Preclinical study of a cost-effective photodynamic therapy protocol for treating oral candidoses.

Photodynamic therapy (PDT) is a promising treatment for oral candidoses. Its use as an alternative to antifungals prevents several adverse effects, including microbial resistance. However, most PDT protocols do not employ devices and consumables commonly available in dental practice, thus influencing treatment affordability. This study aimed to determine the efficacy of a PDT method based on light curing units' blue LEDs combined to a plaque-disclosing composition (5% erythrosine) against C. albicans in culture and in a murine model of oral candidosis. Standard and resistant fungal strains were tested in vitro in planktonic and biofilm forms. PDT (pre-irradiation time periods: 30 and 60 s; irradiation time: 3 min) was compared to control conditions without light and/or erythrosine. Mice with induced oral candidosis (n = 40) randomly received PDT or similar control conditions with subsequent C. albicans count. These mice underwent histological analysis, as well as 12 healthy mice submitted to experimental treatments. PDT completely inactivated C. albicans planktonic cells and biofilm. Control conditions presented minor differences (ANOVA, p < 0.05), with mean values ranging from 5.2 to 6.8 log10 (UFC/mL). Infected mice presented no significant difference in C. albicans counts consequent to treatments (ANOVA, p = 0.721), although the PDT protocol was able to enhance the inflammatory infiltrate in healthy mice. It can be concluded that the tested PDT protocol can inactivate C. albicans but still needs further investigation in order to achieve efficacy and safety.

Photochemically induced spinal cord ischaemia in rats: assessment of blood flow by laser Doppler flowmetry.

A photochemical technique was used to create central nervous system ischaemia in rats. Changes in blood flow in the spinal cord were assessed by laser Doppler flowmetry. The Th11 spinal cord segment was irradiated by an argon ion laser after intravenous injection of an organic dye, erythrosin B, to rats with or without a laminectomy. In the group of laminectomized rats, laser irradiation for 5 s did not influence cord blood flow, but 10 s irradiation caused a 25% decrease of blood flow, which normalized within 20 min. Decreases of 50 and 80% in spinal cord blood flow were noted after 20 s and after 1 min of laser irradiation, respectively, with no recovery observed after 20 min. In the group of rats without a laminectomy, 1 min of laser irradiation caused approximately a 25% decrease of spinal cord blood flow, which gradually recovered within 12 min, whereas 5 min of laser irradiation caused a more severe reduction of spinal cord blood flow (45%) with some recovery was observed 30 min later. We could thus confirm that the interaction between a photosensitizing dye and laser irradiation reduced the regional spinal cord blood flow and the extent of this effect could be modified by varying the duration of laser irradiation. The present results therefore provide further support for using this photochemical technique to create animal models of central nervous system ischaemia.