Enhanced albumin affinity of silicone rubber

The authors have developed a method to increase the albumin affinity of silicone rubber-containing medical devices. A vinyl-methyl silicone co-monomer was hydroxylated via an oxymercuration-demercuration reaction and then film-coated on a silicone rubber sheet. C16 acylation of the -OH coated sheet was carried out by an esterification reaction catalyzed by 4-DMAP. FTIR spectroscopy confirmed the presence of -OH groups following the hydroxylation reaction, and (CH2)n groups following the acylation reaction. 125I-labeled albumin binding studies indicated graded enhancements, according to reagent concentration, with maximal 2.7X and 2.5X increases for 20% -OH coated and 20% -OH/C16 acylated surfaces, respectively. Incubation with a protein denaturant, sodium dodecyl sulfate (SDS), removed 73% of adsorbed albumin from unmodified controls, with only 25 and 34% removal from 20% -OH coated and 20% -OH/C16 acylated surfaces, respectively. These results suggest that -OH and C16 modified surfaces not only preferentially adsorb albumin, but also retain it in a more stable configuration; this is an unexpected finding for -OH modified surfaces. Based on similar albumin affinities for biocompatible C18 alkylated and C16 acylated polyether polyurethanes, the authors expect significant improvements in thromboresistance and complement-activating potential for this modified silicone rubber.