Hydrogel-embedded gold nanorods activated by plasmonic photothermy with potent antimicrobial activity

Plasmonic photothermal therapy (PPTT) has been used as an alternative to chemotherapy for the elimination of resistant microorganisms; however, its in situ evaluation has not been well studied. In the present study, we assessed the antimicrobial activity of a chitosan-based hydrogel embedded with gold nanorods (Ch/AuNRs) using a low power infrared diode laser. The antibacterial activity was measured in both Gram-positive and -negative strains, including clinical isolates of multidrug-resistant pathogens. The cytotoxic effect, cellular proliferation, and the expression of the pro-inflammatory (IL-6 and TNF-α) and anti-inflammatory (IL-10) cytokines were quantified in a murine model of macrophages. Results showed a potent antimicrobial activity of the Ch/AuNRs with MICs ≤4 μg/mL, very low cytotoxicity with cell viability above 80%, and the macrophage proliferation was not affected for a period of 48 h. These results suggest that our Ch/AuNR-embedded hydrogel could be an option to locally control chronic nosocomial infections using PPTT.