Optimal labeling conditions of 68Ga-DOTA-iNGR and its biodistribution in mice / 中华核医学与分子影像杂志

ABSTRACT

Objective To explore the optimal conditions of preparing 68Ga-DOTA-iNGR (NGR peptide containing CendR motif),to evaluate its biodistribution in normal mice and to perform microPET imaging in tumor-bearing nude mice.Methods 68Ga fresh eluent (200 μl,92.5-129.5 MBq) obtaining with 68Ge-68Ga radionuclide generator was used to label DOTA-iNGR.The optimal conditions of labeling including pH,temperature,reacting time and concentration of DOTA-iNGR were determined.Then,the in vitro and in vivo stability and octanol/water partition coefficient of 68Ga-DOTA-iNGR were further analyzed.The biodistribution in normal Kunming mice was examined at 10,20,40,60 and 120 min after injection of 68Ga-DOTA-iNGR.Nude mice bearing HT-1080 (CDl3-positive) and HT-29 (CDl3-negative) tumors were established and underwent microPET imaging at 1 h after the intravenous injection of 68Ga-DOTA-iNGR.Data were analyzed using independent-sample t test.Results The optimal conditions of labeling was mixing 2 μg DOTA-iNGR peptide with 200 μl 68Ga (92.5-129.5 MBq) at pH 4.0,temperature 90-100 ℃ for 5-10 min.Under this condition,labeling rate reached (97.5± 1.3)％.The radiochemical purity of 68Ga-DOTA-iNGR in both saline (room temperature) and mouse serum (37 C) were both above 95％ after 4 h incubation,and the radiochemical purity in urine was greater than 85％ after 1 h metabolism in vivo.The partition coefficient was-2.71±0.18.In normal mice,majority of 68Ga-DOTA-iNGR was excreted from kidneys with a rapid clearance from blood.The in vivo microPET imaging showed that 68Ga-DOTA-iNGR was remarkably accumulated in the CD13-positive HT-1080 tumor.Conclusions Labeling DOTA-iNGR with 68Ga under our condition is a simple and efficient procedure with high labeling rate and high specificity.The product 68Ga-DOTA-iNGR has high stability,ideal biodistribution,and specific binding to CD13-positive tumor,which means that it's a very promising molecular probe for noninvasively detecting CD13-positive tumor.