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.

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