Surface functionalization of titanium with tetracycline loaded chitosan-gelatin nanosphere coatings via EPD: fabrication, characterization and mechanism

Biomedical metallic materials, such as titanium and stainless steel, have already been used in the clinic and tissue engineering fields for many years. However, the bio-inert surface limited and challenged their applications. The present study aimed to fabricate and characterize chitosan-gelatin (CSG) nanosphere based antibacterial coatings for surface functionalization of biomedical metallic materials. A CSG nanosphere coating was fabricated on titanium substrate via electrophoretic deposition (EPD). Tetracycline (Tc), as a model functional agent, was loaded into the coating during fabrication. The mechanism of fabricating Tc loaded CSG nanosphere coatings via EPD was investigated for the first time. Characterization of the coatings showed nanosphere structure, and nanospheres can be released from the coatings. The entrapment of Tc was confirmed by fluorescent microscope, Fourier transform infrared spectroscopy and X-ray diffraction. It could also be proved that new hydrogen bonds formed between Tc and gelatin, as well as the increased crystallinity of the coating. Mechanical test demonstrated enhanced mechanical interlocking in the coating-titanium interface of the high Tc concentration group. After coating preparation, the antibacterial effect of Tc was preserved both qualitatively and quantitatively. These results suggested that a Tc loaded CSG nanosphere coating could be successfully fabricated via EPD, and used for the functionalization of a titanium substrate. CSG nanosphere coating loaded with other functional agents would be a promising surface functionalization strategy for biomedical metallic materials.