Imaging study of 18F-SDM-8 in rat temporal lobe epilepsy model / 中华核医学与分子影像杂志

Objective:To explore whether the specific synaptic vesicle glycoprotein 2A (SV2A) targeted imaging agent ( R)-4-(3-fluoro-5-(fluoro- 18F)phenyl)-1-((3-methylpyridin-4-yl)methyl)pyrrolidin-2-one ( 18F-SDM-8) can be used to detect epileptic foci. Methods:Twenty male Sprague-Dawley (SD) rats (8-9 weeks) were injected with 1.2 μl of kainic acid (16 rats in the epilepsy group) or saline (4 rats in the control group) into the right hippocampus. 18F-SDM-8 and 18F-FDG mircoPET/CT imaging were respectively performed at 1-2 d (acute phase), 6-7 d (incubation period) and 45-60 d (chronic phase) after the seizure. Asymmetric index (AI) was used to evaluate the epileptic foci identify ability of 18F-SDM-8. Paired t test, Mann-Whitney U test and Pearson correlation analysis were used to analyze data. Results:In the three periods of 18F-SDM-8 imaging, the differences of AI of hippocampus between the epilepsy group and control group were statistically significant ( z values: from -2.64 to 2.67, all P<0.05). Both imaging agents had asymmetric uptake in the epilepsy group (right was lower than left), and the decrease in the medial right temporal lobe was the most significant. The pathological staining results were consistent with the imaging results. In the chronic phase of the epilepsy group, the differences of 18F-SDM-8 SUV mean (right versus left) in each brain area of interest were statistically significant ( t value: from -33.40 to -5.60, all P<0.05). The asymmetric uptake of the two imaging agents in the hippocampus had a better correlation ( r=0.97, P=0.001), and the AI of 18F-SDM-8 ((34.2±8.4)%) in this area was 1.4 times higher than that of 18F-FDG ((24.6±4.7)%). Conclusions:18F-SDM-8 PET is a promising method to test the level of SV2A. It can reflect the changes of SV2A in the rat epilepsy model induced by intrahippocampal injection of kainic acid, and improve the sensitivity of molecular imaging for epileptic foci.

MicroPET imaging studies of 89Zr-labeled EGFR and HER2 antibodies in gastric mucinous adenocarcinoma / 中华核医学与分子影像杂志

Objective:To screen 89Zr-labeled anti-epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2) monoclonal antibody molecular probes suitable for monitoring the gastric mucinous adenocarcinoma bearing mouse models with low glucose metabolism. Methods:The expression of EGFR and HER2 in the MGC803 gastric cancer cell line was verified by analyzing cell slides and xenograft tumor sections. 89Zr-Deferoxamine (DFO)-Cetuximab and 89Zr-DFO-Pertuzumab were prepared and the radiochemical purity was detected. Cell binding experiments and blocking experiments were performed to verify the binding ability and specificity of the probes. Twelve gastric mucinous adenocarcinoma bearing mouse models were divided into 3 groups ( n=4 in each group): 89Zr-DFO-Cetuximab group (7.4 MBq/mouse, 74 μg/mouse), 89Zr-DFO-Pertuzumab group (7.4 MBq/mouse, 70 μg/mouse) and 18F-fluorodeoxyglucose (FDG) group (7.4 MBq/mouse). MicroPET imaging was performed at 4, 24 and 48 h ( 18F-FDG group underwent imaging at 1 h only) post-injection. The biodistribution study of 89Zr-DFO-Cetuximab and 89Zr-DFO-Pertuzumab was conducted in 2 groups ( n=4 in each group) 48 h after the injection. The independent sample t test was used for data analysis. Results:The immunofluorescent staining demonstrated EGFR expression was significantly higher than HER2 expression in MGC803 gastric cancer cell line. The radiochemical purity of 89Zr-DFO-Cetuximab and 89Zr-DFO-Pertuzumab were both more than 95%, and the specific activities were 100 and 95 MBq/mg, respectively. The two probes had good stability in normal saline and fetal bovine serum, with the radiochemical purity higher than 80% at 72 h. MicroPET imaging showed that the uptake of 89Zr-DFO-Cetuximab in the MGC803 tumor was significantly higher than that of 18F-FDG and 89Zr-DFO-Pertuzumab. The biodistribution study demonstrated the 89Zr-DFO-Cetuximab uptake (percentage activity of injection dose per gram of tissue, %ID/g) of tumors at 48 h was significantly higher than that of 89Zr-DFO-Pertuzumab (56.3±12.0 vs 22.0±3.6; t=4.31, P<0.05). Conclusion:Compared with 89Zr-DFO-Pertuzumab, 89Zr-DFO-Cetuximab has a better potential for non-invasive monitoring of gastric mucinous adenocarcinoma with low glucose metabolism.

