Electrochemical immunosensor for competitive detection of neuron specific enolase using functional carbon nanotubes and gold nanoprobe

► Using SWNT to enhance electrochemical signal and enlarge antigen domains. ► AP linked secondary antibody labeled AuNP enhanced catalytic activity to α-NP. ► Using SWNT and AuNP lead to a dual signal amplification for sensitive detection. ► The sensor with a wide range can direct detect protein in serum without dilution. ► The assay results were in a good agreement with the reference values. An electrochemical immunosensor for detection of neuron specific enolase (NSE) was designed by immobilizing NSE covalently functionalized single-walled carbon nanotubes (NSE-SWNTs) on a glassy carbon electrode. The NSE-SWNTs not only enhanced electrochemical signal but also presented abundant antigen domains for competitive immunological recognition to anti-NSE primary antibody and then gold nanoprobes labeled with alkaline phosphatase conjugated secondary antibody (AP-anti-IgG/AuNPs). The AP-anti-IgG/AuNPs exhibited highly catalytic activity toward enzyme substrate and significantly amplified the amperometric signal for target molecule detection. Based on the dual signal amplification of SWNTs and gold nanoprobe, the immunosensor could response down to 0.033ngmL−1 NSE with a linear range from 0.1ngmL−1 to 2μgmL−1, and showed acceptable precision and reproducibility. The designed immunosensor was amenable to direct quantification of target protein with a wide range of concentration in complex clinical serum specimens. The assay results were in a good agreement with the reference values. The proposed electrochemical immunosensor provided a pragmatic platform for convenient detection of tumor markers in clinical diagnosis.