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

A facile, sensitive and unmodified Hg2+ 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 Hg2+ mediated thymine-Hg (II)-thymine (T-Hg2+-T) structure, when Hg2+ is introduced, the T-Hg2+-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 Hg2+detection, and the detection limit is as low as 0.6 pM. furthermore, this sensor has high selectivity for Hg2+ detection.