Radiolabeling, autoradiogram and in vivo imaging of atherosclerosis- specific peptide

The aim of this study is the detection of atherosclerosis by using radiolabeled small peptides via non-invasive nuclear imaging. A small peptide, which shows high binding affinity for atherosclerotic lesions in vessels (AP), was synthesized by using a standard Fmoc method and diethylenetriaminepentaacetic acid (DTPA) or tyrosine was conjugated at the N-terminal of the AP to provide DTPA-AP-CC or Y-AP, respectively. The prepared peptide was labeled by " ^99mTc, ¹¹¹In or ¹²³I. The labeled peptides were injected into atherosclerosis-induced mice (LDLr^(-/-) knockout mice) and control mice via the tail vein. At 15 min post injection, the aortas of the LDLr^(-/-) knockout and control mice were excised for an autoradiogram study. Gamma scintigraphic images were obtained at 30 min and 1 h. The optimized labeling yield of [ ^99mTc]DTPA-AP-CC, [¹¹¹In]DTPA-AP-CC and [ ¹²³I]Y-AP was over 35%, 100% and over 20%, respectively. Autoradiographic studies showed that the aorta uptakes of [^99mTc] DTPA-AP-CC and [¹¹¹In]DTPA-AP-CC in the LDLr^(-/-) knockout mice were much higher than the corresponding uptakes in the control mice. In contrast, the aorta uptake of [¹²³I]Y-AP in LDLr^(-/-) and normal mice were comparable. Scintigraphic images, however, did not show any noticeable uptake differences between the LDLr^(-/-) knockout and the control mice, which is mostly due to the high background in the abdominal region and to the non-sufficient resolution of gamma camera imaging for the aorta of the mice.