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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

Edge of the ultrasound field that Hawkes et al. [51] used to deposit bacteria spores on a functionalized surface. A clear distinction between the deposition area where the field is active (right) and the inactive region (left) can be seen. Reproduced with permission from [51].
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biosensors-03-00327-f005: Edge of the ultrasound field that Hawkes et al. [51] used to deposit bacteria spores on a functionalized surface. A clear distinction between the deposition area where the field is active (right) and the inactive region (left) can be seen. Reproduced with permission from [51].

Mentions: Ultrasonic standing waves constitute another way to move beads onto a sensing surface [49]. An ultrasonic actuator, e.g., a piezo ceramic, can create ultrasonic standing waves inside a microfluidic channel system. Particles inside this standing wave experience radiation forces that depend on the distance between the particle and the nearest pressure node, thus driving them towards these nodes. As the force is proportional to the particle volume, this approach works best for particles in the µm range, e.g., cells or beads. Zourob et al. [50] and Hawkes et al. [51] used this method to capture Bacillus subtilis var niger cells on an activated surface. Hawkes et al. reported an efficiency 200 times better than in the absence of the standing wave (see Figure 5). Zourob reported that 96% of the cells were successfully pushed to the surface. Glynne-Jones et al. [52] and Oberti et al. [53] achieved similar results for beads of 6 µm and 9.6 µm/26 µm diameter, respectively. Using a multi-modal approach which allowed them to switch between an attractive and a repulsive force (facing towards or from the surface), Glynne-Jones et al. were even able to remove unfunctionalized beads that were not bound to the surface. Only beads functionalized with streptavidin were left attached to the biotionylated surface. For all of the four systems, operation times were on the order of a few minutes.


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)

Edge of the ultrasound field that Hawkes et al. [51] used to deposit bacteria spores on a functionalized surface. A clear distinction between the deposition area where the field is active (right) and the inactive region (left) can be seen. Reproduced with permission from [51].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

biosensors-03-00327-f005: Edge of the ultrasound field that Hawkes et al. [51] used to deposit bacteria spores on a functionalized surface. A clear distinction between the deposition area where the field is active (right) and the inactive region (left) can be seen. Reproduced with permission from [51].
Mentions: Ultrasonic standing waves constitute another way to move beads onto a sensing surface [49]. An ultrasonic actuator, e.g., a piezo ceramic, can create ultrasonic standing waves inside a microfluidic channel system. Particles inside this standing wave experience radiation forces that depend on the distance between the particle and the nearest pressure node, thus driving them towards these nodes. As the force is proportional to the particle volume, this approach works best for particles in the µm range, e.g., cells or beads. Zourob et al. [50] and Hawkes et al. [51] used this method to capture Bacillus subtilis var niger cells on an activated surface. Hawkes et al. reported an efficiency 200 times better than in the absence of the standing wave (see Figure 5). Zourob reported that 96% of the cells were successfully pushed to the surface. Glynne-Jones et al. [52] and Oberti et al. [53] achieved similar results for beads of 6 µm and 9.6 µm/26 µm diameter, respectively. Using a multi-modal approach which allowed them to switch between an attractive and a repulsive force (facing towards or from the surface), Glynne-Jones et al. were even able to remove unfunctionalized beads that were not bound to the surface. Only beads functionalized with streptavidin were left attached to the biotionylated surface. For all of the four systems, operation times were on the order of a few minutes.

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