High-throughput quantitative screening of peroxidase-mimicking DNAzymes on a microarray by using electrochemical detection.

Some guanine-rich DNA sequences, which are called DNAzymes, can adopt G-quadruplex structures and exhibit peroxidase activity by binding with hemin. Although known DNAzymes show less activity than horseradish peroxidase, they have the potential to be widely used for the detection of target molecules in enzyme-linked immunosorbent assays if sequences that exhibit higher activity can be identified. However, techniques for achieving this have not yet been described. Therefore, we compared the DNAzyme activities of more than 1000 novelistically designed sequences with that of the original DNAzyme by using an electrochemical detection system on a 12K DNA microarray platform. To the best of our knowledge, this is the first description of an array-based assessment of peroxidase activity of G-quadruplex-hemin complexes. By using this novel assay system, more than 200 different mutants were found that had significantly higher activities than the original DNAzyme sequence. This microarray-based DNAzyme evaluation system is useful for identifying highly active new DNAzymes that might have potential as tools for developing DNA-based biosensors with aptamers.