"...4 -c(GX1) 774.9 μM or HYNIC-E-[c(RGDfk)-c(GX1)] 569.5 μM (μg/mL) (CPC Scientific Inc., CA ... 5 /well) were seeded into well culture plates, and it was added the radiotracers 99m Tc-HYNIC-PEG 4 -c ... For nonspecific binding assays, cold conjugate (1 mmol/L/well) was also ..."
Abstract
Introduction
Aiming to develop a novel 99mTc-labeled imaging agent, for angiogenesis and tumor receptors, two peptides obtained from phage display library, namely GX1 and the heterodimer RGD-GX1, were synthesized in a cyclic conformation. They were radiolabeled with 99mTc, employing the HYNIC chelator, for radiochemical evaluation and biological properties.
Methods
Radiolabeling, radiochemical control, plasma protein binding, and partition coefficient were assessed for both radioconjugates. Biodistribution in healthy Balb/c mice was carried out, in order to evaluate the biological behaviour of the radiocomplexes.
Results
The conjugates displayed a rather similar pharmacokinetic profile. They were prepared with high radiochemical purity (> 96%), and both were hydrophilic (log P of − 2.25 and − 2.51 respectively). Preferential renal excretion was observed. Kidney uptake (42.31 ± 5.35 %ID/g) for 99mTc-HYNIC-E-[c(RGDfk)-c(GX1)], 1 h post-injection was about three times higher than the uptake of 99mTc-HYNIC-PEG4-c(GX1) (11.92 ± 4.77%ID/g). Total blood, bone and muscle values revealed a slightly slower clearance for the RGD-GX1 radiocomplex.
Conclusion
The high radiochemical purity achieved, and the similar in vivo profile observed for both radioconjugates, make them potential candidates for radiopharmaceuticals for tumor imaging. Further investigations of binding affinity, and uptake of GX1 and RGD-GX1 peptides in tumor models, are warranted.
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