Source and sink

Three primary human neutrophils within a microfluidic channel responding to a gradient of Interleukin-8 (labeled with a green fluorophore) by chemotaxing to a higher concentration (left). Panels are frames from a movie, taken 10 minutes apart. Credit: Courtesy of Mary Lokuta / University of Wisconsin, Madison" />Three primary human neutrophils within a microfluidic channel responding to a gradient of Interleukin-8 (labeled with a green fluorophore) by chemotaxing to a higher concentration (left)

Josh P. Roberts
Jan 1, 2008
<figcaption>Three primary human neutrophils within a microfluidic channel responding to a gradient of Interleukin-8 (labeled with a green fluorophore) by chemotaxing to a higher concentration (left). Panels are frames from a movie, taken 10 minutes apart. Credit: Courtesy of Mary Lokuta / University of Wisconsin, Madison</figcaption>
Three primary human neutrophils within a microfluidic channel responding to a gradient of Interleukin-8 (labeled with a green fluorophore) by chemotaxing to a higher concentration (left). Panels are frames from a movie, taken 10 minutes apart. Credit: Courtesy of Mary Lokuta / University of Wisconsin, Madison

User:
Anna Huttenlocher, University of Wisconsin, Madison

Project:
Studying the migration of leukocytes along chemotactic gradients.

Problem:
Gradients are best controlled with fluid flow, but fluid flow disperses secreted factors that may be important in cell-cell interactions.

Solution:
Huttenlocher collaborated with an engineer at her university, David Beebe, to create what he calls "the world's simplest microfluidic device." It's less than a centimeter long, composed only of three layers of polydimethylsiloxane (PDMS) plastic and polyester membranes. Near one end is a well covered by a membrane (the sink); near the other, atop another membrane, is a large opening leading to another well (the source)....

Loading cells into the device without disturbing the gradient was tricky, Huttenlocher says, until she tried first introducing a collagen gel into the channel and letting it solidify to give the cells a 3-D matrix to move through.

The duo serialized a subsequent iteration, lining up several channels in parallel on a glass slide to run multiple conditions simultaneously. "You can actually zoom through with a microscope, going from one channel to the next in an automated way," Huttenlocher says. They also further improved ease of cell loading, and are now commercializing a version of the system through BellBrook Labs.

Cost:
The group's prototype can be made for under $10; the cost of the commercialized device isn't yet set.

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