Natural-synthetic hybrid nanoparticles: Polydopamine-Phycocyanin composites for enhanced antibacterial phototherapy...

The rapid rise of antibiotic-resistant bacterial infections demands innovative, non-antibiotic strategies to combat pathogens without driving further resistance. In this study, we developed polydopamine-coated phycocyanin nanoparticles (PDA@PC) by encapsulating the natural antioxidant phycocyanin (PC) within a polydopamine (PDA) matrix. These nanoparticles (146 nm) combine PDA's photothermal and photodynamic properties with PC's antioxidant activity, enabling dual-mode antibacterial action under near-infrared (NIR) laser irradiation. PDA@PC demonstrated excellent biocompatibility (>70 % cell viability) and blood compatibility (<5 % hemolysis), outperforming PDA alone at high doses. Under laser exposure, PDA@PC generated heat and reactive oxygen species (ROS), achieving >50 % inhibition of bacterial biofilms and significant reductions in colony counts for Staphylococcus aureus and Pseudomonas aeruginosa. The nanoparticles also showed enhanced antibacterial efficacy against S. aureus, with minimal inhibitory concentrations (MIC) comparable to conventional antibiotics. By doubling the catechol content of PDA, PDA@PC amplified ROS production while mitigating oxidative stress, offering a safe and effective platform for treating resistant infections. This work highlights the potential of PDA@PC as a multifunctional, laser-activated nano therapy to replace traditional antibiotics and combat the global antimicrobial resistance crisis.