The clinical application of magnesium (Mg)-based alloys as biodegradable orthopedic implants is highly restricted because of their rapid corrosion rate in the physiological environment [1]. Polymeric coatings have been recognized as one of the most effective methods to tailor the corrosion rate of Mg alloys without changing their bulk properties, while providing them with other functionalities such as enhanced biocompatibility [2]. In this study, a composite polymeric coating based on silk fibroin (SF) and cellulose nanocrystal (CNC) was fabricated on AZ31 Mg alloy to enhance its corrosion resistance and cytocompatibility for biodegradable bone implant application. The coating was prepared by drop-cast method on AZ31 Mg alloy and fully characterized by various physiochemical techniques. The corrosion resistance of the coating and the effect of CNC inclusion on the corrosion protection performance of the coating were investigated through extensive electrochemical techniques (open circuit potential, polarization test, and electrochemical impedance spectroscopy) as well as in vitro immersion tests. In addition, the cytocompatibility of the coating in terms of cellular toxicity and adhesion was assessed toward human fetal osteoblast cells. SEM images revealed the formation of a defect-free and uniform SF-CNC coating with a thickness of 11.2 ± 2.5 µm on AZ31 alloy. The results of the electrochemical corrosion and in vitro immersion tests clearly demonstrated an enhanced corrosion resistance of the SF coating after the incorporation of CNCs. Compared to the unmodified Mg alloy, the SF-CNC coated AZ31 exhibited a remarkably improved cytocompatibility with a viability of 114% and excellent adhesion and spreading of human fetal osteoblast cells onto the coating surface. The findings of this work highlight the great potential of SF and CNC as bio-based nature-derived anticorrosive nanofillers for fabrication of protective and biocompatible coatings on Mg-based biodegradable orthopedic implants.

References:

[1] Wang, Jia‐Li, et al. "Biodegradable magnesium‐based implants in orthopedics—a general review and perspectives." Advanced science 7.8 (2020): 1902443.

[2] Asadi, Hamid, et al. "A multifunctional polymeric coating incorporating lawsone with corrosion resistance and antibacterial activity for biomedical Mg alloys." Progress in Organic Coatings 153 (2021): 106157.