Giant Magnetoresistance Technology Research Articles

Qualification of classical biomarkers for Alzheimer’s Disease in a multiplex format in blood using a new technology

AbstractBackgroundProtein biomarker profiling in biological fluids will soon become an established procedure in clinical diagnosis of neurodegenerative disease subtypes. Observed differences between technology platforms in performances can be attributed to technology principles and their development status, selection and characterization of antibody combinations, reproducibility of test results, and pre‐analytical factors and processing of samples. Combination of advantages of emerging technologies, together with availability of precision‐qualified assay formats and innovative sample processing procedures, will create additional possibilities for individual patient management using clinically validated protein biomarker panels.MethodThe Giant Magneto Resistance (GMR) technology platform was used to develop multiplex immunoassays for different biomarker proteoforms in blood (e.g., Aß, (phospho)Tau, NF‐L, and GFAP).ResultWe have developed and optimized performance of multiplex assays using a Design of Experiment (DOE) approach to generate reproducible results. The selectivity and specificity of each antibody combination was confirmed with multiplex assay designs. We have used clinical samples instead of calibrators in buffer to shorten the development time. Process optimization through DOE was done with biotinylated peptides. After optimization, reproducibility was improved by approximately 4‐fold to < 5% CV for each analyte. We have included 3D6 as a capture antibody on the printed circuit boards (PCBs), while analyzing Aß1‐42 & Aß1‐40 using 21F12 and 2G3 as capture antibodies, respectively, to identify the presence of Aß oligomers. PCB selection, printing conditions including environmental factors, buffer selections, and conjugation process were optimized in a stepwise manner while frequently checking biomarker levels in clinical samples. Sample processing is part of our roadmap to generate clinically valuable results. The diagnostic potential for each assay format to identify amyloidopathy in an early phase of the disease will be presented using blood samples from cognitively normal, MCI, and AD subjects, characterized by CSF biomarker profiles and/or amyloid PET status.ConclusionThe GMR technology allows screening of performance of antibodies in multiplex formats, shortening the assay development time. The biomarker panels and novel methods for analysis are uniquely positioned to help the healthcare community. This study was funded by Alzheimer’s Drug Discovery Foundation's Diagnostics Accelerator (DxA) Program.

Integrated Giant Magnetoresistance Technology for Approachable Weak Biomagnetic Signal Detections.

With the extensive applications of biomagnetic signals derived from active biological tissue in both clinical diagnoses and human-computer-interaction, there is an increasing need for approachable weak biomagnetic sensing technology. The inherent merits of giant magnetoresistance (GMR) and its high integration with multiple technologies makes it possible to detect weak biomagnetic signals with micron-sized, non-cooled and low-cost sensors, considering that the magnetic field intensity attenuates rapidly with distance. This paper focuses on the state-of-art in integrated GMR technology for approachable biomagnetic sensing from the perspective of discipline fusion between them. The progress in integrated GMR to overcome the challenges in weak biomagnetic signal detection towards high resolution portable applications is addressed. The various strategies for 1/f noise reduction and sensitivity enhancement in integrated GMR technology for sub-pT biomagnetic signal recording are discussed. In this paper, we review the developments of integrated GMR technology for in vivo/vitro biomagnetic source imaging and demonstrate how integrated GMR can be utilized for biomagnetic field detection. Since the field sensitivity of integrated GMR technology is being pushed to fT/Hz0.5 with the focused efforts, it is believed that the potential of integrated GMR technology will make it preferred choice in weak biomagnetic signal detection in the future.

Quasi‐digital front‐ends for current measurement in integrated circuits with giant magnetoresistance technology

In this study, the authors report on two different electronic interfaces for low-power integrated circuits electric current monitoring through current-to-frequency ( I-f ) conversion schemes. This proposal displays the intrinsic advantages of the quasi-digital systems regarding direct interfacing and self-calibrating capabilities. In addition, as current-sensing devices, they have made use of the giant magnetoresistance (GMR) technology because of its high sensitivity and compatibility with standard complementary metal oxide semiconductor processes. Single elements and Wheatstone bridges based on spin-valves and magnetic tunnel junctions have been considered. In this sense, schematic-level simulations for integration in Austria Microsystems 0.35 μm technology have been corroborated by means of experimental measurements with the help of printed circuit board prototypes and real GMR devices. Tables with relevant parameters (silicon area, power consumption, sensitivity etc.) have been constructed as practical tools for designers. Electric currents down to 2 μA have been resolved in this way.

Giant Magenetoresistive Sensors. 2. Detection of Biorecognition Events at Self-Referencing and Magnetically Tagged Arrays

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.