title: Evaporation-Driven Bioassays in Suspended Droplets.
abstract: The microtiter plate has been an essential tool for diagnostics, high-throughput screening, and biological assays. We present an alternative platform to perform bioassays in a microplate format that exploits evaporation to drive assay reactions. Our method consists of droplets suspended on plastic pillars; reactions occur in these droplets instead of the wells. The pillars are fabricated by milling, and the rough surface created by this fabrication method pins the droplet to a constant contact line during the assay and also acts as a hydrophobic surface. Upon evaporation, natural convection arising from Marangoni currents mixes solutions in the droplet, which speeds up assay reactions, decreases assay times, and increases limits of detection. As a proof of concept we implemented two colorimetric assays to detect glucose and proteins in only 1.5 μL, without any external devices for mixing and with a digital microscope as a readout mechanism. Our platform is an ideal alternative to the microtiter plate, works with different volumes, is compatible with commercially available reagent dispensers and plate-readers, and could have broad applications in diagnostics and high-throughput screening.
authors.affiliation: Unidad Monterrey, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional , Via del Conocimiento 201, Parque PIIT, Apodaca, Nuevo León CP 66628, Mexico.
authors.forename: Ruth
authors.initials: R
authors.lastname: Hernandez-Perez
authors.affiliation: Department of Mechanical and Aerospace Engineering, University of Florida , P.O. Box 116250, Gainesville, Florida 32611, United States.
authors.forename: Z Hugh
authors.initials: ZH
authors.lastname: Fan
authors.affiliation: Unidad Monterrey, Centro de Investigacion y de Estudios Avanzados del Instituto Politecnico Nacional , Via del Conocimiento 201, Parque PIIT, Apodaca, Nuevo León CP 66628, Mexico.
authors.forename: Jose L
authors.initials: JL
authors.lastname: Garcia-Cordero
mesh_terms: D000818:Animals; D002417:Cattle; D003124:Colorimetry / Q000379:methods*; D005947:Glucose / Q000032:analysis* / Q000378:metabolism; D005949:Glucose Oxidase / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D057230:Limit of Detection; D066292:Lipid Droplets / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000032:analysis*
chemical_list: D012710:Serum Albumin, Bovine; D005949:Glucose Oxidase; D005947:Glucose