Efficacy of gallium phthalocyanine as a photosensitizing agent in photodynamic therapy for the treatment of cancer

Photodynamic therapy is a revolutionary treatment aimed at treating cancers without surgery or chemotherapy. It is based on the discovery that certain chemicals known as photosensitizing agents (e. g. porphyrins, phthalocyanines, etc.) can kill cancerous cells when exposed to low level laser light at a specific wavelength. The present study investigates the cellular uptake and photodynamic effect of gallium (III) phthalocyanine chloride (GaPcCl) on Caco-2 cancer cells. Caco-2 cells were treated with different concentrations of GaPcCl for 2 h before treatment with a diode laser (lambda= 661 nm, laser power = 90 mW) delivering a light dose of 2.5 J/cm(2), 4.5 J/cm(2) or 8.5 J/cm(2). After 24 h, the cell viability of post-irradiated cells was measured using the MTT assay. Cellular uptake studies were performed by photosensitizing cells with GaPcCl for 30 min, 2 h, 10 h, 12 h, 18 h and 24 h before lysing the treated cells into solution to measure the GaPcCl fluorescence emission at an excitation wavelength of 600 nm. Results showed an increase in fluorescence intensity of emission peaks at longer incubation times, indicating a greater cellular uptake of GaPcCl by Caco-2 cells at 24 h in comparison to 30 min. GaPcCl at a concentration of 100 mu g/ml activated with a laser light dose of 8.5 J/cm(2) reduced the cell viability of Caco-2 cells to 27%. This concludes that GaPcCl activated with low level laser light can be used as a photosensitizing agent for the in vitro PDT treatment of colon cancer.