title: Fluorescent nanoparticles as labels for immunometric assay of C-reactive protein using two-photon excitation assay technology.
abstract: We describe the use of fluorophore-doped nanoparticles as reporters in a recently developed ArcDia TPX bioaffinity assay technique. The ArcDia TPX technique is based on the use of polymer microspheres as solid-phase reaction carrier, fluorescent bioaffinity reagents, and detection of two-photon excited fluorescence. This new assay technique enables multiplexed, separation-free bioaffinity assays from microvolumes with high sensitivity. As a model analyte we chose C-reactive protein (CRP). The assay of CRP was optimized for assessment of CRP baseline levels using a nanoparticulate fluorescent reporter, 75 nm in diameter, and the assay performance was compared to that of CRP assay based on a molecular reporter of the same fluorophore core. The results show that using fluorescent nanoparticles as the reporter provides two orders of magnitude better sensitivity (87 fM) than using the molecular label, while no difference between precision profiles of the different assay types was found. The new assay method was applied for assessment of baseline levels of CRP in sera of apparently healthy individuals.
authors.affiliation: Laboratory of Biophysics, Institute of Biomedicine, University of Turku, Finland.
authors.forename: Janne O
authors.initials: JO
authors.lastname: Koskinen
authors.forename: Jonne
authors.initials: J
authors.lastname: Vaarno
authors.forename: Niko J
authors.initials: NJ
authors.lastname: Meltola
authors.forename: Juhani T
authors.initials: JT
authors.lastname: Soini
authors.forename: Pekka E
authors.initials: PE
authors.lastname: Hänninen
authors.forename: Juhani
authors.initials: J
authors.lastname: Luotola
authors.forename: Matti E
authors.initials: ME
authors.lastname: Waris
authors.forename: Aleksi E
authors.initials: AE
authors.lastname: Soini
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry; D002097:C-Reactive Protein / Q000032:analysis*; D005456:Fluorescent Dyes; D005470:Fluorometry / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D007700:Kinetics; D007834:Lasers; D008863:Microspheres; D010316:Particle Size; D017785:Photons; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D044967:Serum / Q000737:chemistry; D013194:Staining and Labeling
chemical_list: D000911:Antibodies, Monoclonal; D005456:Fluorescent Dyes; D002097:C-Reactive Protein