Morphological study in B16F10 murine melanoma cells after photodynamic hyperthermal therapy with indocyanine green (ICG).

Photodynamic hyperthermal therapy (PHT) with indocyanine green (ICG) is a combination of photodynamic therapy (PDT) and hyperthermia (HT). The low toxicity of ICG with an absorption wavelength of 700-800 nm is thought to make it a good candidate as a photosensitizer for PHT. Upon irradiation, ICG produces oxygen radicals and generates heat. The optimal concentration of ICG and the PHT post-irradiation time effects were evaluated by the cytotoxicity of the treatment on B16F10 murine melanoma. The cytotoxicity of PHT was determined based on the morphology of apoptotic and necrotic cells under phase-contrast microscope, confocal laser scanning microscope (CLSM) with DAPI and Annexin V-FITC/PI double staining, and cell surface structure evaluation by scanning electron microscopy (SEM). The use of ICG at a concentration of 150 µM was selected, as cell proliferation was inhibited from 0 to 24 hr post-PHT with a 3-fold decrease in cell viability (P<0.001) compared to the control group. A morphological observation revealed apoptotic and some degree of necrotic features in the PHT-treated cells.