Autoluminescent Met-AuNCs mediated coreactant-free electrochemiluminescent biosensor based on DNA walker cascade signal amplification for Vibrio parahaemolyticus detection

Most electrochemiluminescent (ECL) biosensors currently necessitate coreactants that affect sensor detection accuracy and increase sensor construction complexity. This study detailed the creation of an ECL biosensor without coreactant, utilizing Methionine-capped Au nanoclusters (Met-AuNCs) as luminophore and a Pb2+-dependent DNAzyme-mediated DNA walker signal amplification strategy to detect Vibrio parahaemolyticus (Vp) in scallops. Double-stranded DNA (dsDNA) was produced through hybridization of the Vp aptamer with DNA walker. The electrode surface was loaded with cDNA labeled with Met-AuNCs. Upon the presence of Vp, it competitively bound to the aptamer, resulting in dsDNA dissociation and exposing the DNAzyme sequence in the DNA walker. The introduction of Pb2+ initiated the activation and circulation of the DNAzyme-mediated DNA walker on the electrode surface, causing the cDNA to be sheared. As a result, the cDNA-Met-AuNCs on the surface of the electrode decreased, resulting in a reduction of ECL signal intensity. The ECL biosensor detected Vp at a range of 1.00×101-1.00×107 CFU/mL, under optimal conditions, with the limit of detection (LOD) being 1.23 CFU/mL. In this work, the biosensor demonstrated excellent stability and specificity and had proven successful in detecting actual samples of aquatic products. This study offers a novel ECL method without a coreactant for the detection of foodborne pathogens in aquatic products.