In vitro and in vivo biocompatibility study of surface modified TiN deposited on Ti6Al4V using high-power impulse magnetron sputtering technique

Although Ti6Al4V alloy is commonly used as a surgical implant, the toxicity of vanadium is always a serious concern. As a stable and protective coating for Ti6Al4V, TiN deposited using a high-power impulse magnetron sputtering (HiPIMS) technique exhibits great polarization resistance in simulated body fluid and shows excellent cell viability of osteoblast-like MG63 cell. Herein, we report further study on the in vitro and in vivo biocompatibility of the HiPIMS-deposited TiN coatings with various surface modifications. For the in vitro study, the effect of O2 plasma treatment, acrylamide (AAm) graft polymerization, and bone morphogenetic protein-2 (BMP2) immobilization on the viability of osteoblast-like MG63 cell were examined using the MTT assay. For the in vivo study, the pro-inflammatory cytokines and skin pathology in mice using subcutaneous sensitivity test were conducted. In vitro investigation shows that cell viability is significantly improved for TiN having BMP2 on the surface. When BMP2 was coated on bare TiN, the MG63 cell proliferation decreases with time. However, with surface pre-treatment of TiN using O2 plasma and AAm grafting, BMP2 coated TiN exhibits increasing MG63 cell proliferation with time. Likewise, in vivo investigation shows such sample has enhanced wound healing capability, significant increase of the body weights, obvious decrease of pro-inflammatory cytokines, and improved skin section structure, as compared to the bare Ti6Al4V. The pathological result shows that the TiN treated with O2 plasma and AAm graft polymerization, and with a surface BMP2 layer gives long-term stable immobilization of BMP2 and the best in vivo biocompatibility among all the samples.