A highly sensitive aptasensor based on 3D-rGO/AuNPs for Hg2+ determination using HCR amplification strategy triggered by T-Hg2+-T

In this paper, we developed an electrochemical aptasensor with high sensitivity based on the stable T-Hg2+-T structure for Hg2+ determination. The three-dimensional reduced graphene oxide-modified gold nanoparticles (3D-rGO/AuNPs) was served as support material, which offered more immobilization sites for thiolated probe (P1). In the presence of Hg2+, P1 could interact with another probe (P2) by forming T-Hg2+-T structure. Further, the partial sequence of P2 that did not interact with P1 was employed as an initiator sequence, which resulted in the formation of the extended double-stranded DNA through the hybridization chain reaction (HCR) between two harpin DNA strands (HP1 and HP2). Toluidine blue (TB) was used to interact with the double-stranded DNA and bring in effective electrochemical responses. Under the optimal experimental conditions, the aptasensor exhibited pronounced electrochemical signals towards Hg2+ ranging from 10 fM to 50 nM, with a low detection limit of 3.3 fM. Besides, the aptasensor showed excellent performance in water samples for Hg2+ determination.

Automated summary

In this study, an electrochemical aptasensor based on the stable T-Hg2+-T structure was developed for Hg2+ determination. The use of 3D-rGO/AuNPs as support material provided more immobilization sites for thiolated probes, and the hybridization chain reaction (HCR) between non-complementary sequences resulted in the formation of extended double-stranded DNA. The aptasensor showed high sensitivity and low detection limit for Hg2+ detection.