Magainin-modified polydopamine nanoparticles for photothermal killing of bacteria at low temperature

Photothermal therapy (PTT) is a promising method to kill bacteria because of the broad-spectrum of antibacterial activity and the ability of spatiotemporal regulation. In the previously reported systems, light induced high temperature (˜70 °C) was essential for effectively killing of bacteria, which, however, would also damage nearby nontarget cells or tissues. Here we report photothermal nanoparticles (NPs) for more targeting and killing bacteria at a relative low temperature. Polydopamine (PDA) was chosen to prepare NPs because of its excellent capability of photothermal conversion. Magainin I (MagI) which is an antimicrobial peptide was used to modify NPs' surface because it can specifically interact with bacteria. We demonstrate that MagI-PEG@PDA NPs effectively killed E. coli at a low temperature of ˜45 °C upon near-infrared (NIR) light irradiation. In contrast, the native PDA NPs under light irradiation or the MagI-PEG@PDA NPs themselves showed no bacteria killing ability. This work highlights the importance of close interaction between the target bacteria and the photothermal materials and may promote the practical clinical applications of the PTT.