Cellulose nanocrystal reinforced silk fibroin coating for enhanced corrosion protection and biocompatibility of Mg-based alloys for orthopedic implant applications

In this work, a novel coating material based on silk fibroin (SF) and cellulose nanocrystals (CNCs) was developed on biodegradable AZ31 Mg alloy and assessed for corrosion resistance and biocompatibility. Before the application of the coating, AZ31 substrate was modified with a layer of polydopamine to enhance the adhesion of the protective coating to the metal surface as confirmed by the adhesion tape test. SEM images revealed the formation of a defect-free and uniform SF-CNC coating with a thickness of 11.2 +/- 2.5 mu m 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.