Protein Transport and Concentration by Electrophoresis in Two-phase Microflows

This work aims at a new class of methods for electric field-mediated separation of biomolecules. In contrast to standard techniques, electrophoretic transport was not performed in a single-phase homogenous fluid, but in a system of stratified layers. The large surface-to-volume ratio characteristic for microfluidic systems allows the interactions of biomolecules with liquid/liquid interfaces to be examined and the suitability of corresponding effects for applications in the field of biomolecular separations and enrichment to be assessed. To perform these types of studies, a micro flow cell was fabricated into which two coflowing immiscible liquid phases can be introduced. Subsequently, the electrophoretic transport of biomolecules driven by an electric field perpendicular to the channel was examined. To investigate the transport phenomena related to electrophoresis in stratified two-phase systems, aqueous solutions consisting of polyethylene glycol and dextran were prepared, which allowed a stable interface to develop. Transport within one phase and an enrichment of proteins at the phase boundary has been established. In addition, other kinds of fluid combinations such as water and propylene carbonate have been examined, also supporting the enrichment of proteins at the phase boundary.