Abstract: Objective To prepare an ovarian cancer targeted MR molecular probe, and evaluate the feasibility on SKOV3 cells transfection. Methods The optimal weight proportion of superparamagnetic iron oxide modified with Poly-L-lysine（SPIO-PLL） and plasmid pGenesil1-shRNA in probe was determined through agarose gel retardation experiments. Cells transfection with probes was evaluated with fluorescence microscope for green flourescent protein expression detecting. The intracellular distribution of iron particals contained in probes was observed by transmission electron microscope .The cellular toxicity of probes was explored with CCK-8 method. The changes of cells in MR T2* signal intensities were detected after transfection. Result Agarose gel retardation experiments resulted that SPIO-PLL could effectively bind plasmid when the weight ratio of SPIO-PLL and plasmid reached 6:1. After cells transfection with the probes, green fluorescene could be observed, and iron particals could be detected in the cytoplasm. The cell survival rate was higher than 80% when the concentration was less than 50 mg/L. There were significant T2* signal intensities reduction after cells transfected with probes（P<0.01）. Conclusion An ovarian cancer targeted MR molecular probe can be successfully prepared, which can succeed in transfecting ovarian cancer SKOV3 cells with low cellular toxicity, and be detected by MR scanning sensitively.

Key words: ovarian cancer, superaramagnetic iron oxide, molecular probe