Photodynamic therapy (PDT) is a new therapeutic method aimed at the selective destruction of cancer cells. The outcome is death of cancer cells through apoptosis or necrosis. The aim of this study was to investigate the characterization of PDT induced cell death in A549 lung cancer cells.

A549 cells were used as the lung cancer cell. 5 aminolevulinic acid (ALA) was used as the photosensitizer and a 632nm diode laser (Biolitec, Germany) as the light source. Cells were incubated with various concentrations of ALA. The 632nm diode laser was then administered for various laser irradiation times. The treated cells were incubated with 24, 48 and 72 hours. The cell viabilities were measured using the crystal violet assay and light microscopy. To observe the cell death mechanism after PDT, cells were observed under fluorescence microscopy after double staining with Hoechst 33342 and propium iodide after PDT.

In the crystal violet assay at 24 hours after PDT with a 3.2 J/cm² laser irradiation power, the cell viabilities were 89.56 ± 4.11, 87.67 ± 5.48, and 69.37 ± 8.84 with ALA concentrations of 10, 100, and 1 mg/ml, respectively. In crystal violet assay at 24 hours after PDT with 1mg/ml of ALA, the cell viabilities were 74 ± 19.85, 55 ± 6.1, and 49.06 ± 16.64% with 1.6, 3.2 and 6.4 J/cm² laser irradiation powers, respectively. However, increasing the interval time after PDT did not change the cell viabilities. In the apoptosis assay, photodynamic therapy was inducing the apoptotic cell death.

This study shows the apoptotic anticancer effect of photodynamic therapy in A549 lung cancer cells. However, further evaluations with other cancer cells and photosensitizers are necessary.