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The high content of Ba and Sc in Ba
Purpose The aim of this study was to optimize the radiolabeling method of [ 18 F]fluoropropyl-(+)-dihydrotetrabenazine ([ 18 F]FP-(+)-DTBZ) to fulfill the demand of preclinical and clinical application. Procedures Optimized labeling conditions were performed by altering the molar ratio of precursor to base (P/B), base species, solvents, reaction temperature, reaction time, and precursor concentration through manual radiosynthesis of [ 18 F]FP-(+)-DTBZ. The conditions with the highest radiochemical yield (RCY) were applied to automated radiosynthesis, and the crude product was purified with a Sep-Pak Plus C18 cartridge. Quality control and stability of [ 18 F]FP-(+)-DTBZ were carried out by HPLC. In vitro cellular uptake and blocking assays were conducted in human neuroblastoma cell line SH-SY5Y. In vivo imaging with small animal positron emission tomography (microPET) was performed with Sprague–Dawley rats. Results Under the optimized conditions (P/K 2 CO 3 = 1:8, heating at 120 °C for 3 min in dimethyl sulfoxide), an RCY of 88.7 % was obtained with 1.0 mg precursor. The optimized reaction conditions were successfully applied to an automated module and gave a high activity yield (AY) of 30–55 % in about 40 min with a > 99.0 % radiochemical purity (RCP) and a > 44.4 GBq/μmol molar activity ( A m ). Stability test displayed that the RCP retained > 98.0 % in 8 h in saline and in phosphate buffer saline (PBS, pH 7.4). In vitro cellular uptake assay showed accumulation of [ 18 F]FP-(+)-DTBZ in SH-SY5Y cells, which could be significantly inhibited by vesicular monoamine transporter 2 (VMAT2) inhibitor DTBZ. MicroPET images of rat brain displayed that the striatum showed the highest uptake with a standardized uptake value (SUV) of 3.91 ± 0.30 at ~ 70 min. Co-injection with DTBZ (1.0 mg/kg) resulted in a 75 % decrease of the striatal SUV, confirming the specificity of [ 18 F]FP-(+)-DTBZ to VMAT2. Conclusions We obtained an optimized radiolabeling method of [ 18 F]FP-(+)-DTBZ and successfully applied it to a commercial available module. The automated synthesis gave a high AY and RCP of [ 18 F]FP-(+)-DTBZ with high and specific binding to VMAT2, facilitating its routine application for VMAT2 tracing.
Designing electrical insulation materials with excellent surface flashover strength in a vacuum environment is crucial for high-power equipment and aerospace devices. In the present paper, the effect of two types of electronegative groups, the halogen–phenyl groups and the aromatic π-conjugated naphthyl groups, is used to greatly improve the vacuum flashover characteristics of polystyrene (PS), a commonly used polymer dielectric material in high-power devices. By polymerization of the monomers containing these electronegative groups, the bulk insulation material as a whole is modified expediently. In comparison to the base polymer PS, the electron affinity of the structures containing strong electronegative groups is studied with first-principles calculations based on the density functional theory. The nanosecond pulsed vacuum flashover testing results show that the vacuum flashover strength is increased by 10% after replacing the PS pendant phenyl groups with fluorophenyl groups and increased by 44% when replaced with the naphthyl groups. Furthermore, the thermally stimulated current and secondary electron emission yield spectroscopies are measured, to study the influence of strong electronegative groups on the trapping characteristics and further the electron-emitting features of the polymer dielectrics, which are closely related to the charged particle multiplication process during the vacuum flashover. The results prove that introducing strong electronegative groups can inhibit the triggering of vacuum flashover, suppress the electron emission, delay the flashover process, and thus greatly increase the vacuum flashover voltage. The study of this paper not only puts forward two groups of easily processable polymers with excellent vacuum flashover strength but also paves ways for the future material design of special insulation polymers.
Polymers with high surface electric insulation capability are greatly demanded in various electrical devices operating in vacuum ambient. Low secondary electron emission (SEE) is favorable to mitigate vacuum flashover by inhibiting the SEE avalanche across the surface. Although numerous approaches, esp. the surface modifications, promote the flashover strength of the insulator, a facile yet cost-effective modification strategy of a high-quality and scalable flexible insulator remains a formidable challenge. Herein, a facile ion-exchange technique is implemented to fabricate a nanoscale polyimide/chromic oxide (PI/Cr 2 O 3 ) nanocomposite coating comprising hundreds of organic/inorganic interfaces securely adhered to a flexible PI substrate, which features ultralow secondary electron emission yields (SEEY). The low emissivity is achieved by introducing weakly emissive Cr 2 O 3 nanoparticles as well as interfacial traps within the nanocomposite layer, which outperforms the existing and modified polymers. The PI/Cr 2 O 3 shows a remarkable increase in flashover strength while keeping sufficient mechanical durability. The proposed surface engineering strategy is convenient and scalable, bringing up new insight into industrial applications.
