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Application Notes
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MagSIGNAL beads consist of many ferromagnetic grains with random oriented magnetic moments, encapsulated in a non-magnetic silica shell. The size of the ferromagnetic grains is 10-15 nm. Due to the small size and random orientation of the magnetic moments, the beads behave superparamagnetically and the magnetic moment without a magnetic field is 0 (demonstrated in figure 1 below).
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Comment
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Magnetic immunoassays (MIA) use magnetic beads as labels instead of conventional enzymes (ELISA), fluorophores or luminescent molecules. These assays involve the specific binding of an antibody with a conjugated magnetic label to its antigen. The presence of magnetic beads is then detected by a magnetic reader (magnetometer) which measures the magnetic field change induced by the beads. The signal measured by the magnetometer is proportional to the analyte (virus, toxin, bacteria, cardiac marker,etc.) quantity in the initial sample.
Magnetic beads are not affected by reagent chemistry or photobleaching and are therefore stable over time. Because measurements are based on nonlinear magnetic signals, the contribution of linear magnetic signals from materials such as sample matrix and consumables are eliminated. The technology makes magnetic immunoassays possible in a variety of formats such as conventional lateral flow test (replacing gold labels with magnetic labels), microfluidic applications and biochips.
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Protocol
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MagSIGNAL are superparamagnetic beads with a mean diameter of 300 nm, which can be used as a detection label in magnetic immunoassays, or as solid support phase in immunoassays with other readout techniques.
MagSIGNAL-STA 300 is coated with streptavidin and is intended for use with biotinylated antibodies. Binding of molecules onto MagSIGNAL-STA 300 is based on the strong non-covalent interaction between streptavidin and biotin (Ka = 1015 M-1). Biotin is easily conjugated to various molecules and inexpensive biotinylated products are sold by many companies. MagSIGNAL-STA beads are coated with recombinant streptavidin (53 kDa) with shortened N- and C-terminus for improved solubility and accessibility of the sites. Albumin s are eliminated for optimal specificity.
Magnetic content: 90%
Density: 2.5 g/cm3
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Reagent Preparation
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Immobilization Buffer: 0.01M Phosphate Buffered Saline (PBS) pH 7.4
Washing Buffer: PBS pH 7.4 with 0.05 % Tween 20
Resuspension Buffer: PBS pH 7.4 with 0.05 % Tween 20, 0.05 %
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Assay Procedure
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Immobilization protocol
The following protocol describes the immobilization of biotinylated molecules on 1 mL (10 mg) beads. It can be scaled up by adjusting volumes of required reagents.
1.Resuspend MagSIGNAL-STA 300 by vortexing. Transfer 1 mL from the storage bottle to a reaction container.
2.Prepare the beads:Place the reaction container in a magnetic separator and wait until the separation is completed. Discard the buffer and resuspend in 1 mL Immobilization buffer. Repeat this step once more.
3.Add biotinylated molecules to the beads and add Immobilization Buffer to a final volume of 1 mL. Incubate the beads on a shaker for 30 minutes at room temperature.
4.Place the reaction container in a magnetic separator, wait until the separation is completed, and discard the supernatant.
5.Wash the beads 3 x with 1 mL Washing Buffer.
6.Finally resuspend the beads in 1 mL Resuspension Buffer and store at 2-8 °C.
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Restrictions
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For Research Use only
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