MnO switch-bridged DNA walker for ultrasensitive sensing of cholinesterase activity and organophosphorus pesticides.

Cholinesterases (ChEs) are important indicators of neurological disease, hepatocellular carcinoma, and organophosphate poisoning. In this work, a MnO switch-bridged DNA walker was developed for ultrasensitive sensing of ChEs activity. The fuel strands loaded MnO switch was designed to bridge the hydrolysis activity of ChEs and the running of the DNA walker. Under the action of ChE, the substrate butyrylcholine is first catalytically hydrolyzed to thiocholine, which then mediates MnO nanosheet reduction to Mn, releasing the fuel strands into solution. The fuel strands as substitute targets then trigger the continuous operation of DNA walker with the aid of Mn, generating detectable fluorescence responses. The detection of ChE activity is converted to DNA detection in this method. Benefited from the robust operation and amplification effect of DNA walker, a wide linear range between the BChE activity and fluorescence intensity of nearly six orders of magnitude (1000-0.005 U/mL) and a limit of detection as low as 0.0008 U/mL are achieved. This allows the direct determination of BChE activity in clinical serum samples without any pretreatments. Moreover, the proposed method has remarkable capabilities for inhibitor (organophosphorus pesticide) screening and quantification, and organophosphorus pesticide detection in real samples is also achieved. Therefore, the MnO switch-bridged DNA walker represents a powerful tool for ultrasensitive sensing of ChEs and organophosphorus pesticides, and has great application potential in clinical diagnosis, therapeutics, and drug screening.