title: Comparison of label-free biosensing in microplate, microfluidic, and spot-based affinity capture assays.
abstract: Using both experimental assays and fluid-dynamic finite element simulation models, we directly compared the achievable performance limits of four distinct assay configurations for label-free detection of an analyte from a test sample on a biosensor surface. The assay configurations studied in this work included a biosensor incorporated into the bottom surface of a microplate well and a microfluidic channel. For each configuration, we compared assay performance for the scenario in which the entire bottom surface of the fluid-handling vessel is coated with capture ligands with assay performance for the scenario in which the capture ligands are applied in the form of localized spots. As a model system, we used detection of the protein biomarker tumor necrosis factor-alpha (TNF-alpha) using immobilized TNF-alpha capture antibody. Results show that the microfluidic assay format dramatically reduces the time required to establish a stable equilibrium. Spot-based assays are advantageous for microplate-based detection for reducing the time required for equilibrium sensor response. The results derived are generally applicable to any label-free biosensor technology and any ligand-analyte system with adjustable variables that include sensor mass density sensitivity, analyte-ligand adsorption/desorption rate constants, immobilized ligand density, flow channel geometry, flow rate, and spot size.
authors.affiliation: Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Micro and Nanotechnology Laboratory, Urbana, IL 61801, USA.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Choi
authors.forename: Alysia R
authors.initials: AR
authors.lastname: Belobraydich
authors.forename: Leo L
authors.initials: LL
authors.lastname: Chan
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Mathias
authors.forename: Brian T
authors.initials: BT
authors.lastname: Cunningham
mesh_terms: D055910:Antibodies, Immobilized / Q000276:immunology; D015374:Biosensing Techniques / Q000379:methods*; D006801:Humans; D044085:Microfluidics / Q000379:methods*; D055100:Optical Fibers; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
chemical_list: D055910:Antibodies, Immobilized; D014409:Tumor Necrosis Factor-alpha