Improved Automated Radiosynthesis of [11C]PBR28

Abstract

Microglial activation is commonly identified by elevated levels of the 18 kDa translocator protein (TSPO) in response to several inflammatory processes. [11C]PBR28 is one of the most promising PET tracers to image TSPO in both human and non-human primates. In this study, we optimized the radiolabeling procedure of [11C]PBR28 for higher radiochemical yield, radiochemical purity, and specific activity, which can be easily translated to any automated module for clinical trials. Time-activity curves (TACs) derived from the dynamic PET imaging of male rhesus monkey brains demonstrated that [11C]PBR28 had suitable kinetics with radiotracer accumulation observed in the caudate, putamen, cerebellum, and frontal cortex region.

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“…Another fascinating tracer with possible applications in SPECT imaging is [ 123 I]-CLINME. Mattener et al studied the biodistribution of [ 123 I]-CLINME ( Figure 6 ) in an AMPA-induced excitotoxic murine model through SPECT imaging [ 28 ]. After 30 min to 6 h post-injection, a plateau in the adrenal glands was seen.…”

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“…The reaction temperature was raised to 80 °C to reduce the reaction time to only 3 min. Besides that, a “vial” method was used in place of the previously used “loop” method . [ 11 C]­PBR28 showed superior properties, including a high binding affinity, lower lipophilicity, improved signal-to-noise ratio, more suitable pharmacokinetics, and an 80-fold higher in vivo association affinity in the monkey brain. − [ 11 C]­PBR28 has also been used in human subjects and exhibited different activities for in vivo PET imaging of TSPO.…”