Surface functionalization via PEO coating and RGD peptide for nanostructured titanium implants and their in vitro assessment

This research follows a biomimetic approach for implant surface design, and it concerns surface functionalization for nanostructured Ti Grade 4 with a composite coating obtained by plasma electrolytic oxidation (PEO) with organic pore filler of integrin-active RGD containing peptide (Arg-Gly-Asp-Cys). It was shown that Ti nanostructuring via ECAP-C technique almost two-fold improves its mechanical strength; also, the nanostructuring depassivates the surface, both PEO coated and uncoated. The PEO coating on nano-Ti contains 2–3% more biocompatible elements, amorphous and bio-crystalline phases. The RGD peptide was linked to the surface via phosphonate groups allowing the organic pore filler deposition by dipping method; the RGD presence in the PEO coating pores was proven by the EIS. For the in vitro tests, fibroblasts were used; it was shown that PEO coating on nano-Ti gives 43% increase in the number of cells compared to CG-Ti + PEO; the combination of PEO coating and RGD peptide on nano-Ti gives 45% increase in the number of cells compared to nano-Ti, and 66% compared to CG-Ti. Therefore, this surface functionalization contributes to the development of Ti implants having high strength and providing improved cell proliferation.