Triple Helix Molecular Switch Cascade Multiple Signal Amplification Strategies for Ultrasensitive Chloramphenicol Detection

A novel self-powered biosensor has been developed for the detection of chloramphenicol (CAP) based on difunctional triple helix molecular switch (THMS)-mediated DNA walkers. The biosensor utilizes the CAP aptamer as the recognition element, a DNA walker and capacitor as dual signal amplification strategies, and a digital multimeter (DMM) as the data readout equipment. In the presence of the target, the CAP aptamer in THMS specifically binds with CAP to release a signal transduction probe (STP) and opens the H1 hairpin structure in the biocathode to trigger the DNA walker and form a double-stranded DNA structure. Then, [Ru(NH₃)₆]³⁺ is electrostatically adsorbed on the double-stranded DNA structure through electrostatic adsorption and reduced to [Ru(NH₃)₆]²⁺ at the biocathode by accepting electrons entering at the bioanode. In DNA walkers, more double-stranded structures are formed, and a higher open-circuit voltage (<i>E</i>^OCV) is observed. This self-powered biosensor with a detection limit (LOD) of 0.012 fM exhibits ultrasensitive CAP detection in milk in the range of 0.1-10⁴ fM as well as excellent selectivity, stability, and reproducibility.