Use of visible light-based photodynamic therapy to bacterial photoinactivation

The main focus of this laboratory exercise was to investigate the photodynamic therapy ( PDT) acting over Streptococcus mutans. A handheld photopolymerizer and a classical photosensitizer ( Rose Bengal) were used to induce photodynamic response. In this way, a suspension of S. mutans was treated with different concentrations of Rose Bengal ( 0 - 10 mumol/liter), irradiated with a light ( 400 - 600 nm) for 20 s, and then cell viability was evaluated. It was observed that the light ( per se) is not toxic, and in the dark, Rose Bengal is toxic only to the cells tested at concentrations above 5.0 mumol/liter. Under light exposure, concentrations of Rose Bengal above 0.5 mumol/liter killed all S. mutans. Therefore, for the purpose of our work, the photoactivation of Rose Bengal using the handheld photopolymerizer was efficient in bacteria inactivation.