Yukio Seita

Polyether-segmented nylon hemodialysis membranes. I. Preparation and permeability characteristics of polyether-segmented nylon 610 hemodialysis membrane

The effect of the coagulation condition in the phase inversion method on the permeability characteristics of poly(propylene oxide) or poly(tetramethylene oxide)-segmented nylon 610 (PPO-Ny610 or PTMO-Ny610) hemodialysis membranes, the stability of the membrane performance, and the mechanical strength were investigated. The polymers were dissolved in a solvent such as formic acid and methanol saturated with calcium chloride, and thus PPO-Ny610 and PTMO-Ny610 membranes were prepared using formic acid and a calcium chloride/methanol/water mixture as a polymer solvent and a coagulant, respectively. It is concluded that PPO-Ny610 membrane has better permeability characteristics than PTMO-Ny610 membrane, and possesses additional properties for hemodialysis membranes such as mechanical properties and permeability stability in the drying and sterilizing processes. Furthermore, the blood compatibilities of PPO-Ny610 and PTMO-Ny610 membranes were superior to regenerated cellulose membranes on the basis of the result of platelet adhesion test.

Design of a new plasma separation membrane by graft copolymerization

Abstract A new type of hydrophilic membrane for blood plasma separation has been successfully developed by vapor-phase glow discharge-initiated graft copolymerization. After exposing microporous polypropylene (PP) membrane to argon glow discharge, it was allowed to react with 2-methoxyethylacrylate (MEA) vapor to produce graft polymers. The polyMEA-grafted PP (PP-g-PMEA) membrane has the novel property of not causing hemolysis when blood first comes into contact with it in a dry state. It is thought that hydrophilic microporous membranes in a dry state cause hemolysis when they are initially exposed to blood, because plasma immediately penetrates into their pores by capillary attraction and erythrocytes are trapped rapidly on the micropores and lysed. Since PP-g-PMEA membranes have a weakly hydrophilic character, plasma penetrates into the micropores only slowly and hemolysis does not occur. Therefore, priming with physiological saline prior to use is not required, and consequently plasma separation procedures are simplified and shortened. A disk-type plasma separator equipped with a PP-g-PMEA membrane had good hemo-compatibility and an excellent separation capacity, enabling high recovery of plasma components. A decreased adsorption of plasma proteins due to the PMEA-grafted layer may be the reason for the performance of the membrane.

A new blood compatible and permselective hollow fiber membrane for hemodialysis.

&NA; The authors have prepared a blood compatible and highly permselective hemodialysis membrane composed of polyether segmented nylon. This block copolymer was synthesized by polycondensation of bis‐3‐aminopropyl‐poly(tetramethylene oxide) (PTMO) and poly(imino‐1,3‐bismethyl‐cyclohexyl‐iminoisophtharoyl) (NyBI) prepolymer obtained by polycondensation of 1,3‐bis(aminomethyl)cyclohexane (B) and isophthalic acid (I). The molecular weight (MW) calculated from the number of end‐groups was 16,000‐21,000. In vitro blood compatibility was evaluated in terms of platelet adhesion onto the surface. PTMO‐NyBI surfaces showed excellent platelet adhesion preventing properties. The PTMO‐NyBI hollow fiber membrane was obtained by a drywet spinning process. The membranes had higher permeability coefficients for macromolecules ranging from MW 10,000 to 20,000 than polysulfone hollow fiber membrane (PS membrane), and had acceptably low albumin permeability for use as a dialysis membrane. The ex vivo blood compatibilities of PTMO‐NyBI membrane and PS membrane were investigated by extracorporeal circulation in a pig model. The PTMO‐NyBI membrane gave excellent results when assessing hemodialysis leukopenia, oxidative burst, and free platelet count decrease. ASAIO Journal 1996;42:1019‐1026.

