Specific Binding of Streptavidin onto the Nonbiofouling Titanium/Titanium Oxide Surface through Surface-Initiated, Atom Transfer Radical Polymerization and Bioconjugation of Biotin

Abstract

Chemical modification of titanium/titanium oxide (Ti/TiO2) substrates has recently gained a great deal of attention because of the applications of Ti/TiO2-based materials to biomedical areas. The reported modification methods generally involve passive coating of Ti/TiO2 substrates with protein-resistant materials, and poly(ethylene glycol) (PEG) has proven advantageous for bestowing a nonbiofouling property on the surface of Ti/TiO2. However, the wider applications of Ti/TiO2-based materials to biomedical areas will require the introduction of biologically active moieties onto Ti/TiO2, in addition to nonbiofouling property. In this work, we therefore utilized surface-initiated polymerization to coat the Ti/TiO2 substrates with polymers presenting the nonbiofouling PEG moiety and subsequently conjugated biologically active compounds to the PEG-presenting, polymeric films. Specifically, a Ti/TiO2 surface was chemically modified to present an initiator for atom transfer radical polymerization, and poly(ethylene glycol) methacrylate (PEGMA) was polymerized from the surface. After activation of hydroxyl groups of poly(PEGMA) (pPEGMA) with N,N'-disuccinimidyl carbonate, biotin, a model compound, was conjugated to the pPEGMA films. The reactions were confirmed by infrared spectroscopy, X-ray photoelectron spectroscopy, contact angle goniometry, and ellipsometry. The biospecific binding of target proteins was also utilized to generate micropatterns of proteins on the Ti/TiO2 surface.