Abstract
Microfluidic systems are very useful for in vitro studies of interactions between blood cells and vascular endothelial cells under flow, and several commercial solutions exist. However, the availability of customizable, user-designed devices is largely restricted to researchers with expertise in photolithography and access to clean room facilities. Here we describe a strategy for producing tailor-made modular microfluidic systems, cast in PDMS from 3D-printed molds, to facilitate studies of leukocyte adherence to endothelial cells. A dual-chamber barrier module was optimized for culturing two endothelial cell populations, separated by a 250 μm wide dividing wall, on a glass slide. In proof-of-principle experiments one endothelial population was activated by TNFα, while the other served as an internal control. The barrier module was thereafter replaced with a microfluidic flow module, enclosing both endothelial populations in a common channel. A suspension of fluorescently-labeled leukocytes was then perfused through the flow module and leukocyte interactions with control and TNFα-treated endothelial populations were monitored in the same field of view. Time-lapse microscopy analysis confirmed the preferential attachment of leukocytes to the TNFα-activated endothelial cells. We conclude that the functionality of these modular microfluidic systems makes it possible to seed and differentially activate adherent cell types, and conduct controlled side-by-side analysis of their capacity to interact with cells in suspension under flow. Furthermore, we outline a number of practical considerations and solutions associated with connecting and switching between the microfluidic modules, and the advantages of simultaneously and symmetrically analyzing control and experimental conditions in such a microfluidic system.
Highlights
Microfluidic systems for studies of cell behavior are increasingly utilized in biomedical research[1,2], and such systems are well suited for generating in vitro models of blood vessels, and for studying interactions of blood cells under flow with the endothelial cells that line such vessels[3,4,5]
Another important advantage of 3D printing is that it often allows for greater geometrical complexity, such that molds for PDMS casting with combinations of structures of different heights can be generated in a single 3D print
A barrier module is reversibly attached to a glass microscope slide; two adjacent endothelial cultures are seeded, and in a proof-of-principle experiment one is exposed to the inflammatory cytokine tumor necrosis factor α (TNFα), while the other untreated culture serves as an internal control
Summary
Microfluidic systems for studies of cell behavior are increasingly utilized in biomedical research[1,2], and such systems are well suited for generating in vitro models of blood vessels, and for studying interactions of blood cells under flow with the endothelial cells that line such vessels[3,4,5]. The process whereby novel assays are developed is iterative, and one of the many advantages of 3D printing is that www.nature.com/scientificreports/ Handle it radically speeds up the process of going from idea to a first prototype. Another important advantage of 3D printing is that it often allows for greater geometrical complexity, such that molds for PDMS casting with combinations of structures of different heights can be generated in a single 3D print. We present a strategy based on a set of 3D-printed tools and molds for PDMS casting that allow researchers to build a modular system for imaging of the adherence of the Jurkat cell line (a commonly used leukocyte model for T cell leukemia) from a single population to differentially treated endothelial cell cultures. The increasing availability of 3D-printing services permits researchers without design or manufacturing expertise to acquire molds and produce their own devices at low cost; researchers with experience in this field can customize the modules for adaption to their specific applications
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