Functionalized Surface Micro/Nano-textures of Titanium-based Alloys for Bioimplant Applications: A Review

Titanium-based alloys exhibit low elastic modulus, high strength, and a density close to that of human bones, and are widely used in artificial joints, dental implants, cardiac stents, and other replacement surgeries. However, the clinical requirements for the service performance of titanium implants are constantly evolving. Promoting rapid tissue healing and ensuring long-term stability are the latest requirements. A lack of a tight fit between the implant and the body tissues causes mismatch between the implant and the bone tissues, inflammation, and fibrous pockets. Biomimetic studies have shown that altering the micro-nanomorphology of the surface of the titanium implant can improve the ability of the implant to bond with the bone tissue and enhance the mechanical and biological properties of the titanium implant. Surface texturing techniques have become an important means to effectively enhance the biocompatibility of titanium implants with bone tissue. This paper summarizes the fabrication methods of surface textures of titanium implants from the perspectives of additive, subtractive, and equal-material manufacturing. The advantages and disadvantages of existing texture preparation techniques are analyzed. The impact of different textures on the biocompatibility performance of implants is comprehensively reviewed. The mechanisms through which micro-textures, nano-textures, and micro-nano composite textures modulate biological behaviors such as protein adsorption, cell adhesion, and migration are discussed. Compared to single micro- or nano-textures, micro-nano composite textures can better simulate the microenvironments of natural tissues, thus promoting integration between implants and surrounding tissues. Finally, suggestions for developing novel surface texturing techniques and micro-nano composite textures are proposed.