▎ 摘　　要

The interaction of methylene blue (MB) as a photosensitizer with graphene oxide nano-sheets (GO) was examined in aqueous solution using UV-vis spectrophotometric techniques. MB-GO composites were prepared by mixing the solutions of GO nano-sheets and methylene blue due to interacting of the cationic methylene blue photosensitizer via electrostatic and - stacking or hydrophobic cooperative interactions. The cell killing potential of nanocomposite was examined on the MDA-MB-231 breast cancer cells in the absence and presence of red LED irradiation. The results demonstrated that the MB-GO nanocomposite has good performance in photodynamic therapy (PDT) during red LED irradiation. The cytotoxicity of nanocomposite caused reducing cell viability up to 20%. These effects would be due to the nano size structure of composite that could lead to effective cellular penetration. Also the significant difference has seen in lower concentrations of MB and MB-GO nanocomposite. The results show more than 40% increases in cell killing potential in lower concentrations of nanocomposite by using 2.5g/mL of each compound. The ratio of GO/MB can affect the interaction and higher ratios of graphene oxide (GO/MB>1) can induce dimerization of MB. In lower concentrations and ratios of (GO/MB<1) the free MB concentration increases and the electron shuttling effect of GO in photo activity decreases - which could affect the photocatalytic yield in PDT. The cell viability measurements confirm these effects on cancer cell killing potential of nanocomposite. According to microscopic and PDT assay results, the nanocomposite distribution and diffusion in cells enhanced the photochemical reaction yield in photodynamic therapy of MDA-MB-231 breast cancer cell line.