A bistable, multiport valve enables microformulators creating microclinical analyzers that reveal aberrant glutamate metabolism in astrocytes derived from a tuberous sclerosis patient

• Published in: Sensors and actuators. B, Chemical Vol. 341; p. 129972
• Main Authors: Miller, Dusty R., Schaffer, David K., Neely, M. Diana, McClain, Ethan S., Travis, Adam R., Block, Frank E., McKenzie, Jennifer R., Werner, Erik M., Armstrong, Laura, Markov, Dmitry A., Bowman, Aaron B., Ess, Kevin C., Cliffel, David E., Wikswo, John P.
• Format: Journal Article
• Language: English
• Published: Switzerland Elsevier B.V 15.08.2021; Elsevier Science Ltd
• Subjects: Analyzers; Bioreactors; Chemical sensors; Electrochemistry; Flow velocity; Homeostasis; Human influences; Microclinical analyzer; Microfluidics; Mutation; Remote control; Soft lithography; Stem cells; Time-division multiplexing; Tuberous sclerosis complex (TSC); Tuberous sclerosis complex (TSC); Electrochemistry; Soft lithography; Time-division multiplexing; Microclinical analyzer; electrochemistry; microclinical analyzer; time-division multiplexing; soft lithography
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2021.129972

•Design, fabrication and validation of a new class of microfluidic pumps and valves.•Precise control of both flow rate and faithful selection of microscale solutions.•Automated, real-time inline electrochemical monitoring of cellular microphysiology.•Astrocyte differentiation from hiPSCs for both a control subject and a TSC patient.•First report of altered glutamate metabolism in human astrocytes. There is a need for valves and pumps that operate at the microscale with precision and accuracy, are versatile in their application, and are easily fabricated. To that end, we developed a new rotary planar multiport valve to faithfully select solutions (contamination = 5.22 ± 0.06 ppb) and a rotary planar peristaltic pump to precisely control fluid delivery (flow rate = 2.4 ± 1.7–890 ± 77 μL/min). Both the valve and pump were implemented in a planar format amenable to single-layer soft lithographic fabrication. These planar microfluidics were actuated by a rotary motor controlled remotely by custom software. Together, these two devices constitute an innovative microformulator that was used to prepare precise, high-fidelity mixtures of up to five solutions (deviation from prescribed mixture = ±|0.02 ± 0.02| %). This system weighed less than a kilogram, occupied around 500 cm3, and generated pressures of 255 ± 47 kPa. This microformulator was then combined with an electrochemical sensor creating a microclinical analyzer (μCA) for detecting glutamate in real time. Using the chamber of the μCA as an in-line bioreactor, we compared glutamate homeostasis in human astrocytes differentiated from human-induced pluripotent stem cells (hiPSCs) from a control subject (CC-3) and a Tuberous Sclerosis Complex (TSC) patient carrying a pathogenic TSC2 mutation. When challenged with glutamate, TSC astrocytes took up less glutamate than control cells. These data validate the analytical power of the μCA and the utility of the microformulator by leveraging it to assess disease-related alterations in cellular homeostasis.