A multiple signal amplification electrochemiluminescence sensor for Hg2+detection based on Ce2Sn2O7/poly(5-formylindole) nanocomposites

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.