Exploring an ultra-sensitive electrochemiluminescence monitoring strategy for SARS-CoV-2 using hairpin-assisted cycling and dumbbell hybridization chain amplification

Rapid and accurate discrimination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an available approach to implement a rapid diagnosis of the coronavirus disease 2019 (COVID-19). Here we fully exploited the cleavage properties of exonuclease III (Exo III) and hairpin DNA-assisted target cycling technology to generate bulk single-stranded DNA (ssDNA) that was employed to facilitate the constitution of a three-way junction structure on polymetallic particle (Ag-Au NPs) and Ti3C2 (Ti3C2 @Ag-Au) complexes. Ag-Au NPs presented favorable stability without adding extra stabilizers, demonstrating the potential value of Ag-Au NPs as an alternative to Au NPs in the field of bioanalysis. Uppon the three-way junction structure, the dumbbell hybridization chain amplification (DHCA) was occurred which generated DNA nanostructure with tight conformation. Target cycling and DHCA reactions improved the electrochemiluminescence (ECL) signal, which dramatically advanced the assay sensitivity of SARS-CoV-2 (0.59 fM). Moreover, our strategy remained to demonstrate favorable specificity and repeatability in environmental conditions and real human serum samples.