A multifunctional label-free electrochemical impedance biosensor for Hg2+, adenosine triphosphate and thrombin

• A label-free DNA-based impedance biosensor is developed for the detection of Hg2+, ATP and thrombin.
• Hg2+, ATP and thrombin can be recognized by nucleic acid subunits with high specificity.
• The biosensor shows good selectivity, reproducibility, and stability.

A multifunctional label-free biosensor for the detection of Hg2+, adenosine triphosphate and thrombin has been developed based on the changing of the electrochemical impedance spectroscopy (EIS) from the modified electrodes when nucleic acid subunits interacting with different targets. The modified electrode consists of three interaction sections, including DNA with T–T mismatch recognizing Hg2+ to form T–Hg2+–T complex, split DNA chip against ATP, and DNA domin against thrombin to form G-quadruplex. Upon DNA interaction with thrombin or ATP, an increased charge transfer resistance (Rct) had been detected. However, a decreased Rct against Hg2+ was obtained. The Rct difference (ΔRct) has relationship with the concentration of the different targets, Hg2+, ATP and thrombin can be selectively detected with the detection limit of 0.03, 0.25, and 0.20 nmol L−1, respectively. To separately detect the three analytes existing in the same sample, ATP aptamer, G-rich DNA strands and EDTA were applied to mask ATP, Hg2+ or thrombin separately.

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