Gold Nanorods as Photothermal Antibacterial Materials

Biomaterial-associated infections (BAIs) are a considerable challenge in modern medicine, limiting the use of many important medical devices and causing severe patient discomfort as well as high societal costs. The reduced susceptibility of biofilm-forming bacteria to antibiotics, along with the increased occurrence of antimicrobial resistant pathogens, have incited an interest in the development of antibacterial biomaterial modifications that can combat BAIs. In the present work, we have developed a biomaterial modification strategy using surface-immobilized photothermal gold nanorods (AuNRs). AuNRs were immobilized on glass and titanium substrates with well-defined surface coverage of 12-14%, leaving most of the substrate surface unmodified. The antibacterial activity of the AuNR-functionalized materials against Staphylococcus aureus and Escherichia coli was evaluated after irradiation with a near-infrared (NIR) laser (808 nm) at different laser intensities. The AuNR-functionalized glass demonstrated prominent light intensity dependent antibacterial activity upon NIR irradiation, caused by plasmonic heating of the AuNRs, against both S. aureus and E. coli. In contrast, on titanium the NIR light-induced thermal antibacterial activity was attributed to light absorption by the substrate itself, with no significant effect from the AuNRs. This study provides valuable insights into the role of the substrate properties in developing antibacterial biomaterial modifications using gold nanorods and NIR light, and it furthermore demonstrates the potential of using these systems in combatting BAIs.