In Situ Chemical Monitoring and Imaging of Contents within Microfluidic Devices Having a Porous Membrane Wall Using Liquid Microjunction Surface Sampling Probe Mass Spectrometry

• Published in: Journal of the American Society for Mass Spectrometry 2020-04, Vol.31 (4), p.832-839
• Main Authors: Cahill, John F, Khalid, Muneeba, Retterer, Scott T, Walton, Courtney L, Kertesz, Vilmos
• Format: Article
• Language: English
• Subjects: Computer simulations; Equipment Design; Extraction; Lab-On-A-Chip Devices; liquid microjunction; liquid vortex capture; Liquids; Mass Spectrometry - instrumentation; Mass Spectrometry - methods; mass spectrometry imaging; Membranes; Membranes, Artificial; Microfluidic Analytical Techniques; microfluidics; Molecular Imaging - instrumentation; Molecular Imaging - methods; OTHER INSTRUMENTATION; Porosity; Solvents
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1021/jasms.9b00093

The ability to observe dynamic chemical processes (e.g., signaling, transport, etc.) in vivo or in situ using nondestructive chemical imaging opens a new door to understanding the complex dynamics of developing biological systems. With the advent of “biology-on-a-chip” devices has come the ability to monitor dynamic chemical processes in a controlled environment, using these engineered habitats to capture key features of natural systems while allowing visual observation of system development. Having the capability to spatially and temporally map the chemical signals within these devices may yield new insights into the forces that drive biosystem development. Here, a porous membrane sealed microfluidic device was designed to allow normal microfluidic operation while enabling continuous, location specific sampling and chemical characterization by liquid microjunction surface sampling probe mass spectrometry (LMJ-SSP MS). LMJ-SSP was used to extract fluids with nL-to-μL/min flow rates directly from selected areas of the microfluidic device without negatively impacting the device function. These extracts were subsequently characterized using MS. This technique was used to acquire MS images of the entirety of several multi-input microfluidic devices having different degrees of fluid mixing. LMJ-SSP MS imaging visualized the spatial distribution of chemical components within the microfluidic channels and could visualize chemical reactions occurring in the device. These microfluidic devices with a porous membrane wall are wholly compatible with the construction of biology-on-a-chip devices. This ultimately would enable correlation of biosystem physical structure with an evolving chemical environment