The preparation of 10-(2-[ 18 F]fluoroethoxy)-20( S )-camptothecin, a potential positron emission tomography tracer for the imaging of topoisomerase I in cancers, is described. 10-(2-[ 18 F]Fluoroethoxy)-20( S )-camptothecin was synthesized by the [ 18 F]fluoroalkylation of the corresponding hydroxy precursor molecule with 2-[ 18 F]fluoroethyl bromide ([ 18 F]FEtBr) in dimethylsulfoxide (DMSO) at 55 °C for 20 min; this was followed by purification using high performance liquid chromatography (HPLC) with a total preparation time of 60 min. The overall radiochemical yield was approximately 5.4–12 % (uncorrected), and the radiochemical purity was above 96 %.
Studying flashover characteristics in vacuum environment is extremely significant for designing reliable insulation structures. The waveform of applied voltage excitations greatly affects the flashover process. In this study, the influence of nanosecond pulse front steepness on flashover process in vacuum is investigated. Firstly, flashover experiments with nanosecond pulses are conducted. Nanosecond pulses with different front steepness are generated and used to trigger flashovers on sample surface. The relationship between pulse front steepness and flashover voltage is studied. Meanwhile, a particle-in-cell with Monte Carlo collision (PIC-MCC) two-dimensional self-sustaining discharge model based on secondary electron emission avalanche (SEEA) scheme is established. The distribution of charged particles, electric field and their evolution during flashover process are presented. Furthermore, pulses with various rising steepness are applied to the model. The multiplication and propagation of charged particles in different pulse waveform conditions are studied. In all conditions, two stages during flashover process can be obviously distinguished based on charged particle number evolution which divides the overall flashover delay time into two parts. By analyzing the voltage development in these two time slots, the quasi-linear relationship between pulse front steepness and flashover voltage in nanosecond pulse flashover in vacuum is explained.
Surface modification of vacuum insulators is a promising way to improve their surface insulation performance but commonly used surface modification technologies in surface insulation area such as fluorination and plasmas treatment are unable to control the surface chemical components at the molecular level, which makes it hard to explore molecular groups with high surface insulation performance. In this paper, molecule self-assembly is introduced to control the surface molecular structure precisely and vacuum surface insulation performance of a special molecular structure electron-delocalized group is studied. Hexagonal phenyl group containing delocalized electrons and cyclohexyl group with the same hexagonal molecular structure but without delocalized electrons are grafted onto the surface of alumina insulators through molecule self-assembly. Secondary electron emission yield test shows that phenyl group endows alumina insulators lower SEY than cyclohexyl group. Correspondingly, phenyl group grafted alumina insulators show higher surface insulation performance than cyclohexyl group. The results indicate that group containing delocalized electrons can endow insulators higher surface insulation characteristics.
