title: Simultaneous multiple immunoassays in a compact disc-shaped microfluidic device based on centrifugal force.
abstract: BACKGROUND
  We explored the potential of a microfluidic device based on centrifugal force as an immunoassay platform by examining the imprecision of assays carried out with 200 nL of sample.
  
  
  METHODS
  Biotinylated antibodies against alpha-fetoprotein (AFP), interleukin-6 (IL-6), and carcinoembryonic antigen [(CEA); 0.1 g/L each in 15 mmol/L phosphate-buffered saline (PBS) containing 0.1 mL/L Tween 20] were attached to a microcolumn packed with streptavidin-coated particles. A 200-nL sample was then allowed to pass through the microcolumn for 240 s, followed by Alexa 647-labeled detection antibody (7.5 mg/L in 15 mmol/L PBS containing 10 g/L bovine serum albumin). The flow rate was controlled by altering the rotational speed. Up to 104 sandwich type immunoassays were completed within 50 min.
  
  
  RESULTS
  For AFP, IL-6, and CEA the detection limits were, respectively, 0.15, 1.25, and 1.31 pmol/L. Inter- and intraassay imprecisions (CVs) were <10% and <20%, respectively, for analyte concentrations >5 pmol/L. The CEA antibody had the lowest affinity according to fluorescence image analysis of the microcolumn region. The result was confirmed in a comparative study using BIAcore 3000.
  
  
  CONCLUSIONS
  Day-to-day (total) imprecision (CV) of immunoassays on the compact disc-shaped device are <20%. Analysis of fluorescence images allows rapid ranking of antibodies according to their affinities.
authors.affiliation: Methodology Research Group, Research & Development Division, Fujirebio, Inc., Tokyo, Japan. no-honda@fujirebio.co.jp
authors.forename: Nobuo
authors.initials: N
authors.lastname: Honda
authors.forename: Ulrika
authors.initials: U
authors.lastname: Lindberg
authors.forename: Per
authors.initials: P
authors.lastname: Andersson
authors.forename: Stephan
authors.initials: S
authors.lastname: Hoffmann
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Takei
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis; D002272:Carcinoembryonic Antigen / Q000032:analysis; D002417:Cattle; D002498:Centrifugation; D007118:Immunoassay / Q000379:methods; D015850:Interleukin-6 / Q000032:analysis; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods*; D012680:Sensitivity and Specificity; D012710:Serum Albumin, Bovine / Q000032:analysis; D000509:alpha-Fetoproteins / Q000032:analysis
chemical_list: D000906:Antibodies; D002272:Carcinoembryonic Antigen; D015850:Interleukin-6; D000509:alpha-Fetoproteins; D012710:Serum Albumin, Bovine