Entropy-driven amplified electrochemiluminescence biosensor for RdRp gene of SARS-CoV-2 detection with self-assembled DNA tetrahedron scaffolds.

Dependable, specific and rapid diagnostic methods for severe acute respiratory syndrome β-coronavirus (SARS-CoV-2) detection are needed to promote public health interventions for coronavirus disease 2019 (COVID-19). Herein, we have established an entropy-driven amplified electrochemiluminescence (ECL) strategy to detect the RNA-dependent RNA polymerase (RdRp) gene of SARS-CoV-2 known as RdRp-COVID which as the target for SARS-CoV-2 plays an essential role in the diagnosis of COVID-19. For the construction of the sensors, DNA tetrahedron (DT) is modified on the surface of the electrode to furnish robust and programmable scaffolds materials, upon which target DNA-participated entropy-driven amplified reaction is efficiently conducted to link the Ru (bpy)32+ modified S3 to the linear ssDNA at the vertex of the tetrahedron and eventually present an "ECL on" state. The rigid tetrahedral structure of the DT probe enhances the ECL intensity and avoids the cross-reactivity between single-stranded DNA, thus increasing the sensitivity of the assays. The enzyme-free entropy-driven reaction prevents the use of expensive enzyme reagents and facilitates the realization of large-scale screening of SARS-CoV-2 patients. Our DT-based ECL sensor has demonstrated significant specificity and high sensitivity for SARS-CoV-2 with a limit of detection (LOD) down to 2.67 fM. Additionally, our operational method has achieved the detection of RdRp-COVID in human serum samples, which supplies a reliable and feasible sensing platform for the clinical bioanalysis.