title: Rapid and sensitive cardiac troponin I immunoassay based on fluorescent europium(III)-chelate-dyed nanoparticles.
abstract: BACKGROUND
  Cardiac troponins are the preferred and recommended biomarkers of myocardial infarction. Unfortunately, most of the current commercial assays do not meet the guideline recommendations for sensitivity and low-end precision. Therefore, improvements in their analytical performance are still needed.
  
  
  METHODS
  Cardiac troponin I (cTnI) immunoassay was developed. The assay utilized a monoclonal antibody and a F(ab')(2) antibody fragment immobilized onto the microtiter wells for capturing, and a monoclonal antibody covalently conjugated to fluorescent europium(III)-chelate-dyed nanoparticles for detecting. Following a 15-min incubation of the sample and nanoparticle-bioconjugates in the capture wells, cTnI was quantified directly from the washed well surface by time-resolved fluorometry.
  
  
  RESULTS
  The limits of detection and quantification were 0.0020 μg/l and 0.012 μg/l, respectively. The response was linear in the measured range of 0.003-9.6 μg/l. The within-run imprecisions were 9.8, 5.1, 7.7 and 5.4%, and the total imprecisions were 13.1, 10.4, 9.0 and 8.7% at cTnI levels of 0.007, 0.051, 0.52 and 2.62 μg/l, respectively. Plasma recoveries of added cTnI were 72-119%. Regression analysis with Innotrac Aio! 2nd generation cTnI assay yielded a slope (95% confidence intervals) of 1.197 (1.141 to 1.253) and y-intercept of 0.216 (-0.128 to 0.561)μg/l (S(yx) = 2.176 μg/l, n = 212, r = 0.945).
  
  
  CONCLUSIONS
  The developed immunoassay based on europium(III)-chelate-dyed nanoparticle label allows rapid and sensitive measurement of cTnI.
authors.affiliation: Department of Biotechnology, University of Turku, Turku, Finland. mljarv@utu.fi.
authors.forename: Marja-Leena
authors.initials: ML
authors.lastname: Järvenpää
authors.forename: Katri
authors.initials: K
authors.lastname: Kuningas
authors.forename: Ilari
authors.initials: I
authors.lastname: Niemi
authors.forename: Pirjo
authors.initials: P
authors.lastname: Hedberg
authors.forename: Noora
authors.initials: N
authors.lastname: Ristiniemi
authors.forename: Kim
authors.initials: K
authors.lastname: Pettersson
authors.forename: Timo
authors.initials: T
authors.lastname: Lövgren
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology; D000937:Antigen-Antibody Reactions / Q000276:immunology; D002614:Chelating Agents / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry; D005063:Europium / Q000737:chemistry*; D005453:Fluorescence; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007700:Kinetics; D053758:Nanoparticles / Q000737:chemistry*; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood* / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D002614:Chelating Agents; D056831:Coordination Complexes; D019210:Troponin I; D005063:Europium