Combining gold nanorods and antimicrobial peptides for combating biomaterial- associated infections

Abstract

Biomaterials are materials that interact with living tissues and are widely used in modern biomedical devices such as implants. Despite their benefits, inserted biomedical implants are commonly infected by biofilm forming bacteria. Biofilms protect the bacteria from immune responses and antibiotic agents, and often require high doses of antibiotics to be eradicated. Due to patient suffering, clinical costs, and the threat of increased antimicrobial resistance, numerous developments in non-antibiotic antibacterial surface alterations has been made. This thesis investigates a biomaterial surface modification strategy utilizing surface-immobilized gold nanorods (AuNRs) and antimicrobial peptides (AMPs). AuNRs generate heat under near-infrared (NIR) irradiation, killing bacteria, while AMPs offer potent antimicrobial properties. This project aims to investigate the functionalization of AMPs onto material-supported AuNRs, and compare the combined antibacterial effect of NIR-activated AMP-AuNRs with the photothermal effect from only using AuNRs.

Material preparation included AuNR synthesis and AuNR surface immobilization. Vis-NIR spectroscopy was used to verify that the materials would exhibit a photothermal effect upon irradiation with the NIR laser, and scanning electron microscopy was used to quantify AuNR dimensions. Vis-NIR spectroscopy and water contact angle measurements showed that AMPs successfully attached to the AuNRs. The antibacterial evaluation revealed that the AMP-AuNRs did not show a synergistic bactericidal effect upon NIR laser irradiation compared to surfaces with only AuNRs. Some samples exhibited irregularities probably caused by handling errors, which limits the reliability and validity of the results. In order to draw firm conclusions, repeated testing with more rigorous experimental execution uniformity is needed. All in all, this project provided insight into AMP functionalization onto gold nanorods, as well as their antibacterial function in conjuction with photothermal agents.