Cells – The Outsides and Insides with Transverse AC Electrophoresis and Low-Flow Electrospray Interfaces

To characterize intact single-cells, flow cytometry has long been the primary method for analyzing single cells, relying on quick optical characterization, and often using fluorescent antibodies. However, the need for complementary label-free methods has spurred much recent development in microfluidic systems measure properties, such as cellular polarizability and impedance. While most methods measure only a few properties of single cells, we are developing a new method for single-particle analysis. Our method uses microfluidic transverse AC electrophoresis (TrACE) and particle tracking velocimetry (PTV) to measure the zeta potential, size, hydrodynamic shape, and dipole moment of individual particles while allowing for longer observation times. We are extending TrACE to observe cell-cell interactions and to analyze cell surface receptors in a flow-through system that is less perturbing than methods that require protein extraction or planarization of the membrane surface.
For the analysis of the biomolecular composition of single-cells, mass spectrometry is unrivaled in its capability to identify a vast array of species and achieve low limits of detection. Similarly capillary electrophoresis and microchannel electrophoresis (ME) excel and fast and high-efficiency separations. We are furthering ME electrophoresis systems coupled with the mass spectrometer (MS) through a refined electrospray ionization (ESI) interface. We anticipate this system will provide stable electrospray and faster separations at lower flowrates (< 100 nL/min) than are typically achieved with microfluidic-ESI-MS systems and will report on progress in this area.