RESUMO
Objective To sythesize 99Tcm labeled asparagine-glycine-arginine (NGR)- interferon (INF)-α2a and investigate its biodistribution by scintigraphy in tumor bearing mice. Methods NGR-INFα2a was labeled with 99Tcm by a two-step method. Ethylenedicysteine (EC) and MDP were used as bifunctional and transferring chelating agents. The bioactivities of 99Tcm-NGR-IFN-EC-NGR-IFN-α2a, EC-NGRIFN-α2a and NGR-IFN-α2a were compared using least significant difference t-test. The hepatoma bearing mice models were established by subcutaneous injection of MHCC97-H cells. The mice were randomly divided into eight groups and 7.4 MBq 99Tcm-NGR-IFN-α2a was injected via the tail vein. The tissue uptake of the radiolabeled compound was measured as % ID/g. The scintigraphy was performed at 0.5, 1, 2, 4,6, 8, 12 and 24 h after injection. ROI were drawn around tumor and non-tumor tissue and the radioactivity ratio of T/NT was calculated. Results Both the labeling efficiency and radiochemical purity of 99Tcm-EC-NGR-IFN-α2a were more than 90%. The radiochemical purity was 71% after 24 h in saline. The bioactivity showed no significant difference among three compounds (t = 0.416, 0. 120 and 1. 300, all P >0.05). The tracer was mainly excreted through alimentary and urinary tract within 24 h after injection. The peak values of % ID/g in kidney, liver, interstinal tract and tumor were 41.5 ± 8.0_ (at 8 h), 31.3 ± 5.0(at 6 h), 36.0 ± 7.8 (at 6 h), 43.0 ± 4.8 (at 4 h), respectively. The tracer was cleared quickly from the blood and the highest T/NT ratio was 16.5. The optimal imaging time ranged from 4 to 8 h after injection. Conclusions The sythesis of 99Tcm-NGR-IFN-α2a is applicable and it may be used as a potential tumor imaging agent.