title: Rotation-Driven Microfluidic Disc for White Blood Cell Enumeration Using Magnetic Bead Aggregation.
abstract: We recently defined a magnetic bead-based assay that exploited an agglutination-like response for DNA and applied it to DNA-containing cell enumeration using inexpensive benchtop hardware [ J. Am. Chem. Soc. 2012 , 134 ( 12 ), 5689 - 96 ]. Although cost-efficient, the open-well format assay required numerous manual steps, and the magnetic field actuation scheme was not readily adaptable for integration. Here, we demonstrate a low-cost (<$2 in-lab), higher-throughput "pinwheel assay" platform that relies on a combination of a disposable rotation-driven microdisc (RDM), and a simple bidirectional rotating magnetic field (bi-RMF). The assay was transformed into an integrated microfluidic system using a multilayered polyester microfluidic disc created through laser print, cut and laminate fabrication, with fluid flow controlled by rotation speed without any mechanical valves. The RDM accepts four samples that undergo on-chip dilution to five different concentrations that cover the effective concentration range needed for downstream cell counting by pinwheel assay. We show that a bi-RMF is effective for the simultaneous actuation of pinwheel assays in 20 detection chambers. The optimization of the bi-RMF frequencies allows the RDM-based pinwheel assay detect human genomic DNA down to a mass of human genomic DNA (5.5 picograms) that is roughly equal to the mass in a single cell. For proof of principle, enumeration of the white blood cells in human blood samples on the RDM provided data correlating well (C.V. of 10%) with those obtained in a clinical lab. Fusing the cost-effective RDM with a simple bi-RMF provides a promising strategy for automation and multiplexing of magnetic particle-based agglutination assays.
authors: Department of Chemistry, University of Virginia , McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States.
authors: Yiwen
authors: Y
authors: Ouyang
authors: Department of Chemistry, University of Virginia , McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States.
authors: Jingyi
authors: J
authors: Li
authors: Department of Pathology, University of Virginia Health Science Center , Charlottesville, Virginia 22908, United States.
authors: Doris M
authors: DM
authors: Haverstick
authors: Department of Chemistry, University of Virginia , McCormick Road, P.O. Box 400319, Charlottesville, Virginia 22904, United States.|Department of Pathology, University of Virginia Health Science Center , Charlottesville, Virginia 22908, United States.|Department of Mechanical Engineering, University of Virginia , Engineer's Way, Charlottesville, Virginia 22904, United States.
authors: James P
authors: JP
authors: Landers
mesh_terms: D001772:Blood Cell Count / Q000295:instrumentation* / Q000379:methods*; D004247:DNA / Q000032:analysis; D006801:Humans; D018189:Immunomagnetic Separation / Q000295:instrumentation / Q000379:methods*; D007962:Leukocytes / Q000166:cytology*; D060526:Magnetic Fields; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D012399:Rotation
chemical_list: D004247:DNA