en تخصصي Special پژوهشي Research <strong>Background:</strong> Recently, iron oxide nanoparticles have attracted attention in various diagnosis and treatment fields. The aim of the present study was to investigate the cytotoxicity of various concentrations and incubation times of dextran-coated iron oxide nanoparticles (DIONPs) on HeLa and MCF-7 cancerous cell lines.<br> <strong>Methods:</strong> This in-vitro study was conducted at Pharmaceutical Sciences Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran in 2016. The dextran-coated iron oxide nanoparticles (DIONPs) uptake and cytotoxicity at different concentrations (10, 40 and 80 &micro;g/ml) and different incubation times (6, 12 and 24 h) were assessed on HeLa and MCF-7 cell lines. The viability of the cells was measured by MTT assay.<br> <strong>Results:</strong> DIONPs entered into the HeLa and MCF-7 cells. After 6, 12 and 24 h incubation times and in all concentrations, the viability of HeLa cells was more than 94%. For MCF-7 cell line, increasing incubation time from 6 to 24 h at a concentration of 10 &mu;g/ml decreased the cells viability from 98% to 95%. When the cells were exposed to concentrations of 40 and 80 &mu;g/ml of the nanoparticles, significant reductions in the cells viability was observed from 98% to 91.6% and from 95% to 88%, respectively.<br> <strong>Conclusion:</strong> DIONPs cytotoxicity increased by increasing the incubation time from 6 to 24 h and also increased with increasing the nanoparticles concentration from 0 to 80 &mu;g/ml. In general, DIONPs did not cause considerable toxicity in both cell lines especially at lower concentrations. Therefore, these nanoparticles are good candidates for use in biomedical and cancer research studies. Cytotoxicity, Iron oxide, Nanoparticles, Dextran Cytotoxicity, Dextran, HeLa Cells, Iron Oxide Nanoparticles, MCF-7 Cells 31 36 http://ijt.arakmu.ac.ir/browse.php?a_code=A-10-444-1&slc_lang=en&sid=1 Masoud Rezaei 10031947532846006476 10031947532846006476 No MSc Student of Medical Physics, Students Research Committee, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Hossein Mafakheri 10031947532846006477 10031947532846006477 No MSc Student of Medical Physics, Students Research Committee, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Karim Khoshgard khoshgardk@gmail.com 10031947532846006478 10031947532846006478 Yes Department of Medical Physics, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Alireza Montazerabadi 10031947532846006479 10031947532846006479 No Department of Medical Physics & Radiology, School of Medicine, Gonabad University of Medical Sciences, Gonabad, Iran. Ahmad Mohammadbeigi 10031947532846006480 10031947532846006480 No MSc Student of Medical Physics, Students Research Committee, School of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran. Farhad Oubari 10031947532846006481 10031947532846006481 No MSc of Hematology and Blood Bank, Medical Biology Research Center, Kermanshah University of Medical Sciences, Kermanshah, Iran.