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Separation techniques are those that are able to isolate a specific substance from a complex sample, traditionally done through processes that rely on the size, shape, and/or weight of a molecule or compound. Biomolecular separation techniques, sometimes termed cell sorting methods, have become increasingly useful in advancing research and development, biomedical, and pharmaceutical applications. In cell sorting, target biomolecules, like proteins, antigens, and nucleic acids, can be selectively segregated from a heterogeneous solution of biomaterial, like blood,  homogenized tissue, food, water, and soil.

Unlike traditional systems, novel Magnetic Beads Separation techniques employ magnetic forces and chemical binding affinity to separate and purify these target molecules from a sample solution. Magnetic Beads Separation offers many benefits over conventional separation techniques, including increased automation capabilities and the ability to streamline processes to provide reproducibility consistent results. Magnetic Beads Separation is a multifaceted technique, and has numerous capabilities across the life sciences. Just a few of these applications are listed below. 

Immunoassays and Molecular Diagnostics

Applications of Magnetic Bead Separation_Immunoassays and Molecular Diagnostics

Magnetic Beads Separation has also found use in advancing immunoassays, where magnetic beads are biofunctionalized with an antibody, antigen, or streptavidin to attract a specific target with an incredibly high affinity. Commonly, immunoassays that use Magnetic Beads Separation utilize chemiluminescence techniques to detect and quantitate  specific analytes within a sample. In experimentation, the light emitted from the chemiluminescent reaction can be measured using an appropriate instrument like a luminometer. Due to their high stability, precision, and remarkable linearity, chemiluminescent Magnetic Beads Separation techniques have found much use in molecular diagnostics. For example, in clinical laboratories these techniques are often used to detect biomarkers, like hormones, antibodies, or other infectious agents. Methods are also used to quickly and reliably diagnose clinical conditions like cancer, viral or bacterial infections, and autoimmune diseases.

Alternatively, immunoassay magnetic bead-based systems can also use photo-multipliers and/or optical detector technologies instead of chemiluminescence. For example, flow cytometers have widely been explored for Magnetic Beads Separation immunoassays. These systems can provide rapid and reliable cell counting capabilities that are coupled to delicate optical components like focused laser beams and optical detection and/or filtering devices. Some research has even built further on magnetic bead separation-based microfluidic technologies, integrating  real-time optical detection modules to rapidly analyze targeted antibodies within a sample that can provide an accurate diagnosis for various diseases.

Free PDF guide: "Biofunctionalization of magnetic beads in CLIA"

Cell Separation

One particularly useful application of Magnetic Bead Separation is geared towards separating specific cells from a complex biological solution by targeting their unique cell surface markers. Like other methods, cells can be stained with biotinylated antibodies or fluorochrome-conjugates, then magnetically separated and analyzed through various techniques like fluorescence microscopy, flow cytometry, or fluorescence-activated cell sorting. Magnetic bead cell separation is versatile, and can be used in positive or negative assays, or for cell depletion efforts. The key difference between positive and negative selection is quite simple. In positive cell separation, magnetically-labeled cells of interest are immobilized within a vessel or on a solid support until the supernatant is discarded, and they are removed from the electromagnetic field. In negative cell separation, target cells are located in the supernatant and non-target components of the sample are attracted to the electromagnetic field. Comparatively, in cell depletion techniques cell-specific magnetic beads separate specific unwanted cell types from the sample. Cell depletion using Magnetic Bead Separation is particularly useful for serological samples, where for example red blood cells or T-cells should be preliminarily removed from a sample to simplify the detection of other more scarce cellular components.

Nucleic Acids Capture

Applications of Magnetic Bead Separation_nucleic acids capture

Before modern Magnetic Bead Separation, nucleic acid isolation and purification was limited to time consuming, work intensive processes, not well suited for automation or up-scaling. For example, phenol-chloroform extraction,  salting out methods, and silica-gel membrane adsorption techniques require several extraction and centrifugation steps and are severely hindered by small yields with low purities of products. In Magnetic Beads Separation, magnetic beads can be coated with carboxyl molecules that provide charged groups that attract nucleic acids. If preferred, silica coated magnetic beads can be used that depend on the attractive interactions between the DNA phosphate and surface silanol groups on the beads. Similarly, oligo coated magnetic beads can be used for mRNA extraction, as well as other experiments like real-time polymerase chain reaction (RT-PCR), and RNA sequencing.

Protein Purification

Applications of Magnetic Bead Separation_protein purification

Conventional protein or peptide purification done through column chromatography is a tedious process. It includes multiple handling steps, a complicated experimental setup, and generally takes over an hour to complete. In comparison, protein purification using Magnetic Beads Separation requires minimal handling steps, can occur in just a single test tube or vessel, and the entire process happens in a matter of minutes (if not, seconds). Using Magnetic Bead Separation, it is even possible to purify proteins from sample solutions of any consistency, from very thick to very diluted. Magnetic Beads Separation is also an increasingly gentle process, and will not fracture large protein and peptide complexes that may be vulnerable to damage  in column chromatography. 

In conclusion, Magnetic Beads Separation has been a boon to biotech and biomedical industries, used widely across clinical and pharmaceutical applications. Magnetic Beads Separation offers a time efficient, cost effectiveness, and an uncomplicated method of isolating and purifying proteins, peptides, nucleic acids, and antigens from a complicated sample. 

If interested in learning more about Magnetic Beads Separation, check this free eBook:

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Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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