Photoinactivation of Escherichia coli using five photosensitizers and the same number of photons

Abstract

Bacterial resistance is today a matter of great medical concern, so it is urgent to investigate alternatives to alleviate it. Photodynamic inactivation (PDI) is a method that has been endorsed to inactivate different pathogens, including bacteria, fungi and viruses. PDI is achieved by using a photosensitizer (PS) molecule which generates reactive oxygen species under visible or UV radiation. We use visible light and UV-A radiation to excite four commercial PSs (methylene blue, rose bengal, riboflavin and curcumin), and nanoparticles synthesized in our laboratory. Despite these PSs having been thoroughly studied in the past by other research groups, in order to compare their effects in an appropriate way, we matched the number of photons they absorb. We found that methylene blue leads to the major inactivation of Escherichia coli. Furthermore, we evaluated the production of singlet oxygen and hydroxyl radicals in the photoinactivation process.