Antibody functionalization with a dual reactive hydrazide/click crosslinker

A water-soluble, dual reactive hydrazide/click crosslinker (ethynyl hydrazide, EH) was synthesized and characterized. A model antibody, human immunoglobulin G (hIgG), was ethynylated by conventional oxidation/hydrazide reactions with the hydrazide moiety of EH. The terminal alkyne conjugated to the glycan of hIgG was easily functionalized by quantitative and bioorthogonal Cu(I)-catalyzed azide–alkyne cycloaddition. The potential of the hydrazide/click crosslinker as a reagent to functionalize antibodies was demonstrated with fluorophore labeling and antibody immobilization.