Inativacao fotodinamica e fototermica de Escherichia coli e Staphylococcus aureus via nanoparticulas de polimeros conjugados

Abstract

This work investigated the synthesis, characterization and photodynamic action of nanoparticles (NPs) of the conjugated polymers (PCs) poly-(2,5-dihexyloxy-cyanoterephthalylidene) (Cn-PPV), poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT) and the new blend, derived from the mixture of Cn-PPV and PCPDTBT, named Cn-TBT, whose nanostructures were called Cn-TBT-NPs, aiming at bacterial photoinactivation. The efficacy of these NPs was evaluated against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), using visible light irradiation. The NPs demonstrated efficiency in the generation of reactive oxygen species ROS and ¹O₂, in addition to inducing photothermal effects when irradiated with infrared laser (806 nm), resulting in bacterial inviability. Among the synthesized NPs, Cn-TBT-NPs stood out for combining the photodynamic and photothermal properties of the original polymers, resulting in greater efficiency in the inactivation of S. aureus when subjected to a concentration of 8 µg mL-1. This greater efficiency can be attributed to the greater permeability of the S. aureus cell wall, facilitating penetration. Cn-TBT-NPs also showed a higher yield in the generation of ¹O₂. In contrast, E. coli, a Gram-negative bacterium with a more complex cell wall structure, required a concentration greater than 16 µg mL-1 to achieve similar inactivation. The results suggest that Cn-TBT-NPs have great potential as photosensitizers, especially in the fight against Gram-positive bacteria. The synergy between photodynamic and photothermal effects, combined with the visible light absorption capacity, offers a promising approach for antimicrobial photodynamic inactivation. This study reinforces the importance of developing new nanostructures in the fight against antimicrobial resistance, providing an effective and safe alternative to conventional treatments.

Keywords: Photoinduced processes, Applied nanotechnology, Materials engineering and Inactivation mechanisms.