA on an electric current of ferrocene was evaluated. As the result, the faradic current at the electrode grafted in the non-polar solvent was remarkably sensitive to the template in the voltammetry carried out in the non-polar solvent. However, it was insensitive to the enantiomer of the template. The results indicate that the gate effect of MIP can discriminate between the template and its analogue by stereochemical structure even if the difference in the chemical or physical property is omitted. They also indicate that the gate effect could have limited applications with the enantio-selective amperometric sensors working in non-polar solvents where biosensors cannot work. (c) 2007 Elsevier B.V. All rights reserved.

Intracellular distribution of free doxorubicin (DOX) or DOX-loaded in polymeric micelles with thermoresponsive outer shells of poly(N-isopropylacrylamide) or its copolymers in cultured human breast cancer cells (MCF-7) were investigated by fluorescence and confocal laser scanning microscopy. Free DOX accumulated rapidly and selectively in cell nuclei, independent of temperature changes. In contrast to free drugs, the intracellular distribution of DOX-loaded in the thermoresponsive polymeric micelles was significantly affected by temperature changes across lower critical solution temperature (LCST) of the micelles. Above the micelle LCST, DOX delivered by the micelles was localized uniformly inside of MCF-7 cells. By contrast, the amount of DOX delivered to MCF-7 cells drastically decreased below the micelle LCST due to minimal interaction of the micelles with cell membrane surfaces. These results clearly showed that the mechanism of the intracellular drug localization was different between free drugs and DOX-loaded in the micelles. The thermoresponsive micelles aggressively interacted with the cells and carried DOX into the cells via triggered phase transition of the outer shells. In addition, much lower accumulation of free DOX was observed in the resistant cells compared to its parent sensitive MCF-7 due to the resistant mechanism. Of interest, DOX accumulation in the resistant cells was almost in the same level as with MCF-7 (sensitive) cells for the micelle system above the LCST. (c) 2007 Elsevier Ltd. All rights reserved.

The antioxidation property of vitamin E-coated dialysis membrane is effective for reduction of oxidative stress. Effect of amount of vitamin E coating on antioxidation property has been poorly understood yet. In the present study, we evaluated a relationship between amount of vitamin E coating and antioxidation property using a superoxide probe of 2-methyl-6-p-methoxyphenylethynylimidazopyrazinone (MPEC) by the optical fiber method to determine optimum amount of vitamin E coating and to improve antioxidation property of the vitamin E-coated dialysis membrane. Furthermore, from the viewpoint of reuse, we examined recovery of oxidized vitamin E by vitamin C treatment. In conclusion, it is necessary to coat polysulfone dialysis membranes with vitamin E at over 74 mg/m(2). The antioxidation property is recoverable by treating dialysis membrane containing oxidized vitamin E with vitamin C. By administrating vitamin C, higher antioxidation property may be realized with a small amount of vitamin E coating. (c) 2007 Elsevier B.V. All rights reserved.

The tortuous capillary pore diffusion model (TCPDM) has been used for estimating diffusive and pure water permeability from simple structure parameters such as pore diameter, surface porosity, wall thickness and tortuosity. The validity of this model for evaluation of homogeneous membrane has been already confirmed. Recently, there is a trend toward the use of asymmetrical dialysis membranes made of synthetic polymer such as poly(acrylonitrile) (PAN), polysulfone (PS) and a polyethersulfone polyarylate (PEPA) blend polymer. The purpose of the present study is to apply the TCPDM to evaluation of commercially available hollow-fiber dialysis membranes with asymmetrical structures by simplifying them to a double-layer membrane. The TCPDM is capable of estimating pore tortuosity of asymmetrical dialysis membranes having skin and supporting layers from data on membrane thickness, pore diameter, pure water permeability and water content. Values for diffusive permeability obtained by the TCPDM are in a good agreement with experimental data. This TCPDM model is useful for evaluation of not only homogeneous membrane but also asymmetrical membrane. (c) 2006 Elsevier B.V. All rights reserved.

The electrical potential oscillation at and the shape of the water/octanol interface were investigated using hydrophobic fluoroplastic containers. The interfacial potential between a water solution containing 1.5 mM sodium dodecyl sulfate (SDS) and an octanol solution containing 5 mM tetrabutylammonium chloride oscillated with an amplitude of 50-100 mV. The potential oscillation was also observed using a transparent fluoroplastic tube. The water/octanol interface shape was unchanged and no interfacial flow was observed during the oscillation. The interface shape was convex toward the octanol phase for 1.5 mM SDS, meaning that SDS adsorption to the wall was suppressed by the hydrophobic container. Therefore, the octanol system in a hydrophobic container enabled us to elucidate the electrical oscillation without any influence from the wall effect. (c) 2006 Elsevier Inc. All rights reserved.

Rexeed was developed by Asahi Kasei Medical using wave-shaped hollow fibers, a full baffle, and a short taper housing to improve dialysate flow. The present study is clarifies improvement in dialysate flow with Rexeed-15 compared with that of a conventional dialyzer. Dialysate flow was evaluated by the pulse-response method. Dialysate pressure and tracer concentration were measured at a blood-side flow rate (Q(B)) of 200 ml/min, a dialysate-side flow rate (Q(D)) of 500 ml/min, and a net filtration rate (Q(F)) of 0 ml/min using needles placed in the test dialyzer. Dialyzer performance was evaluated by measuring urea and vitamin B-12 clearance at Q(B) = 200 and 400 ml/min, Q(D) = 300-800 ml/min, and Q(F) = 0 ml/min. In the conventional dialyzer, dialysate channeling was observed. In contrast, Rexeed-15 had a uniform dialysate flow. Urea and vitamin B-12 clearance with Rexeed-15 was slightly sensitive to Q(D). The overall mass transfer coefficient for urea with Rexeed-15 was more than 50% higher than that of the conventional dialyzer, indicating the possibility of reduced dialysate usage with Rexeed. Rexeed has a highly optimal dialysate flow, due to the wave-shaped hollow fibers and the new housing, and gives increased clearance for lower-molecular-weight substances.

An oscillating electrical potential across a liquid membrane is studied as a model of a biological system. The oscillating potential is caused by repeated surfactant adsorption and desorption at the interface. The surfactant desorption process was simulated using both Fick's diffusion equation and the Langmuir-Hinshelwood equation. A water/octanol/water liquid membrane containing sodium dodecyl sulfate (SDS) was used and the effect of NaCl was studied. Calculations agree closely with experimental results, supporting the validity of the model we propose. Adsorption rate constants were obtained by comparing the experimental and calculated results. The addition of NaCl increased adsorption rate constants and decreased desorption rate constants. Calculations suggest that surfactant desorbs mainly into the octanol phase and this desorption is not affected by the addition of NaCl. The disordering of potential oscillations by NaCl addition may be caused by decreased SDS accumulation in the octanol phase close to the interface. A lower adsorption rate of the surfactant from the octanol phase onto the water/octanol interface leads to an oscillating electrical potential across the liquid membrane. (c) 2006 Elsevier B.V. All rights reserved.

We designed thenno-responsive and biodegradable polymeric micelles for an ideal drug delivery system whose target sites are where external stimuli selectively release drugs from the polymeric micelles. The thermo-responsive micelles formed from block copolymers that were composed both of a hydrophobic block and a thermo-responsive block. Poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) showing a lower critical solution temperature (LCST) around 40 degrees C was synthesized for the thermo-responsive block, while biodegradable poly(D,L-lactide), poly(epsilon-caprolactone), or poly(D,L-lactide-co-epsilon-caprolactone) was used for the hydrophobic block. By changing both the block lengths of the poly(D,L-lactide)-containing block copolymers, physical parameters such as micelle diameter and critical micelle concentration were varied. On the other hand, the choice of the hydrophobic block was revealed to be critical in relation to both on the thermo-responsive release of the incorporated anticancer drug, doxorubicin, and the temperature-dependent change of the hydrophobicity of the micelles' inner core. One polymeric micelle composition successfully exhibited rapid and thermo-responsive drug release while possessing a biodegradable character. (c) 2006 Elsevier B.V. All rights reserved.

The reactive oxygen species (ROS) have important physiological and protective roles in the maintenance of living systems. However, excessive production of ROS can impact cellular homeostasis and lead to oxidative stress. Superoxide has high reactivity acting as a reductant and an oxidant. Because of the pathophysiological roles of superoxide several methods for its detection have been developed. Spectrophotometric assay is nonspecific for superoxide, which limits its use. Chemiluminescent methods have been used frequently for vascular tissue samples because they are more sensitive than other conventional methods. Fluorescence-based assays have also been widely used in cultured cells and vascular tissues. Electron spin resonance (ESR) spectroscopy, also known as electron paramagnetic resonance (EPR), quantitatively measures superoxide concentration but is less suitable for its in vivo detection. Electrochemical sensors based on cytochrome c reduction or superoxide dismutase (SOD) enzymatic reaction have been developed for real-time monitoring, but lack adequate performance for in vivo superoxide measurement. Newly developed SOD-immobilized superoxide sensors reportedly have satisfactory performance, for in vitro measurement. In this paper, we review superoxide measurement methods from the early spectrophotometric assays to the third generation of electrochemical sensors.

dialysis patients are at risk of amyloidosis attributed to Et. This suggests that Et may affect the blood even if it does not mix with the blood. The objective of the present study is to evaluate the activity of Et trapped by membranes. We made mini modules out of hollow fibers using three different types of membranes and filtered Et solution. The lumen of the hollow fibers was then filled with limulus amebocyte lysate (LAL) for 15 min at 310 K. Et activity was then determined by measuring absorbance of the LAL reagent. The surfaces of test membranes were studied using an atomic force microscope. With polyester polyrner alloy (PEPA), no Et leakage or Et activity was detected in the hollow fibers under any conditions. With polysulfone (PS) and polyether sulfone (PES), no Et leakage was detected under clinical conditions, but Et activity was detected in the hollow fibers. These results show that Et trapped by the inner skin may affect the blood, even if Et does not mix with the blood. Therefore, Et should be trapped by an outer skin or the part somewhat far from the blood which does not contact with the blood directly. (c) 2005 Elsevier B.V. All rights reserved.

Poly (N-isopropylacrylamide) (PIPAAm) of controlled molecular weight was densely grafted onto glass capillary lumenal surfaces using surface-initiated atom transfer radical polymerization (ATRP). Temperature-dependent changes of these thermoresponsive brush surfaces with hydrophobic steroids were investigated by exploiting thermoresponsive aqueous wettability changes of the polymer-modified surfaces in microfluidic systems. IPAAm was polymerized on ATRP initiator-immobilized glass surfaces using CuCl/CuCl2/tris(dimethylaminoethyl)amine (Me6TREN) as an ATRP catalyst in water at 25 C. PIPAAm graft layer thickness and its homogeneity on glass surfaces are controlled by changing ATRP reaction time. Aqueous wettability changes of PIPAAm-grafted surfaces responses drastically changed to both grafted polymer layer thickness and temperature, especially at lower temperatures. Temperature-responsive surface properties of these PIPAAm brushes within capillary inner wall surfaces were then investigated using capillary chromatography. Effective interaction of hydrophobic steroids with dehydrated, hydrophobized PIPAAm-grafted capillary surfaces was observed above 30 C without any column packing materials. Steroid elution behavior from PIPAAm-grafted capillaries contrasted sharply with that from PIPAAm hydrogel-grafted porous monolithic silica capillaries prepared by electron beam (EB) irradiation wherein significant peak broadening was observed at high-temperature regardless of sample hydrophobicity factors (log P values), indicating multistep separation modes in coated monolithic silica capillaries. In conclusion, thermoresponsive polymer-grafted capillary inner wall surfaces prepared by ATRP exhibit useful temperature-dependent surface property alterations effective to regulate interactions with biomolecules without requirements for separation bed packing materials within the capillary lumen.

The interaction of blood with a material surface results in activation of the body's humoral immune system and the generation of reactive oxygen species (ROS). It has recently become clear that ROS are central to the pathology of many diseases. In this study, we evaluated the superoxide generation, permeation, and dismutation in hollow-fiber dialysis membranes by using 2-methyl-6-p-methoxyphenylethynyl-imidazopyrazinone (MPEC) as a superoxide-reactive chemiluminescence producer and an optical fiber probe to detect the resulting chemiluminescence in the hollow fiber lumen. We measured the superoxide generated when bovine blood leukocytes were brought into contact with dialysis membranes. Superoxide permeation was determined by measuring MPEC chemiluminescence in the hollow fiber lumen using an optical fiber probe. Additionally, superoxide dismutation was evaluated by examining the difference in superoxide permeability for membranes with and without vitamin E coating. Superoxide generation varies for different membrane materials, depending on the membrane's biocompatibility. Superoxide permeability depends on the diffusive permeability of membranes. No marked decrease in superoxide permeability was observed among membrane materials. The superoxide permeability of vitamin E-coated membrane was smaller than that of uncoated membrane. The antioxidant property of vitamin E-coated membranes is hence effective in causing superoxide dismutation. © The Japanese Society for Artificial Organs 2005.

Thermally regulated flow control using a thermoresponsive polymer grafted onto surfaces of capillary lumen facilitates rapid, reliable, and repeatable open-close cycles (see Figure). Hydration of the grafted polymer chains on the internal surfaces may increase the microviscosity of the hydration layers at the wall interfaces without physically occluding the lumen, producing complete and reversible on/off flow valving in microchannels under hydrostatic pressures relevant for microfluidics approaches.

For efficient removal of large molecular weight solutes by dialysis, several types of internal filtration-enhancing dialyzers (IFEDs) are commercially available. However, in a pressure-driven membrane separation process (i.e., filtration), membrane fouling caused by adhesion of plasma proteins is a severe problem. The objective of the present study is to investigate the effects of internal filtration on membrane fouling based on the membrane's pure-water permeability, diffusive permeability, and sieving coefficient. Hemodialysis experiments were performed with two different dialyzers, IFEDs and non-IFEDs. Local membrane fouling in each dialyzer was evaluated by measuring the pure-water permeability, the diffusive permeability, and the sieving coefficient of native membranes and membranes treated with bovine blood. The effects of packing ratio on dialysate flow pattern were also evaluated by measuring the time required for an ion tracer to reach electrodes placed in the dialyzers. In the IFED, membrane fouling caused by protein adhesion is increased because of enhanced internal filtration only at the early stage of dialysis, and this fouling tends to occur only near the dialysate outlet port. However, enhanced internal filtration has little effect on measured membrane transfer parameters. © The Japanese Society for Artificial Organs 2005.

Most of the surface patterning methods currently applied are based on lithography techniques and microfabrication onto silicon or glass substrates. Here we report a novel method to prepare patterned surfaces on polystyrene substrates by grafting ultrathin cell-repellent polymer layers utilising both electron beam (EB) polymerisation and local laser ablation techniques for microfabrication. Polyacrylamide was grafted onto tissue culture polystyrene (TCPS) dishes using EB irradiation. Water contact angles for these PAAm-grafted TCPS surfaces were less than 10 degrees (cos theta = 0.99) with PAAm grafted amounts of 1.6 mu g/cm(2) as determined by ATR/FT-IR. UV excimer laser (ArF: 193 nm) ablation resulted in the successful fabrication of micropatterned surfaces composed of hydrophilic PAAm and hydrophobic basal polystyrene layers. Bovine carotid artery endothelial cells adhered only to the ablated domains after pretreatment of the patterned surfaces with 15 mu g/mL fibronectin at 37 degrees C. The ablated domain sizes significantly influenced the number of cells occupying each domain. Cell patterning functionality of the patterned surfaces was maintained for more than 2 months without loss of pattern fidelity, indicating that more durable cell arrays can be obtained compared to those prepared by self-assembled monolayers of alkanethiols, as described in previous reports. The surface fabrication techniques presented here can be utilised for the preparation of cell-based biosensors as well as tissue engineering constructs. (c) 2005 Elsevier Ltd. All rights reserved.

Using the derived mass transfer correlations for hollow fibers, hollow fiber arrangements were optimized for an artificial gill that uses an oxygen carrier solution. FC-40, a perfluorocarbon (PFC), was used as the oxygen carrier solution. In the oxygen uptake module, a hollow fiber arrangement with parallel coiled hollow fibers is preferred. The optimum outside diameter of the hollow fibers and the transverse pitch between them are 300 and 500 μ m. respectively. In the oxygen release module, a hollow fiber arrangement of straight parallel hollow fibers is preferred. The optimum outside diameter of the hollow fibers and transverse pitch between them are 300 and 500 μ m, respectively. In the case of humans, the scaling up was estimated from the oxygen transfer rates using these optimum hollow fiber arrangements. The required total membrane surface area is 50.8 m(2), the total delivered pumping energy is 124 W, and the oxygen partial pressure in inspiration is 17.8 kPa. Importantly, the total membrane surface area required was significantly reduced using the modules with an optimum hollow fiber arrangement in comparison with that using connected membrane oxygenators as a gas exchanger. The optimization of hollow fiber arrangements in an artificial gill significantly enhances oxygen transfer from water to air. © 2005 Elsevier B.V. All rights reserved.

We have evaluated the mass transfer performance of four commercially available membrane oxygenators in which the blood path is external to and approximately perpendicular to the fiber bundle. Water flowed outside the hollow fibers as an oxygen carrier medium and substitution for blood, and nitrogen gas flowed inside the hollow fibers. The oxygen transfer rates in the membrane oxygenators were measured, and their mass transfer coefficients were obtained. When we analyzed the mass transfer performance using the theory of heat transfer across tube banks, the Sherwood numbers were obviously divided into two regions; one was the data for parallel hollow fibers, and the other was the data for crossed hollow fibers. This indicates that the mass transfer performance of the membrane oxygenator is attributable to the hollow fiber arrangement namely, parallel and crossed hollow fibers, in the same manner as that for heat transfer across tube banks (staggered and in-line bank). New mass transfer correlations have been developed for the membrane oxygenators composed of parallel hollow fibers and crossed hollow fibers. These mass transfer correlations may be used as a guide for the design of a new and efficient membrane oxygenator. (c) 2005 Elsevier B.V. All rights reserved.

An artificial gill has been developed that transfers oxygen from water to air, using oxo-molybdenum(IV)5,10,15,20-tetramesitylporphyrin ((MoO)-O-IV(tmp)) dissolved in o-xylene as an oxygen carrier solution and the energy of visible light. The oxygen partial pressure in the oxygen carrier solution is changed by photo-irradiation to enhance both the oxygen uptake from water and the oxygen release to air. The ratio of the oxygen mass transfer coefficient of the oxygen carrier solution to that of water is 0.746 for oxygen uptake and 0.654 for oxygen release. In designing a large-scale artificial gill for supplying oxygen to a closed space underwater such as submerged vessel, the required membrane surface area, the seawater flow rate and the reservoir tank volume were 123 m(2), 0.00533 m(3) s(-1), and 5.06 m(3), respectively. These values increased as the oxygen partial pressure of seawater decreased. However, the high partial pressure of oxygen required for human respiration (20.0 kPa) can be provided in a closed space even from seawater with an oxygen partial pressure as low as 10.0 kPa. This newly developed artificial gill may be useful for deep sea activities, such as underwater exploration, marine research and underwater habitation. (C) 2004 Elsevier B.V. All rights reserved.

Chemiluminescence (CL) of luminol with hydrogen peroxide is useful for the highly sensitive determination of biochemicals by conjugation with oxidase. However, the method has stability problems because reactant-mixing conditions influence the results. However, electrochemiluminescence (ECL) of luminol can be performed on well-mixed solutions of luminol and hydrogen peroxide. ECL has not yet been applied to the quantitative analysis of biochemicals due to low quantum yields at physiological pH. In this work, we evaluated the effect of modifying the electrode with cationic polymer on the ECL intensity of luminol. Transparent indium-tin oxide (ITO) electrode was treated with 1 wt% aqueous solution of polyethyleneimine (MW : 70,000) buffered by 0.1 M borate at pH 8.0. ECL intensity at the ITO electrode was measured in a mixed solution of 1.0 mM luminol and 10-30 muM hydrogen peroxide buffered by phosphate or Tris-HCI (pH 7.4). The electrode potential was applied in alternate pulses of 0.00 V versus Ag/AgCl for 3 s and 1.00 V for 3 s. The sensitivity of ECL to hydrogen peroxide concentration at the treated ITO increased remarkably. Results indicate that the cationic polymer adsorbed on the electrode enhances ECL by increasing pH in the vicinity of the electrode surface. However, the cationic polymer also enhanced inhibition of ECL by ascorbic acid, an anionic reducing reagent.

Several cultured cell types are easily detached from poly(N-isopropylacrylamide) (PIPAAm)-grafted surfaces only by reducing culture temperature without traditional proteolytic treatments that might damage certain cell functions. We have exploited these novel surfaces for tissue engineering applications where harvested intact cell sheets are useful for fabricating tissue-like constructs. We now extend the polymer chemistry of such grafted surfaces with new charged co-monomers. Functional carboxylate groups are incorporated into temperature-responsive surfaces with newly designed analogous carboxylate co-monomers, 2-carboxyisopropylacrylamide (CIPAAm) and 3-carboxy-n-propylacrylamide (CNPAAm), which have a small structural difference in the placement of the carboxylate group (iso or normal to the monomer propyl group). P(IPAAm-co-CIPAAm) demonstrates a similar phase transition behavior to that of pure PIPAAm, and the ionic dissociation of carboxyl groups is suppressed (elevated pK'a) even under physiological conditions. By contrast, P(IPAAm-co-CNPAAm) exhibits a higher charge density (lower pK'a), higher hydration, and reduced temperature-sensitivity under identical conditions. Introduction of 5 mol% CNPAAm into PIPAAm grafted surfaces produces no cell attachment under typical cell culture conditions, while identical introductions of CIPAAm into grafted copolymers functions well for cell attachment. Cultured cell spreading efficiency was essentially similar on PIPAAm-grafted surfaces as on copolymer-grafted surfaces with I mol% introduction of either carboxylate co-monomer. Accelerated cell detachment upon reducing culture temperature was observed for the 1 mol% these copolymer-grafted surfaces since polymer hydration and swelling kinetics are enhanced by the increased ionizable moiety in these grafted surfaces. (C) 2004 Elsevier B.V. All rights reserved.

We have developed temperature-responsive cell culture surfaces to harvest intact cell sheets for tissue-engineering applications. Both cost and safety issues (e.g., prions, bovine spongiform encephalopathy) are compelling reasons to avoid use of animal-derived materials, including serum, in such culture. In the present study, synthetic cell-adhesive peptides are immobilized onto temperature-responsive polymer-grafted surfaces, and cell adhesion and detachment under serum-free conditions were examined. The temperature-responsive polymer poly(N-isopropylacrylamide) (PI-PAAm) was functionalized by copolymerization with a reactive comonomer having both a carboxyl group and an isopropylacrylamide group. These copolymers were covalently grafted onto tissue culture-grade polystyrene dishes. Synthetic cell-adhesive peptides were then immobilized onto these surfaces via carboxyl groups. Bovine aortic endothelial cells both adhered and spread on these surfaces even under serum-free conditions at 37degreesC, similar to those in 10% serum-supplemented culture. Spread cells promptly detached from the surfaces on lowering culture temperatures below the lower critical solution temperature of the polymer, 32degreesC. These surfaces would be useful for serum-free culture for tissue-engineering applications.

