Efficient release of immunocaptured cells using coiled-coils in a microfluidic device.

Label-free and affinity-based cell separation allows highly specific cell capture through simple procedures, but it remains a major challenge to efficiently release the captured cells without changing their structure, phenotype, and function. We report a microfluidic platform for label-free immunocapture of target cells and efficient release of the cells with minimal biochemical and biophysical perturbations. The method capitalizes on self-assembly of a pair of heterodimerizing coiled-coils, A and B. Target cells are captured in microchannels functionalized with an antibody and A and efficiently released by a liquid flow containing B-PEG (a conjugate of B and polyethylene glycol) at a controlled, low shear stress. The released cells have no antibodies attached or endogenous surface molecules cleaved. In a model system, human umbilical vein endothelial cells (HUVECs) were isolated from a mixture of HUVECs and human ovarian carcinoma cells. The capture selectivity, capture capacity, and release efficiency were 96.3% ± 1.8%, 10 735 ± 1897 cells per cm, and 92.5% ± 3.8%, respectively, when the flow was operated at a shear stress of 1 dyn cm. The method can be readily adapted for isolation of any cells that are recognizable by a commercially available antibody, and B-PEG is a universal cell-releasing trigger.