Polyether‐segmented nylon hemodialysis membrane. V. Evaluation of blood compatibility of polyether‐segmented nylons

The biocompatibility of poly(propylene oxide)-segmented nylon610 (PPO-Ny610), poly(ethylene oxide)-segmented nylon610 (PEO-Ny610), poly(ethylene oxide)-segmented nylonM10 (PEO-NyM10), and poly(ethylene oxide)-segmented nylon69/M10 (PEO-Ny69/M10) hollow fibers were investigated in terms of the transient leukopenia by the extracorporeal circulation in a rabbit. PPO-Ny610 and PEO-Ny610 hollow fibers showed that the minimum leukocyte counts during the circulations were > 80% against the initial count of leukocyte. These results indicate that these polymers have good blood compatibility. In PEO-NyM10 and PEO-Ny69/M10, the remarkable decreases of the leukocyte count were observed and the minimum counts were in the range of 45–50%. From the evaluation results of homo nylons (Ny610 and NyM10) hollow fibers, the low blood compatibilities observed in PEO-NyM10 and PEO-Ny69/M10 are not attributed to the chemical structure of the nylon blocks.

Polyether-segmented nylon hemodialysis membrane. VI. Effect of polyether segment on morphology and surface structure of membrane

Amorphous nylon, poly(iminoisophthaloyliminomethylene-1,3-cyclohexylenemethylene) (NyBI) and poly(ethylene oxide) (PEO)-segmented NyBI (PEO–NyBI) membranes were prepared by a phase-inversion method using water/dimethyl sulfoxide (DMSO) mixtures as coagulants. The influence of the PEO segment and coagulant compositions on the morphology of the membranes was investigated. The cloud-point curves in the polymer/DMSO/water ternary system showed that PEO–NyBI and NyBI had the same coagulation processes, that is, instantaneous liquid–liquid phase separation occurred, resulting in a fingerlike structure in the cross section of the membranes. The membrane morphologies observed under a scanning electron microscope (SEM) agreed with the prediction. The PEO segment had little or no effect on the membrane morphologies which were prepared in the coagulants with a low DMSO concentration, and it promoted the change of the phase-separation style from the instantaneous to the delayed one in the case of the DMSO-rich coagulant. The PEO segment, however, significantly influenced the ultrafiltration rate. Additionally, the relationship between the surface composition of the PEO–NyBI membrane and the coagulation condition was also investigated by use of electron spectroscopy for chemical analysis (ESCA) and static secondary ion mass spectrometry (SSIMS). A small enrichment of the PEO segment at the top surface of the membranes was observed with the increase of the DMSO concentration in the coagulant.

Polyether-segmented nylon hemodialysis membranes. II. Morphologies and permeability characteristics of polyether-segmented nylon 610 membrane prepared by the phase inversion method

The relationships between the morphologies and the permeability characteristics as dialysis membrane of polyether-segmented nylon 610 (PE-Ny610) have been investigated. PE-Ny610 used are poly(propylene oxide) (PPO)-segmented nylon 610 containing 25 wt % PPO (PPO-Ny610) and poly(ethylene oxide) (PEO)-segmented nylon 610 containing 15 wt % PEO (PEO-Ny610). The morphologies in the cross section of the membranes exhibit the cellular porous structures due to liquid-liquid phase separation. On the other hand, the structures of the surfaces are mainly composed of the crystalline spherulite due to liquid-solid phase separation. These morphologies are little affected by the composition ratio of the coagulant, calcium chloride/methanol/water mixture. PEO-Ny610 membranes have shown superior membrane performances to the PPO-Ny610 membrane. The effect of PEO content in PEO-Ny610 on the adhesion of platelet onto the PEO-Ny610 film surface was investigated and it is concluded that PEO-Ny610 having > 10 wt % PEO shows a good nonthrombogenicity equal to PPO-Ny610.

