Modification of photosensitizer and its effect on the antimicrobial photodynamic therapy over biofilm of Gram-positive bacteria

Abstract

In addition to mechanical control, different antimicrobial techniques have been used in the control of oral biofilms. The antimicrobial photodynamic therapy (APDT) has been used, and it promotes bacterial death as a result of photosensitization of microbial components. Then, the purpose of this study is to evaluate the effect of APDT using one photosensitizer modified or not, in biofilms of Streptococcus mutans. Biofilm will be induced on the surface of hydroxyapatite discs for 7 days. Methylene blue modified or not by iodine will be used at concentration determined by minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations and irradiated by LED (660nm) with dose of 60J/cm2. Furthermore, it will be evaluate the dark cytotoxicity of the photosensitizer modified or not, as well as the mechanisms involved in photodynamic reaction by optical absorption and estimation of singlet oxygen generation. Antimicrobial activity will be determined using the technique for counting of colony forming units (CFU/mL), percentage survival and metabolism of biofilm by XTT and MTT tests. Different conditions will be tested: a) irradiation with LED (L) using the photosensitizer modified or not (PS) (PS+L+) b) irradiation with LED without the photosensitizer (PS-L+) c) photosensitizer without irradiation (PS+L-) d) without LED irradiation and without photosensitizer (PS-L-) and e) chlorhexidine (C). The results will be submitted to analysis of variance (ANOVA) and Tukey's test at 5% significance level. (AU)