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An enzyme cascade-based electrochemical immunoassay using a polydopamine–carbon nanotube nanocomposite for signal amplification

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Abstract

By coupling tyrosinase (Tyr) and β-galactosidase (Gal) into one redox-cycling scheme, an enzyme cascade-based electrochemical immunosensor with boosted selectivity and sensitivity was constructed using polydopamine-functionalized multiwalled carbon nanotube (MWCNTs–PDA) nanohybrid modified electrodes. The MWCNTs–PDA nanohybrid presented a 5 times enhanced capability for antibody conjugation, which was responsible for signal amplification. In the proposed enzyme cascade scheme, Gal was captured on the immunosensor surface by a sandwiched immunoreaction, which catalyzed phenyl β-D-galactopyranoside (P-GP) into phenol based on a hydrolysis reaction. The resulting phenol was used as a substrate of Tyr, which was catalyzed to catechol and subsequently to o-quinone. The o-quinone was then electrochemically reduced to catechol, forming a redox cycle between catechol and o-quinone. The enzyme cascade-based immunoassay not only significantly amplified the electrochemical signal, but also led to a high selectivity. Taking the detection of CEA as an example, the enzyme cascade-based electrochemical immunosensor showed a detectable range of 10 pg mL−1 to 10 ng mL−1 and a low detection limit of 8.39 pg mL−1 (S/N = 3), which was superior/comparable to those using other methodologies in previous reports. The selectivity of the enzyme cascade-based immunosensor was 44–80% higher than that of a single enzyme-based immunosensor. This work shows great potential of the coupling enzyme cascade in immunosensing for clinical diagnosis with boosted selectivity and sensitivity.

Graphical abstract: An enzyme cascade-based electrochemical immunoassay using a polydopamine–carbon nanotube nanocomposite for signal amplification

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Publication details

The article was received on 09 Oct 2018, accepted on 13 Nov 2018 and first published on 14 Nov 2018


Article type: Paper
DOI: 10.1039/C8TB02659A
Citation: J. Mater. Chem. B, 2018, Advance Article
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    An enzyme cascade-based electrochemical immunoassay using a polydopamine–carbon nanotube nanocomposite for signal amplification

    Y. Zhang, D. Pan, Q. Zhou, J. Zhao, N. Pan, Y. Zhang, L. Wang and Y. Shen, J. Mater. Chem. B, 2018, Advance Article , DOI: 10.1039/C8TB02659A

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