[Preparation of (99m)Tc-EDTA-MN and Its Bioimaging in Mouse]

Hypoxia is an important biological characteristics of solid tumor, it is not sensitive to radiotherapy and chemotherapy for which is the presence of hypoxic cell, thus increasing their resistance to conventional radiotherapy and chemotherapy, therefore, the detection of hypoxia degree of tumor tissue is of great significance. The hypoxia imaging of nuclear medicine can reflect the degree of tissue hypoxia, which can selectively retained on the hypoxic cells or tissues, including nitroimidazole and non nitroimidazole; the nitroimidazole is widely and deeply researched as hypoxic celles developer in China and abroad at present. The research about application of radionuclide labelled technique has clinical application value to develop the hypoxia imaging agent EDTA-MN complexes which was labeled. To study the feasibility of (99m)Tc by direct labeling method, the radiochemical properties evaluation of (99m)Tc-EDTA-MN, and observe the distribution characteristics of (99m)Tc radiolabeled EDTA-MN in the xenograft lung cancer nude mice bearing non-small cell lung cancer cell (A549), and provide experimental evidence for its further research and application.

The radiolabeling of EDTA-MN with (99m)Tc was performed with direct labeling method, respectively, on the reaction dosage (10 mg, 5 mg, 2 mg), stannous chloride dosage (8 mg/mL, 4 mg/mL, 2 mg/mL), mark system pH (2, 4, 5, 6) one by one test, using orthogonal design analysis, to find the optimal labeling conditions. Labelling rate, radiochemical purity, lipid-water partition coefficient and in vitro stability in normal saline (NS) were determined by TLC and HPLC, and the preliminary study on the distribution of (99m)Tc-EDTA-MN in nude mice.

The labeling rate of 99mTc-EDTA-MN with the best labeling conditions was (84.11±2.83)%, and the radiochemical purity was higher than 90% by HPLC purification, without any notable decomposition at room temperature over a period of 12 h. The partition coefficient was lgP=-3.05, indicated that this complex was hydrophilic. At 3 h post-injection, the imaging of (99m)Tc-EDTA-MN in nude mice bearing non-small cell lung cancer cell showed that more radioactive gathered in bladder at 0.5 h, the transplanted tumor was clearly imaged at 1 h post-injection, during whole imaging radioactive in other tissues and organs was low. The radioactivity of tumor uptake by using of ROI technology were (88.14±11.59), (123.17±9.06), (98.08±14.40) and (79.87±10.57) at 0.5, 1, 2, 3 h post-injection, and the ratio of T/NT of tumor and liver area were (1.95±0.19), (3.58±0.78), (3.95±0.39) and (5.01±0.28), respectively. (99m)Tc-EDTA-MN could be quickly cleared from the blood in mice primarily through the kidneys, and the radioactivity in other tissues and organs remained low.

(99m)Tc-EDTA-MN can be easily prepared and labeled compound with high labeling rate and stability, it appears to be suitable for further experiments requirement in vivo and in vitro application.