Peroxidase-like behavior and photothermal effect of chitosan-coated Prussian-blue nanoparticles: Dual-modality antibacterial action with enhanced bioaffinity

Abstract

We have probed the antibacterial potential of Prussian blue nanoparticles, without (PB) and with (CHPB) chitosan-coating. Both these nanoparticles showed peroxidase-like behavior by degrading hydrogen peroxide and generating toxic reactive oxygen species (ROS). The nanoparticles also showed a photothermal effect by generating heat (hyperthermia) upon activation with 635 nm laser light. The antibacterial activity resulting from the combined peroxidase-like behavior and photothermal effect of these nanoparticles was explored in both Gram-positive and Gram-negative bacteria. It was observed that CHPB nanoparticles showed much higher antibacterial activity than PB nanoparticles, which is attributed to the favorable electrostatic interaction at the nanoparticle-bacteria interface upon chitosan coating. Further light activation led to enhanced antibacterial action, with near-complete bacterial cell death observed at CHPB treatment concentrations of 75 μg ml-1 for Gram-negative bacteria and 125 μg ml-1 for Gram-positive bacteria. The mechanism of antibacterial action of the nanoparticles was also explored though a series of assays, such as electron microscopic analysis of nanoparticle-bacteria binding, membrane depolarization, protein leakage, intracellular ROS generation, etc. Based on these studies, we conclude that CHPB nanoparticles act as robust dual-modality antibacterial agents with enhanced affinity at the nanoparticle-bacteria interface.