The mechanism of the change in diffusive permeability of nanometer-ordered thin layers of molecularly imprinted polymer (MIP) in the presence of its template is examined and discussed based on electrostatic interactions. In this work, the theophylline-imprinted copolymer of ethyleneglycol dimethacrylate and methacrylic acid (Theo-MIP) is grafted onto indium-tin oxide (ITO) as an electrode for cyclic voltammetry of ferrocyanide with the grafted ITO, and the permeability of the Theo-MIP is estimated from the faradic current. The permeability is found to decrease with increasing pH, and the change in permeability due to the presence of the template is found to decrease with increasing concentration of the supporting electrolyte. These results indicate that the layer of grafted copolymer swells due to electric repulsion between carboxyl groups, representing a major factor in the gate effect of the Theo-MIP. If the grafted layer is considered to be porous, the porosity of Theo-MIP should increase as the polymer shrinks, and decrease as it swells. The increase in the permeability of the MIP in the presence of the template is therefore due to the increase in porosity due to shrinking.

Protein adsorption on dialysis membrane was studied by time-of-flight secondary ion mass spectrometry (TOF-SIMS), which is expected to be capable of chemical imaging of insulated samples, such as hollow-fiber dialysis membranes. Three commercially available hollow-fiber dialysis membranes having different pore sizes and structures, were tested in the present study. Bovine serum albumin (BSA) solutions were used to adsorb the protein on the samples. TOF-SIMS images and spectra of native membranes and membranes treated with BSA were compared in order to identify secondary ions related to BSA and membranes. Mutual information, one of applications of information theory, was employed to select fragment ions related to BSA. TOF-SIMS images show distribution of adsorbed BSA on the dialysis membranes and indicate that BSA permeability and interaction between the membranes and BSA definitely depend on pore size, structure and material. (C) 2004 Elsevier B.V. All rights reserved.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is capable of chemical imaging of proteins on insulated samples such as hollow-fiber dialysis membranes. Albumin loss and a lowering of diffusive permeability caused by protein adsorption on dialysis membranes should be reduced in order to enhance dialysis adequacy of the patients. Bovine serum albumin (BSA)adsorbed hollow-fiber dialysis membranes were tested in the present study. TOF-SIMS images and spectra of both native membranes and BSA-adsorbed membranes were compared in order to identify secondary ions related to BSA and membranes. Peaks of secondary ions related to BSA and each membrane were selected by means of information theory, and they are characterized by principal component analysis (PCA). Chemical images of BSA adsorption on both native and treated membranes were obtained to find that BSA permeability and interaction between the membranes and BSA definitely depend on the properties of a membrane. TOF-SIMS imaging obtained with information theory is a powerful tool to estimate protein adsorption on the dialysis membranes. (C) 2004 Elsevier B.V. All rights reserved.

Polysulfone (PS) dialysis membranes hydrophilized by blending poly vinylpyrrolidone (PVP) are well known to have excellent biocompatibility in clinical use. The objective of the present study is thus to clarify how PVP improves biocompatibility of PS membranes and furthermore to develop a patient-friendly PS dialysis membrane with higher biocompatibility. Biocompatibility based on both lactate dehydrogenase (LDH) activity and amount of protein adsorption was greatly different among four commercially available PS hollow-fiber dialysis membranes. PVP present on the inner surface of the hollow fiber was quantitatively determined by X-ray photoelectron spectroscopy (XPS), demonstrating the amount of PVP to be varying for each membrane. Structure parameters such as surface roughness, three-dimensional surface area and polymer particle diameter, indications of the physicochemical properties of the membranes, were measured on the observed inner surface images in both wet and dry conditions by atomic force microscopy (AFM) to account for dependence of biocompatibility on these structure parameters. The higher regularity polymer particle structure has in the wet condition, the lower wet/dry ratio surface roughness has and the larger wet/dry ratio polymer particle diameter has, that is, the more greatly the polymer particles swell by wetting, the higher biocompatibility is achieved by "cushion effect". (C) 2004 Elsevier B.V. All rights reserved.

Morphology and solute diffusive permeability of thin layer of molecularly imprinted polymer (MIP) change in the presence of templates, which is termed as "gate effect". To optimize morphological changes induced by the gate effect, the flexibility, density, and the amount of specific binding sites for templates of the MIP-grafted layer must be tightly controlled during radical polymerization. Living radical polymerization with "iniferter" (initiator-transfer agent-terminator) is useful tool for controlling degree of polymerization by reaction time. In this work, photoactive iniferter (benzyl dietyldithiocarbamate) was immobilized on a cellulose membrane via a silane coupler. This treated membrane was grafted with theophylline-imprinted copolymer of methacrylic acid and ethylene glycol dimethacrylate by ultraviolet irradiation. The relationship between the amount of graft copolymer, the degree of the gate effect and the time of UV irradiation was studied. The amount of grafted copolymer increase by repeating polymerization cycle. In addition, the variation of the diffusive permeability by template clearly differs to that by analogue. Therefore, these MIP membranes can discriminate two alkaloids by difference of diffusive permeability. The variation by the template or the analogue and the selectivity of the permeability depended on irradiation time. Those results indicate that synthesized MIP has a "living nature" and the gate effect is feasible to control by irradiation time. Living radical polymerization is a promising method to build sophisticated architecture of MIP membranes possessing self-controllable permeability by gate effect. (C) 2004 Elsevier B.V. All rights reserved.

We revealed morphology and physicochemical behavior of a widely used powerful hydrophilizing agent, polyvinylpyrrolidone (PVP), present on polysulfone (PS)/PVP films by atomic force microscopy (AFM). This is the first time such clear PS/PVP phase-separated morphology was observed by nanoscopic technique. The film surfaces were observed by the identical observation mode, probe and scanning conditions to reveal the change of PVP morphology and behavior between dry and wet conditions. Morphology was related to biocompatibility by combining AFM data with results of surface element composition, contact angle, adhesion amount of rabbit platelet and relative amount of adsorbed fibrinogen. PVP nano-particles of one or several molecules were formed on the dry PS/PVP film surfaces. Amount of PVP present on the surfaces increased with the molecular weight of PVP. At a mixed amount of 1-5 wt%, PVP K90 formed crowded particles on the dry surface. When wet, they swelled, followed by their union to produce a smooth surface leading to improved biocompatibility. The highest biocompatibility with excellent mechanical strength is achieved by blending the highest molecular weight PVP K90 at 1-5 wt%. (C) 2003 Elsevier Ltd. All rights reserved.

In this study, specific interactions between immobilized RGDS (Arg-Gly-Asp-Ser) cell adhesion peptides and cell integrin receptors located on cell membranes are controlled in vitro using stimuli-responsive polymer surface chemistry. Temperature-responsive poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) (P(IPAAm-co-CIPAAm)) copolymer grafted onto tissue culture grade polystyrene (TCPS) dishes permits RGDS immobilization. These surfaces facilitate the spreading of human umbilical vein endothelial cells (HUVECs) without serum depending on RGDS surface content at 37degreesC (above the lower critical solution temperature, LCST, of the copolymer). Moreover, cells spread on RGDS-immobilized surfaces at 37degreesC detach spontaneously by lowering culture temperature below the LCST as hydrated grafted copolymer chains dissociate immobilized RGDS from cell integrins. These cell lifting behaviors upon hydration are similar to results using soluble RGDS in culture as a competitive substitution for immobilized ligands. Binding of cell integrins to immobilized RGDS on cell culture substrates can be reversed spontaneously using mild environmental stimulation, such as temperature, without enzymatic or chemical treatment. These findings are important for control of specific interactions between proteins and cells, and subsequent "on-off" regulation of their function. Furthermore, the method allows serum-free cell culture and trypsin-free cell harvest, essentially removing mammalian-sourced components from the culture process.

We have reported a novel method of visualizing endotoxin (Et) distribution inside an Et-blocking filtration membrane using both fluorescence-labeled Et and a confocal laser scanning fluorescence microscope (CLSFM) in our previous paper [J. Membr. Sci. 210 (2002) 45]. The objective of the present study is to clarify Et-blocking mechanism of dialysis membranes. Six kinds of dialysis membranes with varying materials (hydrophilic and hydrophobic) and varying structures (pore diameter, skin layer location and thickness, and water content) were evaluated by CLSFM together with other techniques such as atomic force microscopy (AFM). Physicochemical property of a membrane material affects Et-adsorbing efficiency, and further membrane structure affects Et-plugging efficiency. Rejected Et distribution in the membranes with varying materials and structures is successfully visualized using fluorescence-labeled Et by CLSFM. Et adsorption on the membranes occurs first, followed by the narrowing of their pores, and afterward pore plugging is continued. Adsorption plays a vital role in Et-blocking. Double skin layer structure is valid for preventing of Et contamination than only inner skin layer structure because the double skin layer structure blocks Et more farther from blood-side surfaces than the only inner skin layer structure. (C) 2003 Elsevier Science B.V. All rights reserved.

Cross-linked, thermoresponsive poly(N-isopropylactylamide-co-acrylic acid-co-N-tert-butylacrylamide) [poly(IPAAm-co-AAc-co-tBAAm)] thin hydrogel layers on silica beads were used as new column matrix modifiers for LC separation of basic bioactive peptides, angiotensin subtypes I, II, and III. Terpolymer poly(IPAAm-co-AAc-co-tBAAm) showed both phase transition and apparent carboxylate pK(a) shifts in water, depending on temperature. Polymer-grafted silica bead surfaces exhibited simultaneous thermally modulated changes in hydrophilic/hydrophobic properties and charge densities. More effective separation of angiotensin peptide subtypes was achieved on columns of these terpolymer thin hydrogel grafted surfaces, as compared to an uncharged control binary copolymer of IPAAm and tBAAm. Although hydrophobic interactions effect separation of angiotensin subtypes, combined electrostatic and hydrophobic interaction resulted in more pronounced retention. At temperature below the terpolymer phase transition, hydrophobic interactions predominated, and minimal changes in electrostatic interactions were supported by little shift in the apparent AAc carboxylate pK(a) values. Above the phase transition temperature, electrostatic interactions were dramatically reduced as a result of the decreased charge densities of the polymer grafted surfaces. Therefore, peptide retention times were also reduced, exhibiting a maximum at near 30-35 degreesC. Interestingly, column retention behavior of angiotensins is dramatically modulated by applied step temperature gradients. Thermoresponsive surface property alteration is a very rapid, reversible phenomenon, allowing step temperature gradients on thermoresponsive columns to enable the analogous performance advantages as gradient elution in reversed-phase HPLC. More importantly, injected peptides were recovered completely from the columns from calculation of peak area. In conclusion, these anionic thermoresponsive polymer-modified surfaces are good candidates for improved separation of bioactive peptides under exclusively aqueous conditions.

Based on the enhancement of fluorescein isothiocyanate (FITC) fluorescence caused by reactions between proteins, we developed a reagentless, regenerable and rapid immunosensing system to determine immunoglobulin G (IgG). Fluorescence intensity of the immobilized FITC depends on IgG concentration, ranging from 10 to 50 mug/ml, specifically, even with co-existing proteins. The response time is 30 min during steady-state measurement and is less than a minute during transient measurement. When the FITC-labeled protein A binds to IgG, the surrounding atmosphere of FITC becomes hydrophobic. Since the fluorescence intensity of fluorescent substances generally increases at a hydrophobic environment, FITC fluorescence intensity increases with the concentration of protein A bonding to IgG. This system is regenerable because the fluorescence enhancement repeatedly occurs every time the immobilized fluorescent reagent is immersed in sample solutions. (C) 2003 Elsevier Science B.V. All rights reserved.

An artificial gill was developed using a concentrated hemoglobin solution containing inositol hexaphosphate (IHP), as the oxygen carrier solution, with the oxygen affinity controlled by temperature. Oxygen dissolved in sea water is first taken up from water to the oxygen carrier solution at 293 K. The oxygen carrier solution is then heated and the oxygen is released from the oxygen carrier solution to expired air at 310 K. The enhancement factors of the oxygen carrier solution that indicate its performance were obtained from the oxygen uptake rate and oxygen release rate. The values were approximately 3 at oxygen uptake and 16 at oxygen release. The scale-up for a human being at rest was estimated using these values, and the optimal operating condition was determined. The required membrane surface area for a human being is 63.8 m(2). The oxygen partial pressure of inspiration is 20.7 kPa, adequate for the respiration. These indicate the feasibility of a compact and portable artificial gill device. (C) 2003 Elsevier Science B.V. All rights reserved.

Acrylic acid (AAc) has been utilized to introduce reactive carboxyl groups to a temperature-responsive polymer, poly(N-isopropylacrylamide) (PIPAAm). However, AAc introduction shifts the copolymer phase transition temperatures higher and dampens the steep homopolymer phase transition with increasing AAc content. We previously synthesized 2-carboxyisopropylacrylamide (CIPAAm) having both a similar side chain structure to IPAAm and a functional carboxylate group in order to overcome these shortcomings. In the present study, these copolymers, grafted onto cell culture plastic, were assessed for cell adhesion control using their phase transition. AAc introduction to PIPAAm-grafted surfaces resulted in excessive surface hydration and hindered cell spreading in culture at 37 degreesC. In contrast, CIPAAm-containing copolymer-grafted surfaces exhibited relatively weak hydrophobicity similar to both homopolymer PIPAAm-grafted surfaces as well as commercial ungrafted tissue culture polystyrene dish surfaces. Cells adhered and spread well on these surfaces at 37 degreesC in culture. As observed previously on PIPAAm-grafted surfaces, cells were spontaneously detached from the copolymer-grafted surfaces by reducing culture temperature. Cell detachment was accelerated on the CIPAAm copolymer-grafted surfaces compared to pure IPAAm surfaces, suggesting that hydrophilic carboxyl group microenvironment in the monomer and polymer is important to accelerate grafted surface hydration below the lower critical solution temperature, detaching cells.

Since the finding Of beta(2)-microglobulin as a causal substance in the carpal tunnel syndrome of chronic hemodialysis patients, removal Of beta(2)-microglobulin has been performed using highly permeable dialysis membranes with larger pores. Such large-pore membranes tend to allow endotoxins (Et), harmful substances contained in dialysate, to enter blood. At present, as a countermeasure, Et-blocking filtration membranes are used to remove Et from dialysate. However, Et removal mechanism by these membranes has not been clarified yet. The objective of this study is thus to visualize distribution of fluorescence-labeled Et trapped inside the polyester-polymer alloy (PEPA) membrane, a widely used Et-blocking filtration membrane using a confocal laser scanning fluorescence microscope (CLSFM). Et were observed mainly in the outer skin layer of the hollow fiber, while some in the void and inner skin layers. No Et were present inside the hollow fiber. In conclusion, we succeeded in visualization of Et distribution inside the Et-blocking filtration membrane using CLSFM. This novel visualization technique may allow evaluation of distribution of Et trapped inside various kinds of Et-blocking filtration membranes. (C) 2002 Elsevier Science B.V. All rights reserved.

A new pH-/temperature-responsive poly(N-isopropylacr-ylarnide-co-acrylicacid-co-N-tert-butylacrylamide) (poly(IPAAmco-AAc-co-tBAAm)) hydrogel grafted on silica beads was evaluated as colunm matrix for a cation-exchange thermoresponsive chromatography. The stationary phase showed simultaneous changes in temperature-responsive surface charge density and hydrophobicity by incorporation of anionic AAc and hydrophobic tBAAm into IPAAm sequences, Thermoresponsive polymer property alterations were confirmed by temperature-responsive phase transition and shift in apparent pK(a) values. Catecholamine derivatives were retained on poly (IPAAm-co-AAc-co-tBAAm)-modified column at pH 7.0. Analyte retention was primarily due to the electrostatic interaction. It was noted that the temperature-induced phase transition of poly(IPAAmco-AAc-co-tBAAm) hydrogel layer on the stationary phases was evidenced by the apparent inflection point in van't Hoff plots around 36 degreesC. This suggests that solute interactions should be changed below and above the stationary phase transition temperature, reducing electrostatic interaction above the transition temperature, (C) 2002 Elsevier Science B.V. All rights reserved.

Determining pore size distribution is important for characterization of a dialysis membrane. However, conventional microscopic techniques cannot present a sufficient image for determining pore size distribution. In the present study, tapping mode atomic force microscopy (TMAFM) has been shown to be a powerful tool for observing and evaluating the small surface pores of a hollow-fiber dialysis membrane. Sample fixing technique described below and a highly sharpened probe have made it possible to observe small pores on a soft and undulant surface of a dialysis membrane. This is the first time that clear TMAFM images of surface pores of a hollow-fiber dialysis membrane at such high resolution have been presented. Pore diameter was determined by image analysis. Average pore diameter of APS-150 (Asahi-kasei, Japan) determined by TMAFM was compared with those by field emission scanning electron microscopy (FESEM) and by the Hagen-Poiseuille equation. The average pore diameter of APS-150 determined by TMAFM was slightly higher than that by FESEM. The average pore diameter determined by the Hagen-Poiseuille equation was intermediate between values for that of inside and outside surfaces determined by TMAFM. (C) 2002 Elsevier Science B.V. All rights reserved.

Superoxide (O-2(-), one of the reactive oxygen species (ROS)) produced in vivo plays various pathphysiological and physiological roles, and thus it is of great importance and value to evaluate quantitatively dynamic changes in superoxide concentration. We thus aimed at developing a superoxide dismutase (SOD)-immobilized sensor. Using a batch cell, the amount of superoxide produced via oxidation of hypoxanthine by xanthine oxidase (XOD) was quantitatively determined based on the measured electrical current. The peak current increased linearly with hypoxanthine concentration (0-100 muM, r(2) = 0.99). Using a flow cell, the concentration of superoxide produced from the isolated heart of an endotoxin-administered rat was successfully measured. Overall, the new superoxide sensor demonstrated satisfying performance and reproducibility for the tissue-derived superoxide. (C) 2002 Elsevier Science B.V. All rights reserved.

In a hollow-fiber dialyzer, uremic toxins are removed by diffusion and convection, which are influenced by the dialysate flow patterns in the dialyzer. Recently available high-performance dialyzers have complicated dialysate flow patterns, because both positive filtration and negative filtration occur. The objective of the present study was to evaluate dialysate flow in high-performance dialyzers experimentally. Glass-coated 0.1 mmφ platinum electrodes were used for the electrode counter and the working electrode. A counter electrode was placed at the inlet of the dialyzer, and working electrodes were placed at 20 different positions. A voltage of 0.5V was applied between the counter and the working electrodes with a potentiostat, and after the dialyzer was filled with water purified by reverse osmosis, 0.9% NaCl solution was caused to flow. The time at which the 0.9% NaCl solution reached each working electrode from the counter electrode was then measured at a dialysate-side flow rate of 300ml/min and blood-side flow rates of 0 and 200 ml/min. It was found that in dialyzers with high permeability to pure water, dialysate flow was affected by both positive and negative filtration. A comparison was then made between the experimental results and the results of simulation by the finite element method
at positions at which positive and negative filtration occurred, good agreement was obtained. This method makes possible the experimental evaluation of dialysate flow in a high-performance dialyzer in which positive and negative filtration occur.

In the purification process of hemoglobin (Hb) from red blood cells, we stabilized Hb as carbonylhemoglobin (HbCO) against pasteurization at 60°C. In this study, the process of carbonylation (HBO2 → HbCO) was tested with a membrane oxygenator (CX-II08
membrane area, 0.8m2
maximum circulation rate, 1.21/min) under the conditions of a solution flow rate of 100-1000 ml/min and a CO gas flow rate of 30-100 ml/min. Comparing the overall O2 transfer coefficient of carbonylation with that of deoxygenation (N2 flow) revealed that the resistance to O2 transfer of carbonylation was about 35 times smaller, indicating that carbonylation hindered O2 rebinding (deoxyHb → HbO2). On the other hand, the O2 released in the course of carbonylation hindered carbonylation at the beginning, because rebinding of O2 is competitive with carbonylation. The time required for carbonylation was significantly shortened from 1000 to 150s when the solution flow rate was increased from 50 to 400 ml/min
however, the CO gas flow rate did not affect it very much. Increasing the Hb concentration from 7.5 to 15 g/dl accelerated carbonylation by 1.3 times. Even though further study is necessary to select a suitable polymer membrane to avoid protein adsorption, a membrane oxygenator will be effective for the large-scale carbonylation of Hb as a starting material of HbV in the production process.

Graft copolymerization of ethyleneglycol dimethacrylate and merthacrylic acid onto cellulosic membrane was performed in the presence and absence of theophylline as the template for imprinting the copolymer molecularly. The effect of the presence of the template on the diffusive permeability of the grafted membrane was estimated by batch-wise dialysis of creatinine. The permeability of the theophylline-imprinted membrane was increased by the presence of theophylline, but was virtually unaffected by caffeine, which is an analogue of theophylline. The permeability of the non-imprinted grafted membrane decreased in the presence of theophylline or caffeine without discrimination. These results indicate that the diffusive permeability of the cellulosic membrane grafted with molecularly imprinted copolymer discriminates between the template and its analogue.

Enhanced hydroxyl radical production in the Fenton reaction with ATP or ADP based on luminol chemiluminescence was clarified. Luminol chemiluminescence intensity increases with the concentration of ATP or ADP due to their influence on the Fenton reagents which produce hydroxyl radicals. Fenton reagents containing hydrogen peroxide and ferrous ion produce hydroxyl radicals which attack luminol and this emits light. The effect of ATP and ADP on the Fenton reaction is detected as luminol CL intensity with a photon counting system. This method allows measurement of ATP or ADP concentration ranging from 0 to 15 mM, which covers the physiological concentration range.

Phosphate ion, which is a cause of metabolic bone disease, is excessively accumulated in the blood of chronic dialysis patients, because many of dialysis membranes have negative charge, which inhibit removal of phosphate ion from their blood. The ability to remove phosphate ion can be evaluated by membrane charge. The electrical charge of the membrane affects the rate of ion permeability, and the phosphate ion is no exception. The membrane charge of sheet dialysis membranes can be readily evaluated by measuring the membrane potential and calculating the effective charge density. Accordingly a study was made of the influence on the phosphate ion permeability exerted by the membrane charge of sheet membranes composed of the same material as the hollow-fiber membranes used in hemodialysis. The diffusive permeability of phosphate ion was greater due to the result that the higher the ionic strength in the solution, the higher the absolute ion mobility. On the other hand, because of their shape, it is impossible to measure the membrane potential of hollow-fiber membranes using conventional techniques, making it difficult to determine the effective charge density. The authors therefore, have proposed a novel technique to enable the measurement of membrane potential in hollow-fiber membranes, and have studied the influence exerted on the phosphate ion permeability by the effective charge density calculated by this technique. The phosphate ion permeability increases when the following situations occur: (1) the smaller the absolute value of effective charge density, (2) the greater the ionic strength of the solution, and (3) the greater the concentration of plasma proteins. This agrees with the theoretical results. By calculating the effective charge density from the membrane potential of the hollow-fiber membranes, as measured by the technique proposed here, it is possible to evaluate the rate of phosphate ion permeability in such membranes. (C) 2001 Elsevier Science B.V. All rights reserved.

A new technique for analysis by means of chemiluminescence (CL) is reported. Conventional CL methods for analysis using a homogeneous catalyst can be unsuitable for stable analysis, because the conditions of mixing of the reactant solutions greatly affects the results. Though, electrochemiluminescence (ECL) is capable of solving this problem, it requires more complicated equipment than CL. A platinum plate-immobilized flow-cell is capable of stably controlling the CL from luminol as in ECL and has the advantage of requiring no electrical equipment. Human serum albumin (HSA) concentrations ranging from 0 to 100 mug ml(-1) in water and in dialysate are measured by means of the CL intensity enhancement of luminol-labeled anti-HSA antibody caused by an antigen-antibody reaction in the presence of hydrogen peroxide using the Pt-immobilized flow-cell. (C) 2001 Elsevier Science B.V. All rights reserved.

