We developed a Tc-99m and fluorescence-labeled
peptide, Tc-99m TAMRA-GHEG-ECG-
VAPG to target
tumor cells and evaluated the diagnostic performance as a dual-modality imaging agent for
tumor in a murine model. TAMRA-GHEG-ECG-
VAPG was synthesized by using Fmoc solid-phase peptide synthesis. Radiolabeling of TAMRA-GHEG-ECG-
VAPG with Tc-99m was done by using
ligand exchange via
tartrate. Binding affinity and in vitro cellular uptake studies were performed.
Gamma camera imaging, biodistribution, and ex vivo imaging studies were performed in murine models with SW620
tumors.
Tumor tissue slides were prepared and analyzed with immunohistochemistry by using confocal microscopy. After radiolabeling procedures with Tc-99m, Tc-99m TAMRA-GHEG-ECG-
VAPG complexes were prepared in high yield (>96%). The Kd of Tc-99m TAMRA-GHEG-ECG-
VAPG determined by saturation binding was 16.8 ± 3.6 nM. Confocal microscopy images of SW620 cells incubated with TAMRA-GHEG-ECG-
VAPG showed strong fluorescence in the cytoplasm.
Gamma camera imaging revealed substantial uptake of Tc-99m TAMRA-GHEG-ECG-
VAPG in
tumors.
Tumor uptake was effectively blocked by the coinjection of an excess concentration of
VAPG. Specific uptake of Tc-99m TAMRA-GHEG-ECG-
VAPG was confirmed by biodistribution, ex vivo imaging, and immunohistochemistry
stain studies. In vivo and in vitro studies revealed substantial uptake of Tc-99m TAMRA-GHEG-ECG-
VAPG in
tumor cells. Tc-99m TAMRA-GHEG-ECG-
VAPG has potential as a dual-modality
tumor imaging agent.