On-demand controlled bidirectional DNAzyme path for ultra-sensitive heavy metal ion detection.

A bidirectional self-powered biosensor is constructed for the quasi-simultaneous detection of Pb and Hg based on MoS@CuS heterostructures as an accelerator and hybridization chain reaction (HCR) as a signal amplification strategy. MoS@CuS heterostructures significantly facilitate electron transfer between glucose and bioelectrodes, thereby greatly improving the detection signal of self-powered biosensors. This novel biosensor employs the unique sequences of DNAzymes to isolate Pb and Hg by the cleavage effect and thymine (T)-Hg-thymine (T) structures, respectively. In the process, Pb cuts the sequence of DNAzyme at the bioanode to trigger glucose oxidation to monitor Pb. The as-formed T-Hg-T structures activate HCR to reduce [Ru(NH)] to detect Hg at the biocathode. It is noteworthy that this biosensor not only realizes Pb or Hg detection in a single-electrode, respectively, but also can quasi-simultaneously detect both Pb and Hg in the bioanode and the biocathode. The novel self-powered biosensor identifies Pb in the range of 10 fM to 10 fM with a limit of detection (LOD) of 3.1 fM and Hg in the range of 10 fM to 1 fM with an LOD of 0.33 fM.