Materials, Processing and Assessment for Bioengineering Applications

Abstract

Titanium alloys, in particular Ti6Al4V, are the current standard of care for orthopedic implants due to their good biological response. But issues such as infection susceptibility and implant failure due to poor osteointegration and stress shielding persist. Furthermore, orthopedic implant infections are challenging to detect and not always completely solved by systemic antibiotic delivery. Thus, it is essential to develop implants with antibacterial properties to prevent infections and antibiotic resistance due to frequent antibiotic delivery, while promoting integration with surrounding tissues and reducing the revision surgeries rate. Biomaterial-tissue interactions at the implant interface play a crucial role in its operation, influencing tissue attachment. The surface of an implant also affects how bacterial pathogens interact and create biofilms. The complexity of the relationship between biomaterial composition, device design, and biological response in living organisms presents challenges in predicting the outcome of the implant. In vitro methods are valuable but have limitations, necessitating the improvement of predictive models. The focus of this work is modifying the surface of the Ti6Al4V titanium alloy, commonly used in skeletal fixation devices. The goal is to address issues related to poor integration, infection, and metal sensitivity. Surface modification techniques, involving mechanical and thermal mechanisms, are herein explored to provide some guidelines for the prediction and modulation of performance. The studied techniques include grit blasting, milling, electrical discharge machining, laser texturing, and coating deposition. The aim is to deepen the influence of implant surface properties on its performance and biological response, with a multi-level approach: (i) modulate the integration of the implants with surrounding bone tissues by acting on surface properties (i.e. surface roughness, microstructure, chemistry, contact angle), employing material deformation and removal techniques, and studying the effects on in vitro bone cells response; (ii) improve the to date insufficient adhesion of biopolymer coatings made of chitosan by: tuning film properties through different deposition techniques, coating composition, and substrate properties; (iii) preliminary analyze the effect of surface modification techniques on in vitro bacterial response.