Electric Field-Induced Specific Preconcentration to Enhance Dna-Based Electrochemical Sensing of Hg2+ Via the Synergy of Enrichment and Self-Cleaning

Efficient preconcentration strategy is of vital importance for the sensitive and selective electrochemical detection of metal ions; rapid specific enrichment with the depressed absorption of interfering ions at electrode, however, is challenging. Here, we proposed an electric field-induced specific preconcentration to boost the analytical performance of DNA-based electrochemical sensor for Hg2+ detection. As for such preconcentration, a positive external electric field is firstly used to enrich Hg2+ at electrode assembled with T-rich DNA, thereby boosting T-Hg2+-T recognitions, and the following applied inverse electric field strips the nonspecifically-absorbed Hg2+ and other interfering ions, depressing matrix interferences by self-cleaning. Based on this principle, we designed a portable device to realize the programmable control of electric field, and a T-Hg2+-T recognition-based electrochemical sensor was fabricated. Experimental results revealed that such strategy decreased the time of T-Hg2+-T-based recognition from 60 to 20 min and endowed the detection with better reproducibility by depressing the influences of free Hg2+ as well as interfering ions. Such a strategy enabled determining Hg2+ with a detection limit of 0.01 pM, 3-fold lower than that without preconcentration, within 22 min. The proposed preconcentration strategy should provide a new way to enhance the analytical performance of biosensing at the solidity-liquid interface.