Microfabricated Devices for Sorting Cells Using Complex Phenotypes

This research involves the development of sorting cytometer architectures for genetic screening of complex phenotypes in biological cells. Approaches combine the ability to observe and isolate individual mutant cells within surveyed populations. In this work we merge the benefits of microscopy and flow-assisted cell sorting (FACS) to offer unique capabilities in a single platform. Biologists will leverage this flexibility to isolate cells based upon imaged dynamic or intracellular responses

The most recent electrical approach to image-based sorting combines microfabricated weir structures and their efficient single-cell capture mechanics with negative dielectrophoretic (n-DEP) actuation. In these designs, we “pin” individual cells in designated on-chip locations using “capture cups” formed from a photopatterned silicone polymer. Negative DEP forces then operate as a switch to unload targeted subgroups of the weirs and prevent site-specific loading altogether in arrayed weir grouping. This functionality enables the placement of multiple cell types in organized single-cell patterns on a common substrate, permitting new screening and response assays for cell-cell signaling dynamics. With this platform, manipulations prove feasible in standard cell-culture media, thus avoiding cell health concerns associated with comparative p-DEP approaches.

We have also continued developing the optical approach to image-based cell sorting. In this approach, cells are captured in a 10,000-site silicone microwell array. Following imaging, we use an infrared laser to levitate and thus sort cells out of microwells. Over the past year we have demonstrated the ability to purify cell populations up to >150 as well as sort cells based upon a localization-based phenotype.

Additionally, we are investigating the effects of DEP manipulation on cell physiology using a microfabricated, high-content screening (HCS) platform that applies electrical stimuli to cells and monitors the resulting subcellular molecular responses via automated fluorescence microscopy. The platform consists of a chip with individually addressable arrayed electrodes and peripheral support electronics. We seed cells onto the chip and then expose them to a variety of electrical stresses. By monitoring the response of the cells via a fluorescent reporter cell line, we can assess how cells respond to the electric fields.