3D DNA walkers integrated with self-reporting MOFs: Pioneering ratiometric electrochemical sensing for Staphylococcus...

The persistent global challenge of high incidence rates of foodborne bacterial pathogens continues to pose significant threats to both human health and public health security. Accurate determination of foodborne bacteria assumes paramount importance in effectively preventing and controlling related diseases. However, conventional bacterial detection methods often suffer limitations of cumbersome operation procedures, long time consumption, susceptibility to contamination or low sensitivity. The utilization of novel materials with direct self-reporting properties for developing ratiometric electrochemical biosensors offers a promising solution. Here, we present a ratiometric electrochemical aptasensor utilizing a magnetic 3D DNA walking machine and self-assembly of MOF for the sensitive detection of foodborne bacteria, with Staphylococcus aureus as the target model. A self-reporting MOF was employed as a signal probe, while [Fe(CN)₆]^3-/4- served as an inner reference probe. The introduction of target triggers the release of walker DNA from the walker/aptamer complexes, thereby initiating the DNA walking machine to produce numerous sticky sequences for further self-assembly of the linker probe-modified MOF on the magnetic beads surface. Quantification is accomplished by analyzing the ratio of the current signals. Attributed to the efficient magnetic separation, the self-reporting functionality of MOF, the cascade signal amplification strategy, and incorporation of a ratiometric signal output mode with self-calibration capability, this approach exhibits exceptional analytical performance and feasibility for testing complex samples. This study presents the first ratiometric aptasensor that integrates a DNA walking machine with a self-reporting MOF for the sensitive detection of bacteria. It offers a rapid, robust, and selective method for whole-cell detection without requiring complex sample preparation, demonstrating considerable potential in food safety monitoring and diagnosis of bacterial infections.