2-[18F]-Fluoro-3-pyridinecarboxaldehyde ([18F]FPCA) is a novel, water-soluble prosthetic group. It's radiochemistry has been developed and fully-automated for application in chemoselective radiolabelling of amino(oxy)-derivatised RI-OR2-TAT peptide, (Aoa-k)-RI-OR2-TAT, using a GE TRACERlab FX-FN. RI-OR2-TAT is a brain-penetrant, retro-inverso peptide that binds to amyloid species associated with Alzheimer's Disease. Radiolabelled (Aoa-k)-RI-OR2-TAT was reproducibly synthesised and the product of the reaction with FPCA has been fully characterised. In-vivo biodistribution of [18F]RI-OR2-TAT has been measured in Wistar rats.
Affinity peptide and protein- (APP) based radiotracers are an increasingly popular class of radiotracer in positron emission tomography (PET), which was once dominated by the use of small molecule radiotracers. Radiolabelled monoclonal antibodies (mAbs) are important examples of APPs, yet a preference for smaller APPs, which exhibit fast pharmacokinetics and permit rapid PET aided diagnosis, has become apparent. F exhibits favourable physical characteristics for APP radiolabelling and has been described as an ideal PET radionuclide. Notwithstanding, F radiolabelling of APP is challenging, and this is echoed in the literature where a number of diverse approaches have been adopted. This review seeks to assess and compare the approaches taken to F APP radiolabelling with the intention of highlighting trends within this expanding field. Generic themes have emerged in the literature, namely the use of mild radiolabelling conditions, a preference of site-specific methodologies with an impetus for short, automated procedures which produce high-yielding [ F]APPs.
Neutral, bis-complexes of oxovanadium(iv) with salicylaldoximes and salicylketoximes react with a range of nitriles t o afford a novel organic ligand type; the prototypical reaction product [VV02{ C6H4(0)CH=N-OC(Me)=NH}] is characterised by single crystal X-ray diffraction and spectroscopic studies.
[18F]Fluoroacetaldehyde is a biocompatible prosthetic group that has been implemented pre‐clinically using a semi‐automated remotely controlled system. Automation of radiosyntheses permits use of higher levels of [18F]fluoride whilst minimising radiochemist exposure and enhancing reproducibility. In order to achieve full‐automation of [18F]fluoroacetaldehyde peptide radiolabelling, a customised GE Tracerlab FX‐FN with fully programmed automated synthesis was developed.The automated synthesis of [18F]fluoroacetaldehyde is carried out using a commercially available precursor, with reproducible yields of 26% ± 3 (decay‐corrected, n = 10) within 45 min. Fully automated radiolabelling of a protein, recombinant human interleukin‐1 receptor antagonist (rhIL‐1RA), with [18F]fluoroacetaldehyde was achieved within 2 h. Radiolabelling efficiency of rhIL‐1RA with [18F]fluoroacetaldehyde was confirmed using HPLC and reached 20% ± 10 (n = 5).Overall RCY of [18F]rhIL‐1RA was 5% ± 2 (decay‐corrected, n = 5) within 2 h starting from 35 to 40 GBq of [18F]fluoride. Specific activity measurements of 8.11–13.5 GBq/µmol were attained (n = 5), a near three‐fold improvement of those achieved using the semi‐automated approach.The strategy can be applied to radiolabelling a range of peptides and proteins with [18F]fluoroacetaldehyde analogous to other aldehyde‐bearing prosthetic groups, yet automation of the method provides reproducibility thereby aiding translation to Good Manufacturing Practice manufacture and the transformation from pre‐clinical to clinical production.
The reactions of trans-[SnF4(PMe3)2] with one, two or three equivalents of Me3SiO3SCF3 (TMSOTF), respectively, in anhydrous CH2Cl2 form six-coordinate [SnF4-n(PMe3)2(OTf)n] (n = 1-3), which have been characterised by microanalysis, IR...
A combination of vanadium K-and L-edge XAFS has been used to characterise a series of monomeric oxovanadium(), monomeric dioxovanadium() and dimeric oxovanadium() complexes with oxyoxime and oxyoximate ligands. The K-and L-edge spectra confirm the presence of V V in the dimeric species and the L-edge spectra have been used to discriminate between six-co-ordinate V᎐N᎐O᎐V bridged oxovanadium() dimers and seven-co-ordinate phenolate bridged oxovanadium() dimers containing η 2 -N᎐O groups.
Positron emission tomography (PET) and fluorescence labelling have been used to assess the pharmacokinetics, biodistribution and eventual fate of a hydrogel‐forming nonapeptide, FEFKFEFKK (F9), in healthy mice, using 18F‐labelled and fluorescein isothiocyanate (FITC)‐labelled F9 analogues. F9 was site‐specifically radiolabelled with 2‐[18F]fluoro‐3‐pyridinecarboxaldehyde ([18F]FPCA) via oxime bond formation. [18F]FPCA‐F9 in vivo fate was evaluated both as a solution, following intravenous administration, and as a hydrogel when subcutaneously injected. The behaviour of FITC‐F9 hydrogel was assessed following subcutaneous injection. [18F]FPCA‐F9 demonstrated high plasma stability and primarily renal excretion; [18F]FPCA‐F9 when in solution and injected into the bloodstream displayed prompt bladder uptake (53.4 ± 16.6 SUV at 20 minutes postinjection) and rapid renal excretion, whereas [18F]FPCA‐F9 hydrogel, formed by co‐assembly of [18F]FPCA‐F9 monomer with unfunctionalised F9 peptide and injected subcutaneously, showed gradual bladder accumulation of hydrogel fragments (3.8 ± 0.4 SUV at 20 minutes postinjection), resulting in slower renal excretion. Gradual disaggregation of the F9 hydrogel from the site of injection was monitored using FITC‐F9 hydrogel in healthy mice (60 ± 3 over 96 hours), indicating a biological half‐life between 1 and 4 days. The in vivo characterisation of F9, both as a gel and a solution, highlights its potential as a biomaterial.
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