Bioorthogonal click chemistry for fluorine-18 labeling protocols under physiologically friendly reaction condition

To expand the applications of positron emission tomography (PET), novel specific radiopharmaceuticals using positron-emitters, such as fluorine-18 (F-18, t(1/2) = 109.8 min), will be needed. Recently, strain-promoted alkyne azide cycloaddition (SPAAC) ha been considered as an alternative bioorthogonal conjugation reaction between bioactive molecules and radiolabeled building blocks for the synthesis of novel radiopharmaceuticals. This mini-review provides a rapid overview of the emerging synthetic strategies based on the copper-free SPAAC conjugation reaction under physiologically-friendly reaction conditions for the high-throughput synthesis of F-18-labeled peptide tracers. Furthermore, an efficient mesoporous silica nanoparticles (MSNs) pretargeting for PET imaging were also introduced through the in situ bioorthogonal SPAAC labeling reaction by forming F-18-labeled MSNs at the tumor site in a living specimen. (C) 2015 Elsevier B.V. All rights reserved.