Visualizing of AuNPs protection aptamer from DNase I enzyme digestion based on Nanopipette and its use for Microcystin-LR detection

A simple and effective fluorescence platform has been established for visualizing nanomaterials' protective effect of DNA from cellular enzyme digestion based on nanopipette. In a proof-of-concept trial, gold nanoparticles (AuNPs) protect aptamer was designed, and it used for Microcystin-LR (MC-LR) sensitive detection. In the absence of MC-LR, FAM-labeled aptamers were combined on AuNPs, resulting in weak fluorescence emission. In the presence of MC-LR, aptamer bound with MC-LR. The formed complex leaves the surface of AuNPs. With the addition of the deoxyribonuclease I (DNase I) enzyme, the aptamer was selectively cleavaged, and MC-LR was released as an additional target molecule to achieve signal amplification and obtain strong fluorescence intensity. At the optimized conditions, a wide linear range (0.25 nM-20 nM) of fluorescence response for MC-LR was obtained. Further, by electrochemically manipulation MC-LR and DNase I inside confining nanopipette, which is filled with aptamer/AuNPs. The fluorescence intensity change with the aptamer and AuNPs interaction, these results directly visualize the process of DNA cleavage, and the interaction with AuNPs can effectively prevent the cleavage at the nanoscale confinement. This convenient nanoscale device provides new kinetic information about the dynamic chemical processes at a single-molecule level.