Signal-on electrochemical aptasensor based on RGO-AuNPs and exonuclease-III with assistance of external probe for Hg2+determination in shellfish

In this work, a signal-on electrochemical aptasensor, based on RGO-AuNPs and exonuclease-III (Exo-III), is introduced for sensitive Hg2+ determination in shellfish. RGO-AuNPs is one-step electrodeposited on screenprinted electrode (SPE) surface as a high-performance sensing platform. Hg2+ aptamer serves as a molecular recognizer and selectively responds to Hg2+, thus triggering thymine-Hg2+-thymine (T-Hg2+-T) coordination. Exo-III is activated to cleavage the T-Hg2+-T structure, leading to partial aptamer breakage on sensor surface. Particularly, the reduction of DNA phosphate skeletons actuates is sensitively recorded by the external signal probe (I[Fe(CN)6]4-) and further amplified, thus composing a signal-on system. Under optimum conditions, asfabricated sensor presents a good linear relationship to Hg2+ level in the range of 3.5x10- 3 - 5.6x10- 1 mg L-1, and the detection limit (LOD) is well found as 1.2x10- 3 mg L-1. In certified ICP-MS and recovery tests of shellfish samples, the errors and recovery rates are calculated as 1.5%-4.4% and 97.5%-103.5%, respectively.