Simultaneous multiple immunoassays in a compact disc-shaped microfluidic device based on centrifugal force

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 a-fetoprotein (AFP), interleukin-6 (IL-6), and carcinoembryonic antigen [(CEA); Al 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. (c) 2005 American Association for Clinical Chemistry.