Convenient PET-tracer production via SuFEx 18F-fluorination of nanomolar precursor amounts

Urinary tetranor-PGDM concentrations in aspirin-intolerant asthma and anaphylaxis

N-Succinimidyl 3-(di-tert-butyl[(18)F]fluorosilyl)benzoate ([(18)F]SiFB) is a highly reactive prosthetic group for radiolabeling of proteins for use in positron emission tomography (PET). It is similar to N-succinimidyl-4-[(18)F]fluorobenzoate ([(18)F]SFB), the 'gold-standard' prosthetic group for protein (18)F-labeling, but can be synthesized using a much shorter and technically easier procedure. A recently reported simple procedure to obtain anhydrous (18)F- by avoiding time-consuming azeotropic drying is applied with a slight modification to prevent basic hydrolysis of the active N-hydroxysuccinimide (NHS) ester moiety of [(18)F]SiFB. The labeling of [(18)F]SiFB is performed by a fast (18)F-(19)F isotopic exchange (IE) reaction at room temperature (20-25 °C) within 30 min. [(18)F]SiFB is purified using a C18 cartridge instead of HPLC, further decreasing the overall time required for protein labeling. High specific activities > 18.5 GBq μmol(-1) (> 500 Ci mmol(-1)) can be obtained. Finally, incubation of [(18)F]SiFB with the desired protein in an aqueous solution at pH 9, followed by HPLC purification, provides the final solution of the labeled protein ready for in vivo applications.

3-Methyl-1-phenyl-2-pyrazolin-5-one (edaravone, 1), known as a potent free radical scavenger, has been developed as a medical drug for the treatment of acute cerebral infarction. With the aim of developing radiotracers for imaging free radicals in vivo, 1-(3'-[(125)I]iodophenyl)-3-methy-2-pyrazolin-5-one ((125)I-2) was synthesized by two methods, via isotopic exchange and interhalogen exchange under solvent-free conditions, in which iodo- and bromo-derivatives were used as labeling precursors, respectively. After HPLC purification, (125)I-2 was obtained in modest isolated radiochemical yields (ca. 20%) with high radiochemical purities by both methods. The former gave specific activities of 0.2-0.6 kBq/micromol, whereas the latter approach achieved specific activities of more than 0.14 GBq/micromol. On attempting to prepare an injectable formulation for (125)I-2 with high specific activity, its radiochemical purities dropped to about 60-70%. Unlabeled analog 2 was found to have lipophilic and antioxidant properties similar to edaravone. Intravenous injection of (125)I-2 with low specific radioactivity into normal mice showed signs of distribution profiles similar to reported results for (14)C-labeled edaravone in normal rats.

A simple and rapid method for 18F radiolabelling of [GaF3(BnMe2‐tacn)] by 18F/19F isotopic exchange is described. The use of MeCN/H2O or EtOH/H2O (75:25) and aqueous [18F]F− (up to 200 MBq) with heating (80 °C, 10 min) gave 66±4 % 18F incorporation at a concentration of 268 nm, and 37±5 % 18F incorporation at even lower concentration (27 nm), without the need for a Lewis acid promoter. A solid‐phase extraction method was established to give [Ga18F19F2(BnMe2‐tacn)] in 99 % radiochemical purity in an EtOH/H2O mixture.

A simple and rapid method for 18F radiolabelling of [GaF3(BnMe2‐tacn)] by 18F/19F isotopic exchange is described. The use of MeCN/H2O or EtOH/H2O (75:25) and aqueous [18F]F− (up to 200 MBq) with heating (80 °C, 10 min) gave 66±4 % 18F incorporation at a concentration of 268 nm, and 37±5 % 18F incorporation at even lower concentration (27 nm), without the need for a Lewis acid promoter. A solid‐phase extraction method was established to give [Ga18F19F2(BnMe2‐tacn)] in 99 % radiochemical purity in an EtOH/H2O mixture.

The synthesis of 7-bromo-5-[123I]-iodokynurenic acid is described. The tracer was prepared using a nucleophilic non-isotopic exchange reaction from the corresponding bromo derivative. Optimisation of the reaction parameters and HPLC purification were performed and the radiotracer was obtained in a chemical and radiochemical purity >95% and a specific activity of 235 Ci/μmol.

Synthesis of the 123I- and 125I-labeled cholinergic nerve marker (-)-5-iodobenzovesamicol

The direct preparation of para-aminophenol (PAP) from nitrobenzene (NB) through Bamberger rearrangement was studied in a biphasic medium using a mixture of NbOx/SiO2 and H2SO4 as an acid catalyst. After optimization of the reaction parameters, PAP was obtained with 85–88% selectivity that represents a 10% selectivity improvement compared to sulfuric acid alone. The optimized conditions were implemented in a scale-up reaction, and PAP was isolated in 84% yield (based on the recovered starting material) with 97% HPLC purity. Overall, this process requires less sulfuric acid than the traditional process, leading to a drastic reduction of the saline waste.

Isotope exchange at equilibrium has been used to study the kinetic mechanism of the choline acetyltransferase reaction. The choline-acetylcholine, acetyl-CoA-acetylcholine, and CoA-acetyl-CoA exchange patterns are qualitatively consistent with a Theorell-Chance mechanism. However, quantitative differences are observed when the experimental results are compared to theoretical fits of the data for a Theorell-Chance mechanism. It is concluded that the kinetic mechanism of the choline acetyltransferase reaction can best be described as a random Theorell-Chance mechanism in which a low but finite amount of ternary complex exists.

