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Jul 1, 2009 (Vol. 29, No. 13)

Meeting Biomagnetic Separation Needs

New Coatings, Beads, Kits, and Customized Products Expedite Research

  • Researchers’ needs are driving advances in the biomagnetic separations market. Recognizing that binding capacity is one of the key criteria scientists use when choosing particles, Thermo Scientific launched SeraMag® SpeedBead™ streptavidin-blocked particles this month. This bead offers many of the same qualities as the SeraMag particles, but magnetic response time occurs at least two times faster, reports Aaron Craig, marketing communications specialist.

    This faster response means that clinical diagnostics assays can be performed more quickly, and that particles move more quickly through viscous solutions in molecular biology, he adds. The more rapid response time is partially attributed to the greater quantity of magnetite that is added, essentially by encapsulating the original SeraMag particle with a second layer of magnetite and a surface coating.

    “These beads offer medium- to high-binding capacities, up to 55 micrograms of biotinylated IgG,” Craig says.

    The greatest value of the newest addition to the SpeedBead family, however, may be the particles’ ability to reduce nonspecific binding, which yields more accurate assays.

    As Craig explains, nonspecific binding of lipids, proteins, etc. can interfere with assay precision and reliability. The streptavidin-blocked particles have a new surface treatment that reduces the tendency for undesired entities bind to the bead.  Blocked beads minimize nonspecific binding in many applications while maintaining their specific biotin binding capacity.

    SpeedBeads are 1 micron in diameter, and so have a slow settling rate minus the magnetic field, Craig says. These superparamagnetic beads are surfactant free and can be sonicated. They are encapsulated, so no iron is exposed.

    Craig says the industry is subtly changing, as researchers gravitate toward kits. “Kits save time for our customers.” The Seradyn division of Thermo Fisher Scientific also develops custom beads. In that segment of the market, he says he is seeing interest in enzymatic coatings.

  • Stem Cell Separation

    Click Image To Enlarge +
    Dynabeads® are superparamagnetic, monosized polymer beads.

    Invitrogen, a division of Life Technologies, launched Dynabeads® SSEA-4 last month to separate undifferentiated stem cells from differentiated cells. “SSEA-4 is a well-known marker for ESCs,” according to Paul Pickering, Ph.D., GM of Invitrogen Cell Therapy Systems. “One of the principle objectives of this is to address a need identified by the translational research community.”

    In embryonic stem cell work, Dr. Pickering explains, the propensity of cells to self-replicate is “helpful in generating enough cells to be useful in clinical applications.” But, he adds, that capability can be dangerous if those cells remain among the final, differentiated cells used for therapy. Working with the Buck Institute for Age Research, scientists found these Dynabeads bind more than 99% of the undifferentiated human ESCs. Removing those cells allows researchers to work with more homogenous—and more stable—cell populations, which are better for transplantation. 

    Invitrogen also recently introduced the Dynal Dynabeads® FlowComp™ Human NKp46 kit and the FlowComp™ Mouse CD49b kit, both of which use positive isolation and tube-based separation for bead-free cells. The Dynabeads® Mouse CD43 (Untouched™ B cells) kit uses negative isolation, leaving the mouse B cells in the sample, untouched by the Dynabeads.


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