Purpose The reversibility of early liver fibrosis highlights the need for improved early detection and monitoring techniques. Fibroblast activation protein (FAP) is a promising theranostics target significantly upregulated during fibrosis. This preclinical and preliminary clinical study investigated a FAP-targeted probe, gallium-68-labeled FAP inhibitor 04 ([ 68 Ga]Ga-DOTA-FAPI-04), for its capability to visualize liver fibrosis. Methods The preclinical study employed [ 68 Ga]Ga-DOTA-FAPI-04 micro-positron emission tomography (PET)/computed tomography (CT) on carbon tetrachloride-induced mice model (n = 34) and olive oil-treated control group (n = 26), followed by validation of the probe's biodistribution. Hepatic uptake was correlated with fibrosis and inflammation levels, quantified through histology and serum assays. FAP and α-smooth muscle actin expression were determined by immunohistochemistry, as well as immunofluorescence. The subsequent clinical trial enrolled 26 patients with suspected or confirmed liver fibrosis to undergo [ 68 Ga]Ga-DOTA-FAPI-04 PET/magnetic resonance imaging or PET/CT. Key endpoints included correlating [ 68 Ga]Ga-DOTA-FAPI-04 uptake with histological inflammation grades and fibrosis stages, and evaluating its diagnostic and differential efficacy compared to established serum markers and liver stiffness measurement (LSM). Results [ 68 Ga]Ga-DOTA-FAPI-04 mean uptake in mice livers was notably higher than in control mice, increasing from week 6 [0.70 ± 0.11 percentage injected dose per cubic centimeter (%ID/cc)], peaking at week 10 (0.97 ± 0.15%ID/cc) and slightly reducing at week 12 (0.89 ± 0.28%ID/cc). The hepatic biodistribution and FAP expression showed a consistent trend. In the patient cohort, hepatic [ 68 Ga]Ga-DOTA-FAPI-04 uptake presented moderate correlations with inflammation grades (r = 0.517 to 0.584, all P < 0.05) and fibrosis stages (r = 0.653 to 0.698, all P < 0.01). The average SUVmax to background ratio in the liver showed superior discriminative ability, especially between stage 0 and stage 1, outperforming LSM (area under curve 0.984 vs. 0.865). Conclusion [ 68 Ga]Ga-DOTA-FAPI-04 PET shows significant potential for non-invasive visualization and dynamic monitoring of liver fibrosis in both preclinical experiment and preliminary clinical trial, especially outperforming other common clinical indicators in the early stage. Trial registration NCT04605939. Registered October 25, 2020, https://clinicaltrials.gov/study/NCT04605939
The acidic microenvironment is one of the remarkable features of tumor and is also a reliable target for tumor theranostics. Ultrasmall gold nanoclusters (AuNCs) have good in vivo behaviors, such as non-retention in liver and spleen, renal clearance, and high tumor permeability, and held great potential for developing novel radiopharmaceuticals. Herein, we developed pH-sensitive ultrasmall gold nanoclusters by introducing quaternary ammonium group (TMA) or tertiary amine motifs (C6A) onto glutathione-coated AuNCs (TMA/GSH@AuNCs, C6A-GSH@AuNCs). Density functional theory simulation revealed that radiometal 89 Sr, 223 Ra, 44 Sc, 90 Y, 177 Lu, 89 Zr, 99m Tc, 188 Re, 106 Rh, 64 Cu, 68 Ga, and 113 Sn could stably dope into AuNCs. Both TMA/GSH@AuNCs and C6A-GSH@AuNCs could assemble into large clusters responding to mild acid condition, with C6A-GSH@AuNCs being more effective. To assess their performance for tumor detection and therapy, TMA/GSH@AuNCs and C6A-GSH@AuNCs were labeled with 68 Ga, 64 Cu, 89 Zr and 89 Sr, respectively. PET imaging of 4T1 tumor-bearing mice revealed TMA/GSH@AuNCs and C6A-GSH@AuNCs were mainly cleared through kidney, and C6A-GSH@AuNCs accumulated in tumors more efficiently. As a result, 89 Sr-labeled C6A-GSH@AuNCs eradicated both the primary tumors and their lung metastases. Therefore, our study suggested that GSH-coated AuNCs held great promise for developing novel radiopharmaceuticals that specifically target the tumor acidic microenvironment for tumor diagnosis and treatments.
18F-Labeled blood pool agents (BPAs) have attracted great attention for identifying bleeding sites. However, many BPAs are not sufficiently evaluated partially due to the limitations of labeling methods. In our previous work, we noticed that 18F-PEG1-vinyl sulfone (18F-VS) could efficiently label red blood cells (RBCs) ex vivo and in situ. However, its application as BPA is not fully evaluated. In this study, we systematically explored the feasibility of using 18F-VS-labeled RBCs as a positron emission tomography (PET) BPA for intra-abdominal bleeding diagnosis. In brief, we first optimized the labeling conditions, which lead to an 80% labeling yield of RBCs after incubating with 18F-VS in phosphate-buffered saline (PBS) at 37°C for 20 min. 18F-VS-labeled RBCs were found to be stable in vitro, which could simplify its transportation/storage for in vivo applications. In normal rat PET study, the cardiovascular system could be clearly imaged up to 5 h post injection (p.i.). An intra-abdominal hemorrhage rat model demonstrated that the 18F-VS-labeled RBCs clearly showed the dynamic changes of extravascular radioactivity due to intra-abdominal hemorrhage. Validation in the model of gastrointestinal bleeding clearly demonstrated the great potential of using 18F-VS-labeled RBCs as a BPA, which could be further evaluated in future studies.
