15 - Bioinspired functionalization of metal surfaces with polymers

Abstract

Surface modifications to metal substrates by polymers to obtain biofunctionality and biocompatibility have been described. Polymers can be fixed on the metal surface after immobilization of chemically active groups, which react with the polymer directly, or initiate polymerization for grafting. The polymer layer deposited on the metal substrate allows various functions. Among the different polymers, the design of a phospholipid polymer contained 2-methacryloyloxyethyl phosphorylcholine (MPC) units is inspired by cell membrane surface structures. The MPC polymers effectively prevented platelet adhesion and thrombus formation resulting from reduced plasma protein adsorption. Such MPC polymers have been used in metal medical devices for clinical applications. A recent progress in surface modification is the use of a biomimetic reaction based on an adhesiveness of mussel protein by the dopamine moiety. The MPC polymer containing dopamine groups in the side chain can stably bind to the Ti substrate. Moreover, this chemistry easily introduces functional groups on the Ti surface by forming a thin film of dopamine. Graft polymerization from the Ti surface provides a well-defined polymer brush layer by surface-initiated living radical polymerization. Another surface modification method consisting of the integration of polymers by a layer-by-layer deposition on the Ti substrate was introduced. The MPC polymer-bearing phenylboronic acid units could covalently form complexes with poly(vinyl alcohol) (PVA). This reaction is used for the construction of thick integrated polymer layers by soaking the Ti substrate alternatively in these aqueous polymer solutions. The biofunctionality and biocompatibility of the MPC polymer brush layer on the metal substrate are explained.