Development of surface modification techniques for the covalent attachment of insulin-like growth factor-1 (IGF-1) on PECVD silica-coated titanium

Osseointegration is a complex process governed by the interaction of many cell types including blood cells (erythrocytes, platelets and leukocytes), phagocytic cells (macrophages) and bone cells (osteoblasts and osteoclasts) on or near the implant surface. The implant surface can be modified through a variety of methods in order to achieve control of some of these cellular interactions and consequently increase the degree of implant fixation with the surrounding bone tissue. In this investigation, titanium was coated with hydroxylated silica by plasma enhanced chemical vapour deposition (PECVD) to increase the surface hydrophilicity and generate reactive surface silanol groups. Subsequently, the silica-coated titanium surface was further modified through silanisation to generate surfaces bearing different reactive chemical functionalities consisting of aldehydes, epoxides and isocyanates, which can react with the amino groups of proteins and growth factors. 2,2,2-trifluoroethylamine (FEAM) was reacted on these surfaces to determine the coupling efficiency of the different surface chemical functionalities. The amino group of FEAM can react with an amino-reactive surface functional group to form a surface terminated with 3 fluorine atoms per FEAM molecule that can be detected by X-ray photoelectron spectroscopy. By analysing the techniques used for protein attachment with the FEAM model molecule, a successful method for isocyanate/amine coupling was found and later adapted for tethering IGF-1 molecules to the functionalised PECVD silica-coated titanium surface. Therefore, this simple method of preliminary testing protein reactivity may prove to be a cost effective strategy in the development of new biomaterial surfaces modified using protein bioconjugation methods.