Tailoring the Sm/Gd-Substituted Hydroxyapatite Coating on Biomedical AISI 316L SS: Exploration of Corrosion Resistance, Protein Profiling, Osteocompatibility, and Osteogenic Differentiation for Orthopedic Implant Applications

In this paper, we have fabricated the samarium/gadolinium-substituted hydroxyapatite (Sm/Gd-HAP) coating on the borate-passivated AISI 316L SS stainless steel. The structural and morphological characteristics of the Sm/Gd-HAP coatings were investigated using various analytical techniques and the anticorrosion behavior of the coating was studied through electrochemical techniques. The antibacterial activity of the coating was tested against Staphylococcus aureus and Escherichia coli bacterial stains and, in particular, S. aureus showed better sensitivity toward the Sm/Gd-HAP coating, which might be due to the Sm substitution in the coating. The in vitro cytotoxicity and biocompatibility of the as-developed coating on passivated AISI 316L SS were investigated using MC3T3-E1 cell line, which exhibited a high cell proliferation rate and provided significantly higher cell viability. Thus, the resultant Sm/Gd-HAP coating on passivated AISI 316L SS could be considered to be an effective bioimplant for bone tissue regeneration applications.