Surface alteration of <i>Candida albicans</i> after antifungal photodynamic therapy: A Raman spectroscopic study

Abstract Candida albicans surface alterations following photodynamic therapy using Raman spectroscopy were studied. Previously effective photosensitizers were tested: 200 μM erythrosine, 100 mM KI, 200 μM erythrosine+100 mM KI irradiated with a 530 ± 10 nm LED (250 mW/cm 2 , 20 J/cm 2 per session for two sessions (total fluence: 40 J/cm 2 )), 60 M bisdemethoxycurcumin irradiated with a 430–480 nm LED (950 mW/cm 2 , 75 J/cm 2 ), 100 μM melatonin irradiated with a 630 ± 10 nm LED (250 mW/cm 2 , 75 J/cm 2 ), and 60 μM bisdemethoxycurcumin+100 μM melatonin with dual light. Treatments were applied to mature C. albicans biofilms. Negative and positive controls were phosphate‐buffered saline and nystatin, respectively. Raman spectroscopy used a 50× objective lens, 600 lines/mm grating, and 785 nm laser. Data were analyzed using principal component analysis. Erythrosine and erythrosine+KI induced specific surface alterations with Raman peaks similar to nystatin and differing from the negative control at 625, 1159, 1270, 1336, 1491, and 1603 cm −1 .Raman peaks at 625 cm −1 correspond to phenylalanine, 1159 cm −1 to carbohydrate, 1270 cm −1 to amide III, 1336 cm −1 to proteins and carbohydrate, 1491 cm −1 to nucleic acid bases, and 1603 cm −1 to ergosterol. Other treatment groups showed no differences from the negative control. Erythrosine and erythrosine+KI exhibited similar mechanistic cell surface alterations to nystatin.