Biomimetic Hydroxyapatite Composite Coatings with a Variable Morphology Mediated by Silk Fibroin and Its Derived Peptides Enhance the Bioactivity on Titanium.

Various modifications performed on titanium alloy surfaces are shown to improve osteointegration and promote the long-term success of implants. In this work, a bioactive nanostructured hydroxyapatite (HA) composite coating with a variable morphology mediated by silk fibroin (SF) and its derived peptides (Cs) was prepared. Numerous experimental techniques were used to characterize the constructed coatings in terms of morphology, roughness, hydrophilicity, protein adsorption, in vitro biomineralization, and adhesion strength. The mixed protein layer with different contents of SF and Cs exhibited different secondary structures at different temperatures, effectively mediating the electrodeposited HA layer with different characteristics and finally forming proteins/HA composite coatings with versatile morphologies. The addition of Cs significantly improved the hydrophilicity and protein adsorption capacity of the composite coatings, while the electrodeposition of the HA layer effectively enhanced the adhesion between the composite coatings and Ti surface. In the in vitro mineralization experiments, all the composite coatings exhibited excellent apatite formation ability. Moreover, the composite coatings showed excellent cell growth and proliferation activity. Osteogenic induction experiments revealed that the coating could significantly increase the expression of specific osteogenic markers, including ALP, Col-I, Runx-2, and OCN. Overall, the proposed modification of the Ti implant surface by protein/HA coatings had good potential for clinical applications in enhancing bone induction and osteogenic activity of implants.