title: High performance wash-free magnetic bioassays through microfluidically enhanced particle specificity.
abstract: Magnetic biosensors have emerged as a sensitive and versatile platform for high performance medical diagnostics. These magnetic biosensors require well-tailored magnetic particles as detection probes, which need to give rise to a large and specific biological signal while showing very low nonspecific binding. This is especially important in wash-free bioassay protocols, which do not require removal of particles before measurement, often a necessity in point of care diagnostics. Here we show that magnetic interactions between magnetic particles and magnetized sensors dramatically impact particle transport and magnetic adhesion to the sensor surfaces. We investigate the dynamics of magnetic particles' biomolecular binding and magnetic adhesion to the sensor surface using microfluidic experiments. We elucidate how flow forces can inhibit magnetic adhesion, greatly diminishing or even eliminating nonspecific signals in wash-free magnetic bioassays, and enhancing signal to noise ratios by several orders of magnitude. Our method is useful for selecting and optimizing magnetic particles for a wide range of magnetic sensor platforms.
authors.affiliation: Department of Mechanical Engineering.
authors.forename: Daniel J B
authors.initials: DJ
authors.lastname: Bechstein
authors.affiliation: Department of Mechanical Engineering.
authors.forename: Jung-Rok
authors.initials: JR
authors.lastname: Lee
authors.affiliation: Department of Chemical Engineering.
authors.forename: Chin Chun
authors.initials: CC
authors.lastname: Ooi
authors.affiliation: Department of Electrical Engineering.
authors.forename: Adi W
authors.initials: AW
authors.lastname: Gani
authors.affiliation: Department of Electrical Engineering.
authors.forename: Kyunglok
authors.initials: K
authors.lastname: Kim
authors.affiliation: Department of Materials Science and Engineering. Address for all: Stanford University, 476 Lomita Mall, Stanford, California 94305, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wilson
authors.affiliation: 1] Department of Electrical Engineering [2] Department of Materials Science and Engineering. Address for all: Stanford University, 476 Lomita Mall, Stanford, California 94305, USA.
authors.forename: Shan X
authors.initials: SX
authors.lastname: Wang
mesh_terms: D000818:Animals; D015374:Biosensing Techniques; D001710:Biotin / Q000737:chemistry / Q000378:metabolism; D002417:Cattle; D008280:Magnetics; D058185:Magnetite Nanoparticles / Q000737:chemistry; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D019809:Streptavidin / Q000737:chemistry / Q000378:metabolism
chemical_list: D058185:Magnetite Nanoparticles; D012710:Serum Albumin, Bovine; D001710:Biotin; D019809:Streptavidin