Building biointegration of Fe₂O₃–FeOOH coated titanium implant by regulating NIR irradiation in an infected model

Killing bacteria, eliminating biofilm and building soft tissue integration are very important for percutaneous implants which service in a complicated environment. In order to endow Ti implants with above abilities, multifunctional coatings consisted of Fe₂O₃–FeOOH nanograins as an outer layer and Zn doped microporous TiO₂ as an inner layer were fabricated by micro-arc oxidation, hydrothermal treatment and annealing treatment. The microstructures, physicochemical properties and photothermal response of the coatings were observed; their antibacterial efficiencies and cell response in vitro as well as biofilm elimination and soft tissue integration in vivo were evaluated. The results show that with the increased annealing temperature, coating morphologies didn't change obviously, but lattices of β-FeOOH gradually disorganized into amorphous state and rearranged to form Fe₂O_3. The coating annealed at 450 °C (MA450) had nanocrystallized Fe₂O₃ and β-FeOOH. With a proper NIR irradiation strategy, MA450 killed adhered bacteria efficiently and increased fibroblast behaviors via up-regulating fibrogenic-related genes in vitro; in an infected model, MA450 eliminated biofilm, reduced inflammatory response and improved biointegration with soft tissue. The good performance of MA450 was due to a synergic effect of photothermal response and released ions (Zn²⁺ and Fe³⁺).