Total serum IgE quantification by microfluidic ELISA using magnetic beads.

The present work reports on the quantification of total IgE in human serum using a microanalytical device whose fluidics is driven by gravity and capillary forces only. Thanks to the eight parallel microchannels in each microchip, calibration and sample analysis are performed simultaneously. A mixture of magnetic bead/analyte/second antibody is incubated off-line and then percolated through the channels where magnetic beads are trapped, enabling the separation of the solid phase from the excess reagents. The entire assay is performed in less than 1 h, and thanks to the miniaturized format, only a small volume of serum is required. Non-specific adsorption was first investigated and a blocking agent compatible with this allergy-based test was chosen. Then, the assay was optimized by determining the best magnetic bead and labelled antibody concentrations. After achievement of a calibration curve with a reference material, the protocol was applied to total IgE quantification of a patient serum sample that showed results in good accordance with those obtained by ImmunoCap® and Immunoaffinity capillary electrophoresis measurements. A detection limit of 17.5 ng ml(-1) was achieved and good reproducibility (RSD < 10%) inter- and intra-chip was observed.