Ratiometric Electrochemical DNAzyme Biosensor for Sensitive Detection of Salmonella in Urban Water Source

Accurate, precise detection of Salmonella typhimurium (Salmonella) is crucial for maintaining water safety and preventing outbreaks of foodborne diseases. Bacterial culture, the gold standard for Salmonella detection, is time-consuming and cumbersome. Herein, a novel ratiometric electrochemical biosensing platform was constructed for Salmonella detection based on combining the electrochemical signals of a DNAzyme and metal-organic framework (MOF) and programmed DNA assembly amplification by target-specific cleavage of catalyzed hairpin assembly (CHA). DNAzyme is used to identify and detect S. typhimurium (ST) due to its release of RNase H2 (STH2) which specifically cleaves the rA site in DNAzyme, causing a subsequent reaction. To achieve proportional dual signaling strategy, the electrochemical signaling tag, ferrocene (Fc), was modified onto the DNA sequence H1, and Fe-MOF, an electrochemical indicator with high redox potential separation, was selected as the signaling probe. The prepared ratiometric electrochemical biosensor was analyzed via alternating current voltammetry (ACV). Salmonella detection in urban water source samples using the novel biosensor yielded essentially the same results as commercial Salmonella test strips, with even higher sensitivity, confirming the accuracy and usefulness of this sensing strategy. This study describes a valuable platform for highly specific, ultrasensitive Salmonella detection in aqueous environments.