Nano-Photothermal ablation effect of Hydrophilic and Hydrophobic Functionalized Gold Nanorods on Staphylococcus aureus and Propionibacterium acnes

The potential photothermal bactericidal activity of hydrophilic functionalized poly ethylene glycol (PEG)-gold nanorods (GNR) and hydrophobic functionalized polystyrene (PS)-GNR was evaluated towards strains of Staphylococcus aureus (S. aureus) and Propionibacterium acnes (P. acnes) by measuring the percentage reduction of bacterial viable count upon GNR excitation with a near infra-red (NIR) laser beam. Our results suggest that functionalized GNR had a minimal bactericidal activity against S. aureus and P. acnes (≤85%, i.e. ≤1 log(10) cycle reduction of bacterial viable count). However, the local heat generated upon exciting the functionalized GNR with NIR laser beam has a significant photothermal ablation effect (≥99.99%, i.e. ≥4 log(10) cycles reduction of bacterial viable count). Such photothermolysis effect could potentiate the antibacterial activity of GNR, which may call for minimum concentration and side effects of these nanotherapeutics.