A cascade amplification strategy for the detection of DNA methyltransferase activity by elemental labeling inductively coupled plasma mass spectrometry

Abstract

A cascade amplification strategy combining strand displacement amplification (SDA) and multicomponent nucleic acid enzyme (MNAzyme) was proposed for detecting DNA MTase activity by AuNPs labeling inductively coupled plasma mass spectrometry (ICP-MS). With the absence of Dam MTase, the hairpin strand containing the recognition site of nicking endonuclease performed SDA reaction and generated abundant short strands. These strands hybridized with partzyme A to block the progress of the MNAzyme reaction. In the presence of Dam MTase, the action of methylation-sensitive nicking endonuclease was blocked and SDA process was inhibited, leading to activation of subsequent MNAzyme reaction. The completely assembled MNAzyme cleaved the substrates on the magnetic beads and the released AuNPs were detected by ICP-MS. The method shows an ultra-high sensitivity with a limit of detection of 1.51 × 10−4 U mL−1, around 1–2 orders of magnitude lower than most reported methods. It was applied to the screening of inhibitors of Dam MTase as well as Dam MTase analysis in serum samples. Recoveries of 94.6–104% were obtained for Dam MTase in spiked serum samples, demonstrating good potential of the method for highly sensitive detecting DNA MTase activity in complex biological samples.