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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

Schematic drawing of the geometry of the ramp structure designed by Weddemann et al. [46]. A rectangular microfluidic channel of height h1 and width a1 changes over a length l into a rectangular channel of height h2 and width a2. Particle targets, e.g., a coated sensor array, are placed in the section of decreasing height (ramp). Reproduced with permission from [46].
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biosensors-03-00327-f003: Schematic drawing of the geometry of the ramp structure designed by Weddemann et al. [46]. A rectangular microfluidic channel of height h1 and width a1 changes over a length l into a rectangular channel of height h2 and width a2. Particle targets, e.g., a coated sensor array, are placed in the section of decreasing height (ramp). Reproduced with permission from [46].

Mentions: Instead of employing magnetic fields to draw beads to the sensor surface, hydrodynamic effects caused by variations in the channel geometry can be utilized to support the bead capture process. Weddemann et al. [46,47] calculated concentration profiles for bead flows through a rectangular channel, like the one shown in Figure 3. Over length l the channel’s height drops from h1 to h2 and broadens in width from a1 to a2, forming a ramp-like structure.


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)

Schematic drawing of the geometry of the ramp structure designed by Weddemann et al. [46]. A rectangular microfluidic channel of height h1 and width a1 changes over a length l into a rectangular channel of height h2 and width a2. Particle targets, e.g., a coated sensor array, are placed in the section of decreasing height (ramp). Reproduced with permission from [46].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

biosensors-03-00327-f003: Schematic drawing of the geometry of the ramp structure designed by Weddemann et al. [46]. A rectangular microfluidic channel of height h1 and width a1 changes over a length l into a rectangular channel of height h2 and width a2. Particle targets, e.g., a coated sensor array, are placed in the section of decreasing height (ramp). Reproduced with permission from [46].
Mentions: Instead of employing magnetic fields to draw beads to the sensor surface, hydrodynamic effects caused by variations in the channel geometry can be utilized to support the bead capture process. Weddemann et al. [46,47] calculated concentration profiles for bead flows through a rectangular channel, like the one shown in Figure 3. Over length l the channel’s height drops from h1 to h2 and broadens in width from a1 to a2, forming a ramp-like structure.

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