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Lab-on-a-Chip Magneto-Immunoassays: How to Ensure Contact between Superparamagnetic Beads and the Sensor Surface.

Eickenberg B, Meyer J, Helmich L, Kappe D, Auge A, Weddemann A, Wittbracht F, Hütten A - Biosensors (Basel) (2013)

Bottom Line: Different solutions, employing magnetic forces, ultrasonic standing waves, or hydrodynamic effects have been found over the past decades.This concept is based on the granular giant magnetoresistance (GMR) effect that can be found in gels containing magnetic nanoparticles.The proposed design could be realized in the shape of paper-based test strips printed with gel-based GMR sensors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. beickenb@physik.uni-bielefeld.de.

ABSTRACT
Lab-on-a-chip immuno assays utilizing superparamagnetic beads as labels suffer from the fact that the majority of beads pass the sensing area without contacting the sensor surface. Different solutions, employing magnetic forces, ultrasonic standing waves, or hydrodynamic effects have been found over the past decades. The first category uses magnetic forces, created by on-chip conducting lines to attract beads towards the sensor surface. Modifications of the magnetic landscape allow for additional transport and separation of different bead species. The hydrodynamic approach uses changes in the channel geometry to enhance the capture volume. In acoustofluidics, ultrasonic standing waves force µm-sized particles onto a surface through radiation forces. As these approaches have their disadvantages, a new sensor concept that circumvents these problems is suggested. This concept is based on the granular giant magnetoresistance (GMR) effect that can be found in gels containing magnetic nanoparticles. The proposed design could be realized in the shape of paper-based test strips printed with gel-based GMR sensors.

No MeSH data available.


Related in: MedlinePlus

The GMR measurement of a granular system consisting of Co nanoparticles embedded in a gel matrix at room temperature and the corresponding AGM measurement are displayed. The measurement during increasing magnetic field is indicated by the solid- and the measurement during decreasing magnetic field by the dashed line.
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biosensors-03-00327-f007: The GMR measurement of a granular system consisting of Co nanoparticles embedded in a gel matrix at room temperature and the corresponding AGM measurement are displayed. The measurement during increasing magnetic field is indicated by the solid- and the measurement during decreasing magnetic field by the dashed line.

Mentions: However, GMR sensors require well defined surfaces and well controlled lithography. They need to be integrated into a µTAS structure, including microfluidic pumps for low flow velocities. This increases production costs for the chips, often preventing a successful market introduction. However, newly developed printing methods employing GMR ink could change that [23]. As an alternative to GMR ink, granular GMR sensors [59] in the form of GMR gels could be utilized. They are based on the granular GMR effect that was reported in systems consisting of fm granules in metallic matrices [60,61]. Contrary to previous granular systems prepared by sputtering or metallurgical procedures, magnetic nanoparticles can also be integrated into conductive nonmagnetic gel matrices, e.g. salt-containing biogels. For Co nanoparticles, magneto-transport measurements at room temperature revealed GMR effects of more than 200% (see Figure 7), which is far above the values known from common systems [62,63,64]. Regarding technological relevance, this results in enhanced sensor sensitivity.


Lab-on-a-Chip Magneto-Immunoassays: How to Ensure Contact between Superparamagnetic Beads and the Sensor Surface.

Eickenberg B, Meyer J, Helmich L, Kappe D, Auge A, Weddemann A, Wittbracht F, Hütten A - Biosensors (Basel) (2013)

The GMR measurement of a granular system consisting of Co nanoparticles embedded in a gel matrix at room temperature and the corresponding AGM measurement are displayed. The measurement during increasing magnetic field is indicated by the solid- and the measurement during decreasing magnetic field by the dashed line.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4263578&req=5

biosensors-03-00327-f007: The GMR measurement of a granular system consisting of Co nanoparticles embedded in a gel matrix at room temperature and the corresponding AGM measurement are displayed. The measurement during increasing magnetic field is indicated by the solid- and the measurement during decreasing magnetic field by the dashed line.
Mentions: However, GMR sensors require well defined surfaces and well controlled lithography. They need to be integrated into a µTAS structure, including microfluidic pumps for low flow velocities. This increases production costs for the chips, often preventing a successful market introduction. However, newly developed printing methods employing GMR ink could change that [23]. As an alternative to GMR ink, granular GMR sensors [59] in the form of GMR gels could be utilized. They are based on the granular GMR effect that was reported in systems consisting of fm granules in metallic matrices [60,61]. Contrary to previous granular systems prepared by sputtering or metallurgical procedures, magnetic nanoparticles can also be integrated into conductive nonmagnetic gel matrices, e.g. salt-containing biogels. For Co nanoparticles, magneto-transport measurements at room temperature revealed GMR effects of more than 200% (see Figure 7), which is far above the values known from common systems [62,63,64]. Regarding technological relevance, this results in enhanced sensor sensitivity.

Bottom Line: Different solutions, employing magnetic forces, ultrasonic standing waves, or hydrodynamic effects have been found over the past decades.This concept is based on the granular giant magnetoresistance (GMR) effect that can be found in gels containing magnetic nanoparticles.The proposed design could be realized in the shape of paper-based test strips printed with gel-based GMR sensors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Thin Films & Physics of Nanostructures, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany. beickenb@physik.uni-bielefeld.de.

ABSTRACT
Lab-on-a-chip immuno assays utilizing superparamagnetic beads as labels suffer from the fact that the majority of beads pass the sensing area without contacting the sensor surface. Different solutions, employing magnetic forces, ultrasonic standing waves, or hydrodynamic effects have been found over the past decades. The first category uses magnetic forces, created by on-chip conducting lines to attract beads towards the sensor surface. Modifications of the magnetic landscape allow for additional transport and separation of different bead species. The hydrodynamic approach uses changes in the channel geometry to enhance the capture volume. In acoustofluidics, ultrasonic standing waves force µm-sized particles onto a surface through radiation forces. As these approaches have their disadvantages, a new sensor concept that circumvents these problems is suggested. This concept is based on the granular giant magnetoresistance (GMR) effect that can be found in gels containing magnetic nanoparticles. The proposed design could be realized in the shape of paper-based test strips printed with gel-based GMR sensors.

No MeSH data available.


Related in: MedlinePlus