"Novel, Ultra-Fast Electrochemical Sensors for the Enhanced Detection o" by Noel Manring

Date of Award

12-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Chemical Engineering

First Advisor

Pavithra Pathirathna, Ph.D.

Second Advisor

Andrew Palmer, Ph.D.

Third Advisor

Roberto Peverati, Ph.D.

Fourth Advisor

Nasri Nesnas, Ph.D.

Abstract

Neurodegenerative diseases (NDDs) are a growing global health concern, affecting millions of people worldwide. NDDs arise from the progressive loss of neuronal cell function, ultimately leading to cell death. Abnormal levels of neurotransmitters, the chemical messengers in the brain, have also been linked to NDDs. Despite various treatments and medications aimed at alleviating physical and mental symptoms, there is currently no cure or means to halt disease progression. While the exact pathogenesis of NDDs remain poorly understood, cognitive decline is largely attributed to brain volume reduction, particularly in the hippocampus. Clinical studies suggest that environmental factors, such as exposure to toxic heavy metals, can initiate neuronal cell death and contribute to this reduction. Despite extensive research into the role of toxic heavy metals in NDDs, the lack of effective in vivo analysis methods eliminates the ability to conduct real-time monitoring, leading to uncertain results. Traditionally, heavy metal ions have been analyzed in vitro using blood, urine, and cerebral spinal fluid samples, an approach that can alter metal speciation. Additionally, current methods for the detection of neurotransmitters, that have shown to play a pivotal role in NDDs, are often limited to analyzing one neurotransmitter at a time, hindering a comprehensive understanding of neuronal communication. Therefore, gaining insights into the interactions between neurotoxic heavy metals and neurotransmitters, while also acquiring accurate metal speciation information, is crucial for uncovering the causes of NDDs and developing effective therapies to halt disease progression. This dissertation presents a series of studies on the development of sensors for the enhanced detection of heavy metals, as well as the simultaneous detection of toxic heavy metals and neurotransmitters in aqueous solutions utilizing fast-scan cyclic voltammetry (FSCV). The first project involves the electrodeposition of polydopamine (PDA) onto carbon fiber microelectrodes (CFMs) for the enhanced detection of Cu2+. The limit of detection (LOD) and sensitivity of this cheap and biocompatible surface modification are fifty and two times greater, respectively, compared to a bare CFM. The second project introduces a simple fabrication protocol of a double-bore CFM capable of performing rapid simultaneous detection of neurotransmitters and Cu2+. Detailed analysis of the performance of this sensor using Cu2+, dopamine (DA), ascorbic acid (AA), and serotonin (5-HT) exhibited enhanced LOD, linear range, and sensitivity when detecting simultaneously with double-bore CFMs compared to single-bore CFMs for every analyte mixture, except Cu2+ and DA. The third project involves the use of gold nanoparticle-modified CFMs for the electrochemical detection of Cd2+. This sensor displays excellent sensitivity and selectivity for Cd2+ in both tris buffer and artificial urine. The fourth project reports the optimization of electrochemical parameters for the detection of As3+ in both acidic and basic tris solutions. This sensor demonstrated high selectivity, distinguishing As3+ from As5+, with high sensitivity using bare CFMs in a physiologically relevant pH environment. The fifth and final project details the fabrication of four-bore CFMs for the ultra-fast detection of neurotransmitters and heavy metals in tris buffer. This sensor exhibited excellent stability while cycling four different analyte-specific waveforms enabling rapid simultaneous detection of four separate analytes.

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