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Posted: Oct 27, 2010
Microfluidics: A thousand captures at a time
(Nanowerk News) Patch clamping is a widely used laboratory technique to study ion channels in living cells. It is conventionally performed by pressing the open tip of a glass pipette against the membrane of a cell, applying gentle suction to establish a tight seal and then rupturing the cell membrane to measure the flow of ions across the entire cell. This approach works well for small-scale studies, but is very time-consuming for large-scale studies, such as in the evaluation of the effects of a massive library of drug candidates on thousands of cells.
Microfluidics technology makes it possible to miniaturize and automate various laboratory techniques, including patch clamping, which can be implemented by fabricating a microscopic aperture to capture the cell and penetrate the cell membrane. Levent Yobas and co-workers at the A*STAR Institute of Microelectronics previously developed a specialized method to form glass capillaries with well-rounded tips that form a tight seal with the cell of interest in a silicon-based microfluidic chip. The researchers have now combined this technology with a micromolding process for efficient fabrication ("Lateral patch-clamping in a standard 1536-well microplate format").
The microfluidic chip consists of a silicon microchip substrate and a PDMS (elastic polymer) capping layer inscribed with tiny wells that serve as reservoirs for drugs and other liquids. The researchers used a standard 1,536-well plate as a cast to shape the capping layer, and a silicon substrate containing 1,536 inlets with associated microfluidic networks and glass capillaries. The researchers aligned and bonded the capping layer and the microchip together, ensuring that the wells of the capping layer were aligned with the inlets of the silicon substrate.
For now, the microfluidic device stands as a proof of concept. A single unit (4 x 4 well array) has been tested with rat basophilic leukemia cells where 12 individual cells were captured by applying suction to the integrated glass capillaries. The remaining 4 wells were used to flow the cell culture and other solutions. In theory, the researchers can scale up the device to capture thousands of cells at a time. The technology will speed up the drug discovery process by providing scientists with a huge array for studying ion channels.
"The use of cheap materials, such as silicon and PDMS, to produce a high-throughput array could dramatically reduce the cost of drug discovery while providing ease of use," says Tushar Bansal, who is currently leading the project. Bansal is currently teaming with other researchers in the field to study multiple drug reactions on insulin cells using the new microfluidic array.