A double signal amplification-based homogeneous electrochemical sensor built on catalytic hairpin assembly and bisferrocene markers.

A facile, sensitive and unmodified Hg homogeneous electrochemical sensor based on bisferrocene signal markers and catalytic hairpin self-assembly (CHA) was built on a gold disk electrode. Three hairpin probes were designed, in which thiol was labeled at both ends of the hairpin probe 1(HP1), while bisferrocene, a redox signal marker, was labeled at both ends of the hairpin probe 2(HP2) and hairpin probe 3(HP3). Due to the Hg mediated thymine-Hg (II)-thymine (T-Hg-T) structure, when Hg is introduced, the T-Hg-T that occurred between the probe DNA and helper DNA could open the hairpin structure of probe DNA and form a rigid DNA triangles structure by CHA. Simultaneously, four bisferrocene signal markers also reached the surface of the electrode and built potential-assisted Au-S self-assembly to achieve signal amplification. Under the optimized condition, the sensor can achieve good electrochemical response Hgdetection, and the detection limit is as low as 0.6 pM. furthermore, this sensor has high selectivity for Hg detection.