Improvement in the surface properties of stainless steel via zein/hydroxyapatite composite coatings for biomedical applications

Although stainless steel is renowned for its wide use as a biomaterial, but relatively higher corrosion rate in physiological environment restricts its clinical applications. To overcome the corrosion resistance of stainless steel bio-implants in physiological environment and to improve the osseointegration behavior we developed zein/hydroxyapatite (HA) composite coatings deposited on stainless steel substrate by Electrophoretic Deposition (EPD). The EPD parameters were optimized using the Taguchi Design of Experiment (DoE) approach. The EPD parameters such as the concentration of bio-ceramic particles in the polymer solution, applied voltage, and deposition time were optimized on stainless steel substrates by applying mixed design orthogonal Taguchi array. The coatings were characterized by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and wettability studies. SEM images and EDX results indicated that zein/HA coating was successfully deposited on stainless steel substrates. The wettability and roughness studies elucidated the mild hydrophilic nature of the zein/HA coatings, which confirmed the suitability of the developed coatings for biomedical applications. Zein/HA coatings improved the corrosion resistance of bare 316L stainless steel. Moreover, zein/HA coatings showed suitable adhesion with the 316L SS substrate for biomedical applications. Zein/HA coatings developed dense HA crystal upon immersion in simulated body fluid, which confirmed the bone binding ability of the coatings. Thus, the zein/HA coatings presented strong potential to be considered for orthopedic applications.