Construction and Properties of SPI/PLA-PCL Composite Coating on Pure Titanium Surface

Titanium and titanium alloys have been widely used in clinical implants such as dental implants due to their high strength and corrosion resistance. However, their inherent biological inertness and mismatch with the elastic modulus of human bone tissue restrict bone healing and reconstruction. In this study, pure titanium was first modified by micro-arc oxidation (MAO), and then a biodegradable soybean protein isolate (SPI)/polylactic acid (PLA)-polycaprolactone (PCL) composite coating was prepared by using the spin-coating method. The coating was systematically characterized by scanning electron microscopy (SEM), an energy spectrometer (EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and atomic force microscopy (AFM), confirming that the composite coating was successfully prepared. An evaluation of the physical and chemical properties showed that the introduction of SPI significantly improved the hydrophilicity, surface roughness and adhesion to the substrate of the coating, regulated the degradation rate, and reduced the elastic modulus to the range of 10-30 GPa, which matches human bone tissue. At the same time, it enhanced corrosion resistance. In vitro MC3T3-E1 osteoblast experiments showed that the coating containing 50% SPI showed better cell compatibility, adhesion ability and osteogenic inducibility, and all groups had good blood compatibility. The SPI/PLA-PCL composite coating effectively improves the biological activity of the pure titanium surface and provides a feasible strategy for the surface modification of titanium implants and bone defect repair.