Cross-linked poly(N-isopropylacrylamide-co-acrylic acid) (poly(IPAAm-co-AAc))-grafted silica bead surfaces mere prepared and applied as new column matric; materials that exploit temperature-responsive anionic chromatography to separate basic bioactive compounds,specifically catecholamine derivatives,in aqueous mobile phases. Since poly(IPAAm-co-AAc); has a well-known temperature-responsive phase transition and apparent pK(a) shift, polymer-grafted silica bead surfaces are expected to exhibit simultaneous hydrophilic/hydrophobic and charge density alterations under thermal stimuli. Elution behavior of catecholamine derivatives from a copolymer-modified head packed column was monitored using aqueous mobile-phase HPLC under varying temperature and pH, Catecholamine derivatives had higher retention times on poly(IPAAm-co-AAc) columns at higher pH in comparison with those or, noncharged PIPAAm reference columns, suggesting an electrostatic interaction as a separation mode. Temperature also affected the retention behavior of catecholamine derivatives. Optimal separation of four catecholamine derivatives aas achieved at elevated temperature, 50 degreesC, and at pH 7.0. This is due to the increased hydrophobicity of the stationary phase as evidenced by the elution of a nonionic hydrophobic steroid. From these results, mutual influences of both electrostatic and hydrophobic interactions between basic catecholamine derivatives and pH-/temperature-responsive surfaces are noted. Consequently, elution of weakly charged bioactive compounds is readily regulated through the modulation of stationary-phase thermoresponsive hydrophilic/hydrophobic and charge density changes.

A measurement without the influence of protein adsorption on the sensor surface has been developed using transient current of an enzyme-immobilized electrode. Response current decreases due to protein adsorption on the sensor surface and the enzyme-immobilized membrane causing glucose concentration gradient. By measuring glucose concentration in the transient state while controlling GOD activity, it is possible to prevent the influence of protein adsorption. A needle-type electrode glucose sensor on which enzyme is immobilized with a polyurethane membrane, with electrochemical on-off control of enzyme activity, is capable of accurate measurement of glucose concentration in bovine serum at least for 24 hrs.

Development of an artificial gill, for the uptake of oxygen from water to air, requires an increase in oxygen transfer rate. In the present study, oxygen transfer rate was enhanced using a washed red blood cell suspension as a thermo-responsive oxygen carrier solution, which changes oxygen affinity with temperature. Oxygen dissolved in water first combined with the oxygen carrier solution at a low temperature using a membrane module. The oxygen carrier solution was then heated to release oxygen into the air using a second membrane module. The water flow rate required to sustain a human being at rest was greatly reduced by heating the oxygen carrier solution due to increase in the limit of the oxygen partial pressure of water of which can be transferred, compared with when oxygen was transferred directly from water. The required membrane surface area is 225 m(2), sufficient for the development of a compact artificial gill. (C) 2001 Elsevier Science B.V. All rights reserved.

Molecular imprinting is a new technology for the synthesis of polymers with antibody-like specificity, which art: potentially useful in sensing or separation devices. Here, we report that a thin layer of molecularly-imprinted copolymer exhibits an increase in its diffusive permeability in the presence of its template. A thin layer of molecularly-imprinted poly(methacrylic acid-co-ethyleneglycol dimethacrylate) of theophylline was observed to form on the surface of electrically conductive indium-tin oxide (ITO) him. Cyclic voltammetry of ferrocyanide was performed using the copolymer-grafted ITO as a working electrode in the presence and absence of the template. The presence of the template was found to enhance the anodic current remarkably, which suggests that the diffusive permeability of the thin layer of the molecularly-imprinted polymer (MIP) is sensitive to the presence of its template molecule. This idea is supported by atomic force microscopy (AFM) in which the surface porosity of the layer of the MIP was observed to increased in the presence of its template. We conclude that the structure and diffusive permeability of a thin layer of molecularly-imprinted poly(methacrylic acid-co-ethyleneglycol dimethacrylate) enables this system to be used as a sensor for a given template, (C) 2001 Elsevier Science B.V. All rights reserved.

Aqueous gel deswelling rates for copolymer hydrogels comprising N-isopro-pylacrylamide (IPAAm) and 2-carboxyisopropylacrylamide (CIPAAm) in response to increasing temperatures were investigated. Compared with pure IPAAm-based gels, IPAAm-CIPAAm gels shrink very rapidly in response to small temperature increases across their lower critical solution temperature (their volume is reduced by five-sixths within 60 s). Shrinking rates for these hydrogels increase with increasing CIPAAm content. In contrast, structurally analogous IPAAm-acrylic acid (AAc) copolymer gels lose their temperature sensitivity with the introduction of only a few mole percent of AAc. Additionally, deswelling rates of IPAAm-AAc gels decrease with increasing AAc content. These results indicate that IPAAm-CIPAAm copolymer gels behave distinctly from IPAAm-AAc systems even if both comonomers, CIPAAm and AAc, possess carboxylic acid groups. Thus, we propose that the sensitive deswelling behavior for lPAAm-CIPAAm gels results from strong hydrophobic chain aggregation maintained between network polymer chains due to the similar chemical structures of CIPAAm and IPAAm. This structural homology facilitates aggregation of chain isopropylamide groups for both IPAAm and CIPAAm sequences with increasing temperature. The incorporation of AAc, however, shows no structural homology to IPAAm, inhibiting chain aggregation and limiting collapse. A functionalized temperature-sensitive poly(N-isopropylacrylamide) hydrogel containing carboxylic acid groups is possible with CIPAAm, producing rapid and large volume changes in response to smaller temperature changes. (C) 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 335-342, 2001.

Blood and dialysate flow patterns in hollow-fiber dialyzers are complicated, and hence the flow patterns and mass transfer are difficult to analyze theoretically. Consequently, dialyzers are usually developed by a trial-and-error method. We attempt to design dialyzers by computer simulation analysis in this work. Blood-side and dialysate-side flows were modeled using the Hagen-Poiseuille equation and the Blake-Kozeny equation, respectively. These flow patterns were evaluated as pressure drop and velocity distribution. The mass transfer rate was evaluated as solute clearance. Computed values of the pressure drops and clearance for urea and vitamin B12 were found to agree closely with those obtained experimentally. We evaluated the influences of the inner diameter of hollow fibers, module geometry, and void fraction on the pressure drop and clearance, and computer-aided design was performed.

Effects of hollow fiber packing fraction on gas transfer rate, blood pressure drop and blood flow characteristics of an intravascular oxygenator (IVOX) were evaluated by in vitro experiments. An IVOX module was prepared by packing hollow fiber membranes, of which packing fraction ranged from 0.056 to 0.338, in a pipe corresponding to vena cava. Overall mass transfer coefficients for oxygen and carbon dioxide were evaluated using water, and gas transfer rates through blood were estimated. Blood flow in the IVOX was evaluated by both pulse response method and electrode method. Blood flow was not uniform and depended on the hollow fiber packing fraction. Easy-flow channels between vascular wall and bundle of the hollow fibers were produced and stagnation of blood flow occurred in the bundle of the hollow fibers at the blood inlet. More uniform blood flow was obtained by optimizing the hollow fiber packing fraction. With respect to gas transfer rate, blood pressure drop and uniformity of the blood how the optimum hollow fiber packing fraction was approximately 0.28 when the outside diameter of the hollow fiber was 300 mum. Effect of inner diameter of the hollow fibers was also evaluated, demonstrating that reduction in the inner;diameter was an effective way to increase oxygen transfer rate. (C) 2000 Elsevier Science B.V. All rights reserved.

Introduction of significant quantities of functional carboxyl groups into temperature-responsive poly(N-isopropylacrylamide) (PIPAAm) hydrogels without compromising their intrinsic temperature sensitivity has proven difficult. We have overcome this problem by incorporating the newly synthesized 2-carboxyisopropylacrylamide (CIPAAm) monomer, with a side chain structure similar to N-isopropylacrylamide (IPAAm). Hydrogels containing more than 10 mol % CIPAAm exhibit large and sensitive volume phase transitions in response to temperature changes. These volume phase transition temperatures were nearly identical to that seen for IPAAm homopolymer gels. This is in contrast to IPAAm-acrylic acid (AAc) copolymer gels whose phase transition temperatures increase with reduced magnitudes of phase transitions with increasing AAc content. Moreover, volume phase transition temperatures and transition magnitudes for IPAAm-CIPAAm gels were not influenced by solution pH, which significantly influences the IPAAm-AAc gel. These results indicate that IPAAm-CIPAAm gels maintain their hydrophobic aggregation forces without disruption by ionized or hydrogen-bonded carboxyl groups. Because of the common carboxyl functionality and the noted apparent differences between the structures of CIPAAm and AAc monomers, differences in respective gel behaviors were rationalized to result from the structural analogy of CIPAAm's isopropylamide side chain groups with those of IPAAm. We therefore propose that maintaining alignment of isopropylamide side chains within the copolymer facilitates introduction of large amounts of functional groups into IPAAm copolymer gels without loss of phase transition behavior. The new monomer, CIPAAm, should prove useful to introduce functional carboxyl groups into temperature-responsive IPAAm hydrogels while maintaining their intrinsic temperature-sensitive behavior.

Collagen gel was prepared by an ordinary method as that used for preparing a cell-culture medium from an aqueous type-1 atelocollagen solution through crosslinking with glutaraldehyde (GA). Solute diffusivity in the gels prepared in the different conditions was discussed, being related to their water content. The water content of the gel decreased with increasing GA concentration at crosslinking but the solute diffusivity in the gel hardly changed. On the other hand, collagen concentration, at crosslinking of the collagen solution, dramatically affected the solute diffusivity of the obtained gel, although the water content of the gel was not changed and maintained at higher value around 0.9. The inconsistency suggested that the gel had a heterogeneous microstructure although the content of the gel was almost water. This result suggests that the process to prepare collagen medium for cell culture affects cell growth in the case that mass transfer is dominant. (C) 2000 Elsevier Science S.A. All rights reserved.

Poly(ethylene glycol) (PEG) and a hydrophobic-hydrophilic microdomain structured block copolymer comprising poly(2-hydroxyethyl methacrylate) and polystyrene (HEMA-St) have been reported to show good blood compatibility owing to inhibition of platelet activation. By using a computer-assisted novel technique to analyze platelet behavior on the surfaces, we found two different mechanisms to prevent platelet adhesion. Platelets were prevented from adhesion and spreading on the microdomain surface and retained cell movement for a long time. The platelet movement velocity was not significantly different between PEG-grafted surfaces and HEMA-SI block copolymer-cast surfaces. However, platelet motion was qualitatively different. Platelets on HEMA-St block copolymer-cast surfaces moved with rolling, spinning, and vibrating, whereas platelet movement was limited to oscillatory vibration on PEG-grafted surfaces. When platelets were treated with NaN3, an adenosine triphosphate (ATP) synthesis inhibitor, before contacting the surfaces, platelets movement velocity was decreased only on HEMA-St block copolymer-cast surfaces. Such an inhibitory effect was hardly observed with platelets on PEG-grafted surfaces. We propose two different mechanisms to prevent platelet adhesion onto surfaces. One is ATP-independent as observed with PEG, and the other is ATP-dependent for HEMA-St block copolymer, where platelets consume ATP to prevent adhesion. (C) 2000 John Wiley & Sons, Inc.

We evaluated effects of the number of tied hollow fibers of an outside blood flow membrane oxygenator with cross-wound hollow fibers on the blood flow pattern and oxygen transfer rate. The number of tied hollow fibers in a bundle was varied from one to six, and the blood flow pattern was observed by X-ray computed tomography. The oxygen transfer rate and blood pressure drop were measured by in vitro experiments using bovine blood. Uniform blood flow patterns were obtained for each number of tied hollow fibers. A decrease in the number of tied hollow fibers caused more effective contact of blood with the tied hollow fibers and oxygen transfer rate was enhanced, demonstrating that single hollow fiber was the most effective. Empirical equations were obtained based on these results and optimum structure parameters of the membrane oxygenator were determined by simulation analysis. Optimum membrane surface area and axial jacket length of the oxygenator were 3.0 m(2) and 320 mm, respectively, at a hollow fiber outside diameter of 250 mu m. (C) 2000 Elsevier Science B.V. All rights reserved.

Interactions between a temperature-responsive poly(N-isopropylacrylamide)-grafted surface and blood platelets have been analyzed with computerized image analysis. Platelet behavior on this surface is dramatically dependent upon temperature in contrast to that on poly(ethylene glycol) (PEG)-grafted surfaces or polystyrene. The poly(N-isopropylacrylamide)-grafted surface interacts with platelets similarly as the poly(ethylene glycol)-rafted surface at 18 degrees C at 37 degrees C, platelets readily adhere onto the poly(N-isopropylacrylamide)-grafted surface similarly as to that of polystyrene.

透析液管理が問われる中, エンドトキシン除去法と同時に, インラインでのエンドトキシンモニタリング法の確立が求められている。我々は, リムルス試験法を用いたインラインモニタリング装置の開発を進めており, 反応時間30minで検出下限40EU/lのモニタリングを可能にした。しかし, 実際にはさらに低濃度域での検出感度が要求され, 感度上昇が課題であった。そこで, 感度に影響する試薬分散を制御し, さらに外部からのエンドトキシンによる汚染を効果的に防止するため, 6連バルブ型インラインモニタリング装置を新たに考案した。フローインジェクション分析法に基づき, 本装置の分散特性を調べ, 中程度の試薬分散を持つように設計した。この条件下で反応生成物の吸光度を測定し, 検量線を作成したところ, 反応時間20minにおいて, 0～125EU/lの範囲で良好な直線関係が得られた。本装置は, インラインでの測定が可能であり, 安全で快適な透析治療に大きく貢献すると考える。

新たに開発されたBIOREX®《AM-BC-X》膜は, 膜最外層の孔径が小さい対称グラディエント孔構造を有するために, 膜外部から体内へのエンドトキシン等汚染物質の逆流入を抑制しつつ, 体内不要物の高除去能を発現できる。今回, 孔構造の異なる4種類の膜 ((1) 均質膜, (2) グラディエント構造膜, (3) 逆グラディエント構造膜, (4) 対称グラディエント構造膜) を試作し, 各々の透析器内で起こる物質透過現象を定量的に把握した上で孔構造と物質透過の異方性との関係について検討し, 《AM-BC-X》膜の上記特性を検証した。その結果, 中空糸両側が緻密であり, かつ内側よりも外側の方が緻密である《AM-BC-X》膜では, 外側から内側よりも, 内側から外側に物質が移動しやすかった。このような孔構造の非対称膜は, 血液からは病因物質を除去しやすく, 透析液から血液中へのエンドトキシン等汚染物質の逆侵入は起こりにくい, 理想的な孔構造の透析膜であると考えられた。

分子インプリントは, 抗体のような基質特異性を持たされた合成高分子であり, センシング用または分離用デバイスとして有望である。我々は, インジウムースズ酸化物 (ITO) の表面に, テオフィリンに対する分子インプリントの薄膜を形成した。そして, この処理を施したITOを用いて試験液中のテオフィリンの存在下または非存在下でフェロシアン化物のサイクリックボルタメトリーを行った。その結果, 分子インプリントの存在によってフェロシアン化物の酸化電流は著しく増大した。この結果は, 鋳型分子の存在によって分子インプリント薄膜は拡散溶質透過速度を増大させることを示唆している。一方, 鋳型物質の存在によって分子インプリント薄膜の表面開孔率が増大することが, 原子問力顕微鏡で確認された。これらの結果より, 分子インプリント薄膜は鋳型物質の共存によって, その構造および溶質透過性を変化させることが示唆された。

我々は既にEVM (Epifluorescent Video Microscopy) を利用したIn vitroでの血液流動下における抗血栓性相対評価システムを開発し, それを用いて材料の抗血栓性相対評価を行ってきた。本研究では, 従来の評価系では不可能であった金属材料等の光不透過材料の評価を可能にした新たな抗血栓性評価システムを開発し, 実際に数種の金属材料の評価を行った。その結果, 共有結合型ヘパリン処理を施した金属表面は基材自身より有意に血小板粘着率を低下させた (p<0.05)。また, 未処理の材料間では有意な差が見られなかった。このことからヘパリン固定化処理が, 金属材料表面への抗血栓性表面改質処理として有効であることが示唆された。そしてこのシステムを用いることで, さらに多様な医療材料の抗血栓性相対評価が可能であると考えられる。

To introduce reactive groups into temperature-responsive polymeric chains of poly(N-isopropylacrylamide) (PIPAAm), IPAAm is copolymerized with other monomer such as acrylic acid (AAc). IPAAm homopolymer exhibited temperature-responsive properties and phase transition at 32 degrees C, however, the lower critical solution temperature (LCST) of the IPAAm-AAc copolymer shifts to a higher temperature and the phase transition becomes insensitive with increasing,AAc content. To achieve a useful bifunctional copolymer containing both reactivity and temperature-sensitivity, we assumed that the homopolymer-like structure in the polymer chain would be required to maintain a sensitive temperature response with functional groups. Therefore, we designed a reactive monomer, 2-carboxyisopropylacrylamide (CIPAAm), and investigated its copolymerization with IPAAm. The important characteristic of the poly(IPAAm-co-CIPAAm) structure is that it was composed of the same polymer backbone and isopropylamide groups and some additional carboxyl groups. The transmittance measurement of the polymer aqueous solution revealed that phase transition of IPAAm-co-CIPAAm random copolymer occurred within a very narrow temperature range in pH 6.4, 7.4, and also even 9.0 phosphate buffered solution. These profiles were almost same as that of IPAAm homopolymer. While, under the same conditions, phase transition properties of poly(IPAAm-co-AAc)s solution were considerably influenced by small AAc content. We succeeded with the preparation of bifunctional polymer that possessed reactive functional groups and very sensitive response to temperature change.

Adriamycin (ADR)-loaded thermally responsive polymeric micelles composed of poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide)-b-poly(D,L-lactide were prepared by dialysis from its dimethylacetamide solution against water. Microfiltration was successfully applied to removal of block copolymer associates, which were smaller than micellar structures. By this microfiltration polymeric micelles showing a lower critical solution temperature (LCST) at 40 degrees C in phosphate buffered saline was obtained with a monodispersed size distribution of 69.2 nm in cumulant average diameter. ADR-loaded micelles released more ADR at 42.5 degrees C (above the LCST) than at 37 degrees C (below the LCST). ADR-loaded micelles did not show much cytotoxic activity against bovine aorta endothelial cells at 37 degrees C, in contrast to high cytotoxicity at 42.5 degrees C. On the other hand, free ADR expressed high cytotoxicity at both the incubation temperatures. Thus, thermally responsive polymeric micelles showed distinct control of ADR cytotoxic activity by temperature, while free ADR did not. From these results, an effective target therapy against solid tumors is feasible for these polymeric micelles by a combination of selective delivery to tumor sites based on stable micellar structures at 37 degrees C and enhanced cytotoxic activity of these drug-loaded micelles at 42.5 degrees C by local heating at tumor sites. (C) 1999 Elsevier Science B.V. All rights reserved.

A great deal of research has been conducted focusing on membrane materials with reference to their blood compatibility, but blood compatibility is influenced both by the material used in membranes and their structure, and by the flow conditions at the membrane surface. Accordingly, the relationship between membrane surface roughness and hemocompatibility has been evaluated using five types of membranes of differing surface roughness by evaluating the inner surfaces of the hollow fibers by atomic force microscopy (AFM) and by measuring platelet adhesion ratios using bovine blood. The yield stress, which equates to flow characteristics, was also evaluated using a glycerol suspension of polymethylmethacrylate (PMMA), a Bingham fluid. It was found that membranes having rough surfaces had high platelet adhesion ratios and poor hemocompatibility, whereas those with smoother surfaces had lower platelet adhesion ratios and better hemocompatibility. Measurement of the yield stresses for these membranes revealed higher values far those with rough surfaces, and lower values for those with smoother polyethylene glycol (PEG) grafted surfaces. This suggests that flow conditions at the membrane surface differ according to its surface roughness, and that this difference in flow conditions also influences hemocompatibility.

An artificial gill, which takes oxygen from water, would enhance the ability of people to function under water for extended periods. Increasing oxygen transfer rate, however, would be essential to the realization of compact, commercially viable equipment. Fish have evolved a variety of techniques to enable them to breathe under water, and their mechanisms must be clarified before compact, high-performance artificial gills can be developed. A model of the secondary lamellae of fish gills, through which oxygen is taken up from water to the blood, was devised, and its structure and oxygen transfer rate were evaluated by computer simulation analysis for carp and dogfish. Oxygen transfer rates were also found for an outside-water-flow artificial gill using a hollow fiber membrane at various fiber packing ratios. The biologic membrane is rate-determining for oxygen transfer through the secondary lamellae. Blood and water side boundary film resistances are small for fish because the blood and water channels are very narrow and numerous. When the fiber packing ratio of the artificial gill is raised, the oxygen transfer rate increases because of lower water side boundary film resistance. An optimum fiber packing ratio should be selected so that there is no major increase in pressure drop and no channeling occurs.

Cross-linked poly(N-isopropylacrylamide) (PIPAAm) hydrogel-modified surfaces were prepared to investigate the effects of a three-dimensionally cross-linked structure of PIPAAm layers on both wettability changes and hydrophobic interactions with hydrophobic solutes in response to temperature changes. The temperature-responsive surface was prepared by polymerization of IPAAm in the presence of cross-linker on the substrates on which an azo polymerization initiator was covalently bonded. The PIPAAm hydrogel-modified surface showed temperature-responsive hydrophilic/hydrophobic surface property alterations as demonstrated by a large and discontinuous wettability changes in a range of 27-32 degrees C, a slightly lower temperature range than the phase transition temperature for soluble PIPAAm in aqueous media. This implies that the dynamic motion in response to temperature for PIPAAm segments in the modified hydrogel is restricted due to the cross-linked structure. The effect of the three-dimensional PIPAAm structure on the separation of hydrophobic steroids was investigated by high-performance liquid chromatography with an aqueous mobile phase. The retention times for steroids with different hydrophobicities were increased as the temperature was raised. Cortisone and prednisolone, those showing close hydrophobicity, were successfully separated at an elevated temperature above 25 degrees C owing to the amplified hydrophobic interaction of prednisolone compared to that of cortisone with the hydrophobic gel surfaces. The separation of relatively hydrophobic steroids was achieved even at lower temperature. The expanded network of the highly hydrated gel layer allowed the penetration of steroid molecules within the hydrogel layer which resulted in the changes in peak width. The cross-linked structure of PIPAAm hydrogels on substrates strongly influences both surface wettability changes and interaction with hydrophobic steroids in response to temperature due to the restricted dynamic motion of PIPAAm segments in the gel.

Improvement in filtration performance of artificial membranes will be possible if their structure mimics the renal glomerulus. Blood filtration with glomerular capillary and artificial membranes was, therefore, modeled to clarify the effects of their structure on filtration rates. Filtration rates were obtained by dividing membrane modules axially into a number of sections and using a calculus of finite differences. The modules were assumed to be composed of straight hollow fibers arranged in parallel, with a membrane surface area of 1.5 m(2). The mean transmembrane pressure (TMP) was assumed to be too low for a protein gel layer to form on the membrane surface. A decrease in the inner diameter of membrane hollow fibers led to an increase in filtration rate because of an increased film mass transfer coefficient. A decrease in hollow fiber length also produced an increase in filtration rate because of decreased axial TMP drop. The glomerular capillary has a higher filtration rate than artificial membranes because of the low TMP drop and the low osmotic pressure at the membrane surface. Decreasing both the inner diameter and the length of the hollow fibers is effective in increasing the filtration rate at constant TMP.

