Simultaneous sample washing and concentration using a “trapping-and-releasing” mechanism of magnetic beads on a microfluidic chip

Abstract

Simultaneous washing and concentration of functionalized magnetic beads in a complex sample solution were demonstrated by applying a rotational magnetic actuation system to a microfluidic chip under continuous flow conditions. The rotation of periodically arranged small permanent magnets close to the fluidic channel carrying a magnetic bead suspension allows trapping and releasing of the beads along the fluidic channel in a periodical manner. Each trapping and releasing event resembles one washing cycle. A purification efficiency of magnetic beads out of a mixed magnetic and non-magnetic bead sample solution of 83 ± 4% at a flow rate of 0.5 µL min⁻¹, and a magnetic bead recovery or concentration efficiency of 91 ± 5% were achieved using a flow rate of 0.2 µL min⁻¹. The detection performance of the device was experimentally evaluated with two different bioassays, using either streptavidin-coated magnetic beads in combination with biotinylated fluorescent isothiocyanate (FITC), or a mouse antigen (Ag)–antibody (Ab) system.