Preparation and microPET imaging of somatostatin receptor antagonist 68Ga-NOTA-JR11

Abstract

Objective To prepare a novel somatostatin receptor (SSTR) antagonist 68Ga-1, 4, 7-triazacyclononane-1, 4, 7-triacetic acid (NOTA)-JR11 (Cpa-c(D-Cys-Aph(Hor)-D-Aph(Cbm)-Lys-Thr-Cys)-D-Tyr-NH2) tracer and observe its biodistribution and microPET imaging in mice. Methods One ml HCl (0.05 mol/L) containing 68GaCl3 (148 MBq) was added into 65 μl NaAc (1 mol/L) and 4 μg NOTA-JR11. The mixture reacted at 95 ℃ for 15 min, and then was purified with Sep-Pak® C18 Light column to obtain 68Ga-NOTA-JR11. 68Ga-NOTA-JR11 was subjected to quality control analysis including radiochemical purity and in vitro stability by radio-high performance liquid chromatography. Biodistribution of 68Ga-NOTA-JR11 (0.37 MBq) in BALB/c mice (n=9) at 5, 30, 60 min postinjection were observed (n=3 for each time point), and the percentage activity of injection dose per gram of tissue (%ID/g) was calculated. 68Ga-NOTA-JR11 (14.8 MBq) microPET imaging of BALB/c mice (n=1) at 60 min postinjection was observed. Results 68Ga-NOTA-JR11 was obtained successfully within 15 min, with yielding rate of 90%, radiochemical purity of more than 99%, and specific activity of 6.10 GBq/μmol. The tracer showed excellent stability (radiochemical purity: 95%) in different buffers within 150 min. The biodistribution was basically consistent with microPET imaging results. 68Ga-NOTA-JR11 was metabolized through the kidneys and had low uptake in the liver ((0.75±0.26) %ID/g) at 60 min postinjection. Conclusions 68Ga-NOTA-JR11 can be prepared rapidly, with high yielding rate and radiochemical purity. Biodistribution and imaging results provide basic information for the further study of somatostatin receptor imaging in neuroendocrine tumors. Key words: Antistatic agents; Receptors, somatostatin; Isotope labeling; Gallium radioisotopes; Positron-emission tomography; Mice