title: Giant magnetoresistive sensors and superparamagnetic nanoparticles: a chip-scale detection strategy for immunosorbent assays.
abstract: Thin structures of alternating magnetic and nonmagnetic layers with a total thickness of a few hundred nanometers exhibit a phenomenon known as giant magnetoresistance. The resistance of microfabricated giant magnetoresistors (GMRs) is dependent on the strength of an external magnetic field. This paper examines magnetic labeling methodologies and surface derivatization approaches based on protein-protein binding that are aimed at forming a general set of protocols to move GMR concepts into the bioanalytical arena. As such, GMRs have been used to observe and quantify the immunological interaction between surface-bound mouse IgG and alpha-mouse IgG coated on superparamagnetic particles. Results show the response of a GMR network connected together as a set of two sense GMRs and two reference GMRs in a Wheatstone bridge as a means to compensate for temperature effects. The response can be readily correlated to the amount of the magnetically labeled alpha-mouse IgG that is captured by an immobilized layer of mouse IgG, the presence of which is confirmed with X-ray photoelectron spectroscopy and atomic force microscopy. These results, along with a detailed description of the experimental testing platform, are described in terms of sensitivity, detection limits, and potential for multiplexing.
authors.affiliation: Department of Chemistry, Ames Laboratory-USDOE, and Institute for Combinatorial Discovery, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Millen
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kawaguchi
authors.forename: Michael C
authors.initials: MC
authors.lastname: Granger
authors.forename: Marc D
authors.initials: MD
authors.lastname: Porter
authors.forename: Mark
authors.initials: M
authors.lastname: Tondra
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D019992:Databases as Topic; D004553:Electric Conductivity; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D004867:Equipment Design; D007074:Immunoglobulin G / Q000737:chemistry; D008280:Magnetics; D051379:Mice; D018625:Microscopy, Atomic Force / Q000379:methods; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D012680:Sensitivity and Specificity; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D013499:Surface Properties
chemical_list: D007074:Immunoglobulin G