| Objective:1. To synthesize a paramagnetic deoxy-glucose-type MR contrast agent diethylenetriamine pentaacetic acid-gadolinium salt deoxy-glucose (Gd-DTPA-DG), analysis of the relaxation rate in vitro, to study the tumor signal intensity pattern in vivo MR imaging in tumor-bearing nude mice model.2. The 99mTc radio-labeled new agent was performed using a one-step approach. To observe its stability and biodistribution application in tumor-bearing nude mice in vivo. Methods:Study protocol was approved by local ethical committee for animal care and use.1. After successfully synthesized diethylenetriamine pentaacetic acid glucosamine (DTPA-DG), Gd2O3 was added to conjugated with it, and Gd-DTPA-DG, an MR contrast agent, was thus prepared. We conducted studies in vitro using nude mice with transplanted human adenocarcinoma of lung as experimental model. The mice were divided into study group (n=10) and control group (n=10). The animals in the experimental group were injected with Gd-DTPA-DG via vena caudalis, whereas the routine Gd-DTPA was used in the control group at the same dosage of gadolinium with the same amount of 0.2mmol/kg as the experimental group. The tumor signal intensities (SI) was evaluated at 15min,30min,60min,90min,120min respectively after injection of contrast agents with GE 1.5-T MR unit by using a 2D inversion recovery sequence FSE T1WI (TR/TE=400ms/14.9 ms) and Quad Ankle coil. The SI of the anterior limb muscles on the same side as control.2. To form 99mTc-Gd-DTPA-DG, Gd-DTPA-DG quality, SnCl2.2H2O dosage, the reaction medium pH value and reaction temperature were concerned on orthogonal experimental design. The radio-labeling efficiency was measured by thin layer chromatography (TLC).3. The marked 99mTc-Gd-DTPA-DG was compared with 99mTc-DTPA and 99mTc-DTPA-DG, radioactive activity established at 0.37MBq/L,3.7MBq/L, 37MBq/L, each hole adding 100μl, cultured in Hela cells for 2h. Cellular uptake rate was measured by gamma counter post-digestion collection.4.100μl of 99mTc-Gd-DTPA-DG (37MBq/L) was added into cervical cancer Hela cells for 2h to observe its distribution in cells under transmission electron microscopy.5. The bio-distribution was observed by the tumor and other major organs taken out from nude mice at different time after intravenous injection of 99mTc-Gd-DTPA-DG.6. SPECT instrument was used to observe the imaging of drug in nude mice. Results:All of the results were statistically analyzed by SPSS statistics 17.0.1. The synthesized Gd-DTPA-DG can improve the contrast of tumor tissue. Gd-DTPA-DG showed a similar relaxation rate with Gd-DTPA in tumor tissues. In comparison with the pre-contrast imaging, the SI of tumor in the experimental group increased greatly at 15 min after injection of Gd-DTPA-DG with significant difference (P＜0.001). The strengthen spread from the tumor edge to the center, and the strengthen performance in different in tumor tissues.2. The radiochemical purity of 99mTc-Gd-DTPA-DG was about 98.5% and remain 96.2% placed at room temperature for 6h.3. 99mTc-Gd-DTPA-DG cellular uptake rate in cervical cancer Hela cells were no statistically significant difference in 3.7MBq/L when compared with 99mTc-DTPA-DG (P=0.66).99mTc-Gd-DTPA-DG cellular uptake rate was significantly higher than 99mTc-DTPA in each radioactive activity, there was a significant difference of the two groups (P<0.001).4. The drug of 99mTc-Gd-DTPA-DG was significantly distributed in the cytoplasm and nucleus under electron microscope.5.99mTc-Gd-DTPA-DG accumulated in the tumor to a higher level than other organ at 2h, the uptake was about 1.48±0.12% ID/g, and the radio-uptake ratio of tumor to muscle (T/NT) was reached 2.91.6. SPECT imaging can easily observe the tumor after injection with 99mTc-Gd-DTPA-DG via the caudalis for 2h later. Conclusion:99mTc labeled the paramagnetic MR contrast agent Gd-DTPA-DG is feasible. Through cellular uptake in vitro and radionuclide imaging in nude mice in vivo, the labeled agent shows excellent tumor targeting.99mTc-Gd-DTPA-DG is potential for a SPECT-MRI dual-modality imaging probes.
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