Neurochemical detection in small volumes by matrix-assisted laser desorption/ionization mass spectrometry

A diverse range of chemicals are used for cell-cell signaling in the brain as a highly dynamic and plastic way to encode and process information. Mass spectrometry (MS) is particularly well-suited to studying this heterogeneous environment owing to its highly sensitive, multiplexed, and untargeted nature. The growing field of single cell MS “-omics” measurements provides an exciting opportunity to develop high throughput methods that can capture the heterogeneity of tissues at the single cell level. By understanding this heterogeneity, we may learn more about cell functions and pinpoint chemical differences between models for behaviors and disease. Additionally, droplet microfluidic techniques have been integrated into microdialysis probes for collection and measurement of neurochemicals from the brain with improved spatiotemporal resolution. These droplet microdialysis probes can be coupled to many MS techniques. Matrix assisted laser desorption/ionization (MALDI)-MS is desirable for analysis of droplets as it is relatively non-destructive compared to other ionization techniques that consume the entire droplet, enabling multiple analyses of the same sample. However, the effects of oil-based continuous phases on small molecule detection by MALDI-MS was not well understood. Furthermore, reproducible printing of individual droplets in chronological order on MALDI compatible substrates is required to measure changes in neurotransmission. Development of techniques that meet these requirements can provide vital insight into the chemical dynamics of the brain. In this dissertation, we develop MALDI-MS methods to meet these requirements. First, droplet microfluidics were coupled to MALDI-MS for detection of small molecule neurotransmitters by optimizing the oil-based continuous phase and developing a microscale droplet printing system. These advances enabled attomole level detection of the neurotransmitter GABA in 40 pL droplets, the smallest volume yet used for this technique. Second, single cell MALDI-MS methods were developed to characterize the lipid and peptide contents of single cells to elucidate their relationship to cell function and behavioral phenotypes, respectively. Using machine learning classification and differential analysis, specific chemical species were shown to be correlated with one sample type. Together, the approaches developed here enable various neuroscience studies. We expect they will continue to be refined to uncover more about the complex chemistry of cell-cell signaling that influences behaviors and disease.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Bell, Sara E

Contributors dc:contributor

• Sweedler, Jonathan V.
• Vlasov, Yurii
• Kraft, Mary L.
• Shen, Mei

• Gaba
• Peptides
• Droplet Microfluidics
• Single Cell
• Three-spined Stickleback
• Mass Spectrometry
• Maldi
• Neurotransmitters

Statement dc:rights

• Copyright 2023 Sara Bell

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/121200

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F121200