Continuous measurement of endotoxin concentration in dialysate, using a separated endotoxin-specific limulus reagent, promises rapid measurement without the complex operating procedures of the limulus reagent. To achieve high sensitivity measurements in a short period of time, an improved system featuring stopped-flow operation was developed. To prevent dispersion of the limulus reagent and residence of reacting solution containing the limulus reagent in the system reactor, the circuit in the reactor was changed from a coil configuration to a straight line, and its length was reduced. An endotoxin test solution was supplied at 760 mu l/min, into which 40 mu l of limulus reagent was pulse-injected. Flow was stopped at the point where the test solution entered the reactor. After the completion of the reaction, the solution was passed through a spectrophotometer and the relationship between reaction time and absorbance was determined. Peak tailing was less than that obtained by the conventional technique, good correlation was obtained from the peak height, and a decrease in sensitivity caused by broadening of the peak was suppressed. The lower detection limit of dialysate was 100 endotoxin units (EU)/L at a reaction time of 20 minutes, and 60 EU/L at 30 minutes. Change from the monitoring system to stop-flow operation made high sensitivity monitoring of endotoxin concentration with a short reaction time possible.

Two types of thermo-responsive hydrogels are synthesized to obtain comb-type grafted gels with different lower critical solution temperatures (LCSTs) between graft chains and crosslinked backbone networks: these are poly(N-isopropylacrylamide) (PIPAAm) cross-linked hydrogels grafted with poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(IPAAm-co-DMAAm)) maintaining a freely mobile end and poly(IPAAm-co-DMAAm) cross-linked hydrogels grafted with PIPAAm chains. The effect of graft chain hydrophilic/hydrophobic balance as well as its mobility on deswelling kinetics of these grafted gels are investigated through the polymer LCST modulation and external temperature changes. The deswelling rate of poly(IPAAm-co-DMAAm)-grafted PIPAAm gel increases with increasing in temperature. This gel shows a discontinuous increase of the deswelling rate when the temperature is applied from below to above the graft chain LCST (37 degrees C). The deswelling rate of PIPAAm-grafted poly(IPAAm-co-DMAAm) gel increases continuously when the temperature is applied from below to above the graft chain LCST (31 degrees C). Due to the strong hydrophilicity of backbone network, the hydrophobic aggregation force weak. In contrast to the graft-type gels, normal-type poly(IPAAm-co-DMAAm) cross-linked gel without graft chains demonstrates the discontinuous decrease for the deswelling rate when the temperature is applied from below to above the polymer LCST (36 degrees C), entrapping water inside the gel due to the formation of an impermeable dense skin layer at the gel surface. These gel deswelling mechanisms are discussed in terms of gel structures.

The pore-size distribution and diffusive permeability of homogeneous cellulosic dialysis membranes were measured by thermoporometry and by radioisotope and photoabsorption techniques, respectively. A tortuous pore model incorporating membrane pore-size distribution in which tortuosity differs with pore size, can predict diffusive permeability for a wide range of solute molecular weights. The tortuosity obtained using the tortuous pore model by fitting the experimentally obtained diffusive permeability varied with molecular weight (Stokes radius). To evaluate the physical meaning of the tortuosity varied with solute Stokes radius, the tortuosity of the tortuous pore model was correlated to permeability parameters of the friction model. Tortuosity is represented by a ratio of intramembrane friction coefficients for solute and water between actual and hypothetical membrane having isodiametric pores for which the straight pore model is valid. The change in the ratio with the solute is attributable to the pore-size distribution.

The objectives of the present study are to clarify the phenomenon of solute transfer occurring inside dialyzers made from asymmetric membranes, to examine the structure of asymmetric membranes capable of suppressing the inflow of endotoxins from the dialysate, and thereby to contribute to the design of a more effective dialysis membrane. Using membranes that have tight layers on both sides (drum-shaped membrane) with the outer one tighter, solutes are more easily transferred from the inside out than from the outside in, leading to effective removal of pathogenic substances from the blood and a significant lowering of endotoxin inflow from the dialysate. The anisotropy of solute permeability of asymmetric dialysis membranes is caused by the difference in the amount of solute transfer due to filtration from the inside out and from the outside in. (C) 1998 Elsevier Science S.A. All rights reserved.

The thermally sensitive block copolymer, poly(N-isopropylacrylamide-b-DL-lactide) (PIPAAm-PLA), was synthesized by ring-opening polymerization of DL-lactide initiated from hydroxy-terminated poly (N-isopropylacrylamide) (PIPAAm). A PIPAAm bearing a single terminal hydroxyl group was prepared by telomerization using 2-hydroxyethanethiol as a chain-transfer agent. Successful preparation of PIPAAm and the PIPAAm-PLA block copolymer was verified by gel permeation chromatography (GPC) and H-1-NMR spectroscopy. Polymeric micelles were prepared from block copolymers using a dialysis method. Their solutions showed reversible changes in optical properties: transparent below a lower critical solution temperature (LCST) and opaque above the LCST. Dynamic light scattering measurements were used to observe the formation of micellar structures approximately 40 nm in diameter, which do not change between 20 degrees C and 30 degrees C, Above the LCST, polymer micelles aggregated, a phenomenon found to be reversible since the aggregates dissociated again by cooling below the LCST. Further observations using atomic force microscopy (AFM) confirmed this behaviour. The properties of this block copolymer system are interesting from both applied and fundamental perspectives, particularly for active targeting as drug carriers. (C) 1998 Elsevier Science B.V.

To develop high performance dialysis membranes, the asymmetric structure should be positively accepted and the relationship between asymmetric structure and diffusive permeability should be further clarified. A little information on the asymmetric structure can be obtained from SEM observation. The objective of the present study is to propose a new method for evaluating asymmetric hollow-fiber dialysis membranes by dye adsorption. Adsorption experiments were carried out using mini-modules composed of test membranes (AM-SD-M, PS-UW, PEPA, PAN-DX, PAN-CX2) of which the inside was packed with paraffin to make solutes diffuse only from the outside inward, or of which the outside was packed with paraffin to make solutes diffuse only from the inside outward. The amount of solutes (cytochrome C, Evans blue, Congo red, ethidium bromide) transferred into the membranes was plotted as a function of time. In membranes of asymmetric structure the shape of the transfer rate curves differed with the direction of transfer, and a difference in the rate of solute transfer was produced which is due to the asymmetric structure of the membrane. Further, depending on the solute size and on the membrane, the directional difference in the transfer rate curves appeared either in the middle portion or the initial portion of the curves. It is concluded that the adsorption technique can be used to evaluate the asymmetric structure and diffusive permeability. (C) 1998 Elsevier Science S.A. All rights reserved.

Glucose reacts with glucose oxidase to form gluconolactone and hydrogen peroxide (H2O2) and the glucose concentration may be determined indirectly from the amount of hydrogen peroxide produced. The authors have developed a method of H2O2 assay that uses the electroluminescence (EL) of indium-tin oxide (ITO). Since this method depends on a reversible reaction of the ITO itself, it does not require the addition of an emitting substance, allowing convenient continuous monitoring of the anylates. In the present work the triangular-wave potential was set at 0 - +1.4 - 0V against the Ag/AgCl reference electrode, and swept at a rate of 200 mV s(-1). The integrated number of photons was taken as the electroluminescence intensity, and its response to changes in H2O2 concentration was investigated. As a result a value that was dependent on H2O2 concentration was obtained. Electroluminescence intensity was measured varying the pH of the test solution from 7 to 13 with a Britton-Robinson buffer solution, and it was found that electroluminescence intensity was constant at pH 9 and above. When glucose and glucose oxidase were mixed in the test solution, measurements of electroluminescence intensity showed a good correlation with glucose concentration.

A glucose sensor, using glucose oxidase immobilized in an electrically conductive polymer membrane, is developed for transient-mode measurement by on-off reaction control in the present work. An implantable glucose sensor loses its stability under the skin by fouling resulting from fibroblast adhesion on the glucose oxidase-immobilized membrane. Change in glucose distribution inside the membrane and in the vicinity of the surface of the membrane resulting from the fouling makes the measurement of the glucose concentration unstable. A technique of measuring transient current of the glucose sensor after activation of glucose oxidase may hardly be affected by the fouling as oxidation of coenzyme of glucose oxidase is rapid and the transient current is sensitive to glucose concentration. A glucose sensor with glucose oxidase immobilized in an electrically conductive polypyrrole membrane was fabricated. The activity of the glucose oxidase is switched on and off by a stepwise change of potential of the polypyrrole membrane from 0.15 V to 0.45 V versus a saturated calomel electrode. The two conditions described above can be confirmed by measuring transient current. Current increased momentarily after activation of glucose oxidase and decreased moderately after that. The oxidation and reduction of glucose oxidase is sufficiently rapid, and current intensity depends on glucose concentration in the test solution.

細胞培養媒体として有用なコラーゲンゲルの微細構造を変化させることにより、物質の拡散透過性の制御を試みた。豚皮由来のtype Iアテロコラーゲン溶液をキャストした後に乾燥させ、さらにグルタルアルデヒド(GA)により架橋することによりコラーゲンゲル平膜を得た。ゲル膜の微細構造を迷宮細孔モデルで検討したところ、架橋時のGA濃度が膜構造因子に及ぼす影響は少なく、微細構造は変化しないと考えられた。一方、77～96wt%まで濃縮したコラーゲン溶液において製膜を行った結果、架橋時のコラーゲン濃度に依存して拡散透過性が大きく異なるゲル膜を作製することができた。さらに、架橋時のコラーゲン濃度と膜構造因子の間に相関性があり、曲路率により膜の微細構造の均質性を推測できた。したがって、架橋時のコラーゲン濃度により微細構造を制御することができ様々な拡散透過性を持つコラーゲンゲル膜が作製可能である。

生体材料のポリエーテルタイプポリウレタン(PEU)に劣化が起こることが明らかとなっている。PEUの優れた機械的特性と生体適合性を温存し、しかも劣化を減少させる目的で、最近ポリエーテルタイプに代わりポリカーボネートタイプのポリウレタン(PCU)が開発されている。本研究では、これらPCUのin vitro加速劣化試験と、我々が開発したepifluorescent video microscopy (EVM)装置を用いた抗血栓性評価を行い、従来のPEUと比較した。加速劣化試験後、PEUは表面が物理的・化学的に劣化することが明らかとなった。一方、PCUではこのような変化は認められなかった。EVM実験の結果より、PCUはPEUに比べ同等またはそれ以上に血小板の粘着を抑制することがわかった。以上の結果から、埋込み型人工心臓をはじめとする長期使用の循環系デバイスの構造材料としてセグメント化ポリウレタンを選択する場合、現状ではPCUを第一選択とするべきであると考える。

One of the factors to reduce the performance of a hemodialyzer during clinical treatment is membrane fouling caused by protein adsorption. Highly permeable dialysis membranes recently developed are of asymmetrical structure and the reduction in permeability after protein adsorption may vary with their asymmetrical structure. Intramembrane diffusion coefficients and rejection factor for several solutes of polysulfone membranes having asymmetrical structure were measured before and after plasma protein adsorption. Ratio of intramembrane diffusion coefficient to diffusion coefficient in water for higher molecular weight solutes is reduced after plasma protein adsorption, but that for lower molecular weight solutes is slightly reduced. Rejection factor after plasma protein adsorption increases at lower filtration flux especially for smaller molecules, but that at higher filtration flux hardly changes.

透析治療に用いられている透析膜の素材には大別してセルロースと合成高分子がある. 透析膜は均質膜であるが, 最近では非対称膜が用いられている. 分子量が大きい病因物質の分離速度 (クリアランス) を大きくするには, 分離に寄与する緻密なスキン層は薄いほど好ましい. その機械的強度を保持するための粗な支持層とから構成された非対称膜の有利性が大いに評価されている.<br>透析器のクリアランスおよび濾過係数は透析膜の性能と透析器の設計に依存する. すなわち濾過係数が数ml/m²hrmmHgの透析膜では分子量が1,000以上, 濾過係数が数十ml/m²hrmmHgの高性能透析膜では分子量が10,000以上の溶質の分離速度は透析膜律速である. すなわち分子量の大きい尿毒症病因物質の除去は透析膜の透過性能 (拡散透過係数および濾過係数) に左右される.<br>基本的には, 透析膜の両側の流体の浸透圧差をゼロに設定し, ある一定の膜間圧力差で一定時間に得られた濾液量のデータから透析膜の濾過係数が求められる. また拡散透過係数は濾過流束をゼロに設定した時に得られる溶質濃度と拡散流束のデータから求められる. 濾過係数を測定するときに透析器内を血液と透析液が流れていると, 両流体の流動方向に (静) 圧力が変化するため, 膜間圧力差を正しく求めることができない. そこで透析器を完全濾過で操作すると, 正しい濾過係数が求められる.<br>本稿では, 透析膜の性能評価について, 透析膜の拡散透過係数および濾過係数の測定法, さらに透析膜の構造と透過性の関係について述べたい.

外部灌流膜型人工肺の設計は、実験的な試行錯誤の結果に基づき、コストと時間を要する。そこで本研究では、外部灌流膜型人工肺内の血液流動状態やガス交換能の解析法として、コンピュータによるシミュレーション解析法を検討した。血液流れのモデル化には、多孔質媒体中の低レイノルズ数流れにおけるDarcyの法則を応用した。酸素移動のモデル化には、血中酸素分圧による物質移動係数の変化を考慮するために反応係数を用いた。得られた支配方程式の数値解を有限要素法により得た。血液流れをシミュレーション解析した結果、異なる膜充填法の場合に生じる偏流について知見が得られ、これらはX線CTによる流れの可視化実験の結果と一致した。また、円管外流れにおける物質移動の無次元相関式より血液側境膜物質移動係数を推算して、酸素移動をシミュレーション解析した。その結果より、外部灌流膜型人工肺における酸素移動速度が計算された。

エンドトキシン(Et)濃度の測定に用いられるリムルステストは、Et混入による測定誤差が生じやすく、煩雑な操作が必要である。そこで我々は、リムルス試薬を用いた簡便かつ連続的なモニタリング装置の開発を進めている。以前報告した測定装置では、反応時間45分で検出下限50EU/lのEtモニタリングを実現している¹⁾。しかし、透析現場ではさらに低濃度域のEtのリアルタイムなモニタリングが望まれる。そこで、従来の装置の反応回路長を95%減少させ、反応時に流動を停止させることで、試薬の分散を抑制し、感度上昇を試みた。これまでの基礎検討から、至適反応時間を30分に設定して検量線を作成した。これより、Et濃度40-200 EU/lの範囲で良好な直線関係が得られた。同様に反応時間20分、10分でも検量線を作成したところ、反応時間20分では40-200EU/lの範囲を、反応時間10分では80-200EU/の範囲をモニタリングできるようになった。

透析膜の血液適合性については、これまでに膜材質の違いに着目した多くの研究がある。しかし、血液適合性は、これら膜材質の違いだけではなく、膜表面での流動状態の影響も受けると考えられる。そこで、膜表面粗さの異なる5種類の膜を用い、ウシ血液を用いて血小板粘着量を測定することにより、膜表面粗さと抗血栓性を評価した。まな、ビンガム流体であるPMMAのglycerolサスペンションを用い、その流動特性である降伏値を測定した。膜表面の粗い膜では血小板粘着量が多く抗血栓性が劣り、膜表面が滑らかな膜ほど血小板粘着量が少なく抗血栓性に優れた。これらの膜について、それぞれ降伏値を測定したところ、膜表面構造の粗い膜では降伏値が大きくなり、PEGでグラフトされた麺の滑らかな膜では降伏値が小さくなった。このことから膜表面の粗さは抗血栓性に影響を与えることが示唆された。

Regarding hemodialysis membranes as layers packed with uniform polymeric particles, the size of the particles is determined using the Kozeny-Carman equation. Diameter of the spheres forming cellulosic membranes is the same order as the size of primary polymeric particles determined by electron microscopy in a previous article. Pore radii of the membranes calculated by the Kozeny-Carman equation are in agreement with those determined by the tortuous capillary pore model. The result suggests that an estimate of a pore radius of a membrane is feasible by the Kozeny-Carman equation only with water permeability of the membrane. Intramembrane diffusion coefficients of vitamin B(12) calculated from an equation derived from the analogy of heat conduction in heterogeneous media consisting of a continuous phase and particles are larger than the experimental values. The result suggests the failure of the analogy between heat conduction and diffusion of vitamin B(12) in a heterogeneous medium. (C) 1998 John Wiley & Sons, Inc.

Deswelling mechanism for comb-type grafted poly(N-isopropylacrylamide) (PIPAAm) hydrogel was investigated to make clear the effect of gel architecture on the gel deswelling kinetics. Deswelling rate and mechanism were compared with those for conventional crosslinked PIPAAm gel and poly(ethylene oxide) (PEO)-grafted PIPAAm gel in response to temperature increase from below to above the gel-phase transition temperatures. The deswelling rate for the conventional PIPAAm gel are reciprocal to the gel size square, indicative of collective diffusion mediated manner for crosslinked network into water. Although PEO graft chains formed water release channels within the network to produce fast gel deswelling changes, deswelling change of PEG-grafted gel also demonstrated collective diffusion mediated manner of crosslinked backbone chains. On the other hand, one order faster rate of deswelling change of PIPAAm-grafted gel was observed than that of PEG-grafted gel with identical gel dimension. The deswelling change of PIPAAm grafted gel did not obey collective diffusion mediated manner, demonstrating reciprocal to the gel size to 1.58th power. This deswelling mechanism was explained in terms of rapid hydrophobic aggregation of freely mobile PIPAAm graft chains and an operation of intrinsic elastic forces of polymer network. The operation of both elastic force and strong hydrophobic aggregation force between the dehydrated PIPAAm graft chains released water inside the gel, causing more rapid deswelling changes of the PIPAAM-grafted gels. (C) 1999 Elsevier Science Ltd. All rights reserved.

On the assumption that continuous treatment is effective in preventing β2-microglobulin deposition in a patient without kidney function, a wearable artificial kidney device was theoretically designed on the basis of using presently commercially available hollow-fiber membrane for hemodialysis. The device was assumed to be connected between an arteriole and a large vein. The device, with an optimal dimension consisting of the membrane with an appropriate filtration permeability, was capable of carrying out continuous hemofiltration using the blood pressure of the patient only and of preventing β2-microglobulin deposition. If dialysate was fed into the device for an appropriate time every day, concentrations of urea nitrogen and creatinine were also maintained at a lower level than that of conventional intermittent hemodialysis. Because the dimension and technical data of the device giving these results are comparable to those of commercially available hemodialyzers, we should reconsider whether the wearable artificial kidney can be put into clinical use. © The Japanese Society for Artificial Organs 1998.

Virtually all of the artificial membranes such as reverse-osmosis membrane, dialysis membrane, ultrafiltration membrane, microfiltration membrane and gas separation membrane in use industrially also have therapeutic applications. Dialysis membranes used clinically in the treatment of patients with renal failure account for by far the largest volume of membranes and, worldwide, their consumption has reached some 70 million square meters a year. Almost all dialyzers now in use are of the hollow-fiber type.
A hollow-fiber dialyzer contains a bundle of approximately 10,000 hollow fibers having an inner diameter of about 200 mu m when wet, a membrane thickness of 20-45 mu m when wet, and a length of 160-250 mm. The walls of the hollow fibers function as the dialysis membrane and the materials used for dialysis membranes are many and varied, and include cellulose-based materials and synthetic polymers.
This paper reviews blood purification and dialysis membranes and also discusses differences in performance between the natural kidney and filters to clarify separation mechanism of glomerular basement membranes and filtration membranes. An intelligent membrane is proposed of temperature-responsive dialysis membrane with pores the size of which varies with temperature.

Since artificial organs are intended to replicate chemical processes, knowledge of chemical engineering is essential in their design so that they will function with the maximum efficiency. The most commonly used artificial organ is the artificial kidney, a machine that performs a treatment known as hemodialysis. This process cleanses the bodies of renal failure patients by dialysis and filtration which are simple physicochemical processes. Hemodialysis membranes act to remove accumulated uremic toxins, excess ions and water from the patient via the dialysate, and to supply from the dialysate those ions that are insufficient.
This paper describes dialysis membranes and dialyzers for blood purification, the solute transport mechanism of the membrane, and a technical evaluation of the dialysis membrane. Lastly, the next generation of artificial kidney is reviewed.

In the present study, cyclic voltammograms obtained with an indium-tin oxide (ITO) anode were compared with those obtained with a platinum anode. The peak currents generated by luminol oxidation at the platinum anode showed convex curves facing upwards with increasing luminol concentration, as the result of the prevention of the oxidation of the platinum electrode by the presence of Luminol. With the ITO anode, no current due to electrode oxidation or reduction was detected. The peak current intensity of luminol oxidation was proportional to the luminol concentration, but the peak current was also in a linear relationship with the square root of the scan rate. However, the intercept current was largely deviated from zero. The deviation suggests radial diffusion of luminol at the ITO anode which has a small active point density. In conclusion, the ITO anode is useful for accurate measurement of the rate of luminol oxidation, but radial diffusion of luminol in the vicinity of the ITO surface should be taken into consideration in analysis of luminol oxidation.

Urea removal by continuous ambulatory peritoneal dialysis (CAPD) was compared with that by hemodialysis (HD) using a mathematical kinetic model. The time-averaged urea-nitrogen concentration (TAG) in the blood of a patient on maintenance HD was calculated by the model. Clearance with HD giving a TAC value equal to the constant urea-nitrogen concentration in the blood of a patient on CAPD was obtained, leading to the relation of equivalent clearances between HD and CAPD on the assumption that the urea-generation rate of the patient on CARD was equal to that of the patient on HD.

