Combining optical and hydrodynamic forces for single cell characterization, isolation and delivery

Abstract

With the existence and emerging importance of cellular heterogeneity there has been a push in the microbiology community for new tools to study at the individual cells. To meet the need to identify, characterize and isolate single cells of interest from bulk samples, precise and directed forces on the order of picoNewtons are necessary. To generate these forces, we combine optical and hydrodynamic methods enabled by microfluidic platforms that operate in regimes where viscous forces dominate and hydrodynamics is readily predicted and controlled. We have developed techniques for the characterization, isolation and delivery of individual cells using combinations of optical and hydrodynamic forces. First, we use optical forces to demonstrate real-time measurement of single-cell dynamic viscoelasticity while using hydrodynamic forces to move cells in and out of the optical trap to enable high-throughput (3000 cells/hr). Second, we use optical forces for the isolation of cells and hydrodynamic properties of laminar flow to amplify this isolation. Finally, we use this single-cell isolation scheme in a microfluidic platform with a novel chip-to-world sample delivery scheme that can be integrated with a variety of available cell isolation technologies. In this, an optical trap was employed to generate the necessary forces to precisely capture and isolate single cells from the bulk population, while hydrodynamic forces were used to amplify this isolation and deliver single cells as falling droplets that can be collected onto 96-well plates. These hydrodynamic forces were generated and precisely directed with microfluidic features including hydraulic resistances, hydrofocusing vaults, compliance reservoirs, and selective surface coatings to scale from the micrometer scale of single cells to the millimeter scale of well plates.