title: Long-range fluorescence quenching by gold nanoparticles in a sandwich immunoassay for cardiac troponin T.
abstract: We report the first homogeneous sandwich immunoassay with gold nanoparticles (AuNPs) as fluorescence quenchers. The sandwich assay is designed for the detection of the protein cardiac troponin T (cTnT) by its simultaneous interaction with two different antibodies, one attached to AuNPs and the other labeled with fluorescent dyes. We demonstrate the working principle of the assay and using time-resolved fluorescence spectroscopy, we determine the quenching efficiency of the gold nanoparticles. In spite of the relatively large separation distance between dye molecules and AuNPs, ranging from 3 to 22 nm, the AuNPs quench the fluorescence with efficiencies as high as 95%. A limit of detection of 0.02 nM (0.7 ng/mL) was obtained for cTnT, which is the lowest value reported for a homogeneous sandwich assay for cTnT. These results illustrate the use of metallic nanoparticles as fluorescence quenchers in immunoassays where the large biomolecules involved impose distances for which energy transfer between fluorophores would be inefficient.
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: Meike A
authors.initials: MA
authors.lastname: Kloster
authors.forename: Michael
authors.initials: M
authors.lastname: Wunderlich
authors.forename: Andrey
authors.initials: A
authors.lastname: Lutich
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Klar
authors.forename: Alfons
authors.initials: A
authors.lastname: Nichtl
authors.forename: Konrad
authors.initials: K
authors.lastname: Kürzinger
authors.forename: Fernando D
authors.initials: FD
authors.lastname: Stefani
authors.forename: Jochen
authors.initials: J
authors.lastname: Feldmann
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D006046:Gold / Q000737:chemistry*; D007118:Immunoassay / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D020107:Troponin T / Q000032:analysis*
chemical_list: D020107:Troponin T; D006046:Gold