A novel one-step triggered 'signal-on/off' electrochemical sensing platform for lead based on the dual-signal ratiometric output and electrode-bound DNAzyme assembly

摘要

Graphical abstractA simple and novel one-step triggered “signal-on/off” ratiometric electrochemical biosensor based on the highly specific lead-dependent DNAzyme and dual-signal output mode was designed for the sensitive and selective determination of lead ions.Display OmittedHighlights•A novel one-step triggered dual-signal ratiometric electrochemical Pb2+biosensor is developed based on the electrode-bound DNAzyme assembly.•The biosensor can detect Pb2+down to 45.8pM level with a dynamic range spanning 4 orders of magnitude.•The biosensor allows selective and sensitive detection of Pb2+in clinical serum samples.•The proposed DNAzyme-based ratiometric electrochemical strategy could be easily expanded into the versatile detection of other metal ions.AbstractA simple and novel one-step triggered ratiometric electrochemical biosensor was designed for lead (Pb2+) based on the highly specific lead-dependent DNAzyme and dual-signal output mode. The biosensor consists of a thiolated methylene blue-labeled DNA (MB-P1) as catalytic probe and “signal-on” readout, and a complementary strand modified with ferrocene (Fc-P2) as substrate probe and “signal-off” output. The presence of Pb2+could activate the DNAzyme and cleave the sessile phosphodiester of the Fc-P2 into two fragments, which lead to the departure of Fc from the sensing interface along with the single stranded MB-P1 near the electrode surface. Therefore, the Pb2+recognition event resulted in both the “signal-on” of MB and the “signal-off” of Fc for dual-signal ratiometric electrochemical readout. Combined with the efficient recognition capacity of the designed DNAzyme and the dual-signal amplification strategy, the proposed biosensor showed a wide detection range from 0.1nM to 5μM with a detection limit of 45.8pM (S/N=3). Meanwhile, this DNAzyme-based Pb2+biosensor exhibits reasonable selectivity, fast analytical speed, acceptable fabrication reproducibility, and operational convenience. More importantly, the system is capable of detecting Pb2+in biological fluid such as serum, suggesting promising applications of this biosensor in on-site and real-time clinical Pb2+detection.