Surface modification of titanium with hydroxyapatite layer induced by phase-transited lysozyme coating

Highlights: • The technology of phase-transited lysozyme is a simple, rapid, low-cost and green process for surface modification. • The technology of phase-transited lysozyme can assist hydroxyapatite formation on the surface of titanium in SBF. - Abstract: Surface modification of titanium with a hydroxyapatite (HAP) coating can improve the bioactivity of pristine titanium. The traditional techniques for coating HAP on titanium involve nonmild treatments using strong bases or acids or high temperatures. In this study, the coating of HAP was carried out by a novel methodology called phase-transited lysozyme-assisted hydroxyapatite formation (PAH); in this process of biomimetic mineralization, the abundant functional carboxyl groups of phase-transited lysozyme (PTL) were responsible for the nucleation of HAP crystals by concentrating Ca²⁺ ions at the interface between PTL and CaCl₂ solution and for the subsequent growth of HAP crystals occurring in simulated body fluid (SBF). In vitro and in vivo experiments verified that the surface of titanium modified with the HAP/PTL-Ti multilayer was endowed with improved biocompatibility and osteoinductivity compared with those of pristine titanium. Therefore, PAH is a simple, rapid, low-cost and green process for the surface modification of titanium with an HAP coating and thus will be a promising methodology for the surface modification of titanium implants.