Boo Ok Yoon

Chemically modified polysulfone hollow fibers with vinylpyrrolidone having improved blood compatibility

Hydrophilic polysulfone membranes (PVP-PSf) were prepared from polysulfone membranes covalently conjugated with polyvinylpyrrolidone (PVP) on the surface. The immobilized amount of vinylpyrrolidone on PVP-PSf membranes was controlled by the amount of vinylpyrrolidone monomer in the reaction solution and the reaction time. The PVP-PSf membranes were found to be the most hydrophilic membranes among the polysulfone and surface-modified polysulfone membranes prepared in this study. This is explained by the long hydrophilic side chain of polyvinylpyrrolidone on the PVP-PSf membranes which contributes to the hydrophilic wiper on the hydrophobic PSf membranes. It was found that PVP-PSf membranes gave lower protein adsorption from a plasma solution than polysulfone and other surface-modified membranes (p < 0.01). This is attributed to the hydrophilic surface of the PVP-PSf membranes, because the hydrophilic surface is known to reduce the protein adsorption on the membranes. The PVP-PSf membranes showed a much suppressed number of adhering platelets on the surface than polysulfone and other surface-modified membranes (p < 0.01). It is suggested that the hydrophilic surface of the PVP-PSf membranes without ionic groups causes the suppression of platelet adhesion on the PVP-PSf membranes and that the long hydrophilic side chain of polyvinylpyrrolidone on PVP-PSf membranes contributes to the hydrophilic and hemocompatible wipers on the surface of the hydrophobic PSf membranes.

Serum protein adsorption and platelet adhesion on pluronic™-adsorbed polysulfone membranes

We examined plasma protein adsorption and platelet adhesion to polysulfone (PSf) flat membranes coated with Pluronic with varying polyethylene oxide (PEO) block length. Adsorption of albumin, globulin and fibrinogen to Pluronic-coated PSf membranes was independent of plasma dilution when concentrations of human blood plasma above 20% were applied. Increasing coating concentrations of aqueous Pluronic solution resulted in decreased protein adsorption by the PSf membranes. Pluronic F68, which was more hydrophilic than Pluronic L62 or L64 and had 80% of PEO content, was the most effective at suppressing the adsorption of plasma proteins and platelet adhesion to PSf membranes. We developed a mixed protein solution containing human albumin, gamma-globulin and fibrinogen to attempt to mimic the competitive and cooperative binding effects found in plasma. Fibrinogen adsorption from plasma could be recapitulated by the mixed protein solution. The number of platelets adhering to the PSf membranes decreased as the coating concentration of Pluronic solution was increased, and platelet adhesion decreased in parallel with fibrinogen adsorption. These results suggest that the bioinert property of PEO segments in the Pluronic, which is ascribed to their high flexibility in aqueous media, suppresses the adsorption of plasma proteins and platelets to the Pluronic-coated PSf membranes.

Removal of endocrine disruptors by selective sorption method using polydimethylsiloxane membranes

Abstract Human milk has unique nutritional and immunological properties and is the most natural and important food source for infants. However, human milk often contains trace amounts of chemical contaminants known as endocrine disruptors, e.g. DDT, hexachlorocyclohexane (HCH), polychlorinated biphenyls (PCBs), and polychlorinated dibenzo- p -dioxin. The concentrations of PCBs and dioxins in human milk in some countries are so high that the breast-fed infant’s intake exceeds the tolerable daily intake (TDI). The goal of this study was the removal of endocrine disruptors from milk without any decomposition nor denaturation of the milk components by a sorption method using hydrophobic polydimethylsiloxane (PDMS) membranes. Endocrine disruptors, e.g. 1,2-dibromo-3-chloropropane, dibenzo- p -dioxin, and hexachlorocyclohexane could be removed efficiently from aqueous solution or milk by the sorption method using hydrophobic PDMS membranes. The removal ratio was high for endocrine disruptors having high octanol–water distribution coefficients. It is possible to estimate the removal ratio of other endocrine disruptors in the sorption experiments using PDMS membranes, if their octanol–water distribution coefficients are known. Sorption of γ-globulin and casein in the PDMS membranes was extremely low, because protein molecules are too large to be sorbed into the PDMS membranes. Other nutrients of water-soluble vitamins, such as Vitamins B 2 and B 12 , and niacin, were also not sorbed into the PDMS membranes.

Visible light is able to regulate neurite outgrowth.

The pheochromocytoma cell line PC12 displays neuronal characteristics. PC12 cells differentiate their phenotype from a proliferating cell to a neurite-bearing neuron upon treatment with nerve growth factor (NGF). The neurite outgrowth of PC12 cells on polystyrene tissue culture flasks and extracellular matrix protein-adsorbed glass plates was reversibly controlled using visible light. The percentage of cells with neurites decreased with increasing light intensity. Furthermore, neurite outgrowth was dramatically suppressed with light intensities over 300 Lux (approximately 130 μW). Neurite outgrowth occurred in the absence of irradiation by visible light, but did not occur or was limited with irradiation, depending on the membranes on which PC12 cells were cultured. These results hold promise for the creation of patterned neuronal networks corresponding to patterned irradiation of visible light on nerve cells.

Optical resolution of amino acid by ultrafiltration through immobilized DNA membranes

Ultrafiltration experiments for the optical resolution of racemic phenylalanine were investigated in a DNA solution system and by using immobilized DNA membranes. L-phenylalanine preferentially existed in the permeate solution and D-phenylalanine preferentially existed in the concentrate solution in the ultrafiltration of racemic phenylalanine through the immobilized DNA membranes. This indicates that L-phenylalanine preferentially enters into the pores of the immobilized DNA membranes and permeates through the membranes due to the interaction between DNA and L-phenylalanine. The immobilized DNA membranes were categorized as channel type membranes.

Serum protein adsorption and platelet adhesion on aspartic-acid-immobilized polysulfone membranes.

Polysulfone (PSf) membranes that covalently conjugated with aspartic acid (ASP-PSf) were prepared and analyzed for hemocompatability. Compared to PSf or other types of surface-modified PSf membranes, the ASP-PSf membranes had a reduced ability to adsorb protein from either a plasma solution or a mixed solution of albumin, globulin and fibrinogen. This appears to be due to the creation of a hydrophilic surface by the aspartic acid zwitterion immobilized on the ASP-PSf membranes. Furthermore, the analyses of membrane protein adsorption showed that a mixed protein solution recapitulates the cooperative adsorption of proteins that occurs in plasma. We also found that the number of adhering platelets was the lowest on the ASP-PSf membranes and, in general, that platelet adhesion decreased in parallel with fibrinogen adsorption. In summary, aspartic acid immobilized on the ASP-PSf membranes, which have zwitterions with a net zero charge, effectively contributes to the hydrophilic and hemocompatible sites on the surface of the hydrophobic PSf membranes.