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Detection of Thiols by o-Quinone Electrocatalytic Sensors

Zhu, Tianxia
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1340981269

Abstract Details

2012, Master of Science, University of Toledo, Chemistry.
In biological systems, thiols play very important roles as components of protein structures and as metabolic intermediates. Thiols are widely distributed in living cells as important antioxidants that can protect cells from any oxidative damage. Thiols are associated with some diseases such as cardiovascular disease, therefore it is necessary to develop new biosensors that can accurately detect and quantify thiols that are considered important biomarkers. In this thesis, new immobilization membranes, co-electrocatalysts and immobilization methods were evaluated using pyrroloquinoline quinone (PQQ) as the primary electrocatalyst. Previous studies have shown that the o-quinone moiety of PQQ exhibits a reversible 2-electron, 2-proton oxidation and reduction reaction. The electron transfer between its oxidized and reduced form is also known to catalyze reactions of the oxidation of thiols to disulfides. Thiols can be determined at lower overpotentials by amperometric detection during the oxidation of the reduced form of PQQH2 to PQQ. Nanoparticles, such as gold (Au NP) and copper (Cu NP), and especially single wall carbon nanotubes (SWNTs) exhibit novel electronic properties making them suitable for enhancing electrochemical sensitivity. Cysteine and homocysteine were detected at micromolar concentration by incorporation of coenzyme PQQ and a co-catalyst of SWNTs-COOH into a Au- PPy nanocomposite conducting polymer film. Cysteine and homocysteine are quantitatively detected by monitoring the amperometric current resulting from oxidation of PQQH2 back to PQQ at a glassy carbon electrode surface. Substituents attached to the quinone moiety are very important in the determing the catalytic activity of an electrocatalyst. They can affect reduction of the quinone and oxidation of the hydroquinone. Therefore changing the substituents and tuning the structure of PQQ can change the redox potential and electrocatalytic power of the resulting compound. Modification of the detection overpotential can also be adjusted through changing the molecule, therefore increasing the sensitivity for oxidizable biological compounds such as thiols. A benzimidazole analogue of PQQ was also synthesized and the electrochemical properties of this compound were evaluated. Similar reversible cyclic voltammetric behavior was observed as in PQQ, which is due to the two-electron redox reaction of the o-quinone moiety. However, the benzimidazole analogue exhibited limited electrocatalytic capabilities.
Jon Kirchhhoff, PhD (Committee Chair)
Liyanaaratchige Tillekeratne, PhD (Other)
Jared Anderson, PhD (Other)
Dragan Isailovic, PhD (Other)
104 p.
Chemistry
Thiols; Sensors; Electrocatalyst

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Citations

  • Zhu, T. (2012). Detection of Thiols by o-Quinone Electrocatalytic Sensors [Master's thesis, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1340981269

    APA Style (7th edition)

  • Zhu, Tianxia. Detection of Thiols by o-Quinone Electrocatalytic Sensors. 2012. University of Toledo, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1340981269.

    MLA Style (8th edition)

  • Zhu, Tianxia. "Detection of Thiols by o-Quinone Electrocatalytic Sensors." Master's thesis, University of Toledo, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1340981269

    Chicago Manual of Style (17th edition)

toledo1340981269
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© 2012, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.