In vitro evaluation of cytotoxicity of TONS504 and blue light irradiation on porcine corneal epithelial cells.

Photodynamic antimicrobial chemotherapy (PACT) for infectious keratitis has attracted increasing attention, and the clinical application of PACT with TONS504, a newly developed chlorin derivative, is anticipated. However, studies evaluating the cytotoxicity of TONS504 combined with light exposure on corneal cells are lacking. We aimed to investigate cytotoxic effects on the corneal epithelium and examined safe irradiation conditions by evaluating the cytotoxicity of TONS504, blue light (405 nm), and their combination using porcine corneal epithelium (PCEP). Additionally, the synergistic cytotoxicity of TONS504 with ethylenediaminetetraacetic acid (EDTA) under blue light-previously shown to have a synergistic antimicrobial effect with PACT-was assessed. Viability of PCEP cells exposed to various TONS504 concentrations (1-100 mg/L), irradiation intensities (5-30 J/cm2, 20 mW/cm2, 405 nm LED), and their combinations were evaluated using the Cell Counting Kit-8 assay. Inhibition of PCEP cell migration under these conditions was assessed using a primary porcine corneal explant model. The synergistic cytotoxicity of TONS504 with EDTA (0.015 M) under blue light irradiation at 5 J/cm2 was also evaluated similarly. TONS504 alone demonstrated low cytotoxicity (up to 10 mg/L), whereas the combination of TONS504 with blue light showed concentration-dependent cytotoxicity or cytotoxicity at high light irradiation intensity against PCEP cells. No clear synergistic cytotoxicity was observed between TONS504 and EDTA under blue light. These findings provide fundamental data for establishing a blue light-based TONS504-PACT protocol.