title: Competitive magnetic immunoassay for protein detection in thin channels.
abstract: 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 determined and used as a reference plot. The IgG concentration in a sample was deduced and determined based on 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.
authors.affiliation: Department of Applied Chemistry, Chung Shan Medical University, Taichung 402, Taiwan.
authors.forename: H Y
authors.initials: HY
authors.lastname: Tsai
authors.forename: S J
authors.initials: SJ
authors.lastname: Jian
authors.forename: S T
authors.initials: ST
authors.lastname: Huang
authors.forename: C Bor
authors.initials: CB
authors.lastname: Fuh
mesh_terms: D000818:Animals; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis* / Q000097:blood*; D008280:Magnetics; D018625:Microscopy, Atomic Force; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology / Q000379:methods*; D011506:Proteins / Q000032:analysis*; D013205:Staphylococcal Protein A / Q000737:chemistry
chemical_list: D007074:Immunoglobulin G; D011506:Proteins; D013205:Staphylococcal Protein A