Cytotoxic Effects of Different ICG Concentrations and Laser Parameters on Neuroblastoma

Photodynamic therapy (PDT) is a minimally invasive treatment for cancer therapy. It can be administered in combination with other treatments such as chemotherapy, radiotherapy, and surgical excision. PDT involves a photosensitizing agent that is activated by exposure to a specific wavelength of light. PDT is a cold photochemical process, there is no tissue heating. In our study, we investigated whether different laser parameters with different concentrations of indocyanine green (ICG) have cytotoxic and anti-proliferative effects on neuroblastoma. Plates were divided groups as control, only ICG concentrations (25 and 50 μg/ml), only laser treatment I (50 J/cm²), only laser treatment II (100 J/cm²), 25 μg/ml ICG + laser treatment I and 25 μg/ml ICG + laser treatment II, 50 μg/ml ICG + laser treatment I and 50 μg/ml ICG + laser treatment II. Neuroblastoma cell lines were irradiated with an in-house developed diode laser system (λ=809 nm, 70 mW/cm², 50 & 100 J/cm²) in continuous wave operation mode after ICG application. Cell proliferation was measured by XTT assay after light irradiation. Cell proliferation was decreased in a dose-dependent manner in 25 and 50 μg/ml ICG concentrations when compared with control. The applied ICG concentrations (especially 50 μg/ml) had cytotoxic effects for neuroblastoma cell lines, SH-SY5Y. There was no difference between laser treatment groups (L 50 & 100 J/cm²). However, PDT groups (laser exposure with ICG) showed significant inhibition of cell viability (p<0.05). Additionally, laser exposure did not increase the well temperature above the incubation parameter. In conclusion, PDT has cytotoxic effects in neuroblastoma cell lines. Appropriate ICG dose - laser parameter combinations must be determined for each cell type. Different energy densities may cause different effects of PDT on inhibition of cell viability.