Antimicrobial Blue Light for Treatment of Candida albicans Keratitis: Efficacy in Ex Vivo Rabbit Corneas and Safety Evaluation in Retinal Cells In Vitro.

Abstract

OBJECTIVES: To assess the efficacy of antimicrobial blue light (aBL) in managing Candida albicans keratitis in rabbit corneas ex vivo and safety to retinal cells in vitro. METHODS: C. albicans (strain CEC-749) suspensions were exposed to aBL with different light irradiance to assess the susceptibility of C. albicans to aBL. An ex vivo C. albicans keratitis model using rabbit corneas infected with a bioluminescent strain CEC-749 was developed. aBL was delivered topically to the infected corneas after fungal inoculation at varying irradiances. Bioluminescent imaging was used to track corneal infection progression in real-time. To evaluate the toxicity of aBL to the retinal cells, photoreceptors (661W) and retinal pigment epithelium cells (ARPE-19) were exposed to aBL in vitro, with cell viability and apoptosis assessed. The viability change of 661W cells under intermittent irradiation of aBL is determined. RESULTS: At varying irradiances of 25, 50, and 100 mW/cmand a constant 405 nm blue light exposure of 216 J/cm, 3.39-, 3.67-, and 2.83-log10 CFU of C. albicans were inactivated in suspensions, respectively. Bioluminescence imaging revealed that C. albicans keratitis was fully developed in ex vivo rabbit corneas 24 h following fungal inoculation. After exposure to 288 J/cmaBL, the fungal burden in the 6, 18, and 24 h-infected rabbit corneas was reduced by approximately 1.57-, 2.18-, and 1.47-log10, as determined by bioluminescence imaging. The viability and apoptosis of both 661W and ARPE-19 cells were significantly affected by continuous aBL delivery at 32.43 J/cm. Intermittent irradiation with a total exposure of 37.50 J/cm, administered as 12.50 J/cmper irradiation session with 2 h intervals for three sessions, did not affect the viability of 661W cells. CONCLUSIONS: aBL is a potential treatment for C. albicans keratitis. The intermittent irradiation approach using aBL to treat fungal keratitis could be a safety modality for clinical application.