Electrophoretic deposition of PEEK/bioactive glass composite coatings on stainless steel for orthopedic applications: an optimization for in vitro bioactivity and adhesion strength

Abstract

Polyether ether ketone (PEEK) is an increasingly investigated biocompatible material for orthopedic and spinal implants. The lack in bioactivity of PEEK has to be addressed, either by surface modification or formation of a composite with bioactive materials, such as hydroxyapatite (HA) or bioglass. The addition of bioactive materials improves the bone ingrowth of implants for biomedical application. Accordingly, this study involves electrophoretic deposition (EPD) to obtain PEEK/bioactive glass (BG) coatings on 316 L stainless steel (SS) substrates. In order to prepare the PEEK/BG suspension 2 wt.% PEEK and 6.67 wt.% BG powder were dispersed in ethanol, while citric acid was used as the charging agent. The optimum EPD parameters were applied electric field of 220 V/cm for 2 min. The deposited green coatings presented a homogeneous microstructure and uniform thickness of ~ 100 μm. Subsequently, sintering temperature was optimized in order to obtainappropriate combination of adhesion strength and the in vitro bioactivity. The optimized sintering parameters (400 °C for 30 min) embedded the BG particles in a PEEK matrix, which improved the adhesion strength of coating to the substrate and also formed apatite crystals upon immersion in simulated body fluid. The coatings sintered at 400 °C showed significant improvement in the corrosion resistance of bare stainless steel. Moreover, the cytocompatibility tests showed that the MG-63 cells proliferate and grow on the surface of PEEK/BG coatings. The results demonstrated that EPD is a convenient method to obtain homogeneous, robust, and bioactive PEEK/BG coatings on 316 L SS substrates for biomedical applications.