A homogenous electrochemical biosensor for ultrasensitive ofloxacin detection based on AuNPs-enhanced synergistic amplification of enzymes

Antibiotic residue in food is still a serious health hazard to human with the various and severe adverse effects, so ultrasensitive detection of antibiotic residue becomes increasingly significant. Herein, a homogenous electrochemical biosensor is established for ultrasensitive detection of antibiotic ofloxacin (OFL) based on AuNPs-enhanced synergistic amplification of dual enzymes. Target OFL is ingeniously designed to initiate the synergistic effect of exonuclease III-catalyzed DNA cycle and terminal deoxynucleotidyl transferase-mediated polymerization, producing a great many polyA@AuNPs which subsequently adsorb onto the surface of gold electrode and finally lead to highly amplified electrochemical signal by binding with numerous electroactive indicator RuHex. Benefiting from the collaboratively multiple signal amplifications enhanced by AuNPs with good electrical conductivity and probe loading capacity, the constructed biosensor exhibits excellent quantitative detection performance for OFL with a linear range of 0.008 to 100 ng mL−1 and a limit of detection as low as 2.73 pg mL−1. Furthermore, the detection system accomplished in homogeneous solution without complex chemical modification and rebuilding of sensing architectures on the electrode endows the biosensor with the advantages of convenient operation, good reproducibility and stability. Moreover, the biosensor shows satisfactory analytical performance for OFL detection in real food samples, providing a potential approach for practical application.