[Natural melanin-based nanoparticles with photothermal/photodynamic activities induce ovarian cancer cell death].

To investigate the physicochemical characteristics of natural melanin-like nanoparticles (PDA NPs) and their synergistic anti-tumor efficacy with photothermal and photodynamic (PTT/PDT) therapy.The chemically synthesized PDA NPs were characterized using transmission electron microscope (TEM), dynamic light scattering (DLS) and Zeta potential analysis, and their photothermal and photodynamic properties were assessed with near-infrared excitation light (NIR). The antitumor efficacy of free PDA or PDA combined with NIR irradiation (0.7 and 1.0 W/cm2) was evaluated in ovarian cancer cells using flow cytometry, Cell Counting Kit-8 (CCK-8), and Transwell assay and in a mouse model bearing subcutaneous ovarian cancer xenograft.The synthesized PDA NPs showed a spherical morphology with diameters around 100 nm and a zeta potential of -20 mV. Upon NIR irradiation at 0.7 and 1.0 W/cm2, the particles underwent temperature changes (ΔT) of about 15 and 30 ℃, respectively, and produced a large amount of singlet oxygen, demonstrating their excellent PTT/PDT properties. In ovarian cancer cells, treatment with PDA NPs alone did not induce obvious changes in reactive oxygen species (ROS) production or mitochondrial membrane potential (MTP), but when combined with NIR irradiation, these particles caused a significant increase of ROS and a reduction of MTP (P < 0.001), and such changes were more prominent with high power NIR (P < 0.01). PDA NPs alone showed no obvious cytotoxicity, but the combination of PDA with NIR irradiation produced potent killing effect on ovarian cancer cells (P < 0.001), and the effect was much stronger with a high power irradiation (P < 0.001). While PDA alone showed no inhibitory effect on tumor cell metastasis, the combined treatment with PDA and NIR irradiation, especially at a high power, significantly suppressed invasion and migration of ovarian cancer cells (P < 0.001). In the tumor-bearing mouse model, the combined treatment, but not PDA alone, produced a significant inhibitory effect on tumor growth (P < 0.001).PDA NPs combined with NIR has a strong anti-tumor effect, suggesting a potential new therapeutic strategy for ovarian cancer.