| The objectives of this research were to expand the scientific understanding of hydrophilic phospholipid (PL) surface modifications on silicone and metal substrates via two unique processes: gamma radiation surface graft polymerization and electro-polymerization. This work was a novel study of these two polymerization techniques to produce phospholipid-modified surfaces using a vinyl functionalized phosphorylcholine-containing monomer.;A number of synthetic functionalized PLs have been reported to produce surfaces which might better mimic the structure of natural cell membranes. Unique polymerization methods for a methacryl-functionalized PL monomer were investigated here to prepare homopolymer and copolymers with other vinyl monomers.;The 2-methacryloyloxyethylphosphorylcholine (MPC) monomer studied, originally developed by Ishihara et al., has a structure that is common PLs with long hydrocarbon tails.;Copolymers of MPC have been effective in reducing cell adhesion and protein deposition in blood environments. To expand our knowledge of polymers and surfaces derived from such vinyl functional PLs as MPC, the research reported here involved two new techniques for the surface modification of silicone and stainless steel biomaterials of particular interest for vascular grafts and stents. Surface modification methods explored were gamma radiation surface graft polymerization and electropolymerization.;The first technique, gamma radiation initiated surface graft polymerization, was used produce NVC, MPC-HEMA, MPC-MAA, and MPC-NVP copolymer surfaces on silicone elastomer (polydimethyl siloxane - PDMS). Results of these experiments indicated a significant reduction in contact angle (30 to 50 degree) compared to control silicone substrates.;The second technique was the electrochemical surface polymerization of WC monomer and copolymerization of MPC with silicone oligomers on stainless steel. The goal of copolymerization of WC and a silicone oligomer is based on our view that such copolymer surfaces might combine the biocompatibility of a phospholipid with the elastomeric properties of silicone to produce a novel biomedical surface coating. Two silicone oligomers with different chemical structures were used in this study. Methacryoloxy-terminated-polydimethylsiloxane (MAOP) oligomer provides the typical poly(dimethylsiloxane) (PDMS) structure and vinylmethoxysiloxane (VMS) is more hydrophilic.;The surfaces produced were characterized by contact angle, XPS and SEM analyses. The MPC surface modifications exhibited a large reduction in contact angle (15°--32° vs. 71°) on stainless steel and (24°--55° vs. ca. 75°) on PDMS and may provide a more lubricious surface with improved non-thrombogenic properties. The novel surface polymerization techniques examined here may allow more facile coating of metal and polymer devices with complex geometries and may provide improved uniformity and adhesion using processes that also may prove to be relatively simple and inexpensive. |