Preparation of 68Ga labeled pre-targeted molecular probe based on bio-orthogonal Diels-Alder click chemistry and CD11b receptor targeted imaging in CT26 colon cancer mouse models / 中华核医学与分子影像杂志

Objective:To prepare a 68Ga labeled probe targeting integrin alpha M(CD11b) receptor, namely 68Ga-1, 4, 7-triazacyclononane-1, 4, 7-triacetic acid-Glycine-Arginine-Glutamate-Arginine-Glutamate-polyethylene glycol 11-1, 2, 4, 5-terazine/CD11b antibody-F(ab′) 2-trans-cyclooctene ( 68Ga-NOTA-Polypeptide-PEG 11-Tz/anti-CD11b-F(ab′) 2-TCO), and to explore its feasibility as a molecular probe for CD11b receptor through microPET imaging. Methods:Immunofluorescence was used to detect the expression of CD11b on the surface of RAW264.7 cell. CD11b specific monoclonal antibody (M1/70) was conjugated with TCO, and anti-CD11b-F(ab′) 2-TCO fragment was obtained. The ligand NOTA-Polypeptide-PEG 11-Tz was labeled with 68Ga, and its specific activity and radiochemical purity were detected. Pre-targeted cell binding experiment was conducted to evaluate the binding ability of molecular probe. CT26 colon cancer bearing mouse models were established, and then pre-targeted biodistribution and imaging experiments were performed. Immunohistochemical experiment was used to verify the expression of CD11b receptor in tumor. The one-way analysis of variance was used to compare the data. Results:The results of immunofluorescence demonstrated CD11b receptor was highly expressed on the surface of RAW264.7 cell. Anti-CD11b-F(ab′) 2-TCO fragment was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). 68Ga-NOTA-Polypeptide-PEG 11-Tz was successfully synthesized, with the labeling efficiency of 94.6%. The specific activity was 7.0-7.4 MBq/μg, and the radiochemical purity was higher than 95%. Pre-targeted cell binding experiment confirmed that the molecular probe bound to the CD11b receptor. The biodistribution and imaging experiments showed that the kidney radioactivity uptake was high at pre-targeted 4, 12 and 24 h intervals, which proved that probe was excreted through the urinary system. In addition, molecular probe had higher radioactive uptake at the tumor site, with the tumor/muscle ratios of 9.23±1.45, 12.53±1.36 and 10.74±1.11 ( F=848.8, P<0.05). When the radioligand was injected 1 h after the pre-positioned 12 h interval, the images contrast was the best, with the standardized uptake value (SUV) in tumor and muscle of 0.67±0.12, 0.09±0.04, respectively. Immunohistochemistry verified the highly expression of CD11b receptor in tumor. Conclusions:The pre-targeted molecular probe 68Ga-NOTA-Polypeptide-PEG 11-Tz/anti-CD11b-F(ab′) 2-TCO is successfully synthesized. The molecular probe has targeting ability for CD11b + colon cancer, and is expected to be used as a tracer targeting CD11b receptor in vivo.

Development of nuclide targeted matrix metalloproteinase inhibitors in atherosclerotic plaque imaging / 中华核医学与分子影像杂志

Atherosclerotic vulnerable plaques may cause acute cardiovascular events.Matrix metalloproteinase (MMP) plays an important role in the pathological process of high-risk plaques.It degrades the extracellular matrix of atherosclerotic plaque,thus making the fibrous cap thinner and the plaque more vulnerable,which lead to rupture.MMP inhibitors (MMPI) can specially bind MMP and inhibit its activity.Taking MMP as the target,nuclear medical imaging can identify and evaluate the unstable plaque in molecular level,and can also be used to explore the biological characteristics of plaque,as well as to monitor drug efficiency.This review summarizes the development of nuclide targeted MMPI in atherosclerotic plaque imaging.

SP94 peptide as a specific probe for hepatocellular carcinoma imaging / 中华核医学与分子影像杂志

Objective To investigate the capability of 99 Tcm?tricine?EDDA/HYNIC?SFSIIHTPILPL ( SP94) as a specific probe for HCC imaging. Methods HYNIC?SP94 peptide was prepared by solid phase synthesis, followed by 99 Tcm labeling with tricine?EDDA as the coligand. After determination of radiochemical purity and stability, cell binding study was carried out by incubating Huh?7 cells with 99 Tcm?tricine?EDDA/HYNIC?SP94 at different specific activities (2.5, 4.0 and 30.0 GBq/μmol). The biodistribution studies and microSPECT/CT imaging were performed in Huh?7 tumor?bearing mice ( study group) and Hela tumor?bear?ing mice ( control group ) . Statistical analysis was by two?sample t test. Results 99 Tcm?tricine?EDDA/HYNIC?SP94 was synthesized with over 95% of labeling yield, which remained stable in saline and FBS up to 12 h. With increasing concentrations of 99 Tcm?tricine?EDDA/HYNIC?SP94, Huh?7 cell binding increased but became gradually saturated. In biodistribution studies, (1.02±0.26) %ID/g of tracer was accumulated in Huh?7 tumors at 0.5 h after injection of 99 Tcm?tricine?EDDA/HYNIC?SP94, higher than that in the HYNIC?SP94 blocking group ((0.34±0.09) %ID/g;t=3.537, P<0.05). Compared to Hela tumors, Huh?7 tumors were clearly visualized by microSPECT/CT, with which better imaging quality could be achieved with higher specific radioactivity. Conclusion 99 Tcm?tricine?EDDA/HYNIC?SP94 could achieve a high labeling effi?ciency and good in vitro stability as a potential diagnostic tracer specifically targeted for HCC.

Research progress of nuclear medicine imaging in detection of vulnerable atherosclerotic plaques / 中华核医学与分子影像杂志

Atherosclerosis is a vascular inflammatory disease.Vulnerable atherosclerotic plaques mainly lead to severe cardiovascular and cerebrovascular diseases,such as myocardial infarction and stroke.The research on the early diagnosis of vulnerable plaques becomes currently urgent.As a noninvasive molecular modality,the nuclear medicine imaging (with specific radiolabeled probes) has been used for the detection of unstable plaques,and for the evaluation of therapeutic effect of anti-atherosclerotic drugs.Nuclear imaging techniques for detecting metabolic activity,inflammation,hypoxia,angiogenesis,apoptosis,and microcalcification in unstable plaques are summarized in this review.