Expanding the Applicability of the Metal Labeling of Biomolecules by the RIKEN Click Reaction: A Case Study with Gallium‐68 Positron Emission Tomography

Abstract Radiolabeled biomolecules with short half‐life times are of increasing importance for positron emission tomography (PET) imaging studies. Herein, we demonstrate an improved and generalized method for synthesizing a [radiometal]‐unsaturated aldehyde as a lysine‐labeling probe that can be easily conjugated into various biomolecules through the RIKEN click reaction. As a case study, 68 Ga‐PET imaging of U87MG xenografted mice is demonstrated by using the 68 Ga‐DOTA‐RGDyK peptide, which is selective to α V β 3 integrins.