Date of Award
Doctor of Philosophy
Marc D. Porter
Giant magnetoresistive sensors utilized for the detection of bioanalytes modified with magnetic labels is a field of study in its beginning stages. Giant magnetoresistors (GMRs) are the magnetic sensors that are used in the read-heads of computer hard drives, and are small, microfabricated devices that display a measurable change in resistance in response to an external magnetic field;The research described in this dissertation focuses on the creation of a small, low-cost, sensitive, and high-speed readout method for the detection of magnetically-labeled bioanalytes. Several methods were examined, including the direct modification of the GMR sensor surface to be a bioactive address for the capture of magnetically-labeled alpha-mouse IgG through an immunosorbent assay. The GMR sensor was coated with gold, which was further modified with mouse IgG through a succinimidyl-terminated thiolate monolayer. The GMR sensors were found to respond linearly to the presence of the magnetically-labeled alpha-mouse IgG;Further explorations of the use of the GMR sensor moved the assay from directly on the sensor surface to a sample stick consisting of 200 x 200 microm alternating nickel reference and gold addresses. The sample stick was then scanned over the GMR sensor in a "credit-card reader" fashion. The nickel reference addresses served as a reference-normalizing tool, and compensated for any variation in sensor to sample separation distance. This detection methodology was verified with the detection of streptavidin-coated magnetic particles (MPs) captured on biotinylated gold addressees. The reference-normalized GMR response varied linearly with MP surface concentration;The utilization of the sample stick for the detection of rabbit IgG in a sandwich assay format was also described. Goat alpha-rabbit IgG capture antibody was bound to the gold addresses through reaction with a succinimidyl-terminated monolayer. After capture of the rabbit IgG and further labeling with biotinylated goat alpha-rabbit IgG, the sample sticks were exposed to streptavidin-coated MPs. Issues related to the small size of the gold addresses, assessments of GMR detection capabilities, and potential applications are described. Finally, the simultaneous detection of three IgG proteins was demonstrated by using the same sandwich assay tactics and modifying each gold address with an individual capture antibody.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Rachel Lora Millen
Millen, Rachel Lora, "Giant magnetoresistive sensors and magnetic labels for chip-scale detection of immunosorbent assays " (2005). Retrospective Theses and Dissertations. 1919.