Electrochemistry and electrocatalysis of covalent hemin-G4 complexes on gold

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Peroxidase-mimicking catalytic DNAzyme labels comprising hemin-guanine quadruplex (G4) complexes are widely used in electrochemical DNA and aptamer assays. However, their catalytic activity and thus the assay performance may be limited by the complex stability. Here, electrochemical properties of the hemin-G4 complexes with hemin covalently attached to the G4 sequence (covalent complexes) and of the non-covalent hemin-G4 complexes were studied and compared in the reaction of electrocatalytic reduction of H2O2. At pH7, non-covalently and covalently bound hemin-G4 complexes immobilized on gold electrodes showed formal potentials of -242 and -220mV vs. Ag/AgCl, being less negative than -316mV exhibited by hemin attached to the alkanethiol SAM. Both complexes were able to electrocatalytically reduce H2O2 starting from 0.4V, and O2 - from 0.15V. In the reaction of H2O2 reduction at 0.2V, within the potential window of no interference from O2, the covalent hemin-G4 complex showed a 20 fold higher specific electrocatalytic activity compared to the non-covalent analogue and the K M (towards H2O2) of 0.58mM (2mM for the non-covalent complex). Both the enhanced catalytic activity and sensitivity for H2O2 were ascribed to the higher integrity/stability of the covalent complexes. The results open new biosensor perspectives for the covalent hemin-G4 complexes as more stable and active labels for DNA and aptamer assays.

Original languageEnglish
JournalJournal of Electroanalytical Chemistry
Pages (from-to)174-179
Publication statusPublished - 1 Mar 2018

    Research areas

  • DNA biosensors, DNAzyme, Electrocatalytic labels, Gold electrodes, Hemin-G4 complex, Peroxidase mimic

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