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Jul 1, 2008 (Vol. 28, No. 13)

Biomagnetic Separations See Increased Use

Manufacturers Are Rendering This Versatile Technology More Widely Available

  • Biomagnetic separations are expanding into nontraditional fields including neurology and proteomics as new disciplines discover the availability of gentle ways to separate cells and even classes of cells. It seems that many people who have never used magnetic separation are now considering this technology. To further boost utility, manufacturers are developing new ways to maximize biomagnetic separations’ potential.

    As Sandrine Godichaud, product manager, Ademtech (www.ademtech.com), points out, “Magnetic particles are a powerful and versatile diagnostic tool and are particularly indicated for use in a number of clinical research applications such as microbiology, immunology, proteomics, molecular biology, drug discovery, and cancer research.

    “Magnetic nanoparticles provide interesting perspectives for realizing novel diagnostic sensors because they allow the detection of magnetic particles specifically bound to the biological target at low concentration. The nature of the magnetic nanoparticles plays a crucial role in developing a sensitive and specific magnetic sensor.” With such benefits, it’s no wonder companies are expanding their uses.

    Automation is entering the field of biomagnetic particle separations. “A lot of people have requirements for sample prep upfront, and biomagnetic separations are quite easy to automate,” notes Rick Galloway, director of particle technology at Seradyn (www.thermo.com/seradyn), a subsidiary of Thermo Fisher. Likewise, “new application fields are exploding,” he says.

    Proteomics is an intense area of research as scientists drill deeper and deeper to identify proteins or groups of proteins that indicate a disease state or disease predisposition. “Some of these proteins are present in extremely small quantities,” Galloway notes. So, considering that human blood contains hundreds of thousands of proteins, mass spectrometry—the traditional quantification method—is impractical. Instead, by applying biomagnetic separation upstream, mass spec analysis is improved by allowing it to focus on the proteins of interest.”

    Nonspecific binding is a universal problem for biomagnetic separations, Galloway says, and Thermo Fisher has next-stage products in development to minimize nonspecific binding. Thermo’s strategy involves the particle itself.

    Rather than making a coated particle that binds to a specific target and then adding a compound to block nonspecific binding, we’re doing the reverse—making a blocked particle and then making it target specific,” he remarks.

    ThermoFisher is also developing surface coatings specific to various classes of targets rather than to specific targets themselves. For example, Galloway says, the particle coating may bind all phosphopeptides in the solution, which would benefit sample prep for mass spec.

  • Fluorescent Beads

    The need for compromise between affinity and specificity is also diminishing. “The technology has advanced far enough so that magnetic beads must perform under a broad range of conditions,” notes Chad Owen, vp, Bangs Laboratories (www.bangslabs.com), which is owned by Polysciences (www.polysciences.com). So, for example, the same streptavidin-coated bead would perform well for virtually any assay appropriate to this coating, he says.

    At Bangs, Owen reports a strong and growing interest in using biomagnetic microspheres. Using fluorescent magnetic beads for flow cytometry applications fulfills requirements related to fluorescence while permitting easy, efficient magnetic separations. “Not all researchers know they’re available,” Owen says, so creating awareness is a challenge. That may change now that the fluorescent beads are available on a commercial scale.

    Another area gaining attention is proteomics, in which microbeads can replace traditional column-based separation. Polysciences’ high-capacity WGA (wheat germ agglutinin) kit, based on its BioMag® bead, is an item of interest for removing glycan-presenting cells and glycoproteins.

    There’s also continual growth in diagnostics, using Polysciences’ProMag™ line, Owen says. To support this, Polysciences now has a 1 micron ProMag bead in stability testing. It provides more surface area per weight than the company’s popular 3 micron ProMag beads, making it advantageous in nucleic acid-based diagnostics and separations, Owens explains. “The challenge,” he says, “is that smaller beads require a higher percentage of magnetite than larger beads, so their density increases.” Bangs is looking at various forms of magnetic material to achieve the optimum balance between density and magnetic properties.

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