Overflow Microfluidic Networks for Open and Closed Cell Cultures on Chip

Abstract

Microfluidics have a huge potential in biomedical research, in particular for studying interactions among cell populations that are involved in complex diseases. Here, we present "overflow" microfluidic networks (oMFNs) for depositing, culturing, and studying cell populations, which are plated in a few microliters of cell suspensions in one or several open cell chambers inside the chip and subsequently cultured for several days in vitro (DIV). After the cells have developed their phenotype, the oMFN is closed with a lid bearing microfluidic connections. The salient features of the chips are (1) overflow zones around the cell chambers for drawing excess liquid by capillarity from the chamber during sealing the oMFN with the lid, (2) flow paths from peripheral pumps to cell chambers and between cell chambers for interactive flow control, (3) transparent cell chambers coated with cell adhesion molecules, and (4) the possibility to remove the lid for staining and visualizing the cells after, for example, fixation. Here, we use a two-chamber oMFN to show the activation of purinergic receptors in microglia grown in one chamber, upon release of adenosine triphosphate (ATP) from astrocytes that are grown in another chamber and challenged with glutamate. These data validate oMFNs as being particularly relevant for studying primary cells and dissecting the specific intercellular pathways involved in neurodegenerative and neuroinflammatory brain diseases.Microfluidics are emerging as invaluable tools for research on cells for a number of reasons. 1-3 First, they enable experiments on cells to be performed with well-defined chemical and topographical environments. 4-9 Second, they can reduce the number of cells needed for experiments. 1 Third, they can be used for experiments in which a precise number of cells can be stimulated and observed accurately. 10-12 Last, they permit experiments to be performed in parallel and/or with high throughput. 13 Despite these possibilities, microfluidics are not well established for daily research work on cells, as they lack user friendliness and require specific and often cumbersome methods for depositing and culturing cells. This is further complicated when taking into consideration more relevant cell systems such as primary cells, 14,15 which may require longer culturing times before being ready for specific assays (i.e., primary neurons need to be cultured several days in vitro (DIV) before establishing mature synaptic contacts). Although progress on sealing a Petri dish with a hybrid microfluidic-vacuum platform was recently demonstrated by Chung et al., 9 interfacing "open" cell cultures with microfluidics for cell cultures that are only a few microliters in volume remains a great challenge. Similarly, depositing cells on a treated glass slide and gluing a lid having ports onto the slide provides a method for enclosing living cells inside a microfluidic flow path. 16 Such a method would be hard to implement with multiple types of cells and can be simplified if the gluing step coul...

Organs-on-a-Chip: A Focus on Compartmentalized Microdevices

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An open-chamber flow-focusing device for focal stimulation of micropatterned cells

“…Many designs seek to create a userfriendly experience for the researcher and a more benign microenvironment for the cells. 22,[32][33][34] In open-chamber designs, in which cells are bathed in the bulk media bath like in a petri dish, results can be directly compared with conventional cell cultures. Open-chamber microfluidic devices circumvent the media-replenishing problem of closed devices by operating within an open reservoir, allowing for easy media exchange.…”

Microfluidic platform for the study of intercellular communication via soluble factor-cell and cell-cell paracrine signaling

“…Microfluidic platforms that allow for precise control over cell seeding, cell culture, and the chemical microenvironment of cells have been developed to study intercellular communication. [13][14][15][16][17][18] Many of these studies are restricted to two-dimensional (2D) cell cultures, whereas 3D cell cultures are known to be more physiologically relevant. [19][20][21][22] Microfluidic platforms have also been developed to pattern cells in 3D constructs using laminar flow.…”