Novel ternary vancomycin/strontium doped hydroxyapatite/graphene oxide bioactive composite coatings electrodeposited on titanium substrate for orthopedic applications

Currently, the clinical application of hydroxyapatite (HA) coatings are limited due to the lack of anti-infection, osteoinductivity and poor mechanical properties. In the present study, the strontium-containing hydroxyapatite (SrHA)/graphene oxide (GO)/vancomycin (Va) nanocomposite coating with drug delivery and antibacterial activity was fabricated by electrochemical deposition (ECD) on titanium substrate. The results showed that by inducing a large number of crystal nucleation points, the oxygen-containing groups on the two-dimensional surface of GO induced the formation of extremely fine SrHA/Va/GO composite coatings. Furthermore, the functional coating exhibited a moderately nanostructured surface with average values of roughness and contact angle of 31.9 degrees and 126 nm, respectively, which provided a suitable contact surface for osteoblast proliferation and differentiation. Moreover, compared with HA coatings without GO, the hardness and elastic modulus of SrHA/Va/GO composite coatings were enhanced by 67.6 % and 121 %, respectively. The release process of Va from the SrHA/Va/GO coating showed a phased release law, which broke out within the first 5 h and then slowly and controlledly released within 14 h, which is due to the physical and chemical adsorption of Va. The inhibition zone and colony count experiments showed that the SrHA/Va/GO coating revealed satisfactory inhibitory effects on S. aureus and S. epidermidis, and the inhibition could last for 3 days. Compared with pure titanium, SrHA/Va/GO composite coating can significantly promote the adhesion, proliferation and differentiation of MC3T3-E1 cells. In conclusion, SrHA/Va/GO exhibited good mechanical properties, excellent osteoinductivity and antibacterial properties, confirming its potential as a new surface modification material for the prevention and treatment of infectious bone defects.