title: Competitive homogeneous digoxigenin immunoassay based on fluorescence quenching by gold nanoparticles.
abstract: We report on a competitive, homogeneous immunoassay for the detection of the hapten digoxigenin. The assay is based on competitive fluorescence quenching by gold nanoparticles. Digoxigenin is indirectly labeled with the fluorophore Cy3B through bovine serum albumin and used as a marker. Gold nanoparticles functionalized with anti-digoxigenin antibodies serve as fluorescence quenchers. Free digoxigenin molecules in the analyte solution compete with the labeled markers for antibodies on the gold nanoparticles. The fluorescence signal depends linearly on the free digoxigenin concentration within a range of concentration from 0.5 to 3 ng mL(-1). The limit of detection is estimated as 0.2 ng mL(-1) and the limit of quantitation is estimated as 0.6 ng mL(-1). The method can be used to detect digoxin, a drug used to cure cardiac arrhythmia.
authors.affiliation: Photonics and Optoelectronics Group, Department of Physics and CeNS, Ludwig-Maximilians-Universität München, Amalienstrasse 54, 80799 Munich, Germany.
authors.forename: Sergiy
authors.initials: S
authors.lastname: Mayilo
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ehlers
authors.forename: Michael
authors.initials: M
authors.lastname: Wunderlich
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Klar
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Josel
authors.forename: Dieter
authors.initials: D
authors.lastname: Heindl
authors.forename: Alfons
authors.initials: A
authors.lastname: Nichtl
authors.forename: Konrad
authors.initials: K
authors.lastname: Kürzinger
authors.forename: Jochen
authors.initials: J
authors.lastname: Feldmann
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000276:immunology; D002417:Cattle; D004076:Digoxigenin / Q000032:analysis* / Q000276:immunology; D004077:Digoxin / Q000032:analysis / Q000276:immunology; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D007118:Immunoassay / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000276:immunology; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000906:Antibodies; D005456:Fluorescent Dyes; D012710:Serum Albumin, Bovine; D004077:Digoxin; D006046:Gold; D004076:Digoxigenin