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 cross-over of analyte 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 106 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 (r2 = 0.995, 7.6 µM - 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.

Instrumented Microphysiological Systems for Real-Time Measurement and Manipulation of Cellular Electrochemical Processes

“…In this work, a 4 × 4 array of intersecting microchannels forming 16 independent testing areas between the electrodes of two MEAs is used to measure TEER. Leveraging this increased capacity, this platform was used to evaluate a broad experimental range of the extracellular matrix compositions and flow rates or shear stress.

Figure 6Examples of Instrumented Organ-on-chip Models of the Vasculature System(A) Permeability study of a mouse-brain-derived endothelial cell (bEnd.3) monolayer cultured on the membrane of a bilayer chip via TEER electrodes.(B) Barrier integrity assessment of bEnd3 cell monolayer cocultured with a murine astrocytic cell line (C8D1A) in a multilayer chip under flow via TEER.(C) Human brain endothelial cell line (hCMEC/D3) tight junction integrity investigated within a bilayer chip with vasculature-like flow via TEER electrodes.(D) BBB integrity assessed within a perfusable trilayer chip, containing brain endothelial cells, astrocytes, and pericytes, in response to physiological stresses via TEER electrodes.(E and F) (E) BBB permeability quantified in using a 2D and (F) 3D side-by-side orientated vascular channel and the brain compartment microfluidic device via TEER electrodes.(G) Electrochemical assessment of red blood cell nitric oxide production via an integrated amperometric detector.Reprinted and adapted with permission from: A (Douville et al., 2010); B (Booth and Kim, 2012); C (Walter et al., 2016); D (Brown et al., 2015); E (Deosarkar et al., 2015); F (Xu et al., 2016); and G (Selimovic et al., 2014). TEER, transepithelial electrical resistance; BBB, blood brain barrier; IDEs, interdigitated electrodes.

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“…Reprinted and adapted with permission from: A (Douville et al., 2010); B (Booth and Kim, 2012); C (Walter et al., 2016); D (Brown et al., 2015); E (Deosarkar et al., 2015); F (Xu et al., 2016); and G (Selimovic et al., 2014). TEER, transepithelial electrical resistance; BBB, blood brain barrier; IDEs, interdigitated electrodes.…”

Microfluidic Device Using a Gold Pillar Array and Integrated Electrodes for On‐chip Endothelial Cell Immobilization, Direct RBC Contact, and Amperometric Detection of Nitric Oxide

“…Pores between two parallel flow channels were created using a 3‐dimensional gold pillar array embedded within the polystyrene base. The pillars gated RBCs in one channel and allowed NO (produced by making the cells hypoxic) to pass through the pores into the adjacent flow channel for subsequent electrochemical detection at the cell‐free electrode . However, this initial design only explored the use of non‐adherent cells (RBCs) and did not involve any cell‐to‐cell communication work.…”

“…The detection electrode was also modified with Nafion, a cation exchange polymer that repels negatively charged interferents such as nitrite, which is oxidized at potentials similar to NO . The use of Nafion to diminish nitrite signals has been previously published . Using the glassy carbon detection electrode modified with platinum‐black and 0.05 % Nafion, a limit of detection of 475 nM NO was observed.…”

Microfluidic Organ/Body-on-a-Chip Devices at the Convergence of Biology and Microengineering

“…Although being still in their very early developmental stage, some microfluidic platforms appear as innovative systems for significant endocrine studies. Concerning the adrenal glands, microfluidics is being applied to detect and study corticosteroids [ 167 , 168 , 170 ] and catecholamines [ 165 , 166 , 171 ]. In the fertility context, Huang and collaborators used microfluidics to isolate, analyze and quantify spermatozoids [ 163 ].…”