Superwettable electrochemical biosensor based on a dual-DNA walker strategy for sensitive E. coli O157: H7 DNA detection

Superwettable microchips exhibit excellent ability to anchor microdroplets and great potential in ultratrace sample detection. Herein, we present a superwettable electrochemical biosensor based on a dual-DNA walker strategy (dual-DW biosensor) for the attomolar detection of food-borne microorganisms ssDNA in microdroplets. In the presence of the target E. coli O157: H7 ssDNA, the blocked walking probe is activated as the first-step DNA walker. With the aid of the Nt.BsmAI nicking endonuclease, the partial sequence of the basal probe was released, thus achieving the first-step signal amplification. Then the hairpin probe 1(H1) was opened by the released basal probe and followed by the autonomous strand displacement of the ferrocene (Fc) labeled hairpin probe 2 (H2) and movement of the basal probe. Under optimized conditions, the dual-DNA walker strategy finally renders the dual-DW biosensor an ultrahigh sensitivity of 30 aM toward E. coli O157: H7 ssDNA and a broad detection linear range. The dual-DW biosensor also enables successful analysis of trace amount of E. coli O157: H7 ssDNA in real food samples. The superwettable electrochemical biosensor based on a dual-DNA walker strategy is expected to be a versatile tool for ultratrace DNA detection and be promising in food analysis.