Photothermal Antibacterial Activity of Gold Nanorods Stabilized by Phospholipid

In this paper, thermal stability of phospholipid-decorated gold nanorods and their photothermal activity against Staphylococcus epidermidis were experimentally studied. For this aim, cetyl trimethyl ammonium bromide (CTAB) stabilized gold nanostructures were first synthesized, and then the chemical bilayers were exchanged with phospholipid (DMPC). The effects of this replacement on the shape and spectral properties of gold nanorods were analyzed by UV–vis and FTIR as well as transmission electron microscopy (TEM). In addition, thermal heating at 95 ± 2 °C caused CTAB-decorated gold nanorods to decompose in less than half an hour, whereas the phospholipid-modified gold nanorods maintained their spectral characteristics for up to 5 h. Furthermore, while the minimum inhibitory concentration (MIC) for CTAB-AuNRs was obtained equal to 5 μg/ml, DMPC-AuNRs did not indicate significant toxicity in concentrations below 20 μg/ml. The photothermal-induced bactericidal activity of DMPC-gold nanorods was investigated through illumination by a laser with the wavelength of 808 nm. It was demonstrated that treating Staphylococcus epidermidis with the nontoxic concentration of phospholipid-stabilized gold nanorod suspension followed by the laser beam exposure for 15 min resulted in a 4.6 log reduction in the bacterial viable count.