title: BaroFuse, a novel pressure-driven, adjustable-throughput perfusion system for tissue maintenance and assessment.
abstract: OBJECTIVE
  Microfluidic perfusion systems are used for assessing cell and tissue function while assuring cellular viability. Low perfusate flow rates, desired both for conserving reagents and for extending the number of channels and duration of experiments, conventionally depend on peristaltic pumps to maintain flow yet such pumps are unwieldy and scale poorly for high-throughput applications requiring 16 or more channels. The goal of the study was to develop a scalable multichannel microfluidics system capable of maintaining and assessing kinetic responses of small amounts of tissue to drugs or changes in test conditions.
  
  
  METHODS
  Here we describe the BaroFuse, a novel, multichannel microfluidics device fabricated using 3D-printing technology that uses gas pressure to drive large numbers of parallel perfusion experiments. The system is versatile with respect to endpoints due to the translucence of the walls of the perifusion chambers, enabling optical methods for interrogating the tissue status. The system was validated by the incorporation of an oxygen detection system that enabled continuous measurement of oxygen consumption rate (OCR).
  
  
  RESULTS
  Stable and low flow rates (1-20 μL/min/channel) were finely controlled by a single pressure regulator (0.5-2 psi). Control of flow in 0.2 μL/min increments was achieved. Low flow rates allowed for changes in OCR in response to glucose to be well resolved with very small numbers of islets (1-10 islets/channel). Effects of acetaminophen on OCR by precision-cut liver slices of were dose dependent and similar to previously published values that used more tissue and peristaltic-pump driven flow.
  
  
  CONCLUSIONS
  The very low flow rates and simplicity of design and operation of the BaroFuse device allow for the efficient generation of large number of kinetic profiles in OCR and other endpoints lasting from hours to days. The use of flow enhances the ability to make measurements on primary tissue where some elements of native three-dimensional structure are preserved. We offer the BaroFuse as a powerful tool for physiological studies and for pharmaceutical assessment of drug effects as well as personalized medicine.
authors.affiliation: UW Diabetes Institute, Department of Medicine, University of Washington, Seattle, WA, 98195, USA.
authors.forename: Austin
authors.initials: A
authors.lastname: Rountree
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Karkamkar
authors.affiliation: EnTox Sciences, LLC, 6901 94th Ave SE, Mercer Island, WA, 98040, USA.
authors.forename: Gamal
authors.initials: G
authors.lastname: Khalil
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
authors.forename: Albert
authors.initials: A
authors.lastname: Folch
authors.affiliation: EnTox Sciences, LLC, 6901 94th Ave SE, Mercer Island, WA, 98040, USA; Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Cook
authors.affiliation: UW Diabetes Institute, Department of Medicine, University of Washington, Seattle, WA, 98195, USA; EnTox Sciences, LLC, 6901 94th Ave SE, Mercer Island, WA, 98040, USA.
authors.forename: Ian R
authors.initials: IR
authors.lastname: Sweet
keywords: Bioengineering; Pharmaceutical Chemistry