Photoinactivation of Multidrug-Resistant <i>mcr-1</i>-Positive <i>E. coli</i> Using PCPDTBT Conjugated Polymer Nanoparticles under White Light

The issue of antimicrobial resistance is an escalating concern within the scope of global health. It is predicted that the existence of antibiotic-resistant bacteria might result in an estimated annual death of up to 10 million by 2050, along with possible economic losses ranging from 100 to 210 trillion. This study reports the production of poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-<i>alt</i>-4,7(2,1,3-benzothiadiazole)] nanoparticles (PCPDTBT-NPs) by nanoprecipitation as an alternative to tackle this problem. The size, shape, and optical features of these conjugated polymer NPs were analyzed. Their efficacy as photosensitizers against nonresistant (ATCC) and multidrug-resistant <i>mcr</i>-1-positive <i>Escherichia coli</i> was assessed under white light doses of 250 and 375 J·cm^-2. PCPDTBT-NPs inactivated both <i>E. coli</i> strains exposed to white light at an intensity of 375 J·cm^-2, while no antimicrobial effect was observed in the group not exposed to white light. Reactive oxygen species and singlet oxygen were detected using DCFH-DA and DPBF probes, allowing the investigation of the photoinactivation pathways. This work showcases PCPDTBT-NPs as photosensitizers to eliminate multidrug-resistant bacteria through photodynamic inactivation employing visible light.