Lighting Up Biochemiluminescence by the Surface Self‐Assembly of DNA–Hemin Complexes

The discovery of catalytic RNAs (ribozymes) has sparked scientific activities directed to the preparation of new biocatalysts and raised the suggestion that these biomolecules participated in the evolutionary process as preprotein catalysts. 2] Analogously, deoxyribozymes, catalytic DNAzymes, are not found in nature but extensive research efforts have demonstrated the successful synthesis of catalytic deoxyribozymes for many chemical transformations. 4] One interesting example of a catalytic DNA that reveals peroxidase-like activity includes a supramolecular complex between hemin and a single-stranded guanine-rich nucleic acid (aptamer). This complex was reported to catalyze the oxidation of 2,2 -azinobis(3-ethylbenzothiozoline)-6-sulfonic acid (ABTS) by H2O2, a common reaction used as an assay for peroxidase activity. It was suggested that the supramolecular docking of the guanine-quadruplex layers facilitates the intercalation of hemin into the complex and the formation of the biocatalytically active hemin center. Enzymes and, specifically, horseradish peroxidase (HRP) 9] are used as biocatalytic labels for the amplified detection of DNA-sensing events. The electrochemical amplified detection of DNA has been accomplished in the presence of different enzymes 8] and the chemiluminescent analysis of DNA in the presence of HRP has been reported. The integration of a DNA biocatalyst into DNA-detection schemes could provide a new method for the detection of nucleic acids that might reveal important advantages: 1) The catalytic DNA may substitute the protein-based biocatalysts, and thus eliminate nonspecific binding phenomena; 2) Tailoring of the DNA biocatalyst as part of the labeled nucleic acid might reduce the number of analytical steps for DNA detection. Here we report that two separated nucleic acids that include the segments A and B–constituting the single-stranded peroxidase deoxyribozyme, which forms a layered G-quadruplex structure (see Scheme 1)–self-assemble in the presence of hemin to form a biocatalyst for the generation of chemiluminescence in the presence of H2O2 and luminol. The effect of hybridization with the DNAzyme compounds on the resulting biochemiluminescence is discussed. We also demonstrate the self-assembly of biocatalytic, supramolecular hemin ±nucleic acid complexes on gold electrodes in monolayer configurations, and describe the biocatalytic and bioelectrocatalytic formation of chemiluminescence at the Acknowledgements