Sensitive determination of Hg(II) based on a hybridization chain recycling amplification reaction and surface-enhanced Raman scattering on gold nanoparticles

A method was developed for the determination of mercuric ion Hg(II). It is based on hybridization chain reaction (HCR) and surface-enhanced Raman scattering (SERS). Raman signal DNA and streptavidin were self-assembled on gold nanoparticles as a novel signal nanoprobe (AuNP-sDNA). A thymine-mercury(II)-thymine structure was immobilized on magnetic beads (MBs). The HCR makes use of two hairpin probes that are initiated by the trigger DNA to form a stable nicked dsDNA structure (MB-TS-hDNAs). A large number of the binding sites is provided to connect the signal nanoprobe. The stable sandwich structure (MB-TS-hDNA/AuNP-sDNA) was isolated by applying a magnetic field and used in the amplification step. In this way, Hg(II) can be determined sensitively after multiple signal amplification. The SERS signal, measured at 1499 cm^-1, increases linearly in the 0.1 pM to 10 nM Hg(II) concentration range, and the limit of detection is 0.08 pM (at an S/N ratio of 3). The method was applied to the detection of Hg(II) in spiked environment water samples, with recoveries ranging from 96 to 119%. Graphical abstract Schematic of a method based on the use of a stable T-Hg(II)-T structure and a self-assembled nanoprobe. It was applied to the trace Hg(II) detection based on hybridization chain reaction (HCR) and surface-enhanced Raman scattering (SERS).