Isomagnetophoresis-based immunoassay system for multiplexed protein detection

Abstract

This thesis presents an isomagnetophoresis-based immunoassay system which analyzes the infinitesimal analytes with high accuracy and resolution and adjusts the dynamic ranges of target analytes. Isomagnetophoresis is an improved magnetophoresis which discriminates materials with subtle magnetic susceptibility difference. Because the magnetophoretic mobility of a particle is in proportion to the magnetic susceptibility difference between a particle and surrounding solution, a particle migrates and stays at the position where the magnetic susceptibility of a particle and the surrounding solution are equal under the magnetic susceptibility gradient of the surrounding solution (gadolinium paramagnetic diethylenetriamine-pentaacetic acid, Gd-DTPA). For the isomagnetophoresis-based immunoassay, a new quantitative analysis method was first proposed using a magnetophoresis-based immunoassay. The quantitative analysis of proteins was conducted by measuring the position of microbeads in the microchannel. Three types of colored microbeads reacted with the respective analytes and superparamagnetic nanoparticles were focused to the opposite side from external magnetic field. They were then deflected from their focused streamlines in a microchannel as much as analytes and SMNPs are conjugated with them. Consequently, the position of each colored microbeads can be correlated with the concentration of each analytes and the detection limits of three analytes are femto-molar level. With this new quantitative analysis method, an isomagnetophoretic immunoassay system has been developed. Here, rabbit IgG-biotin was analyzed as a model and the quantitative analysis was carried out by measuring the positions of microbeads in the outlet of a microfluidic device. To generate a magnetic susceptibility gradient, 10 mM Gd-DTPA and DI water were used. This new isomagnetophoretic immunoassay system could analyze the rabbit IgG-biotins from 19.8 aM to 266.4 fM, and showed the very low coeff...