Abstract: Objective To study the anti-metastasis action and mechanisms of realgar nanoparticles (nano-realgar) on malignant melanoma B16-luc cells in mice by application of in vivo bioluminescence imaging assay. Methods The firefly luciferase (luc) gene was transferred into murine B16 melanoma cells with a lentiviral vector(B16-luc cells). B16-luc cells were injected into tail vein of BALB/c mice to establish the pulmonary and hepatic melanoma metastasis model. The model mice were treated with 4 mg/kg and 8 mg/kg nano-realgar once a day by ig for 24 days, and the optical in vivo imaging system was used continuously and dynamically to observe the tumor metastatic situation in mice. At the end of the treating period the mice were sacrificed, and the lungs and liver were removed, and the fluorescence images of the organs were acquired directly with the optical in vivo imaging system, and the metastasis nodules on the lung and liver surface were also observed for perusal. Finally the lung, liver and tumor stained with HE staining, and the morphological changes were observed under microscope. Results Observation with optical in vivo imaging system showed that nano-realgar administration could markedly suppressed the pulmonary and hepatic metastasis of B16-luc cells (P<0.05). After nano-realgar treatment, the numbers of pulmonary and hepatic metastasis nodules significantly reduced even disappeared, and pathological examinations revealed that, in the nano-realgar treated mice, the metastasis nodules in lungs seems small and little, the liquefactive necrosis appeared in the central area of most nodules, and no metastasis nodules was found in liver. Conclusion Realgar nanoparticles are able to inhibit significantly the abilities of pulmonary and hepatic metastasis of B16-luc malignant melanoma cells in mice.

Key words: Realgar nanoparticle, Murine malignant melanoma, Optical in vivo imaging