With respect to the reported promising results of cyclic peptide CGPRPPC in early detection of thrombotic lesions, we developed a practical approach for technetium-99m labeling of this peptide using the Glycine–Alanine–Glycine–Glycine (GAGG) sequence as a chelating moiety.
The peptide conjugated to GAGG was prepared using the solid-phase method. The optimization of radiolabeling conditions was performed on the basis of such variables as incubation time, reaction temperature, pH, and concentration of peptide and stannous chloride. Moreover, the stability and fibrin-binding affinity of the radiolabeled peptide were measured. The peptide–fibrin interactions were analyzed by docking studies using HEX and Auto dock 4.2. Softwares.
The amounts of synthesized peptide and stannous chloride required for optimal radiolabeling through GAGG were 10 µmol/l and 5 µg, respectively. The best radiochemical purity% (>93%) was achieved at pH 7–8 within 15 min and a reaction temperature of 37°C. On the basis of in silico and in-vitro results, the GAGG-conjugated CGPRPPC peptide showed better binding affinity versus the HYNIC-conjugated one.
We could radiolabel the fibrin-targeting peptide with high radiochemical purity% and stability during a short incubation period without a boiling step. Compared with the HYNIC-conjugated peptide, a higher binding affinity was found. Therefore, the GAGG chelating moiety possesses a considerable potentiality in Technetium 99m labeling of peptides while CGPRPPC maintains its binding properties to thrombotic lesions.
aDepartment of Radiopharmacy, Faculty of Pharmacy, Tehran University of Medical Sciences
bDepartment of Pharmaceutical Chemistry and Radiopharmacy, School of Pharmacy, Protein Technology Research Center
cDepartment of Pharmaceutical Chemistry and Radiopharmacy, School of Pharmacy, Phytochemistry Research Center
dPhytochemistry Research Center, Shahid Beheshti University of Medical Sciences, Tehran
eAlborz University of Medical Sciences, Karaj, Iran
Correspondence to Sedigheh Rezaeianpour, PhD, Phytochemistry Research Center, Shahid Beheshti University of Medical Sciences, Vali-e Asr Avenue, Niayesh Junction, P.O. Box 14155-6153, 19839-63113 Tehran, Iran Tel: +98 912 795 9554; e-mail: email@example.com
Received June 9, 2018
Received in revised form July 8, 2018
Accepted August 6, 2018