Electrochemical Aptasensing of SARS-CoV-2 Based on Triangular Prism DNA Nanostructures and Dumbbell Hybridization Chain Reaction.

Development of convenient, accurate, and sensitive methods for rapid screening of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection is highly desired. In this study, we have developed a facile electrochemical aptasensor for the detection of the SARS-CoV-2 S1 protein amplified by dumbbell hybridization chain reaction (DHCR). A triangular prism DNA (TPDNA) nanostructure is first assembled and modified at the electrode interface. Due to the multiple thiol anchors, the immobilization is quite stable. The TPDNA nanostructure also provides an excellent scaffold for better molecular recognition efficiency on the top single-strand region (DHP0). The aptamer sequence toward the SARS-CoV-2 S1 protein is previously localized by partial hybridization with DHP0. In the presence of the target protein, the aptamer sequence is displaced and DHP0 is exposed. After further introduction of the fuel stands of DHCR, compressed DNA linear assembly occurs, and the product can be stacked on the TPDNA nanostructure for the enrichment of electrochemical species. This electrochemical method successfully detects the target protein in clinical samples, which provides a simple, robust, and accurate platform with great potential utility.

A label-free electrochemical assay for coronavirus IBV H120 strain quantification based on equivalent substitution effect and AuNPs-assisted signal amplification.

A label-free electrochemical strategy is proposed combining equivalent substitution effect with AuNPs-assisted signal amplification. According to the differences of S1 protein in various infectious bronchitis virus (IBV) strains, a target DNA sequence that can specifically recognize H120 RNA forming a DNA-RNA hybridized double-strand structure has been designed. Then, the residual single-stranded target DNA is hydrolyzed by S1 nuclease. Therefore, the content of target DNA becomes equal to the content of virus RNA. After equivalent coronavirus, the target DNA is separated from DNA-RNA hybridized double strand by heating, which can partly hybridize with probe 2 modified on the electrode surface and probe 1 on AuNPs' surface. Thus, AuNPs are pulled to the surface of the electrode and the abundant DNA on AuNPs' surface could adsorb a large amount of hexaammineruthenium (III) chloride (RuHex) molecules, which produce a remarkably amplified electrochemical response. The voltammetric signal of RuHex with a peak near - 0.28 V vs. Ag/AgCl is used as the signal output. The proposed method shows a detection range of 1.56e-9 to 1.56e-6 µM with the detection limit of 2.96e-10 µM for IBV H120 strain selective quantification detection, exhibiting good accuracy, stability, and simplicity, which shows a great potential for IBV detection in vaccine research and avian infectious bronchitis diagnosis. Graphical abstract.