Cell patterning by surface tension pinning in microfluidic channels

Abstract

We present a simple method to pattern multiple cell populations inside a microfluidic channel. The microchannel is partially filled with a cell suspension, and the position of the liquid boundary remains pinned by surface tension. Cells then adhere only in the filled portion of the channel, producing a very sharp boundary. The process can be performed in an unmodified microfluidic channel with only a manual syringe and can be repeated multiple times to pattern cocultures or tricultures. We demonstrate the patterning method with two different mammalian cell types, 3T3 fibroblasts and NMuMG epithelial cells, and channel heights of 1.5 mm and 0.5 mm. We anticipate that this method will be useful for studies of cell–cell interactions where precise control of the fluidic microenvironment is required.

Microfluidic harvesting of breast cancer tumor spheroid-derived extracellular vesicles from immobilized microgels for single-vesicle analysis

“…78 While cancer cells have been immobilized onto surfaces by various chemical approaches, [79][80][81] the marriage of both microfluidic confinement and precise spatial control of cells without ongoing physical forces has presented difficulties. 82,83 We previously reported a method to immobilize cancer cells in distinct surface positions within a microchannel; 84 however, two-dimensional culture lacks the modeling capacity of tumor spheroids, which better simulate the heterogeneity, intercellular communication and physical interactions, proliferation and metabolism profiles, gene expression, and drug resistance observed in vivo. 21,22 Since EV biomolecular signatures reflect the profiles of their parental cells and affect various aspects of the aforementioned cellular mechanisms that are not well modeled in two-dimensional culture, 85 the large-scale immobilization of encapsulated tumor spheroids within a microfluidic system is imperative to advance EV biomarker discovery while providing a convenient platform to extract the physiologically relevant EVs.…”

Recapitulating Tumor Hypoxia in a Cleanroom-Free, Liquid-Pinning-Based Microfluidic Tumor Model

“…The tumor section was surrounded by two microfluidic channels (1 mm width × 800 μm height) for the delivery of oxygen, nutrients, and therapeutic drugs and/or immune cells (Figure D,G). Cancer cells were loaded through cell injection ports to create 2-D and 3-D tumor sections by a liquid-pinning process, where a drop of cells with a desired number (in medium, for 2-D) or density (in ECM gel before curing) was injected and held underneath the central pillar by the surface tension at the liquid–air interface − (Figure E,F). The device geometry and liquid pinning created a micropattern of cancer cell layer/bulk with the desired shape, area, and/or volume as a tumor model.…”

“…Liquid pinning − was chosen to create a cancer cell monolayer or 3-D tumor section in our tumor model, for its ease of operation without requiring additional structural components (such as pillars) that may interfere with oxygen diffusion. It utilized surface tension at the liquid–substrate–air interface to hold the liquid within the small crevices of the device (i.e., the diffusion gap in the current design) (Figure D).…”