RESUMEN
ObjectiveTo synthesize 99Tcm labeled hydrazine-nicotinamide ( HYNIC)-c (RGDfK)and evaluate its biodistribution and imaging in the severe combined immunodeficiency (SCID) nude mice bearing human lung adenocarcinoma.Methods( 1 )Tcm-HYNIC-c(RGDfK) was prepared by a two-step method using tricine and ethylenediamine diacetate (EDDA) as coligands and HYNIC as the dual functional chelator.The bioactivity of 99Tc m-HYNIC-c (RGDfK) was measured by cell binding experiments.(2) The nude mice bearing human A549 lung adenocarcinoma were randomly divided into 7 groups with 5 in each group.The 7 th group was the competitive inhibition control group and was administrated 100 μg HYNIC -c (RDGfK) 30 min earlier before the injection of 99Tcm-H Y N IC-c ( RGDfK ).The nude mice were scanned at 0.5,1,2,4,8 and 12 h respectively after intravenous injection of 7.4 MBq 99Tcm-HYNIC-c(RGDfK).The biodistribution of the agent was measured as ％ ID/g.The uptake ratio of tumor to muscle (T/NT) was also measured by placing ROI on 99Tcm-HYNIC-c(RGDfK) SPECT imaging.(3)Gamma imaging was performed in 6 mice including 3 in the competitive inhibition control group at 0.5,1,2,4,8 and 12 h post injection.ResultsThe labeling yield of 99Tcm-HYNIC-c(RGDfK) was more than 90％,and the radiochemical purity was more than 95％.99Tcm-HYNIC-c(RGDfK) can specifically bind with A549 adenocarcinoma cells with a binding rate up to 36.14％.Biodistribution study showed that the uptake in the kidney was above 20 ％ ID/g during 0.5 - 8 h post injection.The ％ ID/g in tumor was 10.52 ± 1.48 at 0.5 h,17.26 ±2.81 at 8 h,and 8.93 ±0.90 at 12 h.However,the ％ ID/g in tumor was only 2.29 ±0.85 in the competitive inhibition control group at 0.5 h.The highest T/NT was 6.87 at 8 h by the ROI analysis.Xenograffted tumors could be visualized at 1 h and delineated more clearly from 4 to 8 h post injection of 99Tcm-HYNIC-c(RGDfK).Conclusions99 Tcm-HYNIC-c (RGDfK) can be readily synthesized.Its binding with A549 lung adenocarcinoma cells is specific and the binding rate is high.