In vitro photodynamic effect of gallium, indium and iron phthalocyanine chloride on different cancer cell lines

Abstract

Photodynamic therapy (PDT) is emerging as a viable alternative to invasive anti-cancer treatment regimens such as surgery, chemotherapy or radiotherapy. A series of metal – based phthalocyanine complexes have been discovered that may be used as a drug or photosensitizer in photodynamic therapy for the treatment of cancers. During photodynamic therapy the photosensitizer is administrated intravenously or topically to the patient before laser treatment at an appropriate wavelength is delivered to the cancerous site to activate the photosensitizer. The activated photosensitizer will react with oxygen typically present in the cancerous tissue to produce reactive oxygen species for the eradication of the cancerous tissue. This is the first study where gallium (GaPcCl), indium (InPcCl) and iron (FePcCl) Pc chloride complexes were used for photodynamic research. These metal – based phthalocyanine complexes were investigated using different cancer cell lines (Caco-2, MCF-7, melanoma and A549). Also, the baseline cellular uptake and photodynamic effect of these complexes were established on healthy normal cells (human fibroblast cells). Fluorescent spectrophotometry showed that all three photosensitizers accumulated in a time-dependent manner in Caco-2, MCF-7, melanoma and A549 cancer cells, as well as in healthy normal fibroblast cell in amounts which increased over a period of 24 hours, with emission peaking at 24 hours for all cell lines. Dark toxicity effects and photodynamic therapy efficacy were established with a MTT assay. High concentrations of inactive GaPcCl, InPcCl and FePcCl was toxic to Caco-2, melanoma, A549 and fibroblast cells. However, all three photosensitizers were in its inactive state at low and high photosensitizing concentrations were highly toxic to MCF-7 cancer cells. On the other hand, in vitro photodynamic therapy treatment with both low and high concentrations of GaPcCl, InPcCl and FePcCl were observed to be potently cytotoxic towards all four cancer cell lines upon exposure to laser light for 22 seconds (2.5 J/cm2), 39 seconds (4.5 J/cm2) and 74 seconds (8.5 J/cm2). These results revealed that all three photosensitizers reacts to photodynamic therapy in a concentration-dependent (photosensitizer) and dose-dependent (light dose/time) manner. At 24 hours after photodynamic therapy, the most effective treatment parameters were laser treatment for 74 seconds with FePcCl concentrations from 60 µg/ml - 100 µg/ml which resulted in 0% cell survival of Caco-2 cancer cells. A short laser treatment time of 74 seconds for activation of FePcCl (20 µg/ml) resulted in 0% cell survival of MCF-7 cancer cells. Similarly, FePcCl (40 µg/ml - 100 µg/ml) activated for 22 seconds, 39 seconds and 74 seconds resulted in 100% cell death of A549 cancer cells. Photodynamic therapy treatment with GaPcCl and InPcCl were very effective in reducing the cell viability of melanoma cancer cells. Healthy normal fibroblast cells survived in vitro photodynamic therapy treatment with all three photosensitizers much better than the cancer (Caco-2, MCF-7, melanoma and A549) cells. This confirms the previously reported results that photosensitizers such as phthalocyanines and its metal-based complexes preferentially accumulate in cancer cells than normal healthy cells. All three photosensitizers localized in mitochondria and lysosomes of the Caco-2, MCF-7 and A549 cancer cells. In melanoma cancer cells InPcCl also localized in the mitochondria and lysosome, but GaPcCl and FePcCl localized in mitochondria only. Apoptosis was identified via microscopical and flow cytometric investigations, as the dominant mode of cell death induced by GaPcCl, InPcCl and FePcCl mediated photodynamic therapy in cancer cell lines tested. Therefore, this study concludes that GaPcCl, InPcCl and FePcCl are effective photosensitizers for the in vitro PDT treatment of cancer cells. The effective in vitro PDT treatment for each cell line was dependent on the photosensitizer concentration and illumination period for each of the different photosensitizers.