Ph.D. Research Proposal Exam: Jinjing Han

Wednesday, March 3, 2021
3:00 p.m.
Zoom at
Maria Hoo
301 405 3681

ANNOUNCEMENT: Ph.D. Research Proposal Exam

Name: Jinjing Han



Professor Reza Ghodssi (Chair)

Professor Pamela Abshire

Professor Timothy Horiuchi

Date/time: Wednesday, March 3, 2021 at 3-4:30pm


Location: Zoom at


Title: Minimally Invasive Neurochemical Sensing System for ex vivo and in vivo Investigation of Serotonergic Modulation



Serotonin (5-HT, 5-hydroxytryptamine) is a neurotransmitter and hormone that contributes to the regulation of brain functions as well as various physiological processes including mood control, reward processes, and sleep-wake homeostasis. Current gold standard 5-HT measurement techniques, used to study its functions, mostly utilize off-line methods such as high-performance liquid chromatography (HPLC) and enzyme-linked immunosorbent assay (ELISA). However, these techniques lack the ability to measure 5‑HT concentration in vivo with high precision and high spatiotemporal resolution, which hampers the understanding of behavior regulation through 5-HT signaling. To enable quantitative, real-time detection of 5-HT concentration dynamics in vivo, a miniaturized electrochemical sensing system to assess 5-HT signaling in an unconstrained animal model is proposed. This system will facilitate neuroscience research into 5-HT modulation of the gut-brain axis (GBA) and related animal behavior. The proposed work will focus on the design and integration of a customized sensor electrode and potentiostat electronics that will be characterized in three settings: (1) an in vitro benchtop model, (2) an ex vivo crayfish nerve cord and hindgut, and (3) an in vivo freely moving crayfish. In Aim 1, a microelectrode 5-HT sensor will be fabricated using carbon fiber due to its high sensitivity, low electrical resistivity, and small size for non-invasive detection. The electrode will be coated with Nafion and carbon nanotubes (CNTs) to enhance the sensing performance. Electrode sensitivity, specificity, limit of detection (LOD), and fouling will be characterized in vitro using benchtop equipment via various electrochemical sensing techniques. The characterization results will guide the design of electronics in Aim 2, consisting of a miniaturized potentiostat circuit and a wireless communication module using commercial off-the-shelf (COTS) components. The electronics will be characterized in a benchtop setting and then utilized for 5‑HT release and uptake dynamics monitoring in an ex vivo dissected crayfish nerve cord and hindgut to study the GBA in crayfish. Aim 3 will focus on the systems integration and packaging of a carbon fiber microelectrode (CFM) with customized sensing electronics. The miniaturized system will allow the animal to move freely while monitoring 5-HT concentrations in the central nervous system (CNS) in vivo, enabling the correlation of 5‑HT concentrations with animal behavior. Together, the proposed work demonstrates a minimally invasive in vivo neurotransmitter detection approach that facilitates the study of serotonergic modulation in neuroscience research.


Audience: Faculty 

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