This report describes the evaluation of biodistribution properties of three radiotracers, [(99m)Tc(SQ168)(
EDDA)], [(99m)Tc(SQ168)(
tricine)(PDA)], and [(99m)Tc(SQ168)(
tricine)(TPPTS)] (SQ168 = [2-[[[5-[carboonyl]-2-pyridinyl]hydrazono]methyl]
benzenesulfonic acid]-Glu(cyclo{Lys-
Arg-Gly-Asp-d-Phe})-cyclo{Lys-
Arg-Gly-Asp-d-Phe};
EDDA =
ethylenediamine-N,N'-diacetic
acid; PDA = 2,5-pyridinedicarboxylic
acid; TPPTS = trisodium
triphenylphosphine-3,3',3' '-trisulfonate), and their potential to image the
glioma integrin alpha(v)beta(3) expression in BALB/c nude mice bearing the U87MG human
glioma xenografts. It was found that all three radiotracers were able to localize in
glioma tumors with a relatively high
tumor uptake and long
tumor retention time by binding to the
integrin alpha(v)beta(3) expressed on both
tumor cells and endothelial cells of
tumor neovasculature. It seems that the coligand has minimal effect on
integrin alpha(v)beta(3) targeting capability of the (99m)Tc-labeled RGDfK dimer, but it has a significant impact on their biodistribution properties. For example, the complex [(99m)Tc(SQ168)(
tricine)(TPPTS)] has the lowest liver uptake and the highest metabolic stability in normal BALB/c nude mice. Results from SPECT imaging studies show that the
glioma tumors can be clearly visualized with all three radiotracers at 4 h postinjection. Among the three radiotracers evaluated in this study, [(99m)Tc(SQ168)(
tricine)(TPPTS)] has the best imaging quality and is a promising candidate for more preclinical evaluations in the future.