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Jul 1, 2012 (Vol. 32, No. 13)

Biomagnetic Separation Attracting Users

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    The bumpy, cauliflower-like outer surface of Thermo Scientific’s Sera-Mag beads gives them a higher surface area-to-volume ratio for greater attachment of capture probes.

    For better or worse, the technology that performs biological measurements often takes center stage when new discoveries are reported.

    Although the measurement yields the interesting result, in many cases such a result could not have been produced without the careful sample preparation that took place beforehand. Recognizing this fact, a growing number of scientists are becoming interested in using biomagnetic separation products to perform sensitive measurements.

    Biological sample preparation may not be the most glamorous aspect of research, but scientists shouldn’t overlook its importance, says Brett R. Richards, technical account manager at Thermo Scientific. “If you don’t have good sample preparation, the rest of the experiments will suffer.”

    With the goal of developing tools for improved biological sample prep, scientists at Thermo Scientific have developed superparamagnetic beads that come prefunctionalized with antibodies and other capture probes, or present chemical functionalities for the customized attachment of antibodies, oligos, proteins, or nucleic acids.

    The newest line of magnetic bead products from Thermo Scientific, known as Sera-Mag Magnetic SpeedBeads, run as small as 1 micron in diameter and have two layers of magnetite encapsulated with a polymer, carboxylate-modified shell.

    This enables them to respond faster to a magnetic field and gives them a bumpy, cauliflower-like outer surface that provides a greater surface area for attachment of capture probes.

    Since they are superparamagnetic and highly charged, the beads have no residual magnetism outside of an applied magnetic field, resulting in less aggregation, which allows for more reproducible recovery and cleaner sample prep, Richards says.

    Using magnetic beads for biological sample preparation has certain advantages over traditional techniques such as anionic exchange columns, including ease of scalability and the absence of filters and shear forces, which can cause sample loss and degradation, he adds.

    An additional benefit of Thermo’s magnetic bead product line is that separations can be accomplished using a basic rare earth magnetic rack. Researchers interested in scaling up and automating the separations process can take advantage of magnetic particle processor instruments such as the Thermo Scientific KingFisher.

    In the future, scientists at Thermo Scientific hope to develop even smaller beads that settle out of solution less quickly and will open the way to new applications in microfluidics and point-of-care technologies, Richards says. They are also working on developing tools for performing cell separations, in conjunction with partner companies.

  • Biological Sample Prep

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    Sigma Life Science’s MISSION ExpressMag Super 96-Well Magnetic Kit allows researchers to perform high-throughput assay optimization for applications such as lentiviral transduction of cell lines.

    Scientists at Sigma Life Science are also working on magnetic beads for biological sample preparation. The beads are also about 1 micron in diameter, which customers tend to favor over larger beads since they stay in suspension longer and have better surface area to volume ratios, says John Dapron, principal scientist at Sigma Life Science.

    The beads are made of magnetite and encapsulated with a biocompatible coating, such as polystyrene or agarose. Beads are available preconjugated with capture probes, such as anti-FLAG™ or a quadridentate chelate that binds to poly-histidine-tagged proteins, or functionalized with standard bioconjugate coupling groups for custom applications.

    Sigma Life Science’s biomagnetic separations products can be used in a single tube or scaled up to accommodate 96 samples in a plate format that is compatible with liquid-handling platforms.

    Scientists at Sigma Life Science are actively working on the development of affinity-enrichment applications on even smaller beads. One of the big pushes for smaller beads, says George Lipscomb, market segment manager at Sigma Life Science, is for biological sample preparation for mass spectrometry analyses of low-abundance proteins.

    Many biomarkers are present at such low levels that mass spectrometric analysis is not possible without enrichment, Dapron says.

    Also, for diagnostic purposes, scientists need to look at multiple biomolecules in concert, Lipscomb adds. For this reason, smaller beads in conjunction with high-throughