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Sunnyvale, CA, United States

Hall D.A.,Stanford University | Gaster R.S.,Stanford University | Osterfeld S.J.,Magarray, Inc. | Murmann B.,Stanford University | Wang S.X.,Stanford University
Biosensors and Bioelectronics | Year: 2010

Giant magnetoresistive biosensors possess great potential in biomedical applications for quantitatively detecting magnetically tagged biomolecules. Magnetic sensing does not suffer from the high background levels found in optical sensing modalities such as the enzyme linked immunosorbent assay translating into a technology with higher sensitivity. However, to reveal the full potential of these sensors and compensate for non-idealities such as temperature dependence, digital correction and calibration techniques are not only useful but imperative. Using these calibration techniques to correct for process variations and dynamic changes in the sensing environment (such as temperature and magnetic field), we are able to obtain extremely sensitive and, more importantly, reproducible results for quantifiable biomolecular reorganization. The reproducibility of the system was improved by over 3× using digital correction techniques and the sensors are made temperature independent by using a novel background correction technique. © 2010 Elsevier B.V.

Hall D.A.,Stanford University | Gaster R.S.,Stanford University | Lin T.,Stanford University | Osterfeld S.J.,Magarray, Inc. | And 3 more authors.
Biosensors and Bioelectronics | Year: 2010

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1-8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4. s). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multiplexing capability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. © 2010 Elsevier B.V.

Clotilde L.M.,Magarray, Inc. | Salvador A.,California State University, East Bay | Salvador A.,U.S. Department of Agriculture | Bernard C.,U.S. Department of Agriculture | And 5 more authors.
Foodborne Pathogens and Disease | Year: 2015

Traditionally, serotyping of Escherichia coli has been performed via slide agglutination methods using antisera. More recently, multiplex immunoassays and "molecular serotyping" via polymerase chain reaction (PCR) have been validated for this purpose. In this study, the serogroups of 161 Shiga toxin-producing Escherichia coli (STEC) strains isolated from fecal samples of California cattle were typed by conventional methods using antisera as well as two newly developed multiplex PCR- and antibody-based microbead assays using the Luminex technology. Using the Luminex assays, we were capable of serotyping 11 STEC isolates that were previously determined untypeable for the O antigen by conventional methods using antisera. Except for 14 isolates, results from the 2 Luminex assays agreed. Copyright 2015, Mary Ann Liebert, Inc.

Agency: Department of Health and Human Services | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 299.65K | Year: 2007

DESCRIPTION (provided by applicant): We propose, using a high-sensitivity MagArray DNA detection system, to develop a rapid assay for infectious disease pathogens. In particular we will develop an assay for a large number of HPV genotypes using the MagArray platform. The viral origin of cervical cancer is now well established. Recent studies have shown that Human Papilloma Virus (HPV) DNA can be found in 99.7% of all cervical carcinomas. Because different HPV subtypes carry different risks for the development of cancer, a detection method that can distinguish subtypes could guide clinical care and offer new epidemiological insights. Current detection methods are limited to genotyping 30-35 of the more than 100 HPV types, and this is most often done by PCR. Detection, genotyping and analysis of broad spectrum of HPVs using a small amount of DNA that can be extracted from clinical samples would represent significant progress. Here we propose to adapt the MagArray platform to detect a broad spectrum (all types) of HPVs. The MagArray platform is based on using magnetic nanoparticles to tag the target fragments, rather than fluorescent molecules, as is the present practice. The advantage of using magnetic nanoparticles (typically 15 nm in diameter) as tags rather than fluorescent molecules is an enormous increase in sensitivity. With fluorescent labeling, one typically needs 100,000 fluorescently labeled molecules to obtain a signal/noise ratio adequate for reliable identification. MagArray technology will serve as a sensitive, specific diagnostic tool to detect multiple HPV types. In the first year feasibility studies will be performed for the high-risk genotypes HPV-16 and HPV-18 associated with cervical cancer. In the second year, we will determine the sensitivity and selectivity of at least 20 HPV types with a single sample, representing a large portion of the known types, most of which are strongly associated with anogenital and oral cancers. All these HPV types will be detected in a single experiment. This will reduce the cost, the time required for typing, and the amount of DNA sample required on a per-type basis. The application and development of MagArray technology to HPV-related cancer will serve as a basis for many applications in other infectious disease and cancer research and related clinical management. This technology has the potential to be integrated in a compact device that is simple and easy to use as a Point-of-Care system for molecular diagnostic applications.

Provided are high-throughput detection systems. The systems include a magnetic sensor device, a magnetic field source and a reservoir plate that includes a plurality of fluid reservoirs. The magnetic sensor device includes a support with two or more elongated regions each having a magnetic sensor array disposed at a distal end. Also provided are methods in which the subject high-throughput detection systems find use.

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