Evaluation of dual application of photodynamic therapy-PDT in Candida albicans.

This study aimed to evaluate, in vitro, the efficacy of photodynamic therapy - PDT using dimethyl methylene blue zinc chloride double salt (DMMB) and red LED light on planktonic cultures of Candida albicans. The tests were performed using the ATCC 90,028 strain grown at 37 °C for 24 h, according to a growth curve of C. albicans. The colonies were resuspended in sterile saline adjusted to a concentration of 2 × 108 cells / mL, with three experimental protocols being tested (Protocol 1, 2 and 3) with a fixed concentration of 750 ɳg/mL obtained through the IC50, and energy density 20 J/cm2. Protocol 1 was carried out using conventional PDT, Protocol 2 was applied double PDT in a single session, and Protocol 3 was applied double PDT in two sessions with a 24 h interval. The results showed logarithmic reductions of 3 (4.252575 ± 0.068526) and 4 logs (2.669533 ± 0.058592) of total fungal load in protocols 3 and 2 respectively in comparison to the Control (6.633547 ± 0.065384). Our results indicated that double application in a single session of PDT was the most effective approach for inhibiting the proliferation of Candida albicans (99.991% inhibition).

A novel technique of antimicrobial photodynamic therapy - aPDT using 1,9-dimethyl-methylene blue zinc chloride double salt-DMMB and polarized light on Staphylococcus aureus.

Antimicrobial Photodynamic Therapy (aPDT) is an alternative to conventional treatments of local infections such as the use of antibiotics, which may lead to the development of resistance. aPDT besides requiring the use of a photosensitiser also needs a light source do be carried out. In the search for efficient and low-cost procedure the use of multispectral polarized light (λ400-2000 nm) emerges as a possibility for the execution of aPDT. The use of a highly effective photosensitizer is also of great importance. 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt - DMMB is a potent phenothiazine derivative that presents high photodynamic action due to its high lipophilicity as well as a greater quantum yield of Singlet oxygen and phototoxicity when compared to other Photosensitizers. The aim of this study was to assess, In Vitro, the efficacy of aPDT on Staphylococcus aureus (ATCC 25923) using different concentrations of DMMB associated to a Polarized light source (Bioptron®, 40 mW, ᴓ = 15.8 cm2) using different energy densities. Based on the IC50, 150 and 300 ng/mL of DMMB concentrations were chosen for this study. Twelve experimental groups were used: (Control, PLs, PSs and aPDTs). Serial dilutions (up to 10-8) of the bacterial inoculum were used and the DMMB was added using the two previously determined concentrations. After 5 min of preincubation the dilutions of the inoculum were illuminated by the polarized light source. Subsequently, 100 µL of each dilution, in triplicate, were inoculated into Petri dishes containing TSA medium and incubated in a bacteriological oven at 37 °C for 24-h and quantification of UFCs was done. The results showed significant exponential reduction (p < .0001) of 99.93% (150 ng/mL + LP 10 J/cm2) and 99.97% (300 ng/mL + LP 5 J/cm2) the CFU counts in comparison to non-illuminated control. The results of this study allow to conclude that aPDT carried out with 1,9-Dimethyl-Methylene Blue Zinc Chloride Double Salt-DMMB and a PL souce was efficacious on the reduction (99.97%), in vitro, of the bacterial counts of S. aureus.