A reusable and sensitive biosensor for total mercury in canned fish based on fluorescence polarization

In this work, we developed a sensitive and selective sensor technique for total mercury (Hg) detection in canned fish samples based on the fluorescence polarization (FP) method. The detection principle was that ssDNA containing thymine (T) bases was modified on magnetic nanoparticles (MNPs), which were used as enhancement probe. In the presence of Hg2+, the ssDNA on MNPs can hybridize with the fluorophore labeled aptamer owing to the specific interaction between T bases and Hg2+. The formation of thymine–Hg2+–thymine (T–Hg2+–T) complexes leads to the molar mass increase of fluorophore molecules, resulting in the enhancement of FP signal. The increase of FP was in a good linearity with the concentration of Hg2+ in range of 2.0 nM–1.0 mM and the limit of detection was 0.49 nM (3.29 SB/m, according to the recent recommendation of IUPAC). Moreover, the proposed biosensor can be reused for 6 cycling times and was successfully applied in monitoring Hg2+ in real samples.