The Significance of Crystallographic Texture in Dry Etching of Titanium to Engineer Bioinspired Nanostructured Bactericidal Surfaces

Titanium is the prevalent material of choice for metallic implantable devices. However, post-operative bacterial infections remain a major cause of implant failure. Mechanobactericidal surfaces have garnered much attention due to their ability to neutralize bacteria, via physical forces and interactions instead of traditional chemical routes. In this work, the texture of titanium substrates was modified via cold rolling, hot rolling, and annealing treatments, and the resultant crystallographic textures were characterized. Subsequently, nanoscale topographies were generated on the substrates via maskless plasma etching. The results indicated the subtle differences in the topographies of substrates with different textures being critical factors affecting the etching process. All the substrates were then assessed for bactericidal activity against P. aeruginosa and S. aureus bacteria, with killing efficiencies reaching up to 50% for P. aeruginosa. The nanostructures were ineffective against S. aureus due to the presence of a thick peptidoglycan layer in their cell walls. Detailed statistical analysis showed that, in the case of P. aeruginosa, texture plays a significant role in determining the killing efficiency, due to its subtle effects on the etching process and consequently nanostructure dimensions. The results of this study emphasize the importance of material processing in the engineering and development of the next generation of mechanobactericidal surfaces.