New hydrophilic copolymers for biomedical applications.

New hydrophilic copolymers with controlled number of surface hydroxyl groups were prepared using gamma-irradiation. The method involved the copolymerization of 2 monomers of varying feed ratio, using gamma-irradiation from a Cobalt60 unit, followed by partial or full hydrolysis (methanolysis), which leads to linear copolymers of simple structure with surface hydroxyl groups. These surfaces were further heparinized using covalent bonds through acetal bridges between heparin and surface hydroxyl groups. In systems of VAc and NVP, the feed ratio varied between 0.1--0.5 and the irradiation dose between 1--5 megarads. The copolymers obtained by this method were analyzed for nitrogen to establish their chemical structure. The reactivity ratios (r1 and and r2) were determined as 0.322 and 3.26, respectively, and curves of copolymer composition versus feed ratio were constructed. Upon hydrolysis swelling ratios of up to 24 were determined and reported as a function of copolymer hydroxyl composition. These hydrogels of PVA copolymers were heparinized by covalent binding of heparin on the hydroxyl groups and elution of heparin in flow was studied.