従来、ゲルを用いた薬物放出の制御は、ゲル中の薬物の拡散によっていた。これに対し、グラフト鎖を有するゲルを用い、網目の凝集変化による水の押し出しを同期させた薬物の放出を起こす、新しい温度応答性薬物放出制御の実現を目的として研究を行った。ゲルは網目の協同拡散により膨潤状態から収縮状態に変化するため、本来、温度変化に対する収縮変化はサイズに依存し、ゆっくりとしたものであった。これに対し、自由末端を有するポリN-イソプロピルアクリルアミド(PIPAAm)のグラフト鎖がPIPAAm網目中に導入されたグラフト型のゲルは、32℃以上への段階的な温度上昇に対し素早く収縮変化した。これはグラフト鎖が温度変化に対して素早く凝集変化し、凝集したグラフト鎖間に強い疎水性相互作用が働く結果、ゲルは水を素早く外部へと押し出したためと考えられた。このゲルの収縮変化に伴う水の押し出しの相異により、単なる三次元網目の通常型ゲルに対し、グラフト型ゲルからの薬物放出挙動は大きく異なることが明らかにされた。すなわち、通常型のゲルが収縮時に表面スキン層を形成して薬物拡散を停止するのに対し、グラフト型ゲルはその特徴的な水の押し出しにより、温度変化で薬物をパルス的に放出させることができた。このグラフト型の分子構築に基づく温度応答性の薬物放出制御の特性を通常型のゲルと比較しながら議論し、グラフトゲルによって新しく実現されたミクロポンプとしての温度応答性ゲルの機能を詳細に検討した。

Type Iアテロコラーゲンをグルタルアルデヒドで架橋したコラーゲンゲル平膜について、様々な分子量の溶質の透過性を調べた。現行の透析膜と比較すると、アルブミンが両者でほぼ同等に阻止されているのに対し、他の溶質ではコラーゲンゲル平膜が遥かに優れた溶質透過性を示し、コラーゲンゲルは透析膜として理想的な溶質透過性を持つことがわかった。そこでコラーゲンゲルの強度の増大および薄膜化を図るために、コラーゲン溶液を血漿分離膜により濾過することにより、その細孔にコラーゲンゲルを充填した複合膜を作製した。走査型電子顕微鏡による観察、閉塞濾過式および迷宮細孔モデルでの解析により、細孔内へのゲルの充填状態を検討した。充填膜の細孔内にはコラーゲン溶液より作製したゲル平膜と溶質透過性が同等である薄層のゲル充填層が存在することが確認され、本研究で用いた充填法の妥当性が示唆された。

人工心臓などの人工臓器に用いられる抗血栓性材料の評価法として、蛍光顕微鏡、ビデオカメラ、パラレル・プレート・フロー・チャンバーからなるepifluorescent video microscopy (EVM)法を用いて、抗血栓性発現機構の異なる4種類の材料(HEMA-styreneプロック共重合体、ポリエチレングリコール誘導体、ヒトトロンボモジュリン、MPC共重合体)の抗血栓性を相対的に評価した。蛍光色素で標識した血小板を含むヒト全血をシリンジポンプにより壁ずり速度100sec^-1で20分間流し、1分毎に血小板粘着量を測定した。いずれの材料もコントロールに用いたセグメント化ポリウレタンに比べ、有意に血小板粘着を抑制した。また、これまでに発表されている各材料の特性が本実験の結果にも反映され、本実験方法が抗血栓性材料のin vitroにおける相対的評価法として有用であることを確認した。

現在透析に用いられている高透水性の膜の多くは非対称構造を有しておりこのような膜では透析時に溶質透過方向により透過係数が異なる。この原因は非対称膜に見られる濾過方向による阻止率の差であると予想される。この関係を解明すれば血液からは溶質が抜けやすく、透析液からはエンドトキシンなどが侵入しにくい理想的な透析膜の開発が可能になる。そこで溶質にデキストランを用い数種の対称膜、非対称膜についてその阻止率と総括物質移動係数を測定した。その結果、均質膜では濾過方向による阻止率の差はみられず透析時の溶質透過の異方性もみられなかった。中空糸内側に緻密層を有する膜では外側から内側に濾過を行った方が阻止率が小さく、透過係数は大きくなった。中空糸外側に緻密層を有する膜では阻止率、透過係数の大小とも逆になった。したがって、透析時の溶質透過の異方性は非対称膜のみにみられ、その原因は濾過方向による阻止率の違いに起因する。

皮下留置を目的としたグルコースセンサーの抱える最大の問題点は、タンパク質や細胞など吸着による応答電流の変化である。グルコースの酸化反応を断続的に行い、濃度勾配の小さい状態で測定すれば、吸着の影響を小さく抑えて定量できると考えた。本研究では、ウシ血清アルブミンとフェロセンカルボキシアルデヒドの結合体をメディエーターとしたグルコースセンサーを用いた。印加電位をパルス的に変化させることで反応を断続的に行い、非定常状態の応答電流とグルコース濃度の相関を求めた。反応初期の非定常状態では、拡散が律速ではなかった。また、非定常状態のグルコース酸化電流はグルコース濃度に依存した。これらの結果より、本センサーを用いて反応をON-OFF制御しながらの測定が可能であることが示唆され、長期利用の可能性が見いだされた。

Since artificial organs are intended to replicate chemical processes, knowledge of chemical engineering is essential in their design so that they will function with the maximum efficiency. The most commonly used artificial organ is the artificial kidney, a machine that performs a treatment known as hemodialysis. This process cleanses the bodies of renal failure patients by dialysis and filtration which are simple physicochemical processes. Hemodialysis membranes act to remove accumulated uremic toxins, excess ions and water from the patient via the dialysate, and to supply from the dialysate those ions that are insufficient. This paper describes dialysis membranes and dialyzers for blood purification, the solute transport mechanism of the membrane, and a technical evaluation of the dialysis membrane. Lastly, the next generation of artificial kidney is reviewed.

The purpose of the present work is to characterize the cathodic electrochemiluminescence of luminol with a view to its application in continuous immunoassay. The authors designed a method for continuous antibody determination from the change in electrochemiluminescent intensity of luminol resulted from antigen-antibody reactions. The cathodic electrochemiluminescences of luminol-labeled antigens in hydrogen peroxide solution were enhanced by the presence of the respective antibodies. Cathodic electrochemiluminescence Of a luminol-labeled antibody was also enhanced by the presence of antigen. The enhancement of electrochemiluminescence may be useful in homogeneous immunoassay of antibodies or antigens. Analysis of a batchwise reaction suggested that the presence of antibody increases the quantum yield of electrochemiluminescence of luminol-labeled antigen. And analysis of the electrolytic current of luminol and hydrogen peroxide at indium-tin oxide (ITO) cathode revealed that hydrogen peroxide was electrochemically active at the cathode, while luminol was inert. These results suggest that cathodic electrochemiluminescence of luminol or luminol-labeled proteins is triggered by hydroxide radical produced from hydrogen peroxide at the ITO cathode.

The synthesis and characterization of comb-type grafted thermo-sensitive hydrogels is presented. These hydrogels were synthesized by polymerization of N-isopropylacrylamide (IPAAm) with a PlPAAm macromonomer. This process leads to a crosslinked IPAAm backbone polymer, copolymerized with highly mobile comb-type PIPAAm chains. These new thermo-responsive copolymers displayed higher equilibrium swellings at lower temperatures and rapid deswelling kinetics at elevated temperatures. The swelling/deswelling for comb-type gels is dependent on the graft chain lengths, in contrast to normal PIPAAm gel lacking the graft chains. As the temperature is increased above the critical temperature, the dehydrated graft chains aggregated due to hydrophobic attraction. Rapid and reversible kinetics of the graft-type gel were observed in response to stepwise temperature changes within short time cycles: phenomena not observed in normal crosslinked thermo-sensitive gels. The influence of freely mobile graft chains on both the equilibrium and dynamic properties of comb-type PIPAAm gel is demonstrated. Possible application of graft-type gel is discussed for actuator systems.

Some patients on long-term dialysis may suffer from metabolic bone disease owing to abnormal metabolizing of phosphorus and calcium. It is possible to prevent these conditions by controlling serum ion concentrations to an appropriate level, and to do this the rate of ion permeability through the dialysis membrane must be clarified. The rate of ion permeability is influenced by membrane structure and membrane charge. The changes in membrane charge occurring when protein was adsorbed on a polyacrylonitrile dialysis membrane were evaluated for cytochrome C, which is positively charged in an aqueous solution at pH 7.4 and for alpha-lactalbumin, which is negatively charged at pH 7.4, by means of changes in zeta potential, and these were compared with changes in rates of ion permeability. Changes brought about in membrane structure were also evaluated from changes in the diffusive permeability coefficient of urea, which is a non-electrolyte. After cytochrome C adsorption, the absolute zeta potential of the membrane decreased, and the charge on the membrane became electrically closer to neutral than before the adsorption. In membranes on which alpha-lactalbumin was adsorbed, on the contrary, absolute zeta potential increased and the negative charge on the membrane increased. The diffusive permeability coefficient of urea decreased no matter which protein was adsorbed, but the amount of decrease was slight and there was little change in membrane structure. The diffusive permeability coefficients of sodium hydrogen phosphate and NaCl increased after cytochrome C adsorption and decreased after alpha-lactalbumin adsorption. The changes in electric charge evaluated by zeta potential and changes in the rate of ion permeability due to protein adsorption are in qualitative agreement with ion permeability theory. It is therefore suggested that the zeta potential can be used as an index of membrane charge when evaluating the membrane permeability of ions.

臨床における透析膜の性能低下の一因に、血液接触後の膜構造変化による拡散透過性の低下がある。近年開発された高性能透析膜の多くは非対称構造を有しており、その性能低下の起こり方は膜の非対称構造によって異なると考えられる。そこで、非対称構造を有するポリスルホン膜を用いて、血漿タンパク質吸着前後で吸光法により分子量の異なる溶質の膜内拡散係数と溶質透過係数を測定した。血漿タンパク質の吸着により、膜内拡散係数比は小さな溶質ではほとんど減少しなかったのに対し、大きな溶質では顕著に減少した。また、非対称構造を有する高透水性透析膜の場合、従来の透析膜に比べて特に小さな溶質の膜抵抗が小さかった。そのため、これらの膜からなる透析器では、タンパク質の吸着によるクリアランスの低下が少ない溶質の分子量範囲が広い。

高透水性透析膜の多くは非対称構造を有している。しかし、現在、膜の非対称構造を評価する指標はなく、溶質ごとに透過実験をしなければ非対称膜の溶質透過性能は評価できない。そこで、非対称構造を有するポリスルホン透析膜(PS-400膜、PS-UW膜、APS膜)を対象として、SEM観察、染色速度比較法、BET法およびDSC法をそれぞれ適用した。そして、膜の非対称構造の評価への適用限界を明らかにするとともに、膜構造の評価を試みた。SEM観察、BET法、DSC法では、膜の透過性の違いの原因となる構造の違いは見られなかった。染色速度比較法では、他の方法と異なり膜により結果に違いが現れた。今回用いた膜のように緻密層と支持層の構造が大きく異なる非対称膜の場合、BET法では支持層の大きい細孔を評価できないが、DSC法では評価できる。また、今回用いた膜はそれぞれ、支持層の非対称構造にあまり違いはないが、緻密層の構造が大きく異なると考えられる。

透析患者の合併症の軽減めため、非対称構造を有する高透水性膜が開発されている。このような高透水性膜では、濾過による溶質透過が起こりやすく、膜の濾過特性の評価が必要である。そこで、非対称構造を有するポリスルホン膜(PS-UW, PS-NW, APS)について、試験溶質として分子量の異なるDextranを用い、阻止率を血漿接触前後で測定し、非対称構造と阻止率の関係について検討した。高分子量の溶質では、濾過流束が大きくなるにつれ、阻止率が減少したのに対し、低分子量の溶質では増加した。この傾向は膜の外表面に緻密層を有する非対称膜、あるいは内部よりも開孔率の小さい支持層を有する非対称膜に特有のものである。また、阻止率は純水濾過係数が大きい膜ほど小さかった。血漿接触による阻止率の増加は分子量の小さい溶質ほど、低濾過流束で顕著であった。以上より、非対称構造や溶質の分子量の違いによって阻止率の濾過流束依存性が異なると結論づけられる。

著者らは、成形加工したデバイスの血液接触面にin situでヘパリン及びスルホン化ポリマーを固定化し血液適合性を賦与する表面処理技術を開発した。ポリウレタン(PU)表面にこれらの処理を行い、著者らの開発したEpifluorescent Video Microscopy (EVM)システムを用いてin vitro血液適合性を評価した。XPSによる表面解析では、未処理を除く全ての表面で、ヘパリン及びスルホン化ポリマーの固定化を示す硫黄元素が確認された。ヘパリン固定化PUでは高い抗FXa活性(2.13×10^-1IU/cm₂)を示したが、スルホン化ポリマー固定化PUは、その1/10以下の活性であった。表面修飾したPUは、いずれも未処理のPUと比較して、血小板粘着量は有意に低値を示した。β-TGは、血小板粘着率と同様の傾向を示したが、C3aはヘパリン固定化PUのみが有意に低値であった。ヘパリン及びスルホン化ポリマー固定化PUは、未処理PUと比較して、EVM実験において血小板粘着/活性化を抑制し、優れた抗血栓性を示した。

エンドトキシン(Et)濃度の測定に用いられるリムルステストは、Et混入による測定誤差が生じやすく、煩雑な操作が必要である。そこで我たは、簡便な定量が可能なリムルステストの連続測定装置を試作し、その至適操作条件を検討した。まず、リムルス試薬の反応に伴う吸光スペクトルの変化、および反応時間による測定感度の違いを観察した。さらに、その結果を用いて、連続測定装置における至適操作条件を検討した。その結果、新規開発Et特異的比色法リムルス試薬でEt濃度を定量する場合、検出波長を381nmに設定し、定量するEt濃度範囲に最適な反応時間を設定することで感度が高くなることがわかった。しかし、連続測定装置では、反応時間を長くすると試薬が回路内に分散し、感度が低下した。そこで、検出波長を381nmに、反応時間を45分に設定したところ、最も感度が高くなり、連続測定装置でも濃度50-100EU/1のEt濃度を定量できるようになった。

免疫抑制剤の至適投与量の指標となる抗原量や抗体量をリアルタイムで監視するシステムの開発が本研究の目的である。我々は、連続的かつ簡便に操作できる電気化学発光フローセルを試作し、免疫定量法への有効性を確認した。また、抗原抗体反応によって発光強度が変化するメカニズムの解明も試みた。分子量および荷電の異なる抗原にルミノールを標識し、水溶液および血漿混合水溶液中での抗体定量と、水溶液中での標識抗ヒト血清アルブミン(HSA)抗体によるHSA抗原定量を試みた。0～2.2mg/mlの抗HSA抗体、0～200μg/mlの抗免疫グロブリンG抗体の各抗体濃度範囲と、0～3.8μMのHSA抗原濃度範囲で、水溶液中の発光強度が増大した。血漿中でも抗体量に伴って、標識抗原の発光強度が増大した。本法は水溶液系および血漿系での抗原抗体定量に有効であること、さらに発光強度増大の原因は、抗原抗体反応によるルミノール発光の量子収率の増大にあることが示唆された。

Temperature-responsive poly(N-isopropylacrylamide) and its copolymer gels with the hydrophilic comonomer, acrylamide and the hydrophobic comonomer, butyl methacrylate, all exhibit swelling-deswelling changes in response to external temperature changes. These hydrogels show negative swelling thermosensitivities, particularly swelling at lower temperature and complete deswelling over specific phase transition temperatures (T-p). Shrinking kinetics of these gels from swollen to deswollen states at several different temperature changes have been investigated. When temperature changes are performed entirely below T-p, the shrinking process is dominated by polymer network diffusion. On the other hand, shrinking kinetics for temperature changes from below to above T-p are dramatically influenced by gel surface structural changes and formation of a collapsed polymer skin layer. This surface skin formation prompts the accumulation of internal hydrodynamic pressure inside the gels upon shrinking by blocking the outflux of entrapped water. Both rate and magnitude of internal hydrodynamic pressure are modulated by the gel volume, the hydrophobicity of the gel polymer chains and the degree of external temperature changes. This internal pressure eventually causes convective outflow of water from the gel interior. Hydrodynamic internal pressure affects the drug release on-off pattern during gel shrinking.

The distribution volume of water contained in 31 hemodialysis membranes made from seven polymers was measured by three different methods, Water contained in the membranes was classified into three groups according to thermal mobility of the molecules, Structural analysis of the membranes was feasible through determining proportion of nonfreezing water to total water contained in the membranes. (C) 1995 Academic Press, Inc.

Swelling layers formed by poly(ethylene glycol) (PEG) chains grafted onto surfaces of a cellulosic membrane are known to improve hemocompatibility of the membrane. Three types of hemodialysis membranes were derived from the same regenerated-cellulose hollow-fiber membrane by grafting PEG with different formulas onto the surfaces to clarify the influence of the grafted PEG chains on solute permeability of the membranes. Determination of volume fractions of nonfreezing water contained in the membranes by differential scanning calorimetry revealed that most of the PEG chains were grafted onto the external surfaces and less into the pores in the membranes. Permeability of vitamin B-12 for the PEG-grafted membranes except for the one with the shortest PEG chains was reduced as compared with the original membrane, while that of tritium-labeled water for all the PEG-grafted membranes was the same as that of the original membrane. Structural parameters only of the PEG-grafted membrane with the largest alkyl groups at the terminal of the PEG chains were different from those of the other PEG grafted and original membranes. The shorter PEG chains with the larger terminal alkyl groups are suitable for grafting onto a cellulosic membrane to increase hemocompatibility of the membrane without significant reduction in the solute permeability of the membrane. (C) 1995 John Wiley & Sons, Inc.

血液透析膜の基本性能として、溶質透過性および透水性が挙げられる。溶質は膜に含まれる水の中を拡散し、水は膜内外で入れ替わることにより膜を透過するため、膜内の水の状態は溶質透過性および透水性に影響すると考えられる。本研究では、7種類の高分子素材からなる31種類の血液透析膜について、膜に含まれる水の分布状態および体積を測定した。その結果、膜内には分子運動性が異なる3種類の水が存在し、その比率は膜素材によって大きく異なることが明らかになった。再生セルロース系高分子の血液透析膜では、膜内の水の大部分が高分子鎖によって強く束縛を受けており、その内部の溶質拡散現象は疎水性高分子膜におけるそれとは異なることが明らかになった。さらに、自由体積理論によって再生セルロース系高分子の血液透析膜の膜内拡散現象を解析したところ、5種類の溶質の膜内拡散係数を膜内の水の分布体積によって表すことができた。

我々は既に抗血栓性材料のin vitro評価法として、蛍光顕微鏡、ビデオ、パラレル・プレート・フロー・チャンバーからなるepifluorescent video microscopy (EVM)を用いたリアルタイム評価法が有用であることを確認している。この方法を用いて6種類の異なるセグメント化ポリウレタン(PUs)の抗血栓性を評価した。蛍光色素で標識した全血をシリンジポンプにより壁ずり速度200sec^-1で流し、1分毎に血小板粘着量を20分間測定した。ソフトセグメントが高分子量のPTMGより構成されるPUは低分子量のPTMGより構成されるPUと比較して血小板粘着・活性化を抑制したが、補体を活性化した。また、ウレア結合を持つPUUはPUよりも血小板粘着量が多く、血小板および補体のいずれも活性化した。以上から、PUsの化学組成が抗血栓性に大きな影響を及ぼしている可能性が示唆された。また、本評価法の使用により6種類のPUsの抗血栓性に差が認められたことから、本EVM装置が優れたin vitro評価法であることが示された。

イオンの膜透過は、透析膜の荷電と構造の両方に依存する。しかし、実際の透析においては、膜に血漿タンパク質が吸着し、膜構造と膜荷電の双方が変化する。そこで、透水性の異なるPS-600とPS-620からなるダイアライザ(有効長25cm、中空糸本数700本)に、水溶液中で正に荷電するチトクロームCあるいは負に荷電するα-ラクトアルブミンを平衡吸着させ、吸着前後における尿素の溶質透過係数から膜構造の変化を、有効荷電密度の変化から膜荷電の変化を評価した。その結果、いずれのタンパク質吸着後においても尿素の溶質透過係数は減少し、膜構造の変化が示唆された。また、有効荷電密度はチトクロームC吸着後には減少し、α-ラクトアルブミン吸着後にはあまり変化しなかった。これより、タンパク質の吸着により膜構造、膜荷電が変化し、膜荷電の変化はタンパク質により異なることが分かった。

高性能透析膜の多くは非対称膜であるが、膜の非対称構造とその溶質透過性の関連は明らかになっていない。膜に吸着する溶質では、膜の半径方向の位置によって膜内拡散係数および平衡吸着量が異なるため、非対称膜の膜内への移動速度が、溶質の移動方向(内側→外側, 外側→内側)により異なる。これを利用して、非対称構造の評価を試みた。中空糸透析膜に吸着するタンパク質あるいは染料を用い、膜内部への溶質の移動速度を測定し移動速度曲線の移動方向による差異を溶質により比較した。その結果、非対称構造に起因すると考えられる移動速度曲線の違いが現れた。移動速度曲線の形状は、緻密層の構造が非対称であることに起因して移動初期に差が大きく現れるもの、膜全体の非対称構造に起因して中心部で差が現れるものがあった。これより、吸着を利用して透析膜の溶質透過性に影響を与える非対称構造の評価が可能であると考えられる。

One Bag方式のPush/Pull HDF (P/P HDF)における溶質除去特性を水溶液系実験および理論解析を通じ明らかにし、最適操作条件の確立を目的とした。定常状態のpush phase、pull phaseでの濾過流量(QPull、QPush)とクリアランス(CL)の関係を求めた結果、myoglobinではQPullの増加に伴いCLは急激に増加し、QPushの増加に伴い緩やかに減少した。ureaでは逆の、vitamin B12では両者の中間的な傾向を示した。時間平均クリアランス(CLav)はureaで若干HDが、myoglobinでP/P HDFが高値を示した。さらに、浄化器内物質移動非定常モデルを用い検討した結果、非定常の影響によりmyoglobinのCLはpush phaseで負の値を有することが明らかとなった。本モデルを用いmyoglobin除去に関して最適操作条件を検討した結果、QPull、QPushおよびBag容量が大きいほどCLavが上昇することが明らかとなったが、現実的には患者血流量など安全面でのかねあいで設定されるものと思われた。

In porous media such as adsorbents, catalysts or sandy soil, the porosity - the size and distribution and specific surface area of the capillary pores - is an important factor providing such media with their respective functions of adsorbency, catalysis and permeability.
Largely, the synthetic membranes used in separation may also be thought of as porous media. In dialysis membranes, the area in which water is present when the membrane is wet acts as a channel for the solute. Thus, the proportion of water present in the membrane (that is, the prove volume), the width of the layer of water acting as the solute channel (that is, the pore size) and the pore size distribution are the main factors governing the function of dialysis membranes.
Therefore, it is the purpose of this review to provide a general description of the concept and determination of pore size; the size of pores in dialysis membranes in the broad sense and pore size distribution, pore volume, etc.

Poly(N-isopropylacrylamide) gel has negative temperature dependency of swelling behavior in aqueous solution. In this study, IPAAm copolymer gel was utilized to design positive thermosensitive pulsatile drug release system to induce drug release with increasing temperature and stop the release with decreasing temperature. Skin structure of the shrunken gel at higher temperature was controlled by introduction of hydrophilic acrylamide to allow drug release. Using an impermeable capsule equipped with a release orifice, positive thermosensitive pulsatile release was achieved by diffusion area-regulating mechanism, which was different from surface-regulating mechanism to achieve conventional negative thermosensitive pulsatile release. A new concept to convert negative thermosensitivity of IPAAm gels to positive thermosensitive pulsatile release has been demonstrated.

Suitable evaluation systems are critical for ranking various biomaterials in order to develop a method to design and synthesize nonthrombogenic biomaterials. We have recently developed an in vitro test system to evaluate platelet/biomaterial interactions in whole blood. The system consists of a parallel plate flow cell and epifluorescent video microscopy (EVM). A glass coverslip coated with a polymer was incorporated into the flow cell, and blood was perfused using a syringe pump via a polymer-coated PVC tubing connected to the flow cell. Whole human blood was anticoagulated with heparin (2 U/ml), and the platelets were labeled with the fluorescent dye mepacrine (5 mu M). This system permitted real-time and dynamic observations of platelet/biomaterial interactions in whole blood under a defined flow condition. In order to evaluate the feasibility of this system, two different segmented polyether-poryurethanes (SPEUs), PU-PTMG(650) and PU-PTMG(2000), were chosen as test polymers. Surface characteristics verified with electron spectroscopy for chemical analysis (ESCA) and contact angle measurements showed similar results in both SPEUs. Blood was perfused at a wall shear rate of 200 s(-1) for 20 min. Excitation light was applied for 2 s at 1 min intervals. The real-time image was then analyzed at each time point for the percentage of surface area of platelet coverage. Plasma beta-thromboglobulin (beta-TG) levels were also measured before and after each run. PU-PTMG(650) showed a significantly higher number of adhered platelets than PU-PTMG(2000) at each time point. beta-TG levels of PU-PTMG(650) were also higher than those of PU-PTMG(2000), which is comparable to the results of EVM. Thus, this EVM system has been proven to be an excellent and highly sensitive in vitro analytical method for evaluating platelet/biomaterial interactions.

