Magnetoresistive sensors and magnetic nanoparticles for biotechnology
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Magnetoresistive sensors and magnetic nanoparticles for biotechnology Guenter Reiss,a) Hubert Brueckl, Andreas Huetten, Joerg Schotter, Monika Brzeska, Michael Panhorst, and Daniela Sudfeld Department of Physics, University of Bielefeld, 33501 Bielefeld, Germany
Anke Becker, Paul B. Kamp, and Alfred Puehler Department of Biology, University of Bielefeld, 33501 Bielefeld, Germany
Klaus Wojczykowski and Peter Jutzi Department of Chemistry, University of Bielefeld, 33501 Bielefeld, Germany (Received 3 June 2005; accepted 18 August 2005)
Magnetoresistive biosensors use a new detection method for molecular recognition reactions based on two recently developed techniques and devices: Magnetic markers and XMR sensors, where XMR means either giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR). The markers are specifically attached to the target molecules, and their magnetic stray field is picked up by an embedded magnetoresistive sensor as a change of the electrical resistance. Compared to established, e.g., fluorescent, detection methods, magnetic biosensors have a number of advantages, including low molecular detection limits, flexibility, and the direct availability of an electronic signal suitable for further automated analysis. This makes them a promising choice for the detection units of future widespread and easy-to-use lab-on-a-chip systems or biochips. In this article, we discuss recent advances in this field and compare possible approaches toward single molecule detection. I. INTRODUCTION
Magnetic biosensors were made possible by the fast development of devices based on physical effects that relate an electrical resistance directly to an external magnetic field, namely the giant magnetoresistance (GMR) and the tunneling magnetoresistance (TMR) effect in ultrathin multilayered film stacks. These effects have been intensively explored within the field of magneto- and spinelectronics. Due to their direct translation of magnetization directions into resistance changes and their scalable size, which is also compatible with standard complementary metal oxide semiconductor (CMOS) processing, magnetoresistive devices experienced a great boost within the last decade. Both the measurement technique using XMR sensors (meaning either GMR or TMR) as and new developments in the preparation of magnetic carriers are discussed here. Different configurations are discussed, and the results for GMR sensors are compared to an analysis of the same biological systems marked with fluorescent a)
Address all correspondence to this author. e-mail: [email protected] This paper was selected as the Outstanding Meeting Paper for the 2004 MRS Fall Meeting Symposium I Proceedings, Vol. 853E. DOI: 10.1557/JMR.2005.0409 3294
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J. Mater. Res., Vol. 20, No. 12, Dec 2005 Downloaded: 04 Dec 2014
dyes. Down to a concentration of about 10 pg/l of DNA molecules, for example, the magnetoresistive technique is competitive with current standard analysis methods. Additionally, the capability of
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