In Vivo Chemical Monitoring at High Spatiotemporal Resolution Using Microfabricated Sampling Probes and Droplet-Based Microfluidics Coupled to Mass Spectrometry
| Autor: | Alec C. Valenta, Robert T. Kennedy, Thitaphat Ngernsutivorakul, Daniel J. Steyer |
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| Rok vydání: | 2018 |
| Předmět: |
Male
Spectrometry Mass Electrospray Ionization Microfluidics Mass spectrometry 01 natural sciences Article Analytical Chemistry Rats Sprague-Dawley 03 medical and health sciences 0302 clinical medicine Animals Image resolution Brain Chemistry Neurotransmitter Agents Chemistry business.industry 010401 analytical chemistry Sampling (statistics) Equipment Design Microfluidic Analytical Techniques 0104 chemical sciences Temporal resolution Microtechnology Optoelectronics Droplet-based microfluidics Spatiotemporal resolution business 030217 neurology & neurosurgery Microfabrication |
| Zdroj: | Analytical Chemistry. 90:10943-10950 |
| ISSN: | 1520-6882 0003-2700 |
| DOI: | 10.1021/acs.analchem.8b02468 |
| Popis: | An essential approach for in vivo chemical monitoring is to use sampling probes coupled with analytical methods; however, this method traditionally has limited spatial and temporal resolution. To address this problem, we have developed an analytical system that combines microfabricated push-pull sampling probes with droplet-based microfluidics. The microfabricated probe provides approximately 1000-fold better spatial resolution than common microdialysis probes. Microfabrication also facilitated integration of an extra channel into the probe for microinjection. We have created microfluidic devices and interfaces that allowed manipulating nanoliter droplet samples collected from the microfabricated probe at intervals of a few seconds. Use of droplet-based microfluidics prevented broadening of collected zones, yielding 6 s temporal resolution at 100 nL/min perfusion rates. Resulting droplets were analyzed by direct infusion nanoelectrospray ionization (nESI) mass spectrometry for simultaneous determination of glutamine, glutamate, γ-aminobutyric acid, and acetylcholine. Use of low infusion rates that enabled nESI (50 nL/min) was critical to allowing detection in the complex samples. Addition of (13)C-labeled internal standards to the droplet samples was used for improved quantification. Utility of the overall system was demonstrated by monitoring dynamic chemical changes evoked by microinjection of high potassium concentrations into the brain of live rats. The results showed stimulated neurochemical release with rise times of 15 s. This work demonstrates the potential of coupling microfabricated sampling probes to droplet-based mass spectrometric assays for studying chemical dynamics in a complex microenvironment at high spatiotemporal resolution. |
| Databáze: | OpenAIRE |
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