High Sensitivity, Microfluidic Immunoassays utilizing DNA-conjugated Antibodies to Accelerate the Electrophoretic Separation of Antigen-Antibody Complexes.
H.G. Wada, T. Kawabata, I. Kazakova, A. Simeonov, C. Park, P. Kechagia, M. Spaid, M. Watanabe and S. Satomura
Wako Pure Chemical Industries Ltd., US
microfluidic, lab-on-a-chip, immunoassay, diagnostics
The promise of microfluidic immunoassays in microchips has been the miniaturization, integration and automation of rapid immunoassays. The typical microfluidic assays have used fluorescent dye labeled antibodies in direct binding assays or labeled antigens in competitive binding formats. Often electrophoretic or hydrodynamic separation is employed to measure the formation of antigen-antibody complexes. The problem with hydrodynamic separation is that the bead solid-phases that are often used are inconvenient to load into microchannels. The principal problem with the electrophoretic methods has been low sensitivity caused by the low concentration of sample analyte in a narrow injection zone and dispersion of the immune-complex during separation. We have used a two approaches to overcome the problem of low sensitivity. Firstly, a novel method was employed using DNA conjugated antibody to accelerate the electrophoretic mobility of the immune-complex and reduce the separation time and dispersion during the zone electrophoresis step. Secondly, an on-chip sample concentration step was utilized to enhance detection sensitivity. The result has been a rapid and sensitive sandwich immunoassay format that has now been demonstrated using monoclonal antibodies to measure alpha-fetoprotein in human serum. This novel approach has achieved pM sensitivity and should have broad applications whenever cost effective, automated, and rapid immunoassays are required.
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Nanotech 2005 Conference Program Abstract