Preliminary Study of Radioiodination of VP2

The VP2 peptide specifically binding to vasoactive intestinal polypeptide receptor 1(VPAC1) receptor was radioiodinated with ¹³¹I by bi-functional linker N-succinimidyl 5-(tributylstannyl)-3-pyridinecarboxylate (SPC), and in vitro and in vivo stability of the labeled peptide were evaluated. Mice were injected intravenously with either 1.2×10⁶ Bq ¹³¹I-SPC-VP2 or Na ¹³¹I. Radiochemical purity and biodistribution were studied at various time points. The result showed that purified ¹³¹I-SPC-VP2 exhibited radiochemical purity of 97% at room temperature up to 48 h. The tissue uptake of ¹³¹I-SPC-VP2 was low after 6 h injection, especially in thyroid. The result indicated the labeled compound had fast clearance and good stability in vivo.