title: Microfluidic device with tunable post arrays and integrated electrodes for studying cellular release.
abstract: In this paper, we describe the development of a planar, pillar array device that can be used to image either side of a tunable membrane, as well as sample and detect small molecules in a cell-free region of the microchip. The pores are created by sealing two parallel PDMS microchannels (a cell channel and a collector channel) over a gold pillar array (5 or 10 μm in height), with the device being characterized and optimized for small molecule cross-over while excluding a flowing cell line (here, red blood cells, RBCs). The device was characterized in terms of the flow rate dependence of analyte cross-over and cell exclusion as well as the ability to perform amperometric detection of catechol and nitric oxide (NO) as they cross-over into the collector channel. Using catechol as the test analyte, the limits of detection (LOD) of the cross-over for the 10 μm and 5 μm pillar array heights were shown to be 50 nM and 105 nM, respectively. Detection of NO was made possible with a glassy carbon detection electrode (housed in the collector channel) modified with Pt-black and Nafion, to enhance sensitivity and selectivity, respectively. Reproducible cross-over of NO as a function of concentration resulted in a linear correlation (r(2) = 0.995, 7.6-190 μM), with an LOD for NO of 230 nM on the glassy carbon/Pt-black/0.05% Nafion electrode. The applicability of the device was demonstrated by measuring the NO released from hypoxic RBCs, with the device allowing the released NO to cross-over into a cell free channel where it was detected in close to real-time. This type of device is an attractive alternative to the use of 3-dimensional devices with polycarbonate membranes, as either side of the membrane can be imaged and facile integration of electrochemical detection is possible.
authors.affiliation: Department of Chemistry, Saint Louis University, 3501 Laclede Ave, St. Louis, MO 63103, USA. martinrs@slu.edu.
authors.forename: Asmira
authors.initials: A
authors.lastname: Selimovic
authors.forename: Jayda L
authors.initials: JL
authors.lastname: Erkal
authors.forename: Dana M
authors.initials: DM
authors.lastname: Spence
authors.forename: R Scott
authors.initials: RS
authors.lastname: Martin
mesh_terms: D002396:Catechols / Q000032:analysis; D004566:Electrodes; D004912:Erythrocytes / Q000737:chemistry; D017022:Flow Injection Analysis; D006801:Humans; D057230:Limit of Detection; D044085:Microfluidics / Q000295:instrumentation*; D009569:Nitric Oxide / Q000032:analysis
chemical_list: D002396:Catechols; D009569:Nitric Oxide; C034221:catechol
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