title: Lateral flow immunoassay using europium chelate-loaded silica nanoparticles as labels.
abstract: BACKGROUND
  Despite their ease of use, lateral flow immunoassays (LFIAs) often suffer from poor quantitative discrimination and low analytical sensitivity. We explored the use of a novel class of europium chelate-loaded silica nanoparticles as labels to overcome these limitations.
  
  
  METHODS
  Antibodies were covalently conjugated onto europium chelate-loaded silica nanoparticles with dextran as a linker. The resulting conjugates were used as labels in LFIA for detection of hepatitis B surface antigen (HBsAg). We performed quantification with a digital camera and Adobe Photoshop software. We also used 286 clinical samples to compare the proposed method with a quantitative ELISA.
  
  
  RESULTS
  A detection limit of 0.03 microg/L was achieved, which was 100 times lower than the colloidal gold-based LFIAs and lower than ELISA. A precise quantitative dose-response curve was obtained, and the linear measurement range was 0.05-3.13 microg/L, within which the CVs were 2.3%-10.4%. Regression analysis of LFIA on ELISA results gave: log (LFIA) = -0.14 log (ELISA) + 1.03 microg/L with r = 0.99 for the quantification of HBsAg in 35 positive serum samples. Complete agreement was observed for the qualitative comparison of 286 clinical samples assayed with LFIA and ELISA.
  
  
  CONCLUSIONS
  Europium chelate-loaded silica nanoparticle labels have great potential to improve LFIAs, making them useful not only for simple screening applications but also for more sensitive and quantitative immunoassays.
authors.affiliation: Molecular Diagnostics Laboratory, Department of Biomedical Sciences and the Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen, Fujian, China.
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Xia
authors.forename: Ye
authors.initials: Y
authors.lastname: Xu
authors.forename: Xilin
authors.initials: X
authors.lastname: Zhao
authors.forename: Qingge
authors.initials: Q
authors.lastname: Li
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry*; D005063:Europium / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D006511:Hepatitis B Antigens / Q000097:blood / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry*; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012822:Silicon Dioxide / Q000737:chemistry*; D012984:Software; D013194:Staining and Labeling
chemical_list: D000911:Antibodies, Monoclonal; D002614:Chelating Agents; D005456:Fluorescent Dyes; D006511:Hepatitis B Antigens; D005063:Europium; D012822:Silicon Dioxide