Differential Response of BEAS-2B and H-441 Cells to Methylene Blue Photoactivation.

BACKGROUND/AIM: Cancer incidence and mortalities are growing worldwide, therefore research and development of more effective and less invasive treatments, such as photodynamic therapy, are needed. Herein, we investigated the methylene blue (MB) photoactivation effects in lung epithelial cells (BEAS-2B) and lung adenocarcinoma cells (H-441). MATERIALS AND METHODS: The reactive oxygen species (ROS) produced by the laser photoactivation of MB in aqueous solutions and cell cultures were measured with probes, and the cell viability was evaluated with a colorimetric assay. RESULTS: MB up to 31.26 µM did not induce detectable effects in BEAS-2B cells. However, H-441 cells presented adverse effects below that concentration in the same range of fluencies studied. These results are in concordance with the ROS production in H-441 cells, while in BEAS-2B cells the production of ROS was less significant compared to the control. CONCLUSION: Photoactivation of MB at concentrations below 31.26 µM could be used for the selective treatment of H-441 cells over non-cancer cells.

Mathematical modeling and parametrical analysis of the temperature dependency of control drug release from biodegradable nanoparticles.

In this study we describe a mathematical analysis that considers the temperature effects of the controlled drug release process from biodegradable poly-d,l-lactide-co-glycolide (PLGA) nanoparticles. Temperature effects are incorporated and applied to two drug release models. The first one consists of a two-stage release process that considers only simultaneous contributions of initial burst and nanoparticle degradation-relaxation (BR model). The second one is a three release stage model that considers, additionally, a simultaneous drug diffusion (BRD model) step. In these models, the temperature dependency of the release parameters, initial burst constant, k b, the rate of degradation-relaxation constant, k r, time to achieve 50% of release, t max, and effective diffusion coefficient constant (D e), are determined using mathematical expressions analogous to the Arrhenius equation. The temperature dependent models are used to analyze the release of previously encapsulated Rhodamine 6G dye as a model drug in polyethylene glycol modified PLGA nanoparticles. The experimental data used to develop the mathematical model was obtained from release studies carried out in phosphate buffer pH 7.4 at 37 °C, 47 °C, and 57 °C. Multiphasic release behaviors with an overall increase rate associated with the incubation temperature were observed. The study incorporates a parametrical analysis that can evaluate diverse temperature variation effects of the controlled release parameters for the two models.