Preparation and properties of plasma-initiated graft copolymerized membranes for blood plasma separation

Abstract A hydrophilic composite membrane for blood plasma separation has been prepared by surface graft copolymerization initiated by low-temperature plasma (LTP). After short LTP pre-irradiation onto a microporous polypropylene (PP) membrane, N-N -dimethylacrylamide (DMAA) vapor was introduced for grafting. The PP membrane had a 0.45 μm effective pore size and a 130 μm thickness. The rate of DMAA grafting onto PP was very high, even in vapor-solid phase reaction under reduced pressure; DMAA 1 mm Hg (133Pa). The percentage of grafted poly-DMAA (PDMAA) reached 15% within 5 min post graft polymerization, and the membrane surface, including the interior surface of pores, became completely hydrophilic. There was no apparent change observed in the membrane morphology in the dry state after the PDMAA-grafted layer was formed. However, water flux significantly decreased, probably due to swelling of the PDMAA-grafted layer. With a grafting yield below 17%, the PDMAA-grafted PP (PP-g-PDMAA) membrane showed a good separation capability of plasma from whole blood. The PP-g-PDMAA membrane exhibited low complement activating potential, high sieving coefficient for plasma proteins and high blood compatibility. Decreases in adsorption of blood cells, plasma proteins, and other biomolecules may be the reason for the membrane performance.

Polyether‐segmented nylon hemodialysis membranes. III. Preparation and properties of new polyether‐segmented nylon

In order to apply a blood-compatible polymer to hemodialysis membrane, a new polyether-segmented nylon which dissolved in common organic solvents was designed. The basic polyether-segmented nylon was synthesized by melt polycondensation from sebacic acid, m-xylenediamine, and α,ω-bisaminopropyl-poly(ethylene oxide). To improve the solubility, azelaic acid and hexamethylenediamine were copolycondensed with the basic copolymer. The solubility was correlated with the heat of fusion (ΔHm) of the copolymer. When ΔHm is 10 wt % of poly(ethylene oxide), suppresses the adhesion of platelet, and the composition of the nylon block has no effect on the adhesion of platelet.

Polyether-segmented nylon hemodialysis membranes. IV. Membrane morphologies and permeability characteristics of dialysis membrane composed of poly(ethylene oxide)-segmented Ny69/M10

Dialysis membrane was prepared by a phase inversion method using a new polyether-segmented nylon which dissolves in common organic solvents such as dimethylsulfoxide. The polyether-segmented nylon contained poly(ethylene oxide) block and nylon block (random copolyamide: Ny69/M10) prepared by sebacic acid, azelaic acid, m-xylenediamine, and hexamethylenediamine. The morphologies and permeability characteristics of the membranes were investigated. It was shown by scanning electron microscope observation that the membrane had a fingerlike structure when dimethylsulfoxide was used as a polymer solvent, and a spongelike structure when an additive such as calcium chloride was added to the polymer solution. The high permeability for the solutes such as urea and vitamin B12 were observed in comparison with the polyether-segmented Ny610 membranes prepared by a phase inversion method.

Studies on surface structures of poly(ethylene oxide)-segmented nylon films

The surface structures of three kinds of poly(ethylene oxide)-segmented nylon (PEO-Nyl molten films were investigated using a scanning electron microscopy (SEM), an electron spectroscopy for a chemical analysis (ESCA), and a static secondary ion mass spectrometry (SSIMS). The PEO-Nys used were high semicrystalline PEO-segmented poly(iminosebacoyliminohexamethylene) (PEO-Ny610), low semicrystalline PEO-segmented poly(iminosebacoylimino-m-xylene) (PEO-NyM10), and amorphous PEO-segmented poly(iminoisophthaloyliminomethylene-1,3-cyclohexylenemethylene) (PEO-NyBI). SEM observations show that the surfaces of the PEO-Ny610 and PEO-NyMlO films are composed of spherulite, and that PEO-NyBI film has a smooth surface. The results of ESCA and SSIMS exhibit the significant enrichments of PEO segment at the surfaces of all the films regardless of the crystallinity. The reason for the enrichment of PEO segment was discussed in terms of the surface tension of the corresponding homopolymers in the melting state.