[Magnetic Resonance Imaging Tracing the Biodistribution of SPIO-shRNA Molecular Probe in vivo].

OBJECTIVES: To investigate the biodistribution of superparamagnetic iron oxide (SPIO)-shRNA molecular probe by magnetic resonance imaging (MRI) in vivo. METHODS: Six New Zealand white rabbits were injected intravenously with SPIO-shRNA molecular probe (9.6 mg Fe/kg) via ear edge vein. The blood samples were collected to analyse the pharmacokinetic parameters through measuring the iron content by atomic absorption spectrometry (AAS) method at 30 min before and 1 min, 3 min, 5 min, 10 min, 15 min, 30 min and at 1, 2, 3, 6, 12, and 24 h after the injection. Six Kun Ming (KM) mice were injected intravenously with SPIO-shRNA molecular probe (4.8 mg Fe/kg). The biodistribution of SPIO-shRNA molecular probe was traced by MRI in vivo. Ninety six KM mice were randomly divided into control group and experimental group: each mouse in experimental group was injected intravenously with SPIO-shRNA molecular probe (4.8 mg Fe/kg). The liver, spleen, kidney, brain and muscle of the control group and the experimental group on 1, 3, 5, 7, 9, 11 and 14 d after the injection were collected. The organ iron content were measured by AAS method and Prussian blue staining in order to observe the distribution of the SPIO-shRNA molecular probe in the main organ. RESULTS: Our results demonstrated that the pharmacokinetics of the molecular probe complied with two-compartment model, and the blood half-life was (3.692±0.196) h. The data of MRI showed that the probe were distributed in liver and spleen, and the signs were reduced in accord with the increase of probe's doses in liver and spleen. The probe's metabolism was slow, and the probe was cleared from liver and spleen at 2 weeks after the injection. The results of AAS and Prussian blue staining further testified the results of MRI. CONCLUSIONS: Our data showed the biodistribution of SPIO-shRNA molecular probe in main organs can be traced by MRI in vivo. Meanwhile, it provides important information for the effectiveness of the probe by MRI at tumor in vivo.

Effects of external magnetic field on the transfection rate of SPIO-shRNADual functional molecular probe into ovarian carcinoma SKOV3 cells in vitro.

OBJECTIVE: To explore the transfection rate of SPIO-shRNA dual functional molecular probe into ovarian carcinoma SKOV3 cells in external magnetic field. METHODS: Dual functional molecular probe at an iron concentration of 45 mg/L was transfected into SKOV3 cells. The cells with coexisting probe and magnetic fields were set as the intervention group,the probe-transfected cells as negative control group, and normally cultured SKOV3 without any transfection as blank control group. The transfection rate was detected by flow cytometry. Cell viability was observed by CCK-8 assay. Epidermal growth factor receptor (EGFR) expression level in SKOV3 cells was determined by real-time quantitative PCR and Western blot analysis. The signal intensity was measured by magnetic resonance imaging (MRI). RESULTS: The transfection rate of the intervention group was (79.20 ± 3.31)%, which was significantly higher than that of negative control group (P=0.001). Compared with the negative control group,the cell viability of the intervention group significantly decreased (P=0.011), protein and mRNA expression levels of EGFR in the intervention group were significantly decreased (both P<0.05). The signal intensity on T2(*)WI in the intervention group also significantly decreased (P=0.0004). CONCLUSION: The external magnetic field can improve the transfection efficiency SPIO-shRNA dual functional molecular probe into ovarian carcinoma SKOV3 cells.

[Pharmacokinetics and MR imaging of SPIO-shRNA dual functional molecular probe in vivo].

In this study, we investigated the pharmacokinetics parameters of SPIO-shRNA dual functional molecular probe and observed the main organ distribution by MRI in vivo. Eighteen New Zealand white rabbits were randomly divided into three groups and injected intravenously with different doses of SPIO-shRNA molecular probe, respectively. The blood samples were collected to analyze the pharmacokinetic parameters by measuring the iron content at 30 minutes before and after the injection. Twenty-four Kun Ming (KM) mice were randomly divided into 4 groups: the control group was injected intravenously with physiological saline 200 µL per mouse via the tail vein, the other 3 groups were injected intravenously with different doses of SPIO-shRNA molecular probe. MRI observation was performed in 24 hours, and the liver, spleen, kidney, brain and muscle were collected for iron quantification with Prussian blue staining to determine distribution of the SPIO-shRNA molecular probe in the main organ in vivo. Our results suggest that the molecular probe blood half-life is more than 3 hours. The data of MRI suggest the probe was distributed in liver and spleen, and the MRI signal was reduced with the increase in probe's doses (P < 0.05). The results of Prussian blue staining confirmed the results of MRI. Most of the probe could escape the phagocytosis of mononuclear phagocyte system. Our data provide the pharmacokinetic and distribution of SPIO-shRNA molecular probe in organs. Meanwhile, it suggests the choice of the time and dose of probe for MR imaging of tumor in vivo.