Temperature-responsive poly(N-isopropylacrylamide-co-butyl methacrylate) gels exhibit ''on-off'' regulation of drug release in response to temperature. In a previous study, swelling kinetics of these gels from deswollen to swollen states at several temperatures were investigated. It was demonstrated that the swelling behavior of the gel changed at various temperatures, yielding several patterns of drug release profiles. At 20-degrees-C, gel swelling increased with time, which was explained using a Case-II transport mechanism. In this mechanism, the glassy polymer matrix core acts to suppress the swelling of the outer region when swelling forces dominate. By reducing the experimental temperature to 10-degrees-C and utilizing the greatly enhanced hydration of polymer chains after disappearance of the glassy core, a sigmoidal swelling pattern gives rise to novel drug release profiles. In this study, these swelling mechanisms have been verified in detail by theoretical analysis. The existence of a swelling front was confirmed by observation of the colored gel using a dye. When the thickness of gel was changed. the acceleration of swelling was delayed with increasing thickness, and the acceleration times agreed with theoretical values predicted from the model. The observed changes in diameter and thickness of the gel also supported the model. These results demonstrate the validity of the model presented in the previous paper.

Absorbancy of a solution in the narrow lumen of a tubular membrane under dialysis is continuously measurable with a newly-developed apparatus using quartz optical fibers. The solute permeability of the membrane was determined by calculating time-dependent changes in the absorbancy measured with the apparatus by the mathematical solution derived for unsteady-state concentration profiles in an infinitely long composite cylinder. This method was independent of convective mass transport and osmotic flow through membranes, leading to superiority to ordinary techniques with respect to accuracy.

液-液系の人工肺は気泡混入の危険性がほとんどなく、気体との直接接触による血液破損がない。したがって酸素移動量が増加すれば、安全性の高い、高性能な人工肺が得られる可能性がある。そこで、液-液系膜型肺において酸素ガスの代わりにガスキャリア液として水、ストローマフリーヘモグロビン(SFH)、パーフルオロオクチルブロマイド(PFOB)を流し、酸素移動量の増加を試みた。静脈血には水およびウシ血液を使用し、酸素移動速度を測定した。人工肺にはCuprophan®膜からなる中空糸型透析器(S・SP-1.5H:泉工医科工業(株))を用いた。その結果、ガスキャリア液としてPFOBを用い、それを中空糸内側に、血液を中空糸外側に流した場合、実用に十分な酸素移動量が得られることがわかった。また、疎水性であるPFOBは、親水性の中空糸膜を使用しているため、血液側への漏出は見られなかった。

次世代型人工腎システムの1つとして連続的再循環腹膜透析(continuous recirculating peritoneal dialysis, CRPD)を開発した。CRPDでは患者腹腔内へいったん貯液した腹膜透析液の一部を新開発のダブルルーメンカテーテルを通じ体外循環し、外部ダイアライザによって積極的に溶質除去を行う透<br>析システムである。現在までに、(1)イヌ透析実験を通じCRPDの安全性、溶質除去特性などの性能評価を、(2)(1)で得られた結果をcompartment modelを用いたシミュレーショγ解析により腹膜ダイアリザンスを求め、実際に臨床応用した時の治療効果の推算を、(3)水溶液実験により試験ダイアライザの溶質除去特性を把握し、その結果からCRPD用外部ダイアライザの至適設計を行った。CRPDはCAPD同様、腹膜炎合併の恐れはあるものの、HDをはるかに超える性能をもち、原則的に抗凝固剤やブラッドアクセスを必要としないなどの多くの長所を有する治療法であることが確認された。

血液透析膜の基本性能として、溶質透過性および透水性が挙げられる。溶質は膜に含まれる水の中を拡散し、水は膜内外で入れ替わることにより膜を透過するため、膜内の水の状態は溶質透過性および透水性に影響すると考えられる。本研究では、7種類の高分子素材からなる31種類の血液透析膜について、膜に含まれる水の分布状態および体積を測定した。その結果、膜内には分子運動性が異なる3種類の水が存在し、その比率は膜素材によって大きく異なることが明らかになった。再生セルロース系高分子の血液透析膜では、膜内の水の大部分が高分子鎖によって強く束縛を受けており、その内部の溶質拡散現象は疎水性高分子膜におけるそれとは異なることが明らかになった。さらに、自由体積理論によって再生セルロース系高分子の血液透析膜の膜内拡散現象を解析したところ、5種類の溶質の膜内拡散係数を膜内の水の分布体積によって表すことができた。

手術後の感染症などによる血中抗体量変化のモニタリングを目的とした、抗体連続定量法を開発した。現在の抗体定量法は、煩雑な操作を伴うため、連続化は困難である。そこで我々はルミノールの電気化学反応により生ずる発光(電気化学発光)と抗原抗体反応を利用した連続定量が可能なセンサーを開発した。測定は、導電性ガラスを電極としたフローセルを用いた。<br>予めルミノールを標識したヒト血清アルブミン(HSA)溶液に、0.0～2.2mg/mlの濃度の抗HSA抗体を加え、発光強度から抗体量を推算した。発光強度は抗体濃度の増加に伴い直線的に上昇した。これは発光反応を陰極で行う場合にのみ確認される特別な傾向である。<br>本法により、体液中から、特定の抗原に対して特異的に反応する抗体のみを定量できると考えた。

高効率の透析器の設計には、膜を介した溶質移動現象の解明が必要であるが透析器内の流動状態は複雑で、その解明は困難である。溶質移動速度を決定する全抵抗は、膜抵抗、血液側及び透析液側境膜抵抗の和である。そのうち透析液側境膜抵抗は、膜抵抗と共に全抵抗に占める割合が大きい。そこで本研究では、膜同士の接触を抑え、有効膜面積を増加させ、透析液側流動状態を改善する効果が期待される、膜面上にフィンの付いた透析膜について、膜を介した溶質移動現象を検討した。1本の中空糸透析膜での透析実験から膜面上のフィンは溶質移動に影響を及ぼさないことがわかった。またフィン付き中空糸透析膜を用いた市販透析器での透析実験から、フィンは膜同士の接触を抑え、有効膜面積を増加させる効果があることが示唆された。またX線CTを利用した透析器内の透析液側流動状態の観察結果から、フィンはチャンネリングを抑える効果があることが示唆された。

透析排液中の溶質濃度から血中溶質濃度が推算できれば、透析のたびに患者個人個人の詳細なデータを得ることができる。そこで、8名の安定期透析患者を対象に血中および透析排液中の尿素、リン酸イオン、クレアチニン、尿酸の濃度を測定し、血中溶質濃度の推算精度について検討した。あらかじめ定めた見かけの体液量を用いると、尿酸など1-poolモデルに従わない溶質でも、見かけ上1-poolモデルで精度よく推算できた。リン酸イオン以外の溶質については、1、2ヶ月の間見かけの体液量に変化がなかったことから、見かけの体液量を用いて血中溶質濃度を正しく推算できると考えられた。また、見かけの体液量は溶質ごとに特徴があり、尿酸はどの患者についても少なく、リン酸イオンは人により大きく異なった。

臨床における透析膜の性能をタンパク質の吸着のない膜の評価とタンパク質の吸着特性から推算できれば透析器の設計に非常に役立つと考えられる。そこで、タンパク質の吸着による膜構造の変化と荷電状態の変化がイオンの透過性に与える影響を検討するために自作のミニモジュール(長さ10cm、中空糸本数200本)を用い、チトクロームCまたはα-ラクトアルブミンが平衡吸着した後のリン酸水素イオン(濃度3.33mEq/l、pH7.4)および非電解質である尿素(10mg/dl)の溶質透過係数の変化を透析実験によって測定した、実験は、37℃のもとで並流操作によって行った。その結果、リン酸水素イオンの溶質透過係数はチトクロームC吸着後には増加し、α-ラクトアルブミン吸着後には減少した。尿素の場合はどちらの場合も若干減少した。以上より、イオンの膜透過にはタンパク質の吸着による膜構造の変化だけでなく荷電状態の変化も影響することがわかった。

抗血栓性材料のin vitro評価法として、蛍光顕微鏡、ビデオ、パラレル・プレート・フロー・チャンバーから成るEpifluorescent Video Microscopy(EVM)を用いたリアルタイム評価法を検討した。比較的表面特性の類似した2種類のセグメント化ポリエーテルポリウレタンPU-PTMG(650)およびPb-PTMG(2000)をスライドグラスにコートし、フロー・チャンバーに装着した。蛍光色素で標識した血小板を含む血液をシリンジポンプにより壁ずり速度200sec^-1で20分流し、1分毎に血小板粘着量を測定した。PU-PTMG(650)にはPU-PTNG(2000)より有意に多く血小板が粘着した。またPU-PTMG(650)は血小板のβ-TG放出を、PU-PTMG(2000)は補体活性化を促進する傾向を示した。比較的表面特性の類似した2種類の材料間で抗血栓性に差が認められたことから、本EVM装置がin vitroでの抗血栓性材料評価法として有用であることを確認した。

In recent years, temporal control of drug delivery has been of interest to achieve improved drug therapies. Intelligent drug delivery systems (DDS) are one expected result, demonstrating an ability to sense external environmental changes, judge the degree of external signal, and release appropriate amounts of drug. Intelligent DDS may be achieved using stimuli-responsive polymeric hydrogels which alter their structure and physical properties in response to external stimuli. Pulsatile drug release has the advantages of avoiding drug tolerance or matching the body's release of specific peptides or hormones. In this review, recent studies for pulsatile drug delivery in response to stimuli such as chemical agents, pH, electric fields, and temperature are discussed. Achievement of pulsatile drug release from stimuli-responsive polymeric hydrogels as on-off switches and its mechanism are reviewed in terms of control for stimuli-responsive swelling.

タンパク質の吸着による表面荷電状態などの材料表面の性質の変化は、血栓形成などに影響すると考えられる。そこで、チトクロームCの吸着による膜の荷電状態の変化をポリマーブレンド比の異なる三種類のポリエステル系ポリマーアロイ(PEPA)膜とポリアクリロニトリル(PAN)膜について、吸着前後でのζ電位の値を測定し評価した。また、表面性質の変化の速さを吸着速度を用いて評価した。PEPA膜、PAN膜ともにζ電位は負の値を示し、正に荷電しているチトクロームCが吸着するとその絶対値が小さくなった。膜の表面荷電状態は膜自身の荷電だけでなく、吸着したタンパク質の荷電の影響を受けると考えられる。また、PEPA膜の吸着速度は拡散律速であり、PAN膜では拡散速度が速く、タンパク質と材料の吸着反応の速さの違いが吸着速度に影響する。抗血栓性に優れているPAN膜は、吸着反応速度が速い抗血栓性のあるタンパク質が吸着していると考えられる。

形状が全く同じで、膜の溶質透過性のみが異なる2種類の透析器、S・SP-1.5H(通常型)とS・SP-1.5L(高性能型)について透析液流量を変化させてvitamin B₁₂のクリアランスを測定したところ、Hに比べLの流量依存性は大きく、高性能透析器ではvitamin B₁₂程度の中分子量物質の溶質透過性は、もはや膜抵抗支配とはいえないことが分かった。<br>化学工学的手法を用いて、高性能透析器の形状が溶質除去性能、血液側圧力損失、血液充填量に及ぼす影響を理論的に検討した。その結果、中空糸内径の減少は溶質除去能の向上に効果があるものの、圧力損失を急激に増加させるため、200μmが下限値であった。また、ジャケット内径の減少も溶質除去能の向上に効果があるが、糸束率が75%を越えると透析液側境膜抵抗が増加するため、上限値が存在した。<br>S・SP-1.5Lの中空糸寸法およびジャケット内径は、ほぼ至適値に近かった。

新しい人工腎臓治療システムとして、連続的再循環腹膜透析(Continuous recirculating peritoneal dialysis; CRPD)を考案した。CRPDでは患者の腹腔内に貯液した透析液を一部再循環させ外付けのダイアライザにより連続的に浄化することから、その治療効果は外付けのダイアライザの性能に大きく依存する。本報では血液透析(HD)とは異なり、血液側に腹膜透析液が、透析液側にHD用透析液が流れるという条件を考慮してCRPD用ダイアライザの設計を行った。目標の尿素クリアランスを膜抵抗のみが存在すると仮定した場合の97.0ml/minの95%、92.2ml/minとし、中空糸内圧力損失を50mmHgとすると中空糸内径を87μmとすることにより小型、高効率なダイアライザの設計が可能であることが分かった。さらに、このダイアライザを用い1日8時間CRPD治療を施行するとして、その治療効果をcompartment modelを用い推算した。患者の体内尿素窒素濃度(BUN)の週間平均濃度(TAC)は32.2mg/dlとなり、12hr/weekのHDの45.3mg/dlに比較して低値を示した。

再生セルロース膜の表面にpolyethylene glycol(PEG)鎖をグラフトすると、その生体適合性が向上すると報告されている。一方、PEG鎖が形成する散漫層のために、改質再生セルロース膜の溶質透過性能が低下することが危惧される。本研究では迷宮細孔モデルに基づいて改質再生セルロース膜の膜構造モデルを考えると共に、改質再生セルロース膜の膜構造および溶質透過性能に及ぼすPEG鎖の散漫層の影響を検討した。従来の再生セルロース膜(AM-SD)と、SD膜に長さの異なるPEG鎖をグラフトした3種類の改質再生セルロース膜(AM-PC(l), PC(m), PC(s))の膜構造を解析した。SD膜とPC(m)膜およびPC(s)膜の細孔半径は2.8nmであり、膜面開孔率は35%であった。PEG鎖が最も長いPC(l)膜の細孔半径および膜面開孔率は他の膜のそれらよりも小さかった。吸光法で測定したPC(l)膜のビタミンB₁₂の溶質透過係数は他の膜よりも小さく、上記の膜構造の解析結果を反映した。これはPC(l)膜のPEG鎖が膜表面の細孔入口を覆い、溶質の透過に寄与する細孔入口での細孔半径がSD膜のそれより小さかったためであると考える。

血漿分離では時間とともに濾過流束が減少し、定常状態における濾過流束は、同一条件における純水や血漿を用いた時の濾過流束の数十分の一になる。これは、赤血球分極層、堆積層および赤血球による細孔閉塞が濾過流束に対して大きな抵抗になるためである。しかし、多くの血漿分離モデルは赤血球分極層だけに着目している。また、赤血球の血漿中における拡散についての検討も不十分である。<br>本研究では、赤血球分極モデルに赤血球の拡散係数の赤血球体積分率依存性、および細孔閉塞による膜抵抗の増加を考慮した新しい血漿分離モデルを考案した。そして洗浄赤血球懸濁液を用いた定圧濾過実験を行うことにより、モデルの妥当性を検討した。<br>その結果、赤血球分極モデルに赤血球の拡散係数の赤血球体積分率依存性および細孔閉塞による膜抵抗を考慮に入れることによって、実験結果を本モデルで説明できることが明らかとなった。

中空糸膜の荷電状態は、一般的にζ電位により評価されている。しかし、その測定方法は未だ統一されておらず、報告者によって値が異なっている。本研究では、ζ電位の測定値に影響する操作因子の影響を明らかにし、標準的測定法を確立することを目的とした。ζ電位を算出する基となる中空糸両端の圧力差および電位差(流動電位)は、測定セルへの膜の充填方法、セルの組立方法、および流動液組成により大幅に変化し、得られるζ電位は異なった。通常流動電位測定に用いられる流動液(0.01規定KCl水溶液)では流動電位の経時変化が著しく、その1/1000程度の導電率の流動液を用いなければ測定値は安定しなかった。膜素材の異なる8種類の中空糸透析膜について、新しく確立した標準方法でζ電位を測定したところ、リン酸イオンの溶質透過係数と良好な相関関係が得られた。<br>標準手法で測定したζ電位を用いることにより、荷電膜の評価が可能であると思われる。

透析液ライン内のエンドトキシン濃度を連続的に監視するために、リムルステストを用いたエンドトキシンセンサーを開発した。<br>エンドトキシンセンサーに用いる発色試薬をトキシカラーから選択性の高いエンドスペシーに替え、また反応回路の洗浄法および試料の混合効率を改良し、測定精度の向上を試みた。<br>エンドスペシーを用いて0～40pg/ml程度の濃度範囲で十分な定量性の得られる最小反応時間は12分であった。この反応時間で連続測定を行ったところ応答時間15分で0～20pg/mlのエンドトキシン濃度と吸光度の間に良好な直線性が得られた。<br>本センサーは、透析液ラインのエンドトキシン濃度の管理目標値10pg/ml程度の低エンドトキシン濃度の透析液の監視が可能であると考えられる。

Thermo-responsive hydrogels of poly(N-isopropylacrylamide-co-butyl methacrylate) (poly-(IPAAm-co-BMA)) are capable of swelling-deswelling changes in response to external temperature. As poly(IPAAm-co-BMA) gels swell larger at a lower temperature, the degree and rate of the swelling could be controlled by temperature without altering the chemical structure. Therefore, drug release profiles were remarkably changed by alternation of temperature. The release profiles of indomethacin from poly(IPAAm-co-BMA) were observed to be zero-order at 20-degrees-C. This release profile was explained in terms of a Case-II diffusion mechanism; which indicates relaxation of polymer chains with swelling was rate-determining. In the case of 10-degrees-C, release demonstrated a sigmoidal profile. The acceleration of drug release was due to a rapid increase in swelling with disappearance of the glassy core which had constrained swelling. The regulation of the water-uptake process by changing external temperature remarkably affected drug release and resulted in several different release profiles.

The authors have demonstrated that an amphiphilic block co-polymer composed of 2-hydroxyethyl methacrylate (HEMA) and styrene (HEMA-st) showed excellent blood compatibility in in vitro, ex vivo, and in vivo experiments. The poor elastomeric properties of HEMA-st, however, have been an obstacle to its wider application in medical devices. To improve the mechanical properties of HEMA-st, the authors have developed a new amphiphilic block co- polymer composed of HEMA and octylstyrene (HEMA-oct). The size and morphology of the microdomain structures of HEMA-oct observed by transmission electron microscopy were similar to those of HEMA-st. Kink resistance tests showed improved elastomeric properties of HEMA-oct over HEMA-st. The blood compatibility of HEMA-oct was evaluated using an in vitro flow cell system combined with an epifluorescent video microscope, in which real time platelet adhesion and activation in whole blood can be observed and quantified, and ex vivo rabbit A-A shunt experiments. HEMA-st and a polyurethane (Pellethane(TM)2363-80AE) were used for comparison. In a flow cell system, both HEMA-st and HEMA-oct showed minimal platelet coverage on the surfaces and less platelet activation as measured by β-thromboglobulin (β-TG), whereas Pellethane showed a considerable amount of platelet coverage with high β-TG production. A-A shunt occlusion times were 309 ± 31.2 min for HEMA-st, 251 ± 47.7 min for HEMA-oct, and 30 ± 3.4 min for Pellethane. Thus, HEMA-oct has improved elastomeric properties while still preserving excellent blood compatibility, comparable to HEMA-st, and has a significant potential to be widely applied as a coating to the blood contacting surfaces of various medical devices.

To clarify ion transport, dialysis membranes are evaluated in terms of zeta potential calculated by the Helmholtz-Smoluchowski equation from data on streaming potential ΔE and pressure drop ΔP, depending upon the operating conditions at which the values are measured. The objective of the current study is to design an improved method for measurement of ΔE and ΔP of hollow fiber dialysis membranes and to clarify the diffusive permeability of hydrogen phosphate ion. A polytetrafluoroethylene cylindrical cell with an inside diameter of 14 mm and a height of 10 mm was packed with 2,000-3,000 pieces of hollow fibers, and glass filters were set on either side of the cell. Deaerated water purified by ion exchange and reverse osmosis with an electric conductivity of approximately 150 μS/m was caused to flow in the hollows at 293 K to determine ΔE and ΔP. A good linear relationship between ΔE and ΔP and the reproducibility of the data was obtained and is shown in Figures 5 and 6, demonstrating the utility of the improved method to measure ΔE and ΔP, and the validity of the Helmholtz-Smoluchowski equation to calculate zeta potential from data on ΔE and ΔP. Hydrogen phosphate ion permeability increased with zeta potential for the membranes at about the same rate as pure water permeability. This indicates that hydrogen phosphate ion permeability depends upon the charge and internal structure of dialysis membranes.

現在実用化されている血液浄化技術は多岐に渡るが、これらを化学工学の立場で捉えると、ほとんどが分離精製技術の範疇に入る。分離精製技術は不均一系に適用される機械的分離操作と、均一系に適用される輸送的分離操作及び拡散的分離操作に分類される。血漿に溶解した溶質を除去する場合、輸送的分離操作である限外濾過あるいは拡散的分離操作である透析または吸着が用いられる。限外濾過、透析では分子直径と細孔形状で溶質除去性能が決まるため、選択性や鋭い分画特性を発現せしめることは難しい。一方、吸着では分子直径と細孔形状に加え、吸着材表面での吸・脱着特性によって分離特性が決まるため、優れた選択性を付与することができる。血液浄化法では、これらの原理を単一で用いることは少なく、分離特性は用いる原理の組み合わせによって決定される。<br>今後の血液浄化法では、分離媒体とのaffinityを利用した高選択性の実現が望まれる。

感温性のイソプロピルアクリルアミドとアルキルメタクリレートのコポリマーゲルを合成し、このゲルによる薬物放出のON-OFF制御の可能性を検討した。ポリマーの化学構造および温度の変化幅を変え、表面収縮層の形成による放出制御メカニズムを高分子マトリックスの動的変化に注目して検討するとともに、ON-OFF制御が可能となる最小温度変化幅を追求した。ゲルからのインドメタシン放出速度を連続的に測定した結果、一般的に低温で放出が起こり高温で放出が停止する傾向を示した。しかし温度変化幅が大きい場合には温度上昇直後に鋭い放出ピークが生じ、そののち放出速度は減少した。これは表面収縮層形成による急激な薬物の搾り出しによると考えられた。また温度変化幅が小さくなると、温度上昇後ゲル内部に蓄積する圧力により遅れ時間を伴う放出ピークが新たに観察された。収縮層の形成・消失に応答する放出挙動にポリマーのアルキル鎖長および温度変化幅がどのように影響するかをその動的変化に着目して検討し、薬物のON-OFF放出パターンを制御するゲルの構造について考察した。

人工臓器は医と工の連携が医療にもたらした最大の恩恵の一つと言えよう。人工臓器の実用化が治療法の多様化、患者の延命などに大いに貢献したのは事実だが、さらに医学に新しい治療概念を導入したことも見逃せない。新しい発見が往々にして発想の転換から生じるのは医学においても例外ではなかろう。現代医療の発展には目ざましいものがあるが、これは医工学に負うところが大きいといっても過言ではあるまい。そしてこの医工学の発展は医と工の連携なしにはあり得なかった。しかしこれまでの医と工の連携は必ずしも理想的とは言えない面もある。そこで今後人工臓器の一層の発展を期待するならば、医と工の新たな連携の樹立が急務であろう。

In recent years, temporal control of drug delivery has been of interest in basic and applied fields as a new approach to achieve improved drug therapies. This new drug delivery may be achieved by utilization of "intelligent" polymeric materials having auto-feedback functions. Stimuli-responsive polymers have been investigated as potential molecular devices to achieve intelligent drug delivery systems such as self-regulating and externally modulated drug delivery systems. A stimuli-responsive polymer (sensing) can change its structure and physical properties (responding) in response to appropriate external stimuli (signals), which changes can subsequently affect drug release (acting) from a drug reservoir. In this paper, this new concept of intelligent drug delivery system is described in detail and related studies are reviewed and discussed.

