A programmable DNA nanodevice for colorimetric detection of DNA methyltransferase activity using functionalized hemin/G-quadruplex DNAzyme.

The measurement of DNA methyltransferase (MTase) activity and screening of DNA MTase inhibitors holds significant importance for the diagnosis and therapy of methylation-related illness. Herein, we developed a colorimetric biosensor (PER-FHGD nanodevice) to detect DNA MTase activity by integrating the primer exchange reaction (PER) amplification and functionalized hemin/G-quadruplex DNAzyme (FHGD). By replacing the native hemin cofactor into the functionalized cofactor mimics, FHGD has exhibited significantly improved catalytic efficiency, thereby enhancing the detection performance of the FHGD-based system. The proposed PER-FHGD system is capable of detecting Dam MTase with excellent sensitivity, exhibiting a limit of detection (LOD) as low as 0.3 U/mL. Additionally, this assay demonstrates remarkable selectivity and ability for Dam MTase inhibitors screening. Furthermore, using this assay, we successfully detect the Dam MTase activity both in serum and in E. coli cell extracts. Importantly, this system has the potential to serve as a universal strategy for FHGD-based diagnosis in point-of-care (POC) tests, by simply altering the recognition sequence of the substrate for other analytes.