Multiscale Hierarchical Micro- and Nano-Surface Induced by High-Repetition-Rate Femtosecond Laser Promote Peri-Implant Osseointegration

Micro- and nanomorphological modification and roughening of titanium implant surfaces can enhance osseointegration; however, the optimal morphology remains unclear. Laser processing of implant surfaces has demonstrated significant potential due to its precision, controllability, and environmental friendliness. Femtosecond lasers, through precise optimization of processing parameters, can modify the surface of any solid material to generate micro- and nanomorphologies of varying scales and roughness. Inspired by the multiscale micro- and nanostructures of natural bone tissue, this study employed a high-repetition-rate femtosecond laser to fabricate three distinct micro- and nanomorphologies on titanium implant surfaces, characterized by low (LTi), medium (MTi), and high (HTi) roughness, exhibiting multiscale coexistence. Comprehensive characterization of the modified surfaces included analysis of morphology, roughness, wettability, and elemental composition. Furthermore, in vitro and in vivo experiments were conducted to evaluate osteogenic differentiation and osseointegration capabilities. Results revealed that the HTi surface, exhibiting high roughness, presents a multiscale hierarchical micro- and nanostructure composed of micrometer-sized spheres, submicrometer-sized corrugations, and nanometer-sized particles. In vitro studies demonstrated that the HTi surface promoted earlier adhesion, spreading, and enhanced osteogenic differentiation of osteoblasts, while in vivo studies indicated improved bone formation and osseointegration. In conclusion, multiscale hierarchical micro- and nanosurfaces with high roughness generated by high-repetition-rate femtosecond laser processing hold considerable promise for titanium implant applications.