A novel electrochemiluminescence aptasensor based on "ON-OFF-ON" signal switching strategy for chloramphenicol detection.

Chloramphenicol (CAP), a broad-spectrum antibiotic derived from Streptomyces, readily persists and accumulates in humans through pathways such as the food chain, leading to significant toxic effects. Herein, a novel electrochemiluminescence (ECL) aptasensor based on the signal "ON-OFF-ON" strategy is proposed for CAP detection in food. We utilized the immobilization capacity and enzyme-mimicking activity of iron-lanthanum doped prussian blue analogue (Fe-La PBA) to catalytically enhance the luminol-H2O2 luminescent system, thereby engineering the composite nanozyme-based luminophore (luminol-Au@Fe-La PBA). Moreover, polydopamine (PDA)-coordinated cadmium sulfide (CdS) decorated with gold nanoparticles (Au@CdS/PDA) serves as an energy acceptor to quench the signal from emitter luminol-Au@Fe-La PBA. Firstly, the luminol-Au@Fe-La PBA emitter was immobilized on a glassy carbon electrode (GCE), providing a strong initial ECL signal and serving as a platform for anchoring cDNA hybridized with the aptamer (Apt). Then the specific quenching probe (Apt-Au@CdS/PDA) was introduced, leading to substantial signal reduction. Upon the action of CAP, the dissociation of the Apt-cDNA hybrid duplex led to the detachment of the quenching probe from the electrode surface, thereby restoring the ECL signal intensity. The aptasensor demonstrated a linear response over a concentration range of 10 to 107 pg mL- 1, and LOD was 1.18 pg mL- 1, exhibiting satisfactory recoveries in various food samples and quality control samples.