Characterisation of bactericidal titanium surfaces using electron microscopyPart of:
Background and objectives
Despite major improvements in surgical procedures, bacterial infections remain a leading cause of titanium implant failure. Given the significant failure rates in treating implant associated infections, novel approaches are urgently needed to prevent the development of pathogenic biofilms on titanium implants. The specific objectives of this research are to generate nanostructured titanium surfaces that efficiently kill bacteria upon contact, which could be used to develop next generation, anti-infective implants. By studying how bacteria interact with, and respond to titanium dioxide nanostructure arrays, we aim to apply this understanding to design the most effective antibacterial implant surface.
Thermal oxidation was used to generate a library of titanium dioxide nanostructure arrays on grade 5 titanium surfaces. The antibacterial performance of each nanostructured surface was determined by metabolic indicator assays, bacterial viability techniques and confocal microscopy. Electron microscopy techniques (SEM, TEM and FIB-SEM) were used to visualise the interactions between bacteria and nanostructures and determine their effects on bacterial morphology. Quantitative proteomic approaches (TMT) were used to investigate the impact of nanostructures on bacterial cell physiology
Significant reductions in viability were observed against Gram-positive (Staphylococcus aureus, Staphylococcus epidermidis) and Gram-negative (Escherichia coli, Klebsiella pneumoniae) bacteria. Combined imaging analysis confirmed that nanostructures can stretch and penetrate the bacterial cell envelope upon contact. Nanostructures also acted as physical barriers, effectively trapping cells and impeding their growth.
Titanium dioxide nanostructured surfaces showed a broad antimicrobial effect compared to flat titanium surfaces; the interplay between envelope stretching and cell trapping are proposed to have caused the reduction in bacterial viability.