Double-Caging Linker for AND-Type Fluorogenic Construction of Protein/Antibody Bioconjugates and in situ Quantification
We report on in situ fluorescent quantification of the conjugation efficiency between azide-terminated synthetic polymers/ imaging probes and thiol-functionalized antibodies/proteins/peptides, by utilizing a doubly caged profluorescent and heterodifunctional core molecule (C1) as the self-sorting bridging unit. Orthogonal dual 'click' coupling of C1 with azide- and thiol-functionalized precursors leads to highly fluorescent bioconjugates, whereas single click products of C1 remain essentially nonfluorescent. This 'AND' logic gate-type fluorogenic feature also enables further integration with FRET processes. For the construction of antibody-probe conjugates from an anti-carcinoembryonic antigen and a quinone-caged profluorescent naphthalimide derivative, the dual 'click' coupling process with C1 can be conveniently monitored via emission turn-on of C1, whereas prominent changes in FRET ratios occur for antibody-probe conjugates when triggered by specific tumor-associated enzymes.
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