title: Density-Gradient Mediated Band Extraction of Leukocytes from Whole Blood Using Centrifugo-Pneumatic Siphon Valving on Centrifugal Microfluidic Discs.
abstract: Here we present retrieval of Peripheral Blood Mononuclear Cells by density-gradient medium based centrifugation for subsequent analysis of the leukocytes on an integrated microfluidic "Lab-on-a-Disc" cartridge. Isolation of white blood cells constitutes a critical sample preparation step for many bioassays. Centrifugo-pneumatic siphon valves are particularly suited for blood processing as they function without need of surface treatment and are 'low-pass', i.e., holding at high centrifugation speeds and opening upon reduction of the spin rate. Both 'hydrostatically' and 'hydrodynamically' triggered centrifugo-pneumatic siphon valving schemes are presented. Firstly, the geometry of the pneumatic chamber of hydrostatically primed centrifugo-pneumatic siphon valves is optimised to enable smooth and uniform layering of blood on top of the density-gradient medium; this feature proves to be key for efficient Peripheral Blood Mononuclear Cell extraction. A theoretical analysis of hydrostatically primed valves is also presented which determines the optimum priming pressure for the individual valves. Next, 'dual siphon' configurations for both hydrostatically and hydrodynamically primed centrifugo-pneumatic siphon valves are introduced; here plasma and Peripheral Blood Mononuclear Cells are extracted through a distinct siphon valve. This work represents a first step towards enabling on disc multi-parameter analysis. Finally, the efficiency of Peripheral Blood Mononuclear Cells extraction in these structures is characterised using a simplified design. A microfluidic mechanism, which we termed phase switching, is identified which affects the efficiency of Peripheral Blood Mononuclear Cell extraction.
authors.affiliation: School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.|Biomedical Diagnostics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: David J
authors.identifier: 0000-0003-1968-2016
authors.initials: DJ
authors.lastname: Kinahan
authors.affiliation: School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.|Biomedical Diagnostics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Sinéad M
authors.initials: SM
authors.lastname: Kearney
authors.affiliation: School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.|Biomedical Diagnostics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Niamh A
authors.initials: NA
authors.lastname: Kilcawley
authors.affiliation: School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.|Biomedical Diagnostics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Philip L
authors.initials: PL
authors.lastname: Early
authors.affiliation: School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.|Biomedical Diagnostics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Macdara T
authors.initials: MT
authors.lastname: Glynn
authors.affiliation: School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.|Biomedical Diagnostics Institute, Dublin City University, Glasnevin, Dublin 9, Ireland.
authors.forename: Jens
authors.initials: J
authors.lastname: Ducrée
mesh_terms: D001681:Biological Assay / Q000295:instrumentation / Q000379:methods; D002500:Centrifugation, Isopycnic / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D006801:Humans; D057446:Hydrodynamics; D007963:Leukocytes, Mononuclear / Q000737:chemistry*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D011312:Pressure