title: Femtomolar sensitivity using a channel-etched thin film waveguide fluoroimmunosensor.
abstract: A dual channel, evanescent fluoroimmunoassay format is used to detect femtomolar analyte concentrations (i.e. less than 1 part per trillion [w/w]) on an etched channel siliconoxynitride thin film integrated optical waveguide. Two assays are used to demonstrate the dose-response behaviour of the sensor: (1) a direct assay of a fluorescently-labeled protein ligand binding to an immobilized protein receptor, and (2) an indirect sandwich assay of a non-fluorescent protein ligand binding to an immobilized protein receptor, as detected by the binding of a fluorescently-labeled secondary receptor protein. A red-emitting cyanine dye (Cy-5), which minimized background fluorescence and scatter losses of the waveguide, was used in both assays. To our knowledge, this is the first report of femtomolar sensitivity in an immunosensing instrument.
authors.affiliation: Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281, USA.
authors.forename: T E
authors.initials: TE
authors.lastname: Plowman
authors.forename: W M
authors.initials: WM
authors.lastname: Reichert
authors.forename: C R
authors.initials: CR
authors.lastname: Peters
authors.forename: H K
authors.initials: HK
authors.lastname: Wang
authors.forename: D A
authors.initials: DA
authors.lastname: Christensen
authors.forename: J N
authors.initials: JN
authors.lastname: Herron
mesh_terms: D015374:Biosensing Techniques; D005069:Evaluation Studies as Topic; D015200:Fluoroimmunoassay / Q000379:methods* / Q000706:statistics & numerical data; D008024:Ligands; D008832:Microchemistry; D055095:Optics and Photonics; D011506:Proteins; D012680:Sensitivity and Specificity; D017655:Silicon Compounds
chemical_list: D008024:Ligands; D011506:Proteins; D017655:Silicon Compounds