Issue 24, 2011

Detection of cortisol at a gold nanoparticle|Protein G–DTBP-scaffold modified electrochemical immunosensor

Abstract

An ultrasensitive electrochemical immmunosensor was demonstrated to be capable of detecting the hormone cortisol down to concentrations as low as 16 pg mL−1. In addition, the immunosensor displayed a sensitivity of 1.6 μA pg−1 mL−1 and a linear range up to ∼2500 pg mL−1 of cortisol. This immunosensor was constructed based on a Au nanoparticle|dimethyl 3,3′-dithiobispropionimidate·2HCl (DTBP)–Protein G scaffold-modified Au electrode. In this work, the Au nanoparticles were used to increase the electrochemically active surface area by 28% (with a standard deviation of 3%) to enhance the quantity of the Protein G scaffold on the electrode. Thiolation of Protein G by DTBP aided in avoiding the confirmation change of Protein G, while this Protein G–DTBP component offered an orientation-controlled immobilisation of the capture antibody on the Au electrode. In this immunosensor, a monoclonal anti-cortisol capture antibody was optimally aligned by the scaffold before a competitive immunoassay between sample cortisol and a horseradish peroxidase-labelled cortisol conjugate was conducted. For quantitative analysis, square wave voltammetry was used to monitor the reduction current of benzoquinone produced from a horseradish peroxidase catalysed reaction. The improved analytical performance of our immunosensor was attributed to the synergetic effect of Au nanoparticles and the Protein G–DTBP scaffold.

Graphical abstract: Detection of cortisol at a gold nanoparticle|Protein G–DTBP-scaffold modified electrochemical immunosensor

Article information

Article type
Paper
Submitted
19 May 2011
Accepted
13 Sep 2011
First published
18 Oct 2011

Analyst, 2011,136, 5204-5210

Detection of cortisol at a gold nanoparticle|Protein G–DTBP-scaffold modified electrochemical immunosensor

X. Liu, R. Zhao, W. Mao, H. Feng, X. Liu and D. K. Y. Wong, Analyst, 2011, 136, 5204 DOI: 10.1039/C1AN15411G

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