Electrochemical immunosensor with Cu(I)/Cu(II)-chitosan-graphene nanocomposite-based signal amplification for the detection of newcastle disease virus

An electrochemical immunoassay for the ultrasensitive detection of Newcastle disease virus (NDV) was developed using graphene and chitosan-conjugated Cu(I)/Cu(II) (Cu(I)/Cu(II)-Chi-Gra) for signal amplification. Graphene (Gra) was used for both the conjugation of an anti-Newcastle disease virus monoclonal antibody (MAb/NDV) and the immobilization of anti-Newcastle disease virus polyclonal antibodies (PAb/NDV). Cu(I)/Cu(II) was selected as an electroactive probe, immobilized on a chitosan-graphene (Chi-Gra) hybrid material, and detected by differential pulse voltammetry (DPV) after a sandwich-type immune response. Because Gra had a large surface area, many antibodies were loaded onto the electrochemical immunosensor to effectively increase the electrical signal. Additionally, the introduction of Gra significantly increased the loading amount of electroactive probes (Cu(I)/Cu(II)), and the electrical signal was further amplified. Cu(I)/Cu(II) and Cu(I)/Cu(II)-Chi-Gra were compared in detail to characterize the signal amplification ability of this platform. The results showed that this immunosensor exhibited excellent analytical performance in the detection of NDV in the concentration range of 10(0.13) to 10(5.13) EID(50)/0.1 mL, and it had a detection limit of 10(0.68) EID(50)/0.1 mL, which was calculated based on a signal-to-noise (S/N) ratio of 3. The resulting immunosensor also exhibited high sensitivity, good reproducibility and acceptable stability.