Enhanced bioactivity of 316L stainless steel with deposition of polypyrrole/hydroxyapatite layered hybrid coating: Orthopedic applications

Abstract

316 L stainless steel (316 L SS) is a class of alloy materials enabling good corrosion performance, noticeable biocompatibility, high mechanical properties, and fulfills the economic aspects. While the biomedical applications of 316 L SS are under severe development, some technical hurdles, e.g., low bioactivity are remained to bypass. In this work, a series of the polymer-ceramic layered hybrid systems containing polypyrrole (PPY)-hydroxyapatite (HAp) was electrodeposited on 316 L SS after modifying the electrolyte and electrodeposition parameters. Morphological aspects along with chemical and phase structure of the films were investigated by scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), and X-ray diffraction (XRD), respectively. The adhesion strength, corrosion resistance, and bioactivity of the electrodeposited systems were analyzed using tensile test, potentiodynamic polarization, and in vitro assay in simulated body fluid (SBF), respectively. The results illustrated a ≈20% increment in adhesion strength and a≈60% decrement in corrosion current density of four-layered coating compared to HAp single layer. The bilayered and four-layered coatings stimulate the formation of a compact apatite layer upon immersion assay as a marker of appropriate bioactivity. It is envisaged that the proposed strategy to fabricate a layered hybrid coating system creates new opportunities in the biomedical applications of 316 L SS.