Neuron whispers: a dual-functional nano-electrode for probing cotransmission/co-release

Edappalil Satheesan, Anupriya

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https://hdl.handle.net/2142/127506 Copy

Description

Title

Neuron whispers: a dual-functional nano-electrode for probing cotransmission/co-release

Author(s)

Edappalil Satheesan, Anupriya

Issue Date

2024-12-06

Director of Research (if dissertation) or Advisor (if thesis)

Shen, Mei

Doctoral Committee Chair(s)

Shen, Mei

Committee Member(s)

• Murphy, Catherine J
• Sweedler, Jonathan
• Rodrὶguez-Lὸpez, Joaquὶn

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Dual-functional
• ITIES
• Nano-electrode

Abstract

This thesis presents a novel dual-channel nano-carbon-liquid/liquid junction electrode (nano-carbon-ITIES) probe specifically designed to investigate the simultaneous release dynamics of dopamine (DA) and acetylcholine (ACh) from. Dopamine, a redox-active neurotransmitter, plays a crucial role in motor control, reward systems, and the pathophysiology of neurodegenerative diseases like Parkinson’s. In contrast, acetylcholine, a non-redox-active neurotransmitter, is vital for learning, memory, and cognitive function, with its dysregulation linked to Alzheimer’s disease and age-related cognitive decline. Despite their significant biological roles, the simultaneous detection of DA and ACh at nanoscale has proven challenging due to their distinct electrochemical properties, i.e., DA is redox-active whereas ACh is non-redox active. This research advances the field by providing a dual-functional nanoelectrode platform capable of studying the real-time concentration dynamics of both redox-active and non-redox-active analytes at nanometer spatial resolution and millisecond temporal resolution. The developed nano-carbon-ITIES probe features two key components: a disk-shaped carbon nanoelectrode channel, sensitive to redox-active molecules such as DA, and a nanoITIES electrode channel tailored for the detection of non-redox-active analytes like ACh. The fabrication process, detailed in Chapter 2, involves precise steps, beginning with the laser-pulling of dual-channel theta capillaries to create symmetrical nanometer-sized orifices. One channel was transformed into a carbon electrode through pyrolysis, followed by focused ion beam (FIB) milling to achieve a disk-shaped carbon surface. The second channel was subsequently developed into the nanoITIES channel. To establish a stable nanoITIES interphase, it is essential to render the electrode surface hydrophobic through silanization. We explored a novel liquid silanization method, discussed in Chapter 3, which selectively silanizes a single channel in a dual-channel pipette platform. While traditional vapor silanization methods have been widely used for nano/micrometer-sized electrodes, our approach allowed for effective liquid silanization at the nanoscale. We demonstrated the capability of this method by successfully achieving a stable cyclic voltammogram for tetrabutylammonium ion transfer across the water/dichloroethane interface, addressing challenges and strategies for liquid silanization at the nanoscale. Chapter 2 also discussed the characterization of the nano-carbon-ITIES electrode platform, which was conducted using electrochemical techniques, scanning electron microscopy, and transmission electron microscopy. Both dopamine and acetylcholine were successfully measured using the dual-channel system, with cyclic voltammetry revealing a linear increase in the diffusion-limited current for both analytes as their concentrations increased. Chronoamperometry further demonstrated the simultaneous detection of DA and ACh, marking the first-ever application of a dual-functional nano-carbon-ITIES electrode in multi-purpose analysis—an emerging area of research. This capability is crucial for advancing our understanding of diseases and disorders involving these neurotransmitters. The next phase of this project involves using the dual-functional nanoelectrode to study the simultaneous release dynamics from an appropriate neuronal model. The initial experimental results of the project is discussed in Chapter 4. We selected Aplysia californica pedal neurons based on existing literature suggesting the co-existence of ACh and DA in this model. While our lab has previously studied ACh release, this study focuses on detecting DA and conducting simultaneous detection experiments. We successfully fabricated disk-shaped carbon nanoelectrodes via pyrolysis of nanopipettes and FIB milling, ensuring a flat electrode surface essential for high-resolution electrochemical measurements. Cyclic voltammetry confirmed the efficacy of these electrodes in detecting redox-active compounds, particularly dopamine. Moreover, our studies on neuronal cell represent the first demonstration of using disk-shaped carbon nanoelectrodes to measure dopamine release from Aplysia californica pedal neurons, revealing dynamic neurotransmitter release in response to chemical stimulation. Amperometric peak analysis indicated that the observed signals corresponded to single-vesicle release events, corroborating findings from PC12 cell studies. Overall, the successful implementation of disk-shaped carbon nanoelectrodes for real-time detection of neurotransmitter release in living neuronal systems opens new avenues for exploring neurotransmission dynamics. This work not only advances the field of electrochemical sensing but also lays the groundwork for future studies investigating the intricacies of neuronal signaling across various biological models.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127506

Copyright and License Information

Copyright 2024 Anupriya Edappalil Satheesan

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