12 - Biocompatible polymer assembly on metal surfaces

Abstract

A description is given of surface modifications to a titanium (Ti) alloy substrate by phospholipid polymers to obtain antithrombogenicity and biocompatibility. The phospholipid polymers contained 2-methacryloyloxyethyl phosphorylcholine (MPC) units, whose design was inspired by cell membrane surface structures. The MPC polymers effectively prevented platelet adhesion and thrombus formation as a result of reduced plasma protein adsorption. Silane chemistry was used to carry out surface grafting of the MPC polymer onto the Ti substrate. Long chains of MPC were much more effective in reducing protein adsorption than short ones. Another surface modification method, the integration of polymers by a layer-by-layer procedure on the Ti substrate, was introduced. The MPC polymer bearing phenylboronic acid units could form complexes covalently with poly(vinyl alcohol). This reaction was used to construct polymer integrated layers by soaking the Ti substrate alternatively in aqueous solutions of these polymers. The MPC polymer could be immobilized by this procedure on the substrate. The layer effectively prevented cell adhesion and also functioned as a drug reservoir by maintaining drugs inside the layer and controlling their release pattern. These observations clearly indicate that surface modifications using MPC polymer provide excellent functions on the Ti substrate.