DNAzyme-Catalyzed Click Chemistry for Facilitated Immobilization of Redox Functionalities on Self-Assembled Monolayers

Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), the representative reaction of modern “click chemistry”, has been broadly employed in organic synthesis, bio-labeling, and surface functionalization. Nevertheless, it has limitations such as posing a dilemma of either using high concentrations of Cu(I) catalyst or suffering from slow kinetics. Herein, we demonstrate that a newly selected DNAzyme (CLICK-17; a 79-nucleotide, catalytic DNA single strand) can rapidly catalyze CuAAC to tether redox functionalities onto an electrode surface using low concentrations of either Cu(I) or Cu (II). Particularly, the CLICK-17 DNAzyme, at μM concentrations, facilitated the covalent immobilization of ethynylferrocene (Fc-C≡CH) onto 1-azido-11-undecanethiolate self-assembled monolayers on gold (N3C11S-Au SAMs); as low as 50 μM Cu(I) together with 4 μM DNAzyme was able to complete the coupling reaction within 30 min and the pseudo first-order reaction rate constant is 7 times higher than that using the Cu(I) catalyst alone. It was also remarkable that the CLICK-17 DNAzyme is functional with Cu(II) in the absence of an explicit reductant for the catalyzed surface immobilization of Fc-C≡CH on N3C11S-Au SAMs.