Effects of photodynamic therapy mediated by Fotoenticine® against Streptococcus mutans cells

Abstract

Photodynamic therapy (PDT) is a promising technique that can be used to control Streptococcus mutans. However, it has been necessary to identify photosensitizers with greater effectiveness against S. mutans and to understand how PDT acts on biofilms formed by these microorganisms. In this context, the objective will be to study the Fotoenticine® (FTC) activity in photodynamic therapy against Streptococcus mutans biofilms, investigating its antimicrobial effects in cells through microbiological and microscopic analysis. During the study, the antimicrobial effects of Fotoenticine® will be compared with Methylene Blue, a conventional photosensitizer already released for clinical use in Dentistry. One standard strain (UA 159) and two clinical strains of S. mutans will be used. Photosensitization will be performed on biofilms of S. mutans formed on bovine dentin specimens, using Fotoenticine® (0,6 to 0,0075 mg/mL) or Methylene Blue (0,6 mg/mL), associated with irradiation with LED (660nm). Control groups will be treated with PBS without light. After photosensitization, colony-forming units (CFU/mL) will be counted, and the Minimum Biofilm Eradication Inhibitory Concentration (MBEC) of FTC will be determined. Then, the effects of PDT with FTC (in inhibitory and sub-inhibitory concentrations) and AM on the biofilms of S. mutans will be evaluated by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM), in which size and morphology of cells, cell damages and stiffness change will be studied. The obtained data will be analyzed to select the most appropriate statistical test for each experiment, considering a significance level of 5%.