Colorimetric detection of methyltransferase activity based on the enhancement of CoOOH nanozyme activity by ssDNA

A label-free colorimetric assay for MTase activity based on the nanozyme activity of cobalt oxyhydroxide (CoOOH) nanoflakes and the difference in affinity of the nanoflakes with single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) has been developed. In this strategy, ssDNA can enhance the nanozyme activity of CoOOH nanoflakes, which could be attributed to the electrostatic attraction and π-π stacking interaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and ssDNA. The proposed method presents a wide linear range from 0.08 to 50 U/mL and a low detection limit (LOD) of 0.069 U/mL. Additionally, this colorimetric sensor also has been proved to detect MTase in the cell lysates of lung cancer cells (A549) with good recovery and reproducibility. Furthermore, the novel strategy can be applied for high-throughput evaluation and screening the inhibitors for M.SssI MTase by using representative anticancer drugs as model inhibitors, therefore, the colorimetric sensor can not only achieve the purpose of sensitively detecting the activity of MTase, but also has the potential in clinical diagnostics and drug discovery.