Improving the cell adhesion and antibacterial behaviour on Ti6Al4V through micro and nano hierarchical laser surface texturing

Abstract

Titanium alloy (Ti6Al4V) is widely recognized for its use in orthopaedic and dental implants due to its exceptional mechanical properties and biocompatibility. However, a plain Ti6Al4V surface may not be sufficient to ensure optimal integration and performance when implanted in the body due to the limited interfacial area. The long-term performance of such implants can be compromised due to insufficient cell adhesion and bacterial infections. Therefore, it is necessary to improve biocompatibility by enhancing the cell adhesion and antibacterial surface response. It has been observed that microscale features on implant surfaces can enhance cellular integration, while nanoscale features could damage bacterial cell membranes and thus improve antibacterial efficacy. This study investigates the development of hierarchical textured surfaces that combine microscale features generated using a nanosecond laser with superimposed sub-micron ripple structures produced by a femtosecond laser. Microscale patterns were formed through direct laser ablation, while nanoscale laser-induced periodic surface structures (LIPSS) were formed on top of these patterns using femtosecond laser processing. NIH3T3 fibroblast cells and Escherichia coli (E. coli) bacteria were cultured separately on these hierarchically textured surfaces alongside two control surfaces, a manually polished surface and a LIPSS-textured surface, and analyzed after 24 h using confocal microscopy. The results reveal approximately 230 % improvement in cell density and 14.5 % increase in cell spreading compared to the control surfaces. Additionally, the hierarchical textures demonstrated approximately 81.5 % dead bacterial cells on the surface. These findings suggest that laser-based hierarchical surface texturing can effectively enhance cell adhesion and antibacterial properties, making this technique a very promising approach for developing advanced Ti6Al4V implants and in general for other biomedical applications.