Surface characteristics and bioactivity of mussel-inspired coating for implant

As a robust structural element for spontaneous deposition of bone-stimulating agents, tightly adherent polydopamine (PDA) layer was coated with titanium (Ti) by self-polymerisation to achieve a facile surface-modified orthopedic implant in this paper. The surface characteristics and bioactivity of the self-polymerised dopamine-coated titanium implant were investigated by spectroscopic ellipsometry, atomic force microscopy (AFM), contact angle test, X-ray photoelectron spectroscopy, electrochemical measurements and in vitro cell experiment. In the results, the thickness of self-polymerised dopamine film increased with time as measured by spectroscopic ellipsometry. A concavo-convex morphology of PDA film was observed by AFM, and the contact angle analysis showed an increase in surface hydrophilicity. Both the polarisation curves and electrochemical impedance spectroscopy demonstrated that the PDA film acts as a passive barrier, along with the spontaneously formed compact oxide layer, to further strengthen the corrosion resistance of titanium. In vitro MC3T3-E1 cell adhesion and alkaline phosphate activity on PDA-coated titanium were both significantly improved compared with those on the uncoated titanium. The self-polymerised PDA-coated titanium implant showed better hydrophilicity, higher corrosion resistance and enhanced bioactivity and was demonstrated as a reliable surface modification method.