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Activity-based DNA-gold nanoparticle probe as colorimetric biosensor for DNA methyltransferase/glycosylase assay.

We have developed a novel biosensor platform for colorimetric detection of active DNA methyltransferase/glycosylase based on terminal protection of the DNA-gold nanoparticle (AuNP) probes by mechanistically covalent trapping of target enzymes. This biosensor relied on covalent capture of target enzymes by activity-based DNA probes which created terminal protection of the DNA probes tethered on AuNPs from degradation by Exo I and III. This biosensor has the advantages of having highly sensitive, rapid, and convenient detection due to its use of the homogeneous assay format and strong surface plasmon absorption. Because the activity-based probes (ABPs) are mechanistically specific to target enzymes, this strategy also offers improved selectivity and can achieve the information about both abundance and activity of the enzymes. We have demonstrated this strategy using a human DNA (cytosine-5) methyltransferase (Dnmt 1) and a human 8-oxoguanine glycosylase (hOGG 1). The results reveal that the colorimetric response increases dynamically with increasing activity of the enzymes, implying a great potential of this strategy for DNA methyltransferase/glycosylase detection and molecular diagnostics and drug screening. Our strategy can also be used as a promising and convenient approach for visualized screening of ABPs for DNA modifying enzymes.