Rapid protein depletion from complex samples using a bead-based microfluidic device for the point of care

Translation of sample preparation methods to point-of-care formats has remained a challenge. We present a plastic laminate microfluidic device for protein depletion from human plasma using ligand immobilized porous beads stored dry within a novel, pneumatically-driven mixer. The card design accelerated the protein depletion process from hours to minutes. Using immunoglobulin G as a model protein, we have successfully shown protein removal efficiency from spiked buffer between 70-80% and from diluted human plasma samples between 66-77%. Low non-specific binding of our downstream target ligand, immunoglobulin M, was observed with the spiked buffer and diluted human plasma samples. For future device optimization, the physical limitations to rapid protein removal on card were also explored. Bench-top experiments with improved mixing efficiency and a lower sample dilution factor achieved 99% IgG removal using the same amount of mixing time. This design can easily be adapted for depletion of other high abundance or interfering proteins by inclusion of other ligand immobilized beads.