Antimicrobial Photothermal Treatment of Pseudomonas Aeruginosa by a Carbon Nanoparticles-Polypyrrole Nanocomposite

Background: Nowadays, it is needed to explore new routes to treat infectious bacterial pathogens due to prevalence of antibiotic-resistant bacteria. Antimicrobial photothermal therapy (PTT), as a new strategy, eradicates pathogenic bacteria. Objective: In this study, the antimicrobial effects of a carbon nanoparticles-polypyrrole nanocomposite (C-PPy) upon laser irradiation were investigated to destroy the pathogenic gram-negative Pseudomonas aeruginosa. Material and Methods: In this experimental study, the bacterial cells were incubated with 50, 100 and 250 μg mL-1 concentrations of C-PPy and irradiated with a 808-nm laser at two power densities of 0.5 and 1.0 W cm-2. CFU numbers were counted for the irradiated cells, and compared to an untreated sample (kept in dark). To explore the antibacterial properties and mechanism(s) of C-PPy, temperature increment, reactive oxygen species formation, and protein and DNA leakages were evaluated. Field emission scanning electron microscopy was also employed to investigate morphological changes in the bacterial cell structures. Results: The results showed that following C-PPy attachment to the bacteria surface, irradiation of near-infrared light resulted in a significant decrement in the bacterial cell viability due to photothermal lysis. Slightly increase in protein leakage and significantly increase intracellular reactive oxygen species (ROS) were observed in the bacteria upon treating with C-PPy. Conclusion: Photo-ablation strategy is a new minimally invasive and inexpensive method without overdose risk manner for combat with bacteria.