Ultrasensitive Photoelectrochemical Detection of Multiple Metal Ions Based on Wavelength-Resolved Dual-Signal Output Triggered by Click Reaction.

In this work, a click reaction-triggered wavelength-resolved dual-signal output photoelectrochemical (PEC) biosensor with DNAzymes-assisted cleavage recycling amplification was proposed for sensitive triplex metal ions assay. Substantial DNA fragments azido-S1 and azido-S2, derived from the Pb2+ (target 1) and Mg2+ (target 2) dependent cleavage cycle of DNAzymes, respectively, were grafted efficiently on the same alkynyl-DNA (capture DNA) modified electrode via the Cu2+ (target 3) and ascorbic acid (AA) cocatalyzed click reaction, which thus could be subsequently used for immobilization of two different photoactive nanomaterials labeled with single DNA to generate distinguishing dual-signal output for simultaneously sensitive detection of Pb2+ and Mg2+. Furthermore, the control variable method was used for detecting Cu2+ by altering the concentration of Cu2+ in the click reaction. Owing to the usage of the click reaction and target-converted signal amplifying strategy, the utilization rate of cycle output DNAs was largely increased, significantly improving the detection sensitivity of the proposed approach. As a result, low detection limits down to picomolar were acquired for the detection of Pb2+, Mg2+, and Cu2+, providing a versatile, efficient, and sensitive PEC method for multiple assays of various targets such as metal ions, small molecules, and tumor markers.