title: Magnetic fluidized bed for solid phase extraction in microfluidic systems.
abstract: Fluidization, a process in which a granular solid phase behaves like a fluid under the influence of an imposed upward fluid flow, is routinely used in many chemical and biological engineering applications. It brings, to applications involving fluid-solid exchanges, advantages such as high surface to volume ratio, constant mixing, low flow resistance, continuous operation and high heat transfer. We present here the physics of a new miniaturized, microfluidic fluidized bed, in which gravity is replaced by a magnetic field created by an external permanent magnet, and the solid phase is composed of magnetic microbeads with diameters ranging from 1 to 5 μm. These beads can be functionalized with different ligands, catalysts or enzymes, in order to use the fluidized bed as a continuous purification column or bioreactor. It allows flow-through operations at flow rates ranging from 100 nL min-1up to 5 μL min-1at low driving pressures (<100 mbar) with intimate liquid/solid contact and a continuous recirculation of beads for enhanced target capture efficiencies. The physics of the system presents significant differences as compared to conventional fluidized beds, which are studied here. The effects of magnetic field profile, flow chamber shape and magnetic bead dipolar interactions on flow regimes are investigated, and the different regimes of operation are described. Qualitative rules to obtain optimal operation are deduced. Finally, an exemplary use as a platform for immunocapture is provided, presenting a limit of detection of 0.2 ng mL-1for 200 μL volume samples.
authors.affiliation: Laboratoire Physico Chimie Curie, Institut Curie, PSL Research University, CNRS UMR168, 75005, Paris, France. jean-louis.viovy@curie.fr laurent.malaquin@laas.fr.
authors.forename: Iago
authors.initials: I
authors.lastname: Pereiro
authors.forename: Sanae
authors.initials: S
authors.lastname: Tabnaoui
authors.forename: Marc
authors.initials: M
authors.lastname: Fermigier
authors.forename: Olivia
authors.initials: O
authors.lastname: du Roure
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Descroix
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Viovy
authors.forename: Laurent
authors.initials: L
authors.lastname: Malaquin
mesh_terms: D015415:Biomarkers / Q000032:analysis; D004867:Equipment Design; D006801:Humans; D007118:Immunoassay; D007074:Immunoglobulin G / Q000302:isolation & purification; D057230:Limit of Detection; D059346:Magnets; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D008956:Models, Chemical; D016062:Porosity; D052616:Solid Phase Extraction / Q000295:instrumentation* / Q000379:methods*
chemical_list: D015415:Biomarkers; D007074:Immunoglobulin G