title: Dynamic bioprocessing and microfluidic transport control with smart magnetic nanoparticles in laminar-flow devices.
abstract: In the absence of applied forces, the transport of molecules and particulate reagents across laminar flowstreams in microfluidic devices is dominated by the diffusivities of the transported species. While the differential diffusional properties between smaller and larger diagnostic targets and reagents have been exploited for bioseparation and assay applications, there are limitations to methods that depend on these intrinsic size differences. Here a new strategy is described for exploiting the sharply reversible change in size and magnetophoretic mobility of "smart" magnetic nanoparticles (mNPs) to perform bioseparation and target isolation under continuous flow processing conditions. The isolated 5 nm mNPs do not exhibit significant magnetophoretic velocities, but do exhibit high magnetophoretic velocities when aggregated by the action of a pH-responsive polymer coating. A simple external magnet is used to magnetophorese the aggregated mNPs that have captured a diagnostic target from a lower pH laminar flowstream (pH 7.3) to a second higher pH flowstream (pH 8.4) that induces rapid mNP disaggregation. In this second dis-aggregated state and flowstream, the mNPs continue to flow past the magnet rather than being immobilized at the channel surface near the magnet. This stimuli-responsive reagent system has been shown to transfer 81% of a model protein target from an input flowstream to a second flowstream in a continuous flow H-filter device.
authors: Department of Bioengineering, University of Washington, Seattle, WA 98195, USA.
authors: James J
authors: JJ
authors: Lai
authors: Kjell E
authors: KE
authors: Nelson
authors: Michael A
authors: MA
authors: Nash
authors: Allan S
authors: AS
authors: Hoffman
authors: Paul
authors: P
authors: Yager
authors: Patrick S
authors: PS
authors: Stayton
mesh_terms: D019921:Biotinylation; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D008280:Magnetics; D008823:Micelles; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry; D013194:Staining and Labeling; D019809:Streptavidin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D008823:Micelles; D011108:Polymers; D019809:Streptavidin