A Bistable, Multiport Valve Enables Microformulators Creating Microclinical Analyzers That Reveal Aberrant Glutamate Metabolism In Astrocytes Derived From A Tuberous Sclerosis Patient

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 mu L/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 (mu CA) for detecting glutamate in real time. Using the chamber of the mu CA as an in-line bioreactor, we compared glutamate homeostasis in human astrocytes differentiated from humaninduced 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 mu CA and the utility of the microformulator by leveraging it to assess disease-related alterations in cellular homeostasis.