Investigation of the photodynamic antimicrobial effect of led LİGHT with 660 NM wavelength

Photodynamic therapy (PDT); it is defined as the generation of reactive oxygen species in the target cell with the application of light at the appropriate wavelength and dose and the termination of the viability of these cells. Reactive oxygen radicals formed by light activation as a result of PDT irreversibly impair the structure and function of the cell. In this study, the photodynamic effect of LED light with a wavelength of 660 nm on some pathogenic microorganisms (Staphylococcus aureus ATCC 25923, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Bacillus subtilis ATCC 6633, Candida albicans ATCC 90028, Candida parapsilosis ATCC 90018, Candida tropicalis ATCC 750) was investigated. The LED light source with a wavelength of 660 nm, which was used as a light source in the study, was applied to certain microorganism suspensions at certain time intervals (5, 30, 60, 120, 240, 480 min) in light and dark environments. The morphological changes of the cells with photoinactivation were examined by Gram staining, and the viability of microorganisms was examined using a thoma slide and Live/Dead viability kit. Gel electrophoresis method was used to determine DNA damage. As a result of the study, no inhibition effect was observed on S. aureus of the LED light source used, but photoinactivation effect was detected on B. subtilis, P. aeruginosa and E. faecalis at certain dilutions and at different times. It was observed that there was a change in the morphological structures of the microorganisms from which photoinactivation was obtained, and this change was more evident especially in yeasts. As a result of photoinactivation, it was observed that the viability and the cell number of microorganisms decreased, and the results were found to be compatible with thoma slide and fluorescent microscope images. It has been found that LED light with a wavelength of 660 nm has a photodynamic effect on these pathogenic microorganisms.