Controlled release of BMP-2 by chitosan/γ-PGA polyelectrolyte multilayers coating on titanium alloy promotes osteogenic differentiation in rat bone-marrow mesenchymal stem cells

The excellent biocompatibility and mechanical properties of titanium alloys have led to their wide-scale application in orthopedic implants. Appropriate surface treatment of these alloys can greatly improve cellular attachment as well as interactions between implants and tissue. This paper reports on the preparation of polyelectrolyte multilayers (PEM) coating comprising chitosan and gamma-poly(glutamic acid) on a Ti6Al4V substrate via spin-coating. Bone morphogenetic protein 2 was then loaded directly into the coating. Following sample preparation, we performed in vitro studies using SD rat bone-marrow mesenchymal stem cells (rBMSCs) to investigate the biological effects of the coating. Our results demonstrate that this chitosan/γ-PGA PEM coating is highly stable and does not have any adverse effects on rBMSCs. The proposed coating proved highly effective in carrying and enabling the gradual release of BMP-2. At day 14, the coated samples presented osteogenic differentiation far exceeding that of the non-coated samples. After co-culturing for 21. days, the calcium content in the PEM coating group was double that of the non-coated group, which is a clear indication of enhanced cellular mineralization.