Polymethine dyes incorporated in PLGA nanoparticles: New nanophotosensitizers with potential application in antimicrobial PDT

The wide spread of antibiotic resistance is closely connected to the high index of human morbidity and mortality, as well as hospital costs. The developed antibiotic resistant strains of bacteria to conventional antibiotic therapy imply the demand for alternative treatments for infectious diseases. In this context, over the recent years, antimicrobial photodynamic therapy (aPDT) has emerged as a promising strategy to improve antimicrobial treatments. Despite the high number of photosensitizers (PSs) designed for aPDT, the search for ideal PSs with high selectivity and suitable photochemical properties is still in progress. Among the different PSs, organic Near Infrared (NIR) polymethine dyes (i.e Squaraines, SQs and Cyanines, CYs) has attracted considerable attention for a wide range of application such as PDT and theragnostic, thanks to their excellent photochemical properties with strong absorbance in the NIR, perfectly matching the phototherapeutic window [1]. Nevertheless, their poor solubility and stability in physiological conditions still limit their wide application. To overcome these drawbacks, a possible solution would be the incorporation of these dyes inside nanoparticles (NPs), which, in addition to preventing the formation of dye aggregates in aqueous media and protecting their photochemical characteristics, have shown an important role in the treatment of infection [2,3].