ABSTRACT
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.
ABSTRACT
Objective (1) To evaluate the effect of insertion of two 15-amino-4,7,10,13-tetraoxapentadecanoic (2 PEG4 ) linkers into cyclic Arg-Gly-Asp (RGD) Dimer E [c(RGDfK)]2 on receptor binding in vitro, (2) to assess its biodistribution in vivo and (3) to investigate the value of 99Tcm labeled 2PEG4-Dimer for integrin αvβ3-positive tumors imaging.Methods The expression of U87 human glioma cells and integrin αv β3 was determined by immunofluorescence staining.The half-inhibition concentrations (IC50) for 125 I-cyclo (Arg-Gly-Asp-D-Tyr-Lys) (c(RGDyK) ) of c ( RGDyK ), hydrazinonictinamide ( HYNIC )-Dimer and HYNIC-2PEG4-Dimer binding to integrin αvβ3 were measured.99Tcm-HYNIC-Dimer and 99Tcm-HYNIC-2PEG4-Dimer were synthesized using non-SnCl2 formulation.Biodistribution and imaging studies were performed in nude mice bearing human glioma xenografts.The unpaired t test was used for statistical analysis.Results The labeling yield of the two radiotracers was more than 95%, and the radiochemical purity was more than 99% through Sep-Pek C18 cartridge.HYNIC-2PEG4-Dimer had significantly higher binding affinity of integrin αvβ3 than c(RGDyK) and HYNIC-Dimer (IC50 = 0.8 nmol/L, 27 nmol/L and 2.4 nmol/L, respectively).Biodistribution study showed that 99Tcm-HYNIC-2PEG4-Dimer was mainly excreted via the kidney.The tumor uptake of 99Tcm-HYNIC-2PEG4-Dimer was higher than that of 99Tcm-HYNIC-Dimer at 2h post injection ((5.71 ±0.96) and (2.10 ±0.50) % ID/g, t =4.80, P＜0.05).The xenografted tumors were visible at 0.5 h post injection and the image contrast increased with time due to the tracer clearance of the background tissue.Conclusion 99 Tcm-HYNIC-2PEG4-Dimer is a promising radiotracer for integrin αvβ3-positive tumor imaging.