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Indocyanine green acts as a photosensitizer but not a radiosensitizer: combined chemo-, photo- and radiotherapy of DFW human melanoma cells
Ameneh Sazgarnia, Mohammad Hossein Bahreyni-Toosi, Ali Reza Montazerabadi and Amirhossein Ahmadi

This study aimed to evaluate the effects of indocyanine green as a sensitizer for both photodynamic and radiation therapy in the DFW human melanoma cell line. The cells were incubated with indocyanine green at different concentrations for 24 hours and then exposed in independent treatment groups to non-coherent light at different fluence rates and X-ray ionizing radiation at different dose rates. In addition, the combined effects of this chemo-, photo-, and radiotherapy were evaluated using the MTT assay. The results showed that indocyanine green had no significant cytotoxic effects at concentrations up to 100 μM. However, when the compound was used as a photosensitizer, it had a strong cytotoxic effect on cancer cells. No radiosensitizing activity was detected. Surprisingly, treatment with 50 μM indocyanine green in combination with 30 J/cm2 light and 4 Gy X-ray radiation reduced the percentage of viable cancer cells to 1.22%. The inclusion of the photosensitizer with the low dose of radiation and reduced light fluence rate therefore yielded the same treatment efficacy as more toxic, high-dose radiation and light therapies.

Keywords: Ionizing radiation; Photodynamic therapy; Indocyanine green; Melanoma

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