A multiple signal amplification electrochemiluminescence sensor for Hg²⁺ detection based on...

A novel electrochemiluminescence (ECL) sensor for the detection of Hg²⁺ is constructed based on the synthesized cerium stannate/poly(5-formylindole) (Ce₂Sn₂O₇/P5FIn) composite and multiple DNA signal amplification techniques, including strand displacement amplification (SDA) reaction and hybridization chain reaction (HCR). On the one hand, the combination of Ce₂Sn₂O₇ and P5FIn improves the electrochemical reaction rate between Ce₂Sn₂O₇ and the co-reactant, and significantly enhances the ECL signal. On the other hand, compared to P5FIn, Ce₂Sn₂O₇/P5FIn has a larger specific surface area to facilitate the effective fixation of hairpin DNA H1. The target Hg²⁺ is bound to the DNA strand (mDNA) rich in thymine bases (T) by T-Hg²⁺-T. Subsequently, with the assistance of polymerase (phi29 DNA) and restriction endonuclease (Nt.BbvCI), strand displacement amplification (SDA) reaction is triggered to generate a large number of simulated target (MT). Hairpin DNA H1 captures MT, which then further triggers a hybridization chain reaction (HCR) to produce long strand DNA (dsDNA) rich in cytosine. Finally, a large amount of Ag⁺ is introduced through C-Ag⁺-C, which is used as a co-reaction accelerator of Ce₂Sn₂O₇-K₂S₂O₈ system to significantly enhance the ECL signal strength. Under optimal conditions, the constructed ECL sensor can detect Hg²⁺ in a wide linear response range of 1.0 fM-100 nM, with a detection limit of 0.30 fM. The sensor also has high sensitivity and good applicability in the detection of seawater samples.