Terapia fotodinâmica com azul de metileno em células derivadas de carcinoma espinocelular: estudo in vitro.

Abstract

Nowadays, oral cancer is one of the most frequent cancer in the world and the gold standard treatments are surgery, chemotherapy and radiotherapy. However, such therapies cause many side effects and damages the patient's quality of life. Photodynamic therapy (PDT) usually induces fewer side effects and may be an option in these cases. This therapy consists in the use of a photosensitizer that is activated by a specific light and in the presence of oxygen releases reactive oxygen species, promoting cell damage and death. Among the existing photosensitizers, methylene blue (MB) is one of the most used because of its proven antimicrobial effect, few side effects and low cost. Nonetheless, there are still few studies on PDT with MB in oral squamous cell carcinoma (OSCC). The aim of this study was to evaluate the effect of PDT with MB in a cell line derived from squamous cell carcinoma of tongue (SCC-4), as well as to compare it with a non-neoplastic cell line (3T3 fibroblasts). For this purpose, the SCC-4 and 3T3 cells were incubated with MB solutions at concentrations ranging from 25 µM to 3200 µM for 30 min. After defining the least cytotoxic concentrations, PDT was performed on SCC-4 cells with a laser device with a wavelength of 660 nm, 50 mW, 6 J, 120 seconds of irradiation and energy density of 150 J/cm². Cell viability was evaluated at two different times (immediately after treatment with PDT and after 24 h) using the MTT test. In the SCC-4 line, the photosensitizer (MB) reduced cell viability from a concentration of 200 µM and was cytotoxic to the 3T3 line from a concentration of 100 µM. MB PDT was performed on SCC-4 cells at concentrations of 25 µM and 50 µM. In the two post-treatment times (0 and 24 h) the PDT with MB affected the cell viability of the SCC-4 line at both concentrations, however only in the evaluation post-24 h treatment with PDT was considered cytotoxic (cell viability < 70%). Based on the data obtained, it is concluded that PDT with MB negatively affects the cell viability of SCC-4 cells after 30 minutes of exposure to photosensitizer at concentrations of 25 and 50 µM and 02 minutes of laser irradiation (660 nm, 50 mW, area of 0.04 cm2, that is, 150 J/cm²).