Fabrication of nanoporous sodium niobate coating on 316L SS for orthopaedics

Niobium oxide is known for its biocompatibility; however it lacks on bioactivity. Sodium is one of the essential elements required for the formation and maintenance of bone. In this present study, we focus on improving the bioactivity of niobium oxide by incorporating sodium ions and obtaining nanoporous morphology by adding polyethylene glycol. Sodium niobate was prepared using sol-gel method and dip coated on 316L SS. The coated sample was sintered at the optimised heating rate of 0.5 °C min−1. The surface morphology, chemical composition, phase composition and porosity were analysed using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD) and porosimetry. The BET analysis and AFM studies showed that the coating exhibited pores with the average diameter of 97 and 101 nm. The Vicker's microhardness test showed that sodium niobate coating exhibits three fold higher microhardness compared to 316L SS. In vitro studies show that the coating exhibited good bioactivity. Electrochemical studies confirmed that the coating offers better corrosion resistance to the substrate at pH 5.2 and pH 7.4. The hemolysis percentage of the coating was found to be 1.54% and anticoagulation studies showed that coagulation time of sodium niobate coating was similar to that of the plasma. Better adhesion, proliferation and differentiation of MG-63 cells with significant cell spreading were observed in the coating.