Sub-additive effects of photodynamic therapy combined with erlotinib for the treatment of epidermoid carcinoma: An in vitro study.

BACKGROUND: Photodynamic therapy (PDT) is an antitumour treatment that employs the combination of a photosensitive compound, oxygen and visible light. To improve the antitumour activity of PDT, the present study used the strategy of combining PDT with erlotinib (ERL), a drug frequently used in the treatment of epidermoid carcinoma. METHODS: An MTT cell viability assay was used to evaluate the cytotoxicity of PDT combined with ERL on A431 epidermoid carcinoma cells in vitro. This study evaluated the cytotoxicity of the following treatments: red laser irradiation (660nm) at different power densities (1.25-180J/cm2), the photosensitizer methylene blue (MB) at concentrations of 0.39-100µM, PDT (12.5µM MB and laser power densities from 1.25 to 180J/cm2), and PDT (12.5µM MB and a laser density of 120J/cm2) plus ERL (1µM). RESULTS: The laser power densities that were tested showed no cytotoxicity in A431 cells. MB showed a dose-dependent cytotoxicity. In PDT, an increase in the dose of light resulted in an increase in the cytotoxicity of MB. In addition, there was a sub-additive effect between PDT and ERL compared to the effect of each therapy alone. CONCLUSIONS: The sub-additive effect between PDT and ERL suggests that their combination may be an important strategy in the treatment of epidermoid carcinoma.

In vitro lethal photosensitization of S. mutans using methylene blue and toluidine blue O as photosensitizers.

The purpose of this in vitro study was to evaluate the antimicrobial effect of photodynamic therapy on Streptococcus mutans (A TCC 25175) suspensions, using a red laser for one minute in combination with toluidine blue O (TBO) or methylene blue (MB). Both photosensitizers were used in three concentrations (25, 10 and 5 mg/L). The activity ofphotosensitizers and laser irradiation were tested separately on the bacteria, as well as the irradiation of this light source in the presence of the TBO or MB. These groups were compared to a control group, in which the microorganism did not receive any treatment. The activity of both TBO and MB or laser irradiation, alone, were not able to reduce the number of S. mutans. In the groups of lethal photosensitization, a bacterial reduction of 70% for TBO and 73% for MB was observed when these photosensitizers were used at 25 mg/L and a reduction of 48% was observed for MB at 5mg/L. In other concentrations there were no significant differences in comparison to the control group. Both the TBO and the MB at 25 mg/L associated with a red laser had an excellent potential for use in PDT in lethal sensitization of S. mutans.

In vitro lethal photosensitization of S. mutans using methylene blue and toluidine blue o as photosensitizers

The purpose of this in vitro study was to evaluate the antimicrobial effect of photodynamic therapy on Streptococcus mutans (ATCC 25175) suspensions, using a red laser for one minute in combination with toluidine blue O (TBO) or methylene blue (MB). Both photosensitizers were used in three concentrations (25, 10 and 5 mg/L). The activity of photosensitizers and laser irradiation were tested separately on the bacteria, as well as the irradiation of this light source in the presence of the TBO or MB. These groups were compared to a control group, in which the microorganism did not receive any treatment. The activity of both TBO and MB or laser irradiation, alone, were not able to reduce the number of S.mutans. In the groups of lethal photosensitization, a bacterial reduction of 70% for TBO and 73% for MB was observed when these photosensitizers were used at 25 mg/L and a reduction of 48% was observed for MB at 5mg/L. In other concentrations there were no significant differences in comparison to the control group. Both the TBO and the MB at 25 mg/L associated with a red laser had an excellent potential for use in PDT in lethal sensitization of S. mutans.

O objetivo deste estudo in vitro foi avaliar o efeito antimicrobiano da terapia fotodinamica em suspensoes de Streptococcus mutans (ATCC 25175), utilizando um laser vermelho durante um minuto associado a dois agentes fotossensibilizantes: azul de toluidina (TBO) ou azul de metileno (MB). Os agentes fotossensibilizantes foram utilizados em tres diferentes concentracoes (25, 10 and 5 mg/L). A atividade destes agentes e da fonte de luz foi testada separadamente sobre a suspensao bacteriana, assim como a irradiacao desta fonte de luz na presenca de TBO ou MB (terapia fotodinamica). Estes grupos foram comparados a um grupo controle, onde nenhum tratamento foi realizado. A aplicacao dos dois fotossensibilizantes (TBO ou MB) e da fonte de luz, separadamente, nao foi capaz de reduzir o numero de colonias viaveis do S. mutans. Nos grupos onde a terapia fotodinamica foi aplicada, uma reducao bacteriana de 70% foi observada para o TBO e de 73% para o MB, quando estes agentes foram utilizados na concentracao de 25 mg/L. O uso do MB a 5mg/L causou uma reducao de 48%. Para as outras concentracoes testadas nao se observou nenhuma reducao em relacao ao grupo controle. Pode-se concluir que tanto o TBO quanto o MB a 25 mg/L associados ao laser vermelho demonstraram um excelente potencial para promover a fotossensibilizacao letal do S. mutans.