A singlet state oxygen generation model based on the Monte Carlo method of visible antibacterial blue light inactivation.

Abstract

Visible antibacterial blue light (VABL) has received much attention recently as a nondestructive inactivation approach. However, due to the sparse distribution of bacteria, the light energy evaluation method used in existing studies is inaccurate. Thus, the sensitivity of microorganisms to VABL in different experiments cannot be compared. In this paper, a Monte Carlo-based photon transport model with the optimized scattering phase function was constructed. The model calculated the spatial light energy distribution and the temporal distribution of cumulative singlet state oxygen (CSO) under various cell and medium parameters. The simulation results show that when the cells are sparsely distributed, <30% of light energy from the light source is absorbed by microbes and participates in photochemical reactions. The CSO produced increases with cell density and cell size. Little light energy is available, and thus, the concentration of CSO produced is insufficient to inactivate microbes at deeper depths. As the light intensity and inactivation time increased, the production of singlet state oxygen tended to level off. The model proposed here can quantify the generation of singlet state oxygen and provide a more accurate light energy guide for the VABL inactivation process.