Microbead (research)

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Microbeads are uniformly polymer particles, typically 0.5 to 500 micrometers in diameter. Bio-reactive molecules can be absorbed or incorporated onto the surface, and used to separate biological materials such as cells, proteins, or nucleic acids.

Microbeads have been used for the isolation and handling of certain materials or molecules, as well as for analyzing sensitive molecules, or those with low abundance, eg. in miniature and automatic settings.

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Microbeads were created when John Ugelstad succeeded in forming a polystyrene bead with the same ball size at the University of Trondheim, Norway in 1976. He created superparamagnetic microbeads (Dynabeads), which showed magnetic properties when placed in a magnetic field. When they are removed from the magnetic field, there is no residual magnet, which leads to the development of magnetic separation technology. Other processes such as centrifugation, filtration, columns or precipitation, are not required.

Microbeads display large surface area per volume. This along with the uniformity of size and shape provides excellent accessibility and quick liquid phase reaction kinetics, and fast and efficient binding.

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Use

Black polyethylene microspheres can have magnetic or conductive functions, and have utility in electronic devices, EMI shielding techniques and microscopy.

Polyethylene fluorescent microspheres are commonly used to run blind tests in laboratories and industrial processes, to develop appropriate methods and minimize cross-contamination of equipment and materials. Microspheres that appear invisible during the day can be illuminated to display bright fluorescent responses under UV light.

Colored polyethylene microspheres are used to visualize fluid flow to allow observation and characterization of particle flow within the device or used as markers visible in microscopy and biotechnology.

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Apps

Microbeads serve as a primary tool for bio-magnetic separation. Various patented processes and applications have been developed based on the use of microbeads in academic and industrial research. Microbeads paired with ligands; biomolecules such as antibodies, streptavidin, proteins, antigens, DNA/RNA or other molecules. There are three steps involved in the magnetic separation process:

1. Bind - Microbeads bind the desired target, relative to the ligant specific affinity on the surface of the bead.
2. Wash - Microbeads will move to the side of the tube in response to the magnetic field, along with the bonded material. This happens quickly and efficiently because of the magnetic field and the micro-sized particles. Unrestricted and undesirable substances left in the sample are removed by piping/aspiration. The bead bound material is washed using the proper buffer, by applying magnets.
3. Elute - Once the bead bound target is isolated and washed, it can be released in the proper solution and desired volume. These can then be used for any downstream application directly, or microbeads can be removed and removed.

Microbeads are used for cell isolation and cell expansion. The protein and protein complexes can be separated, eg. in the immunoprecipitation protocol. Molecular and diagnostic studies also benefit from microbeads (eg IVD immunoassay and IVD nucleic acid). When microbeads are combined with streptavidin, they offer a very efficient way to isolate each biotinylated molecule. It is often used in the study of DNA/RNA binding proteins, sequencing, and for preparing single-stranded templates. Gene expression analysis is also useful from microbeads, such as isolating mRNA for transcriptional analysis.

There are many uses for microbeads, mostly for biotechnology and biomedical research. Microbeads and magnetic separation technologies have enabled a variety of innovative methods to benefit research on disease prevention, drugs, and other fields to improve human conditions.

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See also

• Microspheres

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References

• Kemshead, JT, Ugelstad, J (1985). "Magnetic separation technique: their application for drugs", Mol Cell Biochem , 67 (1): 11-8.
• Vetvicka, V, Fornusek, L (1987). "Polymer microbeads in immunology", Biomaterials , 8 (5) 341-5.
• Arshady, R (1993). "Microspheres for biomedical applications: preparation of reactive and labeled microspheres", Biomaterials , 14 (1): 5-15.
• Fonnum, G, Johansson, C, Molteberg, A, Morup, S, Aksnes, E (2005). "Characterization of Dynabeads by magnetization measurements and MÃÆ'¶ssbauer spectroscopy", Journal of Magnetism and Magnetic Materials , 293: 41-47.

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External links

• Dynabeads

Source of the article : Wikipedia