[18F]FEPPA a TSPO Radioligand: Optimized Radiosynthesis and Evaluation as a PET Radiotracer for Brain Inflammation in a Peripheral LPS-Injected Mouse Model
2018
[18F]FEPPA is a specific ligand for the
translocator proteinof 18 kDa (TSPO) used as a positron emission tomography (PET) biomarker for glial activation and
neuroinflammation. [18F]FEPPA
radiosynthesiswas optimized to assess in a mouse model the cerebral inflammation induced by an intraperitoneal injection of
Salmonella entericaserovar Typhimurium lipopolysaccharides (LPS; 5 mg/kg) 24 h before PET imaging. [18F]FEPPA was synthesized by
nucleophilic substitution(90 °C, 10 min) with
tosylatedprecursor, followed by improved semi-preparative HPLC purification (retention time 14 min). [18F]FEPPA
radiosynthesiswere carried out in 55 min (from EOB). The non-
decay correctedradiochemical yield were 34 ± 2% (n = 17), and the radiochemical purity greater than 99%, with a molar activity of 198 ± 125 GBq/µmol at the end of synthesis. Western blot analysis demonstrated a 2.2-fold increase in TSPO brain expression in the LPS treated mice compared to controls. This was consistent with the significant increase of [18F]FEPPA brain total
volumeof
distribution(VT) estimated with pharmacokinetic modelling. In conclusion, [18F]FEPPA
radiosynthesiswas implemented with high yields. The new purification/formulation with only class 3 solvents is more suitable for in vivo studies.
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