An in vitro assessment of surface modification strategies for orthopedic applications

• Surface functionalization strategies were assessed on titanium alloy.
• Mitogenic effect was evaluated over an extended period.
• Covalent immobilization appears to have the best results.

Despite current advances in orthopedic implant technology, there are still problems associated with their usage including loosening and tissue rejection. The utilization of biosignal proteins such as growth factors for development of bioactive implant materials holds great potential. Therefore in this study various techniques of surface modification (physical adsorption, cross-linking and covalent binding) of vascular endothelial growth factor on titanium alloy were investigated. The binding efficiency of the surface conjugation was determined using an enzyme-linked immunosorbent assay kit. X-ray photoelectron spectroscopy was used to determine the chemical composition of the surfaces. Cellular functions were investigated with human dermal microvascular endothelial cells and human mesenchymal stem cells. The results indicated covalent binding to be the most viable methodology, conferring enhancement of cell–implant interactions without demonstrable cell toxicity, which is beneficial for orthopedic applications.