The demand for polymeric medical devices is expected to increase rapidly in the next few decades. However, the risk of bacterial infection of medical devices remains a major issue. Due to the problem of biomaterial-associated infections (BAIs) and growing numbers of antimicrobial resistant bacteria, it is crucial to develop novel materials that can combat BAIs. One such option is to develop a scalable nanofabrication technique that can exploit the antibacterial properties shown by nanostructured surfaces found in nature. This research project focused on the development of a scalable nanofabrication protocol to synthesise tuneable nanotopography that is compatible with a wide range of polymer substrates. The correlation between physical properties of the resulting nanopillars and antibacterial properties of the nanostructured surfaces was then investigated. Nanopillars were characterised using a range of analytical techniques, including DSA, SEM, and AFM, to quantify the contact angle, surface energy, surface roughness, and nanotribological properties. Using three model bacterial species (Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus), the antibacterial performance of the nanostructured surfaces was quantified in terms of capacity to damage the bacterial cell wall and to reduce the number of metabolically active adherent cells. It was found that the tip diameter, interpillar distance, surface energy, adhesive energy, and frictional instabilities of the nanopillars had a direct correlation with the antibacterial properties of the nanostructured surfaces. Previous theoretical work proposed that the susceptibility of particularly Gram-negative bacterial cells to nanotopography-mediated lysis is due to stretching of the bacterial cell wall and eventual rupture. To better understand the adhesive forces that may cause this cell wall rupture, this project also explored the role of bacterial surface proteins in mediating interactions with the nanostructured surfaces. Trypsinisation was found to reduce the hydrophobicity and negative charge of the bacterial cells and impaired the antibacterial action of the nanostructured surfaces. Thus, bacterial surface proteins may contribute to the antibacterial performance of nanostructured surfaces by mediating the strong adhesive forces with the nanopillars required for effective cell disruption. Taken together, these data provide important information that could be exploited to inform the fabrication of antimicrobial surfaces for polymeric medical devices and provide an experimental basis from which a new theoretical model of bacterial attachment to nanostructured surfaces may be developed.
