Surface alteration of Candida albicans 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.