Competitive magnetic immunoassay for protein detection in thin channels

Functional magnetic nanoparticles are prepared and characterized for protein detection in a magnetic separation channel This detection method is based on a competitive immunoassay of magnetic separation in thin channels using functional magnetic nanoparticles. We used protein A-IgG complex to demonstrate the feasibility. Free IgG and fixed number of IgG-labeled microparticles were used to compete for limited sites of protein A on the magnetic nanoparticles. Several experimental parameters were investigated for protein detection The deposited percentages of IgG-labeled microparticles at various concentrations of free IgG were deter mined and Used as a reference plot. The IgG concentration in a sample was deduced and determined based oil the reference plot using the deposited percentage of IgG-labeled microparticles from the sample The linear range of IgG detection was from 5.0 x 10(-8) to 1.0 x 10(-11) M The detection limit was 3.69 x 10(-12) M The running time was less than 10 min Selectivities were higher than 92% and the relative errors were less than 7%. The IgG concentration of serum was determined to be 3.6 mg ml(-1) This measurement differed by 8.3% from the ELISA measurement The recoveries of IgG spiked in serum were found to be higher-than 94%. This method can provide simple, fast, and selective analysis for protein detection and other immunoassay-related applications (C) 2009 Elsevier B.V. All rights reserved.