Electrochemically ultrasensitive detection of ampicillin using enzyme-mediated metallo-β-lactamase/CS/Bi2WO6/MWCNTs-COOH biosensor

The misuse of the antibiotic ampicillin (AMP) has led to the presence of antibiotic residues in related products, which enter the human body through the ecological or food chain to produce a variety of toxic side effects. There is an urgent need to develop enzyme-based assays with higher specificity to determine antibiotic residues in food. Hereby, bismuth tungstate (Bi 2 WO 6 ) was synthesized using a simple hydrothermal and calcination process. Carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) were mixed with Bi 2 WO 6 by ultrasonication to form composite as modifier on glassy carbon electrode (GCE) surface. Meanwhile, metal β-lactamases (MBLs) were mixed with chitosan to be immobilized on it to obtain the MBLs/CS/Bi 2 WO 6 /MWCNTs-COOH/GCE. Under the optimal conditions, differential pulse voltammetry (DPV) was used for the quantitative detection of AMP. The experimental results showed that the peak currents were linearly correlated with the concentrations of AMP (0.0007–0.05 μM) and (0.1–10 µM) (R 2  = 0.9965 and 0.9956), and the detection limit was 0.17 nM (S/N = 3). The method has good repeatability, reproducibility, stability and immunity to interference, and can be applied to the highly sensitive detection of AMP in real samples with recoveries of 92.4–96.8 % and 94.3–103.0 %.