Abolghasem Haeri - Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
Hossein Rajabi - Department of Medical Physics, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran
Fariba Johari - Department of Radioisotope, Nuclear Science and Technology Research Institute, Tehran, Iran
Shahram Akhlaghpoor - Department of Radiology, Sina Hospital, Tehran University of Medical Science, Tehran, Iran

Introduction: Apoptosis is a major consequence of ionizing radiation in proliferative tissues and quantification of the apoptotic cells could be helpful for noninvasive assessment and estimation of the radiation absorbed dose. Annexin V conjugated with super paramagnetic iron oxide nanoparticles (ANX-SPIO) is a biological probe for detection of apoptotic cells using magnetic resonance imaging. This study aimed at assessing the biodistribution alterations of the labeled ANX-SPIO within the mice body shortly after exposure to different doses of ionizing radiation. Methods: 99mTc-EC-ANX-SPIO was prepared and its in vitro stability was tested. The binding affinity of radiocomplex to apoptotic cells was validated in vitro. Mice irradiated whole body with 2, 4 and 6 Gy (60Co gamma rays) and six hours later, radiocomplex was administrated intravenously and the biodistribution study was conducted 0.5, 1 and 2 hours later. Results: The radiochemical purity of radiocomplex was 94% ± 3.4% and it showed a good stability in PBS and serum. The radiocomplex maintained its efficacy for in vitro binding to apoptotic cells.radiocomplex accumulated in the bone marrow of all irradiated mice (p <0.05). However, statistical analysis did not show significant correlation between the %ID/g of the femoral bones and the received radiation doses. Conclusion: Quantification of ANX-SPIO in bone marrow can be used as an indicator for radiation exposure but development and optimization of the assay are necessary for discrimination between different radiation doses.

Radiation, Apoptosis, Annexin V, SPIO, Biodistribution