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Objective:To explore the application potential of 18F-Asp-Glu-val-Asp (DEVD)-Cys(StBu)-PPG(CBT)-AmBF 3 ( 18F-1; PPG: propargyl-glycine; CBT: 2-cyanobenzothiazole; AmBF 3: ammoniomethyl-trifluoroborate) PET imaging in early monitoring of triple-negative breast cancer (TNBC) radiotherapy response. Methods:Ten MDA-MB-231 tumor bearing nude mice models were constructed and divided into radiotherapy group ( n=5) and non-radiotherapy group ( n=5) by random sampling method. The radiotherapy group was treated with single irradiation at a dose of 8 Gy. 18F-1 microPET imaging was performed in the radiotherapy and non-radiotherapy groups, and the tumor uptake and muscle uptake in 2 groups at different time points (2.5, 7.5, 12.5, 17.5, 22.5, 27.5, 32.5, 37.5, 42.5, 47.5, 52.5, 57.5 min after injection) were analyzed. The specific uptake of the probe in apoptotic cells was verified by radioautography, HE staining and immunofluorescent staining. Repeated measures analysis of variance and one-way analysis of variance were used to analyze data. Results:18F-1 microPET imaging showed that there was significant difference between tumor uptake and muscle uptake in radiotherapy group ( F=20.27, P=0.011). The uptake of radiotherapy group was the highest at 7.5 min after injection ((4.64±0.35) percentage activity of injection dose per gram of tissue(%ID/g)). There was no significant difference between tumor uptake and muscle uptake in the non-radiotherapy group ( F=1.81, P=0.215). The tumor/muscle (T/M) ratio of radiotherapy group was higher than that of non-radiotherapy group ( F=31.95, P=0.005), with the highest at 47.5 min after injection (2.49±0.46). Radioautography showed that the tumor radioactivity in radiotherapy group was higher than that of muscle in radiotherapy group, and was also higher than tumor and muscle radioactivies in non-radiotherapy group ( F=116.79, P<0.001). HE staining and immunofluorescent staining verified that 18F-1 could specifically detect the activity of caspase-3 activated in tumor cells after radiotherapy. Conclusion:18F-1 can specifically recognize the activated caspase-3 after TNBC radiotherapy, and monitor radiotherapy response at the molecular level by apoptosis PET imaging.
ABSTRACT
Despite advances in immunotherapy for the treatment of cancers,not all patients can benefit from programmed cell death ligand 1(PD-L1)immune checkpoint blockade therapy.Anti-PD-L1 therapeutic effects reportedly correlate with the PD-L1 expression level;hence,accurate detection of PD-L1 expression can guide immunotherapy to achieve better therapeutic effects.Therefore,based on the high affinity antibody Nb109,a new site-specifically radiolabeled tracer,68Ga-NODA-cysteine,aspartic acid,and valine(CDV)-Nb109,was designed and synthesized to accurately monitor PD-L1 expression.The tracer 68Ga-NODA-CDV-Nb109 was obtained using a site-specific conjugation strategy with a radiochemical yield of about 95％and radiochemical purity of 97％.It showed high affinity for PD-L1 with a dissociation constant of 12.34±1.65 nM.Both the cell uptake assay and positron emission tomography(PET)imaging revealed higher tracer uptake in PD-L1-positive A375-hPD-L1 and U87 tumor cells than in PD-L1-negative A375 tumor cells.Meanwhile,dynamic PET imaging of a NC1-H1299 xenograft indicated that doxorubicin could upregulate PD-L1 expression,allowing timely interventional immunotherapy.In conclusion,this tracer could sensitively and dynamically monitor changes in PD-L1 expression levels in different cancers and help screen patients who can benefit from anti-PD-L1 immunotherapy.
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Objective:To synthesize a novel site-specifically labelled probe 68Ga-1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA)-Cys-Asp-Val (CDV)-Nb109 and explore its potential for detection of the programmed cell death ligand 1 (PD-L1) expression level in different tumors. Methods:Firstly, CDV was inserted into the tail of the sequence of Nb109 by genetic engineering. Then the precursor DOTA-CDV-Nb109 was prepared by mixing the maleimide-DOTA and the single-domain antibody CDV-Nb109 (amount of substance ratio 1∶1) via the maleimide-cysteine site-specific coupling strategy. Subsequently, the DOTA-CDV-Nb109 was labeled with 68Ga and purified by PD-10 column. Human melanoma A375, human PD-L1 transfected melanoma A375-hPD-L1 and human glioma U87 tumor-bearing mice models were established, and the diagnostic value of 68Ga-DOTA-CDV-Nb109 was evaluated by stability assay, cellular uptake, and microPET imaging. One-way analysis of variance and the least significant difference t test were used to analyze the data. Results:The probe 68Ga-DOTA-CDV-Nb109 was obtained with the radiochemical yield of (69.79±4.69)%, radiochemical purity more than 97%, and molar activity of (12.85±1.51) GBq/μmol. 68Ga-DOTA-CDV-Nb109 had strong binding affinity for A375-hPD-L1 with the dissociation constant ( Kd) of (66.43±17.89) nmol/L. The uptake of 68Ga-DOTA-CDV-Nb109 in A375-hPD-L1 and U87 cells were (3.17±0.15) percentage of the added radioactivity dose (%AD) and (2.08±0.03) %AD respectively, which were significantly higher than that in A375 cells ((1.21±0.14) %AD; F=82.87, t values: 15.23, 9.98, P values: <0.001, 0.003). The tumor uptake of the probe in A375-hPD-L1 ((5.21±0.35) percentage of injected dose per ml (%ID/ml)) and U87 tumor-bearing mice ((3.44±0.69) %ID/ml) were significantly higher than that in A375 tumor-bearing mice ((2.17±0.36) %ID/ml; F=249.72, t values: 35.70, 3.43, both P<0.001). Conclusion:The site-specifically labelled probe 68Ga-DOTA-CDV-Nb109, which can non-invasively and dynamically monitor the change of PD-L1 expression level in different tumors and help screen patients who can benefit from PD-L1 immune checkpoint blocking therapy, is successfully synthesized with high radiochemical purity.
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Objective:To prepare specific molecular probe 18F-AlF-1, 4, 7-triazacylononane-1, 4, 7-triacetic acid-(polyethylene glycol) 4-ZD2 ( 18F-AlF-NOTA-PEG 4-ZD2) for targeting extradomain-B fibronectin (EDB-FN), and evaluate its properties in vitro and in vivo. Methods:18F-AlF-NOTA-PEG 4-ZD2 was prepared by one-step chelation labeling with Al 18F. The radiochemical purity and in vitro stability were determined by high performance liquid chromatography (HPLC). The partition coefficient (logP) of 18F-AlF-NOTA-PEG 4-ZD2 was evaluated, and the cell uptake experiment was carried out (triple-negative breast cancer (MDA-MB-231) cells (1×10 6/tube) were divided into 3 groups ( n=3 per group); positive group, inhibition group, control group). MicroPET imaging was performed on MDA-MB-231 bearing nude mice ( n=3) after 18F-AlF-NOTA-PEG 4-ZD2 injection (30, 60, 90, 120 min) and compared with blocking group ( n=3, NOTA-PEG 4-ZQ 2 was preinjected at 0.5 h before 18F-AIF-NOTA-PEG a-ZD2 injection). Independent-sample t test was used to analyze the data. Results:18F-AlF-NOTA-PEG 4-ZD2 was successfully prepared. The optimized radiochemical yield was (33.8±2.1)% (undecay corrected, n=8) and the radiochemical purity was >96%. After incubating 120 min at 37 ℃, the radiochemical purity of 18F-AlF-NOTA-PEG 4-ZD2 in human serum and PBS was >93%, indicating its good stability in vitro. The specific activity was (11.1±3.2) GBq/μmol, and logP was -1.43±0.05. The uptake value of tumor cells was (1.77±0.28) percentage applied activity (%AR)/10 6 cells at 120 min post-injection in positive group, and the total uptake value of the inhibition group was (0.76±0.07) %AR/10 6 cells ( t=4.30, P=0.032). MicroPET imaging in tumor bearing nude mice showed that 18F-AlF-NOTA-PEG 4-ZD2 was mainly metabolized by the liver and kidneys. The tumor uptake value was (1.94±0.21) percentage activity of injection dose per gram of tissue (%ID/g) at 60 min post-injection and the tumor/muscle ratio was 3.80±0.25 at 90 min post-injection in the experimental group, while the tumor uptake value of tumor bearing nude mice in the blocking group was (0.43±0.09) %ID/g at 60 min post-injection ( t=3.18, P=0.006). Conclusions:18F-AlF-NOTA-PEG 4-ZD2 can be prepared simply with high labeling rate and good stability in vitro, with high tumor uptake and tumor/muscle ratio in microPET imaging, and good specificity and long tumor residence time. The probe has good application prospect in breast cancer with high expression of fibronectin subtype EDB-FN.
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Developing novel superior bone-seeking radiopharmaceutical for the detection of malignant bone lesions could further improve the diagnostic value of routine bone scanning and shorten the interval between injection and imaging. In order to further evaluate the bone imaging efficiency of 99mTc-HBIDP [1-hydroxy-2-[1-butyl-imidazol-2-yl]-ethane-1, 1-diphosphonic acid], the pharmacokinetic in mice and single photon emission computed tomography [SPECT] bone scanning in rabbit for 99mTc-HBIDP was investigated. Kinetics of blood clearance showed that the distribution half-life [T1/2a] and elimination half-life [T1/2] of 99mTc-HBIDP are 2.73 and 24.87 min, respectively. Excellent bone images can be obtained at 1 h post injection with SPECT bone scanning, which is clearer and quicker than 99mTc-ZL [zoledronate] and 99mTc-MDP [methylenediphosphonate]. All results indicate that 99mTc-HBIDP holds great potential as a novel improved bone imaging agent
ABSTRACT
A method for the determination of methylmercury in seafood has been developed using dispersive liquid-liquid microextraction followed by direct mercury analyzer. Total mercury was detected by direct mercury analyzer, and inorganic mercury was calculated by the difference. The parameters affecting the extraction efficiency, including the selection of extractant and dispersant, their volume ratio, concentration of HCl and NaCl have been optimized in this study. The results showed that CH2 Cl2 as extractant, ethanol as dispersant, Volume ration of 1:5, 1 mol/L HCl and 120 g/L NaCl were chosen. The detection limit and the dynamic liner range were 0. 10 μg/L and 0. 2-20 μg/L, respectively. The relative standard deviation was 6. 0% for eleven replicates at the spiked level of 2. 0 μg/L. The enrichment factor was 8. For total Hg determination, the detection limit and the dynamic liner range for methylmercury were 0. 10 μg/kg and 0. 2-50 μg/kg, respectively. The relative standard deviation was 2. 4%. The method was simple, fast and a little solvent needed. Some certified reference materials were analyzed to validate the accuracy of the proposed method, and the results were in good agreement with the reference value. Besides, the method was applied to the real samples with satisfactory results.