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 and antibacterial properties [2]. In this study, a bi-layered anti-corrosive polymeric coating based on polycaprolactone (PCL) and lawsone, a natural corrosion inhibitor extracted from the leaves of Lawsonia inermis plant, was fabricated on AZ31 Mg alloy to improve its corrosion resistance. The result of electrochemical and in vitro immersion studies clearly demonstrated the corrosion inhibitory effect of lawsone and the enhanced corrosion resistance of AZ31 alloy by almost two orders of magnitude (inhibition efficiency of 98.3%) after being coated with PCL-lawsone. Moreover, coated AZ31 substrates exhibited significantly hampered local alkalization and excessive H₂ generation. Apart from the corrosion inhibition properties, incorporation of lawsone imparted a strong antibacterial activity to the coating, which is helpful in the prevention of microbial infection and early implant failure. While most of the commonly used corrosion inhibitors are known to be toxic and have limited biomedical applications, no cytotoxic effect was observed for lawsone-containing coating toward human fetal osteoblast cells (viability of > 85%). The findings of this work highlighted the great potential of lawsone as a natural corrosion inhibitor for fabrication of corrosion protective, antibacterial, and biocompatible coatings on Mg-based biodegradable 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.