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Chromatographic cell separation based on size and rigidity using dynamic microstructures Gerhardt, Thomas


The separation of cells by phenotype from heterogeneous mixtures, such as whole blood, is important in a wide range of fields in medicine and biology. Cell separation methods can be classified as either chemical or physical. Chemical separation methods are based on affinity capture and flow cytometry to label and select for specific target cell species. These techniques can be limited by the lack of specific chemistry that uniquely select for the target cell types, including the inability to extract viable cells for propagation in culture. When chemical separation methods cannot be applied, it is sometimes possible to discriminate cells based on their physical properties. As material systems, cells have an enormous range in size and rigidity and these differences can be exploited to achieve separation. Recent advances in microfabrication and microfluidic technologies have presented several innovative methods to approach mechanical cell separation. Our research leverages key characteristics of microfluidic technologies to approach cell separation in a manner similar to liquid chromatography. In chromatography, target species are separated from mixtures by imparting different velocities based on interactions with the column. We apply this process to separate cells based on differences in their size and rigidity using a microfluidic channel with dynamic geometry. This channel is formed between a static surface, containing a series of traps, and a flexible membrane. The device is fabricated using standard microfabrication methods, including photolithography and multi-layer soft lithography. As the cell mixture is flowed through the channel, the height of the channel is varied repeatedly causing periodic entrapment of the larger and more rigid cells, which impart a reduced average velocity to these cells compared to smaller and more deformable cells. Using this technique, we demonstrated chromatographic separation of L5178Y mouse lymphoma cells, representing larger and more rigid species, from human red blood cells, representing smaller and less rigid species. The ratio of the velocities of the target versus background cell types depends upon the duty cycle of the oscillation. We demonstrate the accumulation of mouse lymphoma cells in the microfluidic channel while maintaining cell viability. The system is simple, low-cost and label free.

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