Immuno-DNA binding directed template-free DNA extension and enzyme catalysis for sensitive electrochemical DNA...

Sensitive and accurate determination of DNA methyltransferase (DNA Mtase) activity is highly pursued for understanding fundamental biological processes related to DNA methylation, clinical disease diagnosis and drug discovery. Herein, we propose a new electrochemical immuno-DNA sensing platform for DNA Mtase activity assay and inhibitor screening. After homogeneous DNA methylation by CpG methyltransferase (M.SssI Mtase), the methylated DNA can be specifically recruited onto an electrode via its immunological binding with the immobilized anti-5-methylcytosine antibody. The recruited methylated DNA was simultaneously used as a substrate to facilitate successive template-free DNA extension and enzyme catalysis for the dual-step signal amplification of DNA Mtase activity. The developed immuno-DNA sensing strategy effectively integrates solution-phase DNA methylation, surface affinity binding recognition, and successive template-free DNA extension and enzyme catalysis-based signal amplification, rendering a highly specific, sensitive and accurate assay of DNA Mtase activity. A low detection limit of 0.039 U mL^-1 could be achieved with a high selectivity. It was also applied for efficient evaluation of various inhibitors. Current affinity recognition of the immobilized antibody with methylated DNA switches the sensing platform into a DNA operation interface, facilitating the opportunity for combining various DNA-based signal amplification strategies to improve the detection performance. It would be used as a general strategy for the analysis of DNA Mtase activity, inhibitors and more analytes, and is anticipated to show potential for applications in disease diagnosis and drug discovery.