Development of topical formulation containing methylene blue for photodynamic therapy

Methylene blue (MB) has already showed promising results in photodynamic treatment of cutaneous infections, but no topical formulation has been standardized yet1. A gel system is a proper option due to several advantages, e.g., a longer contact time with the skin and excelent transparency allowing a greater light irradiation efficiency. In this study we prepared carbomer 940® (CBP) or hydroxyethylcellulose (HEC) based gels containing 0.15% methylparaben, triethanolamine s.q. pH ~7.0, distilled water or 10% hydroalcoholic solution or 10% urea solution s.q.t. and MB (1%) and tested their reactive oxygen species (ROS) production. Formulations presented a blue color (Fig. 1), pH ~7.0 and maximum spreadability close to 5,000 mm2 for CBP and 6,500 mm2 for HEC gels. Figure 1 presents the results of ROS production observed for all formulations.The best formulations, in terms of ROS generation, were CBP with ethanol 10% (61% ROS) and HEC (60% ROS), presenting a 23% increase in relation to the aqueous solution of MB (48% ROS). These matrices provided a favorable physicochemical environment for the amplification of the photodynamic effect showing a great potential to be applied as topical formulations against cutaneous infections.