Initial evaluation of ^99m Tc-tricarbonyl-cyclopentadienyl fatty acids derivatives as SPECT tracers for myocardium

Abstract

Fatty acids are myocardial metabolic agent for detecting myocardial ischemia and infraction. However, no Tc-labeled fatty acids had potential use in clinical practice. In this study, Tc-CpTT-10-oxo-para-PPA (1d), Tc-CpTT-11-oxo-para-PPA (2d), Tc-CpTT-12-oxo-para-PPA (3d), Tc-CpTT-11-oxo-ortho-PPA (4d), and Tc-CpTT-11-oxo-meta-PPA (5d) were synthesized by a double ligand transfer reaction, and their biological behaviors were investigated. Compound 2d achieved good heart to blood ratio (3.39 at 5 min after intravenous), and 2d showed high-heart uptake of 6.20% ID/g at 5 minutes after injection. Compound 3d displayed a prolonged retention in the myocardium (1.43% ID/g at 60 min after injection). Radioactivity accumulation in the lungs, spleen, and blood was eliminated rapidly. In vivo, metabolite analysis presented that compound 6d may be metabolite of 2d through β-oxidation in tissue. Unfortunately, the biodistribution studies of 1d, 2d, 3d, 4d, and 5d showed fast heart clearance and poor heart to liver ratios, which suggested that the 5 Tc-labeled fatty acid analogues cannot be used for diagnosis.

99mTc‐labeled oligomeric nanoparticles as potential agents for folate receptor‐positive tumor targeting

“…Single photon emission computed tomography (SPECT) is a nuclear medicine technology by which γ ‐ray emissions from a radioisotope are used to localize cancer and its products. Among the radioisotopes used in diagnostic imaging nuclear medicine by SPECT, technetium 99m ( 99m Tc) is so far the most widely used material for the following reasons: It can be readily produced by commercial 99 Mo/ 99m Tc generator in clinic as well as its low cost; besides, its moderate gamma‐ray energy (141 keV photon) and favorable decay properties (T 1/2 = 6.01 h) extremely fulfill the SPECT imaging requirements . Thus, new 99m Tc‐labeled imaging probes can provide convenient, economical, and widespread SPECT‐based imaging methods for early cancer diagnosis.…”