Development of Electrochemical Sensors Based on Polymer Nanocomposites for Sensing of Neurotransmitter Dopamine
AuthorZamani Keteklahijani, Yalda
Committee MemberRoberts, Edward P.L.
Electrochemical (Chemical) Polymerization
Differential Pulse Voltammetry
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AbstractParkinson’s disease is a long-term, degenerative, neurological disorder of central nervous system affecting our body motor and non-motor systems to a variable degree. Due to lack of any specific test for diagnosis of Parkinson’s, it is diagnosed through reviewing patients’ medical history, and conducting some physical and neurological examinations. Dopamine is a significant neurotransmitter facilitating the transmission of messages within the central nervous system of human beings. It was discovered that abnormal concentrations of dopamine in the striatum of brain could be linked to some neurological disorders such as Parkinson’s disease. Thus, the ability to detect dopamine with high sensitivity and selectivity could be of critical significance for molecular diagnosis of such neurological disorders. Most of the available electrochemical methods for in vivo and in vitro detection of dopamine exploit its ease of oxidation. However, there are a number of issues associated with electrochemical methods due to the nature of the oxidative electrode reaction of dopamine. One of the most common problems is that the concentration of dopamine in the extracellular fluids of the caudate nucleus is extremely low (0.01-1µM) for a healthy individual and in the nanomolar range for patients with Parkinson’s disease; while the concentration of the main severe interferents, e.g. ascorbic acid, is several orders of magnitude greater. Moreover, ascorbic acid undergoes oxidation within the same potential window as dopamine. As a result, an overlapping response signal from the oxidation of a mixture of dopamine and ascorbic acid is obtained. Numerous surface modifications have been taken up to modify the electrode surface to solve the aforementioned issues. One approach that alleviates the above-mentioned problems is an electrochemical detection approach that does not rely on oxidation or reduction of dopamine itself. These typically-called non-oxidative approaches have not been frequently studied and it was found that the detection limits of most of these techniques were in the micromolar range, and therefore, are not sufficiently sensitive for molecular diagnosis of Parkinson’s disease. In this thesis we developed a novel, and high-performance non-oxidative electrochemical technique in which the problems associated with direct oxidation of dopamine could be naturally eliminated. To accomplish this, a nanocomposite of poly(anilineboronic acid) was fabricated through in situ electrochemical polymerization of 3-aminophenylboronic acid monomers on the surface of a glassy carbon electrode modified with nanohybrid structures of DNA-functionalized carbon nanotubes and nitrogen-doped graphene (DNA_CNT_NEG) and without them using cyclic voltammetry technique. The assembled nanocomposite electrodes were used for electrochemical detection of dopamine in physiologically-relevant solutions using differential pulse voltammetry. The nanocomposite electrodes containing nanohybrid structures of DNA-functionalized carbon nanostructures (DNA_CNT_NEG) could detect nanomolar concentrations of dopamine with a very low limit of detection (6nM), remarkable stability and repeatability, along with a very wide linear range (0.007-1µM). The high affinity binding of dopamine to the boronic acid groups of the poly(anilineboronic acid) nanocomposites eliminated the interference of other biomolecules such as ascorbic acid and enhanced the selectivity of this non-oxidative sensor towards dopamine biomolecules. The dopamine sensor developed in this work demonstrates excellent potential toward molecular diagnosis of neurological disorders such as Parkinson’s disease.
CitationZamani Keteklahijani, Y. (2020). Development of Electrochemical Sensors Based on Polymer Nanocomposites for Sensing of Neurotransmitter Dopamine (Unpublished doctoral thesis). University of Calgary, Calgary, AB.
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