title: Giant magenetoresistive sensors. 2. Detection of biorecognition events at self-referencing and magnetically tagged arrays.
abstract: Microfabricated devices formed from alternating layers of magnetic and nonmagnetic materials at combined thicknesses of a few hundred nanometers exhibit a phenomenon known as the giant magnetoresistance effect. Devices based on this effect are known as giant magnetoresistive (GMR) sensors. The resistance of a GMR is dependent on the strength of an external magnetic field, which has resulted in the widespread usage of such platforms in high-speed, high-data density storage drives. The same attributes (i.e., sensitivity, small size, and speed) are also important embodiments of many types of bioanalytical sensors, pointing to an intriguing opportunity via an integration of GMR technology, magnetic labeling strategies, and biorecognition elements (e.g., antibodies). This paper describes the utilization of GMRs for the detection of streptavidin-coated magnetic particles that are selectively captured by biotinylated gold addresses on a 2 x 0.3 cm sample stick. A GMR sensor network reads the addresses on a sample stick in a manner that begins to emulate that of a "card-swipe" system. This study also takes advantage of on-sample magnetic addresses that function as references for internal calibration of the GMR response and as a facile means to account for small variations in the gap between the sample stick and sensor. The magnetic particle surface coverage at the limit of detection was determined to be approximately 2%, which corresponds to approximately 800 binding events over the 200 x 200 microm capture address. These findings, along with the potential use of streptavidin-coated magnetic particles as a universal label for antigen detection in, for example, heterogeneous assays, are discussed.
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: John
authors.initials: J
authors.lastname: Nordling
authors.forename: Heather A
authors.initials: HA
authors.lastname: Bullen
authors.forename: Marc D
authors.initials: MD
authors.lastname: Porter
authors.forename: Mark
authors.initials: M
authors.lastname: Tondra
authors.forename: Michael C
authors.initials: MC
authors.lastname: Granger
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002138:Calibration; D008280:Magnetics; D046228:Microarray Analysis / Q000379:methods*; D012680:Sensitivity and Specificity