NIR-induced antimicrobial efficacy of TPA-BOIMPY conjugate through photothermal and photodynamic synergy

Microbial infections, particularly those produced by multidrug-resistant bacteria, are a major risk to global wellness. In place of conventional antibiotics, photothermal therapy (PTT) and photodynamic therapy (PDT) use light-activated antimicrobial agents to transform near-infrared (NIR) light into heat and reactive oxygen species (ROS), respectively, which effectively eradicate pathogens. This study explored the potential of a new organic dye, bis-(borondifluoride)-8-imidazodipyrromethene (BOIMPY), as a NIR PTT/PDT agent. To increase its phototherapy characteristics, triphenylamines (TPA) were conjugated to BOIMPY to yield TPA-BOIMPY, and Pluronic F127 was utilized to improve the hydrophilicity of TPA-BOIMPY by forming TPA-BOIMPY@F127 nanoparticles with an average particle size of 79 nm. These nanoparticles exhibited a maximum absorption peak at 757 nm, a photothermal conversion efficiency of 34 %, a singlet oxygen quantum yield of 0.02, and excellent photostability. Under 808 nm NIR irradiation, TPA-BOIMPY@F127 remarkably reduced the viability of both E. coli and S. aureus to 0.4% and 7.3%, respectively. The exceptional photostability and promising PTT/PDT capabilities of TPA-BOIMPY@F127 highlight its potential as a new class of NIR PTT/PDT agents for combating bacterial infections, contributing to the ongoing development of innovative therapeutic strategies.