The principal soy phytoestrogen genistein has an array of biological actions. It binds to estrogen receptor (ER) alpha and beta and has ER-mediated estrogenic effects. In addition, it has antiestrogenic effects as well as non-ER-mediated effects such as inhibition of tyrosine kinase. Because of its complex biological actions, the molecular mechanisms of action of genistein are poorly understood. Here we show that genistein dose-dependently increases estrogenic transcriptional activity in mesenchymal progenitor cells, but its biological effects on osteogenesis and adipogenesis are different. At low concentrations (< or =1 microm), genistein acts as estrogen, stimulating osteogenesis and inhibiting adipogenesis. At high concentrations (>1 microm), however, genistein acts as a ligand of PPARgamma, leading to up-regulation of adipogenesis and down-regulation of osteogenesis. Transfection experiments show that activation of PPARgamma by genistein at the micromolar concentrations down-regulates its estrogenic transcriptional activity, while activation of ERalpha or ERbeta by genistein down-regulates PPARgamma transcriptional activity. Genistein concurrently activates two different transcriptional factors, ERs and PPARgamma, which have opposite effects on osteogenesis or adipogenesis. As a result, the balance between activated ERs and PPARgamma determines the biological effects of genistein on osteogenesis and adipogenesis. Our findings may explain distinct effects of genistein in different tissues.

PurposeIn neurodegenerative diseases and neuropsychiatric disorders dysregulation of the norepinephrine transporter (NET) has been reported. For visualization of NET availability and occupancy in the human brain PET imaging can be used. Therefore, selective NET-PET tracers with high affinity are required. Amongst these, [18F]FMeNER-D2 is showing the best results so far. Furthermore, a reliable fully automated radiosynthesis is a prerequisite for successful application of PET-tracers.The aim of this work was the automation of [18F]FMeNER-D2 radiolabelling for subsequent clinical use. The presented study comprises 25 automated large-scale syntheses, which were directly applied to healthy volunteers and adult patients suffering from attention deficit hyperactivity disorder (ADHD). Procedures: Synthesis of [18F]FMeNER-D2 was automated within a Nuclear Interface Module. Starting from 20–30 GBq [18F]fluoride, azeotropic drying, reaction with Br2CD2, distillation of 1-bromo-2-[18F]fluoromethane-D2 ([18F]BFM) and reaction of the pure [18F]BFM with unprotected precursor NER were optimized and completely automated. HPLC purification and SPE procedure were completed, formulation and sterile filtration were achieved on-line and full quality control was performed.ResultsPurified product was obtained in a fully automated synthesis in clinical scale allowing maximum radiation safety and routine production under GMP-like manner. So far, more than 25 fully automated syntheses were successfully performed, yielding 1.0–2.5 GBq of formulated [18F]FMeNER-D2 with specific activities between 430 and 1707 GBq/μmol within 95 min total preparation time.ConclusionsA first fully automated [18F]FMeNER-D2 synthesis was established, allowing routine production of this NET-PET tracer under maximum radiation safety and standardization.

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Sewage sludges have been used for years as fertilizers but little information exists on the availability of P in these complex materials. Isotopically exchangeable P was measured in 12 urban sewage sludges using the isotopic exchange kinetics method. The results obtained with this method were then interpreted according to the multicompartmental model recently proposed. The two activated sludges and the composted sludge had the highest quantities of P isotopically exchangeable within 1 min ( E 1min higher than 0.77 g P kg ‐1 sludge). The flocculated and heat‐treated sludges contained low quantities of rapidly exchangeable P but high quantities of slowly exchangeable P ( E &gt;12wk higher than 9 g P kg ‐1 sludge). The quantity of P exchangeable within 1 d was positively correlated to the sum of water‐ and bicarbonate‐extractable P while slowly exchangeable P was positively correlated to the quantity of P present in precipitated forms deduced from a sequential extraction (i.e., HCl plus NaOH‐extractable P for FeSO 4 ‐flocculated sludges and HCl‐extractable P for the other sludges). Results of this study demonstrate that the isotopic exchange kinetics method can give valuable information on inorganic P forms and exchangeability in urban sewage sludges.

The design of dual mode fluorescent-PET peptidic tracers that can be labeled with [(18)F]fluoride at high specific activity and high yield has been challenged by the short half-life of (18)F and its aqueous indolence toward nucleophilic displacement, that often necessitates multistep reactions that start with punctiliously dry conditions. Here we present a modular approach to constructing a fluorescent dimeric peptide with a pendant radioprosthesis that is labeled in water with [(18)F]fluoride ion in a single, user-friendly step. The modular approach starts with grafting a new zwitterionic organotrifluoroborate radioprosthesis onto a pentaerythritol core with three pendent alkynes that enable successive grafting of a bright fluorophore (rhodamine) followed by two peptides (cylcoRGD). The construct is labeled with [(18)F]fluoride via isotope exchange within 20 min in a single step at high specific activity (>3 Ci/μmol) and in good yield to provide 275 mCi and high radiochemical purity. Neither drying of the [(18)F]fluoride ion solution nor HPLC purification of the labeled tracer is required. Facile chemical synthesis of this dual mode tracer along with a user-friendly one-step radiolabeling method affords very high specific activity. In vivo PET images of the dual mode tracer are acquired at both high and low specific activities. At very high specific activity, i.e., 3.5 Ci/μmol, tumor uptake is relatively high (5.5%ID/g), yet the associated mass is below the limits of fluorescent detection. At low specific activity, i.e., 0.01 Ci/μmol, tumor uptake in the PET image is reduced by approximately 50% (2.9%ID/g), but the greater associated mass enables fluorescence detection in the tumor. These data highlight a facile production of a dual mode fluorescent-PET tracer which is validated with in vivo and ex vivo images. These data also define critical limitations for the use of dual mode tracers in small animals.

Activation of hydrogen on FeHY zeolites