血液の生化学検査における検体の処理能力および検査精度を向上させるため、迅速かつ簡便な血漿採取法の開発を目的とし、基礎的な検討を行った。<br>中空糸血漿分離膜ミニモジュールを作製し、ポンプおよびシリンジによりミニモジュールに血液を流して血漿採取を試みた。得られた試料の評価には、ふるい係数および溶血度を用いた。<br>膜間圧力差100mmHg、壁ずり速度5000s^-1、血液量11mlの条件下、ポンプにより血液を灌流する方法においては、有効長3.5cm、膜面積74.7cm²のポリエチレン膜ミニモジュールにより約14秒、シリンジにより灌流した場合には、膜面積37.4cm²のモジュールにより約75秒で2mlの血漿が得られた。溶血は許容範囲であり、生理的食塩水による希釈は、添加生理的食塩水量と血漿採取量から換算が可能であった。

糖尿病患者の血糖値を非侵襲的に監視できる、高感度で安定性の高い人工膵臓用センサの開発を本研究の目的としている。高感度なグルコース定量法である化学発光法では、試薬溶液を完全混合で反応させることができず、安定性の高い測定は困難であった。そこで我々は、化学発光の反応過程を電気化学的に操作する装置を開発し、試薬溶液を完全混合状態で反応させることを可能とした。さらにこの装置を高感度型のヴルコースセンサに利用し、安定性および感度を確認した。連続供給される一定濃度のゲルコース濃度に対して応答する発光強度の変動は8時間で5%以内であった。この安定性から本センサは人工膵臓への利用が期待できることが分かった。一方、本ゲルコースセンサの濃度測定可能範囲は0.1～1.0mg/dlであり、汗のゲルコース濃度範囲を包括している。本センサでの汗のゲルコース濃度測定による非侵襲的な血糖値監視の実現が有望である。

ポリマーアロイは成型条件によって高次構造を変化させられるという特徴を持つ。ポリマーアロイを透析膜に用いる意義は、透水性能、細孔半径及びその分布、ひいては分画特性の制御を任意に行なえる点にある。本研究では、polyarylateとpolyethersulfonとをブレンドしたポリエステル系ポリマーアロイ膜について、反撥係数による分画特性を測定し、溶質透過能を評価した。測定には、すでに臨床で用いられている透析器のFLX-12GWと、製膜時における凝固速度を変えた3つの膜からなる試作透析器を用いた。その結果、FLX-12GWは分子量10,000から50,000で反撥係数の変化が見られ、β₂-microglobulinなど低分子量タンパク質の除去に優れていると考えられた。また、ポリエステル系ポリマーアロイ膜の製膜時における凝固速度を遅くすると、反撥係数は小さくなった。

従来の透析膜に比べより高い溶質透過性能を示すHighly permeable membrane(HP膜)の実用化により、総括物質移動抵抗に占める境膜物質移動抵抗の割合が増加している。血液側および透析液側境膜物質移動抵抗は透析器内部の流動状態に左右されるため、透析器の性能を向上させるためには流動状態の把握が不可欠となっている。<br>現在まで我々は膜性能および透析液側流動状態について研究し、多くの重要な知見を得ている¹⁾。そこで本研究では血液側流動状態に着目し、血液側流量、中空糸内径および中空糸有効長が総括物質移動係数に及ぼす影響について検討した。その結果、中空糸有効長が23.5cmの透析器よりも19.4cmの透析器の方が溶質除去効率は高かった。総括物質移動係数および血液側境膜物質移動係数は血液側流量によって変化しなかった。また総括物質移動係数は中空糸内径によって変化しなかった。

長期透析患者における骨代謝障害の原因となる無機リンの透析膜透過性を論じるには、膜の荷電状態の指標である有効荷電密度を知ることが不可欠である。しかし中空糸膜については、膜電位の測定が困難ぐあるため、透折膜の持つ荷電が無機リン透過性に与える影響を定量的に把握するに至っていない。そこで、中空糸膜(再生セルロース(RC)膜、Hemophan膜)と同じ素材からなる平膜(膜厚16μm)の膜電位を測定し、中空糸膜における有効荷電密度と無機リンの透析膜透過性との関係について検討した。また中空糸膜のζ電位を測定し、無機リン透過性をζ電位で評価できるかどうか検討した。その結果、平膜の膜電位測定から有効荷電密度の絶対植が等しいと考えられたRC膜とHemophan膜における無機リンの溶質透過係数は、負荷電膜であるRC膜より正荷電膜であるHemophan膜の方が高く、溶媒に純水を用いた場合より生理的食塩水を用いた場合の方が高かった。またζ電位は両者とも負値を示したが、その絶対値が小さいHemophan膜の方が高い無機リン透過性を示した。両者の細孔構造が等しいことから、無機リンの溶質透過係数の差は電気的抵抗の違いによると考えられる。これより無機リンの透析膜透過には膜の有効荷電密度が影響し、透析膜の正荷電性が無機リン透過性を促進することがわかった。また膜素材の等しい中空糸膜の無機リン透過性は、ζ電位で評価できると考えられた。

透析膜の微小荷電は電解質の膜透過に影響を与えることが報告されているが、中空糸透析膜の荷電量を直接実測することは技術的に困難である。本報では、生体膜の膜電位測定法として知られている蛍光法を応用することにより、膜荷電状態を直接測定する方法について検討した。蛍光物質として用いたl-anilinonaphthalene-8-sulfonic acid(ANS)は、疎水性部分をもつ物質とイオン的に結合すると蛍光量が増大する性質を有する。膜構造が等しく、正と負の荷電をもつ2種類の再生セル[コース製中空糸透析膜について、蛍光の強度測定を行った。その結果ANSの蛍光強度は、膜荷電状態および周囲の電解質濃度変化に伴う荷電状態の変化を、定性的に表していることが示された。さらに、膜に対する電解質であるANSの結合量を求めることにより、膜荷電量の定量化および膜構造の解析ができる可能性が示唆された。

透析器の至適設計のためには、透折器内部における流動と物質移動の関係を把握することが重要である。しかし、透析器内の流動は複雑であり、特に透析液側の物質移動現象の解析は困難である。<br>本研究では、最も理想系に近い中空糸膜一本の単位において、透析液側物質移動現象の基礎的検討をおこなった。測定には吸光法を用い、Stevensonの解析方法を利用して、吸光法による透析液側物質移動係数の新しい算出法を考案した。<br>ConventionalタイプのAM-SD-10MおよびHigh FluxタイプのAM-FP-15の二種類の透析膜について検討した結果、透析液側境膜における物質移動は膜構造には依存せず、流動のみに依存した。また、透析液側物質移動現象は円管内層流におけるLevequeの式で説明できることが確認された。

薬物の血漿タンパクへの結合は一種の吸着現象と見なすことができる。タンパク結合性薬物の透析器内における挙動を明らかにするために、実験とシミュレーションを行った。数種類のセフェム系抗生物質と人血清アルブミンを用いて、吸着平衡及び吸着速度を測定した。吸着平衡実験より、薬物総濃度の増加に対してタンパク結合率が増加する抗生物質と、減少する抗生物質のあることがわかった。吸着速度実験より、抗生物質によってHSAとの吸着速度が大きく異なるこ、とが明らかになった。また、実験結果をもとに透析器内の薬物輸送現象を表すモデルを作成し、シミュレーションを行った。その結果、結合状態及び遊離状態の抗生物質の挙動は吸着速度の影響を受けて大きく変化したが、血液中の総薬物濃度で計算したクリアランスは、吸着速度にそれほど大きく影響されなかった。

中空糸透析膜の溶質透過係数は、Wilson-Plot法、Klein法、RI法および吸光法により測定される。しかし、同一の膜について各測定法により得られる溶質透過係数は大きく異なり、それらの信頼性は明らかではない。本研究では、各測定法の差異とそれらより得られた溶質透過係数の真の溶質透過係数としての妥当性を検討した。中空糸透析膜の真の溶質透過係数は、吸光法により測定されることがわかった。透析膜の膜構造および溶質の膜透過機構の解明には、吸光法により測定された溶質透過係数を用いるのが最も適当である。さらに測定された真の溶質透過係数を用いて、各種HP透析膜の膜構造と溶質透過性の関係について検討した。分子量6,000以上の高分予量物質については、AM-EP膜よりもPAN-DX膜の拡散除去能の方が大きかった。逆に、分子量6,000以下の物質については、AM-EP膜の拡散除去能の方が大きかった。

エンドトキシン(ET)による透析液汚染の問題は、近年のハイパフォーマンス・ダイアライザの発達に伴ない患者の血液へのETの移動という形で表面化してきた。透析液ライン内のET濃度は連続的に監視されていることが望ましい。訂濃度の測定に広く使用されているリムルステストは、煩雑な操作を必要とし、かつ大気からの汚染を受けやすい。そのためET濃度の検査は充分に行なわれていない。これらの問題を解決するために、リムルステストのサンプリング、混合、反応、測定の各操作を連続化して行なう方法の開発を試みた。<br>透析液のET濃度変化に対する応答の高速化を目的として、リムルステストの連続化とともに反応時間の短縮を検討した。<br>結果として、0～80pg/mlのET濃度範囲において定量性を示す連続測定法を開発できた。

新しい人工腎治療システムとして, ダブルルーメンカテーテル, 外付けダイアライザからなる連続的再循環腹膜透析(Con-tinuous Recirculation Peritoneal Dialysis, CRPD)を考案し, in vitro, イヌex vivo実験を通じその溶質透過性, 安全性について検討した。1.25リットルの透析液を貯液したex vivo再循環実験の結果, 最大200ml/minで180min間, 顕著な圧力損失の上昇やフィブリン析出もなく安全に循環することができた。また, 体重9Kgの成犬に820mlの尿素添加透析液を貯液し, FB-50H(0.5m²)で再循環流量100ml/min, 透析液流量200ml/minの条件下で180min間透析したところ, 尿素の腹膜ダイアリザンス3.05ml/min, ダイアライザ"のダイアリザンス33.3ml/minが得られた。この結果をもとに体重60Kgの仮想患者の週間平均クリアランスを尿素について推算したところ, 12hr/dayのCRPDで115.51/weekとなり, 12hr/weekのHD99.8l/week, 4回/dayのCAPD70.01/weekに比べ高値を示した。

Exposure of platelets to shear stress leads to aggregation in the absence of exogenous agonists. We have now found that different adhesive proteins and platelet membrane glycoproteins are involved in aggregation depending on the shear stress conditions and the concentration of divalent cations in the medium. When blood is collected with trisodium citrate as anticoagulant, which causes a decrease in the levels of external ionized calcium ([Ca2+]0), platelet aggregation can be induced under low shear force (12 dyn/cm2) and is mediated by fibrinogen binding to the glycoprotein IIb-IIIa complex. Aggregates formed under these conditions are not stable, and when shear force is increased to 68 dyn/cm2, disaggregation results. By contrast, platelets from blood collected with hirudin as anticoagulant, wherein [Ca2+]0 is within normal plasma levels, do not undergo low shear-induced aggregation; however, after exposure to a shear force above 80 dyn/cm2, aggregation is observed but only when von Willebrand factor is present and can interact with both its platelet binding sites, glycoprotein Ib-IX and glycoprotein IIb-IIIa. Fibrinogen is not involved in high shear-induced aggregation which, in fact, occurs normally in patients with severe afibrinogenemia. Thus, von Willebrand factor in the absence of exogenous agonists can mediate platelet aggregation in experimental conditions that may mimic the hemorheological situation of partially occluded arteries. This pathway of platelet aggregation involving only one adhesive ligand and two membrane adhesion receptors may play a relevant role in thrombogenesis.

体外循環に用いられている動脈フィルタが赤血球の損傷に及ぼす影響について検討した。開心術における体外循環操作に基づいて実験条件を定め、モデル装置を作製してスクリーンフィルタの影響を調べた。<br>血漿中のヘモゲロビン濃度から求めた溶血量は処理時間とともに上昇した。しかし、ヘマトクリット、流量・操作圧力等を変化させても、溶血量に対するフィルタの影響は確認されなかった。そこで、赤血球浸透圧脆弱性試験により赤血球の損傷程度を検討した。その結果、赤血球の損傷の影響はNaCI濃度0.69/dl付近の浸透圧脆弱性で最もよく現れた。浸透圧脆弱性が小さい血液ではフィルタによる溶血はほとんど起こらないが、浸透圧脆弱性が大きい血液ではフィルタによる溶血がみられた。<br>浸透圧脆弱性が小さい通常の血液においては、スクリーンフィルタによる溶血はほとんど問題とならなかった。

蛍光物質の消光現象を利用した光ファイバ酸素センサを作成し、その気体中および水中での応答特性について検討した。今回使用した蛍光物質のDecacycleneは、酸素分子の存在により特異的に消光される性質がある。本研究では、Decacycleneを含浸させたシリコーン膜中を光ファイバの先端に装着した幾つかの酸素センサを用い、その気体中および水中での酸素分圧変化に対する蛍光強度を、光電子増倍管を用いて計測した。本装置により、気体中および液体中での、温度、流動状態に依らない酸素分圧測定が可能であった。また、シリコーン膜厚を46.36μmとすることにより、従来の装置と比較して高速応答性に優れた酸素センサを作成することができた。本センサは人工肺などの酸素モニタリングへの応用が可能と考えられる。

Swan-Ganz熱希釈カテーテルにおけるサーミスタの時定数のばらつきに影響されない新しい心拍出量算出法を考案した。心臓を模した自作伝熱撹拌槽を用いて牛血液の流量を測定し、時定数が流量の測定値に及ぼす影響について検討した。サーミスタの時定数はカテーテルにより大きくばらつき、従来の流量算出法では測定流量に大きな誤差が生じた。低流量で最大32%、高流量でも大きい時定数で最大9%の誤差が得られ、実測流量と一致しなかった。一方、ニュートンの冷却の法則に基づく新しい流量算出法による測定流量は実測流量と有意に一致し(p<0.01, NS)、時定数のばらつきに影響されなかった。さらに、新しい流量算出法は指示薬の注入条件に影響されず、モニタへの補正係数の代入が不要となる。新しい流量算出法により、各力テーテルの時定数のばらつきと指示薬の注入条件に影響されない心拍出量測定が可能となる。

膜型人工肺における酸素透過抵抗の大部分は血液側に存在する。外部灌流膜型肺は血液の流れが乱れているため、血液側の境膜が有効に破壊される。中空糸を斜めに編み込むことで、この血流の乱れを促進することが可能である。流動状態がガス交換能に及ぼす影響を検討するために、中空糸の編み込み本数を変化させた。編み込み本数を1本にしたとき、最も高い総括物質移動係数が得られた。X線CTおよびパルスリスポンス法を用いて流動状態を観察したところ、編み込み本数1本で均一な流動状態が観察された。また、編み込み本数1本は中空糸同志の接触面積が少ないため、有効膜面積が増加している。これよりガス交換能の向上は流動状態の均一化と、有効膜面積の増加に起因するものと考えられる。しかしモジュール単位でのガス交換能は編み込み本数2本が最も優れており、良野な流動状態を損なわずに高膜面積が得られる充填方法の開発が望まれる。

Na₂O-B₂O₃-SiO₂-Al₂O₃-CaO系の多孔質ガラス膜は耐摩耗性、耐薬品性、耐熱性に優れている。また細孔直径分布が狭く、薬品洗浄などにより再生が可能という利点を持つ。合成高分子膜における血漿分離では膜間圧力差約50mmHgで溶血を起こすが、多孔質ガラス膜を用いると約100mmHgでも溶血を起こさない。多孔質ガラス膜における血漿濾過流束と総タンパク質のふるい係数は平均孔直径が1～1.5μm、膜間圧力差25mmHg、壁ずり速度2000s^-1の条件において最も適切となる。血漿濾過流束は壁ずり速度が変化しても管長の(-/3)乗に比例した。濾過流束のヘマトクリツト依存性は限外濾過理論では説明できない。低温における血漿分離は、膜間圧力差25～50mmHg、壁ずり速度2000s^-1の条件で実施可能である。

透析膜の溶質透過性能の向上にともない、従来拡散で除去不可能と思われていた低分子タンパク質の除去が可能となった。しかし、拡散で除去し得るということは、透析液側に同程度の低分子タンパク質などが存在する場合、同様にそれらが拡散で血液側に移動することを意味している。抗原性を有するタンパク質などが移動した場合は種々の免疫反応を惹起し、新たな透析合併症をきたすことにもなりかねない。そこで、ダイアライザー直前でこれら低分子タンパク質などを除去すべく、一つの試みとしてセラミックパウダーを用いた吸着除去方法を検討した。<br>使用したセラミックパウダーは粒径100～200μm、細孔直径1,500Åである。ビーカーバッチによる吸着試験では、リゾチーム・チトクロムC・リボヌクレアーゼA・α-ラクトアルブミンの順に吸着がみられた。これは等電点の順と一致する。つぎに、濃度を1.000ng/mlに調整したリゾチームを用いて内径10mmの自作カラムに詰めたセラミックパウダーへの吸着実験を行ったところ、滞留時間2～11秒で除去率が変わらず、いずれも80%前後であった。すなわち、吸着はきわめて速やかに行われることがわかる。しかし、カラム出口濃度を厳密に0とすることはできず、低分子タンパク質の除去には限界がある。低等電点を有するタンパク質は高等電点タンパク質ほど吸着されないが、細孔径・表面基の操作により幅広い等電点における吸着能の向上が期待できる。

溶質透過係数測定法の確立は中空糸透析膜の溶質透過機構を解明する上で不可欠である。我々は溶液の光学的特性を利用することにより、単成分系水溶液中の溶質透過係数測定が可能であることを明らかにした。ところが、不透明懸濁液である血液や半透明溶液である血漿中の溶質濃度の測定には多くの問題点が存在した。そこで、今回、牛血清、牛血漿および牛血液中の溶質透過係数を光ファイバを用いて測定する方法を考案した。尿素、クレアチニン、ビタミンB₁₂等の小中分子は中空糸透析膜を透過するが、蛋白質や赤血球などの光学的測定を阻害する分子、粒子は透過できない。この現象を利用し、中空糸透析膜外側に牛血液、牛血漿などの試験溶液を配し、中空糸膜内側に透過した溶質の濃度を光ファイバを用いて測定した。この時の溶質濃度変化より溶質透過係数を算出した。<br>牛血液および牛血漿中で測定したビタミンB₁₂の溶質透過係数は蛋白質や赤血球に影響されず一定であり、水溶液中のそれとほぼ等しかった。溶質透過係数は溶質半径や膜特性に支配されるため、共存する粒子、溶質に影響されなかった。

無機リンが透析膜を透過する際に受ける電気的影響について検討するため、溶液のイオン強度を変化させて無機リンの溶質透過係数を測定した。NaClやKClを加えてイオン強度を変化させた³²P-Na₂HPO₄水溶液(放射量185GBq/m³、無機リン濃度3.33mEq/l)を中空糸透析膜一本に充填して一定時間透析実験を行い、中空糸内の残存溶質濃度から溶質透過係数を算出した。透析液には試験溶液と同じイオン強度のNaClあるいはKClの水溶液を用いた。再生セルロース膜、PMMA膜、いずれの膜の場合も溶液中のイオン強度が大きいほど、また同じイオン強度では対イオンの移動度が大きいほど、得られた溶質透過係数は大きかった。またT. M. S. 理論に基づいて無機リンの膜透過性を解析した結果、無機リンの膜透過では、膜の荷電状態のみならず、膜構造も考慮しなければならないことが明らかになった。

Highly permeable membrane(HP膜)は薄膜で大きな細孔を持つため、従来の透折膜に比べより大きな溶質透過性を示す。HP膜を用いたHP透析器では通常の透析器に比べて、総透過抵抗に占める血液側および透析液側境膜物質移動抵抗の割合が大きい。したがって、境膜物質移動抵抗を減少させることによって透析器の性能をさらに向上させることができる。そこで、中空糸内径および糸束率の異なる透析器を試作し、これらのパラメータと溶質除去能との関係から、透析器の至適形状について検討した。糸束率の増加に伴い透析液側境膜物質移動係数が増加し、それにより総括物質移動係数およびクリアランスも増加した。この傾向は通常の透析器よりも膜の溶質透過抵抗が小さいHP透析器において、より顕著に現れた。また、従来解析に用いられてきたKellerによる無次元相関式より推算した透析液側境膜物質移動係数とその実測値は一致せず、新たに理論式を考察する必要があることが示唆された。

透析膜の選択性に寄与する細孔直径分布を窒素ガス吸着法(BET法)および示差走査型熱量測定法(DSC法)を用いて測定した。BET法では透析膜への窒素ガス吸着量と、そのときの平衡圧から吸着等温線を作成し、Inkley法により細孔直径分布を算出した。DSC法では凍結した細孔内自由水の融解過程におけるDSC曲線を記録し、凝固点降下度および細孔内自由水の吸熱量より細孔直径分布を算出した。われわれが採用してきた湿潤透析膜の真空乾燥処理では、透析膜が中空糸軸方向と膜厚方向に収縮し、その割合は膜材質、含水率および膜厚によって変化すると考えられる。どの透析膜においても、凍結乾燥処理した方が真空乾燥処理よりもBET法により得られた細孔容積が大きくなり、凍結乾燥により湿潤状態に近い細孔容積が得られることがわかった。DSC法による透析膜の細孔直径分布の測定は簡便であり、BET法により求められた細孔直径分布と同様の傾向が得られ、その有用性が確かめられた。また、透析膜の細孔容積が大きいほどβ2-microglobulinの溶質透過係数および純水濾過係数が大きく、含水率、曲路率、膜面開孔率などの膜構造因子とともに細孔容積を考慮すれば、β2-microglobulinの除去に適した透析膜の至適設計が可能であると考えられる。

β₂-MGを除去可能なhighly permeable membrane(HP膜)は従来の膜に比べて透水性が高いため、逆濾過が起こると指摘されている。しかし、逆濾過の起こらない透析器の至適設計についてはまだ十分に検討されていない。本研究では、透析器形状を変化させた透析器において逆濾過量を求め、逆濾過の抑制を目的とした透析器の設計について検討した。向流操作で逆濾過の起こりにくい透析器の至適設計を理論的に検討した結果、FB-190UGAおよびPAN-12CX2透析器では中空糸有効長を短かくして5cm、かつハウジング径を大きくして各々7.7, 8.8cmにすることによって逆濾過を完全に抑制できた。並流操作では、膜面積および中空糸長さ(L=25cm)を一定にして糸束率を増加させると、逆濾過量は極小値を持った。中空糸有効長を25cmに設定した場合、FB-190UGAおよびPAN-12CX2透析器において逆濾過量を完全に抑制できる糸束率は各々0.52, 0.62となった。

