Effect of C4-, C8- and C18- alkylation of poly(vinyl alcohol) hydrogels on the adsorption of albumin and fibrinogen from buffer and plasma: limited correlation with platelet interactions
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Polyvinyl alcohol (PVA) hydrogel was partially alkylated with short (C4), intermediate (C8) and long (C18) alkyl chains to test the hypothesis that an alkylated surface might promote enhanced interaction with albumin and thus exhibit low platelet thrombogenicity. PVA hydrogel was reacted with alkyl halides (C4, C8 or C18) and coated onto polyethylene. The effect of surface alkylation (extent of alkylation and alkyl chain length) on the adsorption of human serum albumin and fibrinogen to these surfaces was investigated in both buffer and plasma. Platelet interactions were investigated in vitro using flow cytometry methods. The maximum surface concentrations of albumin and fibrinogen adsorbed from buffer onto PVA and alkylated PVA were characteristic of monolayers. At low concentrations differences in adsorption among the surfaces appeared to be related to hydrophobicity as determined by dynamic advancing water contact angle, and to degree of alkylation as determined by angle dependent XPS analysis. Alkyl chain length dependence was not observed. Adsorption from plasma was considerably lower than from buffer, except for albumin on C8-PVA where monolayer adsorption was observed. Fibrinogen adsorption from plasma was similar on PVA, C8-PVA and C18-PVA, but was higher on C4-PVA. For albumin adsorption from plasma, the initial slope of the adsorption-concentration curve was highest for C18-PVA, suggesting higher albumin affinity despite the low degree of substitution of the C18-PVA material. These data suggest possible selectivity of the C18 alkylated PVA for albumin. Platelet studies showed that C4-PVA was the least platelet reactive (microparticle generation and P-selectin expression) of the alkyl derivatized materials.
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