Photodynamic therapy (PDT) is a novel approach to cancer treatment that applies light and molecular oxygen in combination with a photosensitizing agent to selectively damage tumor tissue. The present study evaluated the effectiveness of 5-aminolevulinic acid (ALA) mediated PDT for inducing in vitro death in MG-63 osteosarcoma cells. To determine the accumulation of the photosensitizer (protoporphyrin IX, PpIX) in response to increasing ALA concentrations in the osteosarcoma cells, cells were treated with varying concentrations of ALA (0, 0.1, 0.25, 0.5, 1, 2, 5, 10 mM) for 4 and 24 h and the intracellular conversion of ALA to PpIX was measured using spectrofluorometry. To identify the optimal ALA concentration and light exposure to induce maximum cell death, cells were treated with varying concentrations of ALA for 4 and 24 h and then exposed to different light dosages (0, 0.5, 1, 5, 10 J/cm2) using an LED array (λ= 636 nm). Cell viability was assessed using an MTT assay. It was found that the highest PpIX accumulation occurred in MG-63 cells treated with 0.5 mM and 1 mM ALA for 24 h. Consistent with these results, the greatest cell death was seen in cells treated with 0.5 mM and 1 mM ALA—there were more PpIX within those cells to generate a greater number of reactive oxygen species (ROS), the toxic element in the PDT mechanism. Overall, these findings suggest that ALA-mediated PDT significantly induces MG-63 cell death, supporting its potential use as a minimally invasive, alternative treatment of human osteosarcoma.
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