Preparation and primary evaluation of 66Ga-DTPA-chitosan in fibrosarcoma bearing mice

Chitosan was chemically modified by diethylenetetraaminepentaacetic acid (DTPA) in different degrees of modification (DM = 6.1, 10.3, 15.7 and 20.9%). DTPA-chitosans were radiolabeled with gallium-66 radionuclide. The effect of several factors on labeling yield such as degree of modification, acidity and concentration of DTPA-chitosan solution, contact time and radioactivity was investigated. Radiolabeled DTPA chitosans were intratumorally injected to fibrosarcoma bearing mice and the leakage of radioactivity from the injection site was evaluated. In comparison with chitosan, all DTPA chitosans showed better efficiency in preventing the leakage of radioactivity from tumor lesion and DTPA-chitosan (DM = 10.3%) was the best which led to remaining 97% of injected dose in the injection site after 54 h of injection. The highest leaked radioactivity from the injection site was in the lungs, liver, spleen and the kidneys. Our results indicated that the DTPA modified chitosan can be an effective carrier for therapeutic radionuclides for tumor treatment by the intratumoral injection technique.