A sensitive electrochemical biosensor for quinolones detection based on Cu2+-modulated signal amplification

In this work, a sensitive electrochemical biosensor is developed for the detection of quinolones based on Cu2+-modulated signal amplification. In the presence of target quinolones, the formation of quinolones-Cu2+ complex inhibits the activity of Cu2+-specific DNAzyme. As a result, the intact substrate DNA probe of Cu2+-specific DNAzyme is reserved to trigger the hybridization chain reaction, forming long dsDNA nanowires on the surface of the electrode and finally generating a significant amplification of electrochemical signal positively correlated with the concentration of target quinolones. Benefiting from the Cu2+-modulated signal amplification, a good linear relationship between the electrochemical signal and the logarithm of ciprofloxacin concentration can be obtained in the range from 0.1 ng mL−1 to 200 ng mL−1, and the limit of detection is low to 0.052 ng mL−1. With the advantages of simple operation, high sensitivity and specificity, the electrochemical biosensor has been utilized to assay ciprofloxacin in real foodstuff samples, exhibiting satisfactory analytical performance and showing latent practicability in food safety detection.