Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC Davis Electronic Theses and Dissertations (2023)

AbstractIn vitro cell culture models are quickly replacing animal models for drug development, mechanistic studies, and precision medicine. Visual methods are the primary means of studying organ-on-a-chip (OoC) models, but are limited to microscopy and immunofluorescent staining protocols. These techniques expose tissues to an adverse environment outside of an incubator or must be prepared with fluorescent proteins, which may affect the underlying cellular processes. In addition, these quantification approaches are often end-point assessments, limiting the number of measurements from a sample. Impedance-based methods allow for continuous monitoring of the electrical properties of tissues that provide insight into biochemical and cellular mechanisms. Transepithelial electrical resistance (TEER) is a useful metric for quantifying the integrity of an epithelial cell layer (e.g., gut epithelium), but lacks the spatial resolution of the microscopic techniques. This thesis reports on the design and experimental validation of a distributed hardware including a voltage-controlled current source (VCCS) for safe current injection, TEER measurement circuitry to sample the impedance across conductive phantoms, and real-time data conversion for monitoring changes in the system. Tomographic concepts will be adapted from electrical impedance tomography (EIT) systems to realize a distributed TEER device capable of continuous, non-invasive spatial imaging of tissues. Multiplexers will spatially expand the TEER measurement circuitry to detect minor changes in impedance by gathering a representative sample of data from the entire chip. The system is validated using conductive and insulating phantoms in saline tanks with varying size and orientation. Finally, EIT image reconstruction techniques are used for converting the raw data to images with high spatial resolution. This platform should be broadly applicable to real-time monitoring of developing in vitro tissue cultures and spatial detection of barrier disruptions, and can be scaled for studies requiring frequency sweeps or higher resolution images.

    Cover page: Development of a Planar Multiple Electrode Array for Spatially-Resolved Transepithelial Electrical Resistance Measurements
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2023)
    Neuroinflammation plays a central role in many neurological disorders, ranging from traumatic brain injuries to neurodegeneration. Electrophysiological activity is an essential measure of neuronal function, which is influenced by neuroinflammation. In order to study neuroinflammation and its electrophysiological fingerprints, there is a need for in vitro models that accurately capture the in vivo phenomena. In this study, we employed a new tri-culture of primary rat neurons, astrocytes, and microglia in combination with extracellular electrophysiological recording techniques using multiple electrode arrays (MEAs) to determine the effect of microglia on neural function and the response to neuroinflammatory stimuli. Specifically, we established the tri-culture and its corresponding neuron-astrocyte co-culture (lacking microglia) counterpart on custom MEAs and monitored their electrophysiological activity for 21 days to assess culture maturation and network formation. As a complementary assessment, we quantified synaptic puncta and averaged spike waveforms to determine the difference in excitatory to inhibitory neuron ratio (E/I ratio) of the neurons. The results demonstrate that the microglia in the tri-culture do not disrupt neural network formation and stability and may be a better representation of the in vivo rat cortex due to its more similar E/I ratio as compared to more traditional isolated neuron and neuron-astrocyte co-cultures. In addition, only the tri-culture displayed a significant decrease in both the number of active channels and spike frequency following pro-inflammatory lipopolysaccharide exposure, highlighting the critical role of microglia in capturing electrophysiological manifestations of a representative neuroinflammatory insult. We expect the demonstrated technology to assist in studying various brain disease mechanisms.
      Creative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Davis Previously Published Works (2022)
      Compartmentalized microfluidic neural cell culture platforms, which physically separate axons from the neural soma using a series of microchannels, have been used for studying a wide range of pathological conditions and basic neuroscience questions. While each study has different experimental needs, the fundamental design of these devices has largely remained unchanged and a systematic study to establish long-term neural cultures in this format is lacking. Here, we investigate the influence of microchannel geometry and cell seeding density on device performance particularly in the context of long-term studies of synaptically-connected, yet fluidically-isolated neural populations of neurons and glia. Of the different experimental parameters, the microchannel height was the principal determinant of device performance, where the other parameters offer additional degrees of freedom in customizing such devices for specific applications. We condense the effects of these parameters into design rules and demonstrate their utility in engineering a microfluidic neural culture platform with integrated microelectrode arrays. The engineered device successfully recorded from primary rat cortical cells for 59 days in vitro with more than on order of magnitude enhancement in signal-to-noise ratio in the microchannels.
        Cover page: Influence of microchannel geometry on device performance and electrophysiological recording fidelity during long-term studies of connected neural populations
        Top