感温性を有するイソプロピルアクリルアミドとアルキルメタクリレートのコポリマーゲルを用いて薬物透過・放出のON-OFF制御を行い、ポリマーの化学構造変化とゲル表面の収縮過程との関連を、ゲル内部における薬物移動の制御という立場から検討した。アルキル鎖長の異なるゲル膜を2-チャンバーセルの間にはさみ、抗炎症剤であるインドメタシンの膜透過性を20℃と30℃の段階的温度変化下で測定した結果、透過の完全なON-OFFを確認した。これは20℃から30℃に変化したときにゲル表面に生じる収縮層が薬物の透過を妨げることによる。再び20℃に下げると薬物は透過を開始し、30℃で薄い収縮層を形成するゲルでは大きな初期透過速度を示した。このことはOFF状態の間で薬物がゲル内部で移動することを示唆し、ゲルを放出制御素材とした場合放出速度の低下を抑制する。ポリマーのアルキル鎖長を変えることで表面収縮層の生成過程が変化し、ゲル内部の薬物移動を制御できる。

回転円筒膜型血漿分離装置を用い、変形能の異なる粒子を用いて精密濾過のメカニズムを検討した。赤血球およびグルタールアルデヒド(GA)で固定処理した赤血球の5vol%のサスペンションを用いて定圧濾過実験を行い、濾過流束や濾過抵抗が変形粒子と剛体粒子とでどのように異なるかを調べ、粒子の変形能を利用して濾過機構を検討した。濾過流束は入ロ圧力に対してピークを持った。最大濾過流束は、赤血球サスペンションの方がGA固定赤血球サスペンションよりも大きくなった。そのため、流体中では変形能のある粒子の方が変形能の無い粒子よりも大きな揚力を受けることがわかる。TMP=49mmHgにおける分極層抵抗の値は、回転速度の増加とともに減少した。低回転領域ではGA固定赤血球の方が大きく、高回転領域ではほとんど差がみられなかった。低回転領域では粒子の変形能の違いによって、分極層の形成に差が現れるためと考える。

溶質分子の大きさに対する溶質透過係数の変化から透析膜の孔径分布を解析する新しい手法を考案した。尿素、ブドウ糖、ショ糖の溶質透過係数のデータから、ストークス半径と溶質透過係数の相関を求め、それから面積基準の孔径分布を解析した。対象の透析膜はMCO.8H、TAF10、AM10、AM2000U、B2-100であり、再生セルロース膜は合成膜に比べて孔径分布が狭いという結果が得られた。さらにmaltodextrin溶液を用いてTAF10の透析実験を行い、ブドウ糖の単量体から8量体までのクリアランスを測定し、その値から溶質透過係数を算出した。その結果、良好な分布曲線を得ることができた。

温度により膨潤性を著しく変化させるイソプロピルアクリルアミドとメタクリル酸エステルのコポリマーを用い、薬物放出の量的制御およびON-OFF制御を試みた。ポリマー膜を合成した後インドメタシンをloadingして放出デバイスを作製し、リン酸緩衝溶液中で薬物放出パターンを調べた。一定温度下では、ポリマーの膨潤度が大きくなるほど0次放出に近づいた。これは疎水性薬物の場合薬物消失領域の透過性が増加するためであり、モデルによるシュミレーション結果と一致した。また温度を20℃と30℃の間で段階的に変化させて放出実験を行った結果、表面収縮層の生成により薬物放出の完全なON-OFFが得られた。このパルス型放出パターンは、OFF状態が長いほど0次放出が長く保たれ、OFF状態の間に薬物がポリマー内で再分布することが示唆された。感温性ポリマーゲルの膨潤-収縮特性を変化させることで温度変化に伴う薬物放出のON-OFFおよび放出速度の制御が可能である。

膜蒸留法は、海水の淡水化やアルコールの脱水の分野で注目を集めている新しい膜分離技術である。我々は、この膜蒸留法による血液からの除水について研究を進めてきた。牛血液系で膜蒸留実験を行った場合、膜面近傍に形成される温度および濃度分極層が透過抵抗となる。このため、装置の設計に半たっては、この分極層抵抗の解析が不可欠である。本報では、ポリテトラフルオロエチレン(PTFE)平膜を装着した二連式撹拌バッチセル装置にてエチレンゲリコール水溶液-水系および牛血液-水系における膜蒸留実験を行った。濃度分極層の解析に限外濾過理論を適用することにより、膜面濃度の算出が可能となった。また、牛血液-水系では、200rpmの低撹拌回転数において温度分極層抵抗が総抵抗の61%を占め分極層律速となった。これに対して、1000rpmでは、膜抵抗が総抵抗の5鏡を占め膜律速となった。これより、実用化には分極層の破壊と膜の薄膜化が必要となることがわかった。

イオンは、透析膜透過時に膜からの電気的抵抗を受けていると考えられる。この電気的抵抗の濃度依存性を検討するため無機リン(ip)の濃度を変化させてipの溶質透過係数(Pm)を測定した。また、透析液側のイオン強度を大きくしてipのPmを測定した。また、牛血清系でipのPmを測定し、水系実験の時と比較検討を行った。また、使用した透析膜のζ電位の測定も行った。ipのPmは、放射性同位元素で標識したNaHPO(5μCi/ml)水溶液を1本の中空糸透析膜内に密封し、一定時間透析を行い、中空糸内部の残存溶質濃度を測定して算出した。ζ電位測定には流動電位法を用いた。湿潤状態の1本の中空糸透析膜内に窒素ガスを用いてKCl水溶液を圧入し測定した。ip濃度が低いとipのPmは一定の値を示したが、濃度を大きくすると急激にPmは大きくなり、約2倍になり、一定値となった。イオン強度が大きくなると膜が見かけ上電気的に中性になり、ipのPmは大きくなった。また、牛血清系の方が水系に比べてipのPmが大きくなることが分かった。

低分子量物質の除去は, 膜性能のほかにも透析液および血液側の流動状態により大きく左右される。そこで, 市販ダイアライザーの透析液側流動状態をX線CTを用いて観察したところ, 多くは中心部にチャンネリングやデッドスペースを持っており, 有効膜面積の減少をきたしていた。充填率の異なるダイアライザーを試作し, 小分子量物質ならびに低分子タンパク質の除去能を比較検討しところ, 充填率の低いダイアライザーではチャンネリングが多く,透析効率が低い。また, この結果をもとにダイアライザー中心部へPS膜を, その周囲にEVAL-D5膜の配置を試みた。この試作ダイアライザーではPS膜の比率が多くなるほど小分子量物質の除去能が上昇する傾向にある。これはPS膜が湿潤により伸張することなく, 良好な充填状態が維持されるためと考えられる。また, 低分子タンパク質はPSに吸着するため, やはりPSの割合が増えるにつれて除去能は上昇する。

β2-microglobulin(以下β2MG)の除去を目的とした数多くのHP透析膜が開発されている。拡散だけでβ2MGを除去できれば安価で簡便な治療が可能となる。新しく開発された再生セルロースを膜素材とするHP透析膜AM-EP-19を用いて、拡散によるβ2MG透過性の検討を行った。放射性同位元素で標識したβ2MGを中空糸透析膜一本に充填して一定時間透析実験を行い、中空糸内部の残存溶質濃度を測定し溶質透過係数を求めた。得られた溶質透過係数は、拡散による除去が可能な酢酸セルロースを膜素材とするFB-190UGAと同等に大きく、AM-EP-19も拡散だけで十分β2MGの除去が可能であることがわかった。迷宮細孔理論を用いてAM-EP-19の細孔構造を解析したところ、大孔半径と高膜面開孔率を有することがわかった。各溶質半径に対するクリアランスは通常透析膜に比べ高く、また除去可能な溶質半径も広範囲に渡っていることが確認された。

中空糸透析膜の溶質透過係数の正確かつ簡便な測定方法は未だ確立されてない。我々はこれまでラジオアイソトープ(RI)を用いた溶質透過係数測定法を開発してきたが、放射能の危険性、特殊施設の必要性など様々な問題を抱えている。今回我々は溶質の光学的特性を利用し、光の吸光度の時間による変化より中空糸透析膜の溶質透過係数を測定する新しい方法を開発した。我々が開発した測定装置において各種単成分溶液濃度と透過光強度の関係は低濃度領域においてLambert-Beerの法則に従うことが確認された。また今回の方法による各種溶質の溶質透過係数測定値はクリアランスから算出される総括物質移動係数、もしくは従来のラジオアイソトープ法による溶質透過係数測定値とほぼ一致した。<br>今回の光を用いる溶質透過係数測定法はRI法に比べ安全かつ簡便であり、本法による多成分同時測定の可能性も示唆された。

透析で除去すべき物質として低分子タンパク質が挙げられる。低分子タンパク質は分子量が膜の除去限界に近いため, 拡散による除去は困難である。効率よく除去するためには, 濾過, 吸着現象を利用しなければならない. 濾過による除去具合はふるい係数が目安となるが, 吸着による除去具合を知る簡便な目安はない。また, 吸着現象は膜材質のほかタンパク質そのものの物性による影響も受ける。そこで, 等電点の異なる低分子タンパク質を用い, 数種類の膜への吸着実験を行いその程度を調べた。使用した膜は吸着が起こらないとされる再生セルロース, 適度に吸着すると思われるPMMA, 吸着能の高いポリスルフォンである。再生セルロース, ポリスルフォンでは等電点の影響はみられないがPMMAでは同一分子量でも等電点により吸着量が異なる。また, 水溶液系での実験結果は血清を用いた実験結果と同一であり, 水溶液系での結果をもって臨床使用の目安とすることができる。

近年、β2-microglobulinの除去を目的として、新しい透析膜(HP透析膜)が開発されている。目的とする溶質の除去には、どのような膜構造が適しているかを検討することにより、優れた透析膜の開発がより効率的に行われる。そこで膜構造の最も基本的な因子である細孔直径を各種測定法を用いて検討した。TPM法(細孔理論)、DSC法により測定された細孔直径と、BET法により測定された細孔直径分布との比較を行ったところ、BET法の細孔直径は他の方法に比べ小さくなった。これは主に試料乾燥時における細孔構造に起因するものと思われる。また、HP透析膜と通常の透析膜との比較を行ったところ、HP透析膜は代表細孔直径が大きく、細孔容積も大きい。さらに大孔径部に多くの細孔が存在する特徴を持っている。再生セルロース膜と合成高分子膜では、細孔直径分布曲線の形状において大孔径部で差異が認められた。

現在、外部灌流クロスワインド中空糸膜型人工肺は6本の中空糸を束ねて巻き込むことにより生産されている。しかし、中空糸巻き込み本数(以下、フィラメント数)はモジュールに膜面積および流動状態の変化を与える。これらがガス交換能に与える影響は未だ検討されていない。今回、フィラメント数を1本から6本までと24本の外部潅流クロスワインド型人工肺を作成し、O₂-水系実験、牛血液を用いたin vitro実験を行い、フィラメント数がガス交換能に与える影響を比較した。フィラメント数は従来の6本より少ない方が総括物質係数は増加したが、これは低充填率による流動の均一化と中空糸同志の接触面積の減少による有効膜面積の増加に起因する。また、X線CTにより、血液側の流動状態を観察した。フィラメント数3、6本の人工肺にはモジュール中心部にチャンネリンゲが観察されたが、フイラメント数1本では均一な流れが観察され、有効膜面積の増加が視覚的にも確認された。

Various materials are presently available for hollow fiber dialysis membranes which satisfy technical and medical requirements such as high permeability to uremic toxins and water, biocompatibility, resistance to sterilization, and high mechanical strength. New dialysis membranes with high permeability to β₂-microglobulin and with biocompatibility leading to low complement activation have been developed for more optimal hemodialysis. Data on structure and permeability are then required to prepare the new dialysis membranes. Much attention should be paid also to the geometry of hollow fiber dialysis membranes available for chronic renal failure patients with elevated hematocrits caused by the administration of erythropoietin.

血漿タンパク質の成分分離への応用を目的として、多孔質ガラス膜およびアルミニウム陽極酸化皮膜の2種類の無機多孔質膜および対照として有機多孔質膜を用いて、牛血漿の定圧濾過実験を行った。多孔質ガラス漠などの無機多孔質膜は細孔直径分布、細孔の屈曲率などが小さく、細孔直径を任意に変化させることができることから、分離性能に優れているだけでなく、薬品処理や熱処理によって再生が可能であるなど、有機膜にはない長所を持つ。血漿タンパク質分離実験および2次元電気泳動による血漿タンパク質の分折の結果、多孔質ガラス膜は血漿処理能力に優れていること、および血漿タンパク質をシヤープに分離ずることができることがわかった。また、現在のアルミニウム陽極酸化皮膜は血漿成分分離膜として不適であるが、吸着を抑えることがでぎれば、多孔質ガラス膜以上の性能を持つ可能性が示唆された。

β2-microglobulin(以下β2-MG)は濾過で除去するのが好ましいが、通常の透析治療で除去できれば、安価で操作が煩雑とならずに透析患者を治療することが可能となる。拡散だけでどこまでβ2-MGの除去が可能か、新しく開発されたハイフラクッス透析膜を用いて検討を行った。放射性同位元素で標識したβ2-MGを中空糸透析膜一本に充填して一定時間透析を行い、中空糸内部の残存溶質濃度を測定し溶質透過係数を求めた。得られた溶質透過係数よりdiffusive clearanceを算出したところ、酢酸セルロースを膜素材とするCT-190GAは拡散だけで十分なclearanceが得られることがわかった。逆濾過がβ2-MGの溶質移動に及ぼす影響を検討するため、並流および向流で操作したときのmyoglobinのclearanceを測定した。並流と向流でclearanceはほぼ同じ値を示し、中分子量物質の除去においては逆濾過は溶質の移動にほとんど影響していないことがわかった。

拍動流体外循環は、定常流に比べて生体に有利であることが多数報告されている。しかし、拍動流ポンプを用いた内部および外部灌流型人工肺のガス交換特性については、いまだ十分に解明されていない。我々は、牛血液を用いたin vitro実験を行い、拍動流が灌流方式の異なる人工肺に与えるガス交換能の影響を比較検討した。さらに外部灌流型人工肺において、モジュール内の部位によるガス交換能の差異を検討するため、有効膜面積を変化させガス交換能を比較検討した。その結果、拍動流では、灌流方式の違いによらず、定常流よりもガス移動量が増加した。とくに、内部灌流においてその差が大きかった。これは、拍動流により液に乱れが生じ液側境膜を効果的にはがしたためと考えた。モジュールの外縁部の方が中心部よりガス交換能に優れていた。これは、モジュール内において偏流が生じており、外縁部を中心に流れているためと考えた。

Appropriate design of dialysis membranes requires correct values of structural parameters such as pore radius, surface porosity, water content and tortuosity. It is impossible, however, to find the pore radius of dialy sis membranes using a mercury porosimeter or an electron microscope because the pores are only several tens of angstroms in radius. Consequently, diffu sional and convectional procedures such as the Lw method that uses both pure water permeability and water content, the Lw and Pm method which uses both solute and pure water permeability, and the σ method which uses the reflection coefficient, have been employed extensively to determine the pore radius of dialysis membranes. The structural parameters of symmetric membranes are determined from water content, solute and pure water permeability data based on the Lw and Pm method combined with the tortuous pore model we have pro posed. Determination of the structural parameters of microfiltration mem branes for plasma separation having huge pores by various methods is required to verify the method of characterizing dialysis membranes based on the tor tuous pore model. A dyeing method is also suitable for characterizing dialysis membranes of regenerated cellulose. Pore model studies using permeability and water content data for sterilized and treated membranes facilitate optimal design of dialysis membranes for clinical applications. © 1989, Sage Publications. All rights reserved.

外部灌流膜型人工肺は内部灌流膜型人工肺に比べて、液体の流動状態に違いがあることからガス交換能に優れていることが報告されている。今回、我々は牛血液を用いたin vitro実験を行い、CO₂-水系の実験結果と比較することによって、内部および外部灌流膜型人工肺のガス交換特性の機構の解明を試みた。CO₂-水系実験および牛血液実験において、外部灌流におけるガスの総括物質移動係数は内部灌流のそれに比べ大きな値を示した。血液1リットルに対する酸素の付加能力という点から見ると、外部灌流は内部灌流の約2倍の性能を示した。また、総括物質移動係数がレイノルズ数に依存することがCO₂-水系実験において確認された。外部灌流膜型人工肺の灌流方式が血液側圧力損失を大きくすることなくレイノルズ数を増加させることが可能で、その結果液側境膜抵抗が減少し、物質輸送に有利に働いている。外部および内部灌流膜型人工肺のガス交換能の差を確認するのに、CO₂-水系実験による基礎的検討が有用であった

管状型多孔質ガラス膜を用いて血漿分離実験を行い、膜間圧力差を25mmHg、50mmHgに変化させて孔直径および管長が血漿分離特性に与える影響を検討した。濾過流束およびタンパク質のふるい係数は膜の孔直径の増加とともに上昇するが、孔直径が1μm以上になると一定値を示した。濾過流束は管長の(-1/3)乗および壁ずり速度の1乗に比例した。これらの関係は膜間圧力差が50mmHgから25mmHgに低下しても変化しなかった。しかし孔直径が1μmの多孔質ガラス膜の場合、膜間圧力差低下に伴いふるい係数が大きく上昇し、他の孔直径の膜と異なった現象を示した。血漿分離においては赤血球の分極層が支配的な抵抗になる。膜間圧力差が低下すると分極層抵抗および付着層抵抗は減少した。濾過流束なヘマトクリットの対数値の増加に対して直線的に減少せず、限外濾過理論による濾過流束の原液濃度依存性と異なった結果が得られた。

血漿成分分離への応用を目的として、定圧濾過実験により3種類の無機多孔質膜のデキストラン分画特性を明らかにした。無機多孔質膜の孔直後分布は現行の合成高分子膜より極めて小さく、タンパク質の成分分離に適すると考えられる。多孔質ガラス膜およびアルミニウム陽極酸化皮膜は孔直径を変化させることにより、ふるい係数を変化させることが可能である。膜を用いたタンパク質の成分分離において主要な阻害因子は濃度分極による抵抗である。壁ずり速度を増加させると、膜表面に生成した濃度分極層が破壊されるためタンパク質の分離がシャープとなる。孔直径を変化させ、高壁ずり速度下で過を行うことにより希望する分離を行うことができる。多孔質ガラス膜およびアルミニウム陽極酸化皮膜は血漿タンパク質の成分分離に適用可能である。

回転二重円筒管膜を用いた血漿分離システムの濾過機構を解明するために、入口圧力、膜回転数および血液性状を変化させ血漿分離実験を行った。入口圧力が遠心力による圧力に打ち勝つと濾過が開始され、さらに入口圧力を上昇させると濾過流束は急激に上昇し極値をもち定常に達する。回転による遠心力は濾過開始圧力を支配し、またテイラー渦発生の原因となる。膜回転数が増加すると濾過流束は増加し、約4000rpmを超えるとやがてプラトーに達し、従来のクロスフロー濾過の10倍以上の濾過性能を示す。これは本システム特有のテイラー渦流、高勢断力による血球の撹拌効果に伴い、分極層抵抗が従来のシステムに比べて大きく減少したためである。また軸方向の物性値変化を考慮した物質移動モデルを提案し、実験データのシミユレーシヨンを行ったところ、データと理論の良好な一致を見た。

ハイフラックスダイアライザを含む9種類の市販中空糸型透析器を用いて、牛血漿接触前後の透水能を比較・検討した。また、各種透析膜への牛血清アルブミン(BSA)吸着量を、放射性同位元素を用いて測定した。いずれの透析膜でも血漿接触後の純水濾過係数は低下した。低下の度合は膜材質や純水濾過係数の値によって異なる。各膜へのBSA吸着量はPMMA>EVAL・CA>RCの順である。BK-1.0に用いられているPMMA膜のBSA吸着量、透水能低下率はともに著しく大きかった。これは、膜の孔直径が大きいため、アルブミンなどが膜細孔内に進入し、膜細孔が狭窄したためと考えられる。EVAL膜はBSA吸着量が少ないにもかかわらず、透水能低下率は大きい。これは孔入口にタンパク質分子が入り込み、有効孔個数が減少するためと考える。透水能の低下とタンパク質の吸着には、いずれも膜構造が大きな因子になると思われた。

透析中に体内電解質の移動を制御する方法の一つとして透析膜に荷電を付加することが有効と考えられる。本報では、血液透析膜を用いて、無機リンおよびナトリウムイオンの膜透過性、無機リンの溶質透過性. 膜表面電位(ζ電位)を測定し膜透過性と膜表面電位の関係を検討した。ζ電位は湿潤状態の中空糸透析膜1本について、流動電位測定装置を用いて中空糸内にKCi水溶液を圧入して測定した。無機リンの溶質透過係数は放射性同位元素で標識した³²P-Na₂HPO₄ (5μCi/ml)の水溶液を中空糸透析膜1本に充填して一席時間透析を行い、中空糸内部の残存溶質濃度を測定して算出した。再生セルロース膜では、無機リンの総括物質移動係数および無機リンの溶質透過係数Pmに及ぼすζ電位の影響はない。PMMA膜では、ζ電位が無機リンおよびナトリウムイオンの総括物質移動係数および無機リンの溶質透過係数Pmに影響を及ぼしている。

手根幹症候群の原因物質として長期透析患者にて注目されているβ2-microglobulinの血中濃度変化を推算すべく、3プールモデル解析を試みた。その際、ダイアライザーでの除去速度を正確に求めるため、臨床検査に用いた後の透析患者廃棄血漿を集め、血清処理後1プールin vitro実験を行った。ダイアライザーに旭メディカルのAM-Neo-1000-HPを用いたところ、膜のふるい係数は0.30であった。この値から計算したクリアランスを用いて血中濃度変化をトレースすべくモデルのパラメータを求めた。細胞膜クリアランスはβ2-microglobulinの分子量より予想される値よりもはるかに大きかった。また、毛細血管クリアランスはダイアライザーでの除去速度よりも大きく、文献値と一致した。透析終了直後の急激なリパウンド現象はこのモデルでおおよそ説明できる。見掛けの溶質生成速度は一般に言われている値よりも小さく、100mg/day以下であった。

長期透析患者にはアミロイド沈着がみられるが、このアミロイドーシスにβ2-microglobulin (以下β2-MG)が関与していることが報告されて以来、β2-MGの効率のよい体外排除が検討されている。我々は回分式吸着実験を行い、コラーゲン、ヒドロキシアパタイト、多孔質ガラス微粒体、Amberlite XAD-7、8、DHP-1活性炭のβ2-MG吸着特性を測定した。その結果、コラーゲンビーズ、DHP-1活性炭およびXAD-7、8に優れたβ2-MG吸着能が認められ、平衡吸着量はそれぞれ1.9、1.3、6.6、2.7×10^-3kg/kg-sorbentであった。弱疎水性材料であるXAD-7は、最も優れた吸着能を示した。吸着平衡に達するまでにDHP-1活性炭では60時間以上、多孔質ガラス微粒体では24時間以上を要した。これは吸着剤の細孔直径が40Å以下であるため、細孔内拡散が律速となるためである。吸着量および吸着速度の点から考えて、β2-MGの除去には弱疎水性素材で、細孔直径が40Å以上の細孔構造を有する吸着剤が適当と思われる。