Background A novel positron emission tomography (PET) imaging tracer, [ 18 F] SynVesT-1, targeting synaptic vesicle glycoprotein 2 (SV2A), has been developed to meet clinical demand. Utilizing the Trasis AllinOne-36 (AIO) module, we’ve automated synthesis to Good Manufacturing Practice (GMP) standards, ensuring sterile, pyrogen-free production. The fully GMP-compliant robust synthesis of [ 18 F] SynVesT-1 boosting reliability and introducing a significant degree of simplicity and its comprehensive validation for routine human use. Results [ 18 F] SynVesT-1 was synthesized by small modifications to the original [ 18 F] SynVesT-1 synthesis protocol to better fit AIO module using an in-house designed cassette and sequence. With a relatively small precursor load of 5 mg, [ 18 F] SynVesT-1 was obtained with consistently high radiochemical yields (RCY) of 20.6 ± 1.2% (the decay-corrected RCY, n = 3) at end of synthesis. Each of the final formulated batches demonstrated radiochemical purity (RCP) and enantiomeric purity surpassing 99%. The entire synthesis process was completed within a timeframe of 80 min (75 ± 3.1 min, n = 3), saves 11 min compared to reported GMP automated synthesis procedures. The in-human PET imaging of total body PET/CT and time-of-flight (TOF) PET/MR showed that [ 18 F] SynVesT-1 is an excellent tracer for SV2A. It is advantageous for decentralized promotion and application in multi-center studies. Conclusion The use of AIO synthesizer maintains high production yields and increases reliability, reduces production time and allows rapid training of production staff. Besides, the as-prepared [ 18 F] SynVesT-1 displays excellent in vivo binding properties in humans and holds great potential for the imaging and quantification of synaptic density in vivo.
Purpose The dopamine transporter (DAT) is a marker of the occurrence and development of Parkinson’s disease (PD) and other diseases with nigrostriatal degeneration. 2β-Carbomethoxy-3β-(4-chlorophenyl)-8-(2-[ 18 F]-fluoroethyl)nortropane ([ 18 F]FECNT), an 18 F-labelled tropane derivative, was reported to be a useful positron-emitting probe for DAT. However, the rapid formation of brain-penetrating radioactive metabolites is an impediment to the proper quantitation of DAT in PET studies with [ 18 F]FECNT. Deuterium-substituted analogues have presented better in vivo stability to reduce metabolites. This study aimed to synthesize a deuterium-substituted DAT radiotracer, [ 18 F]FECNT- d 4 , and to make a preliminary investigation of its properties as a DAT tracer in vivo . Procedures The ligand [ 18 F]FECNT- d 4 was obtained by one-step radiolabelling reaction. The lipophilicity was measured by the shake-flask method. Binding properties of [ 18 F]FECNT- d 4 were estimated by in vitro binding assay, biodistribution, and microPET imaging in rats. In vivo stability of [ 18 F]FECNT- d 4 was estimated by radio-HPLC. Results [ 18 F]FECNT- d 4 was synthesized at an average activity yield of 46 ± 17 % ( n = 15) and the molar activity was 67 ± 12 GBq/μmol. The deuterated tracer showed suitable lipophilicity and the ability to penetrate the blood-brain barrier (brain uptake of 1.72 % ID at 5 min). [ 18 F]FECNT- d 4 displayed a high binding affinity for DAT comparable to that of [ 18 F]FECNT in rat striatum homogenates. Biodistribution results in normal rats showed that [ 18 F]FECNT- d 4 exhibited a higher ratio of the target to non-target (striatum/cerebellum) at 15 min post administration (5.00 ± 0.44 vs 3.84 ± 0.24 for [ 18 F]FECNT- d 4 vs [ 18 F]FECNT). MicroPET imaging studies of [ 18 F]FECNT- d 4 in normal rats showed that the ligand selectively localized to DAT-rich striatal regions and the accumulation could be blocked with DAT inhibitor. Furthermore, in the unilateral PD model rat, a significant reduction of the signal was found in the lesioned side relative to the unlesioned side. Striatal standardized uptake value of [ 18 F]FECNT- d 4 remained ~4.02 in the striatum between 5 and 20 min, whereas that of [ 18 F]FECNT fell rapidly from 4.11 to 2.95. Radio-HPLC analysis of the plasma demonstrated better in vivo stability of [ 18 F]FECNT- d 4 than [ 18 F]FECNT. Conclusion The deuterated compound [ 18 F]FECNT- d 4 may serve as a promising PET imaging agent to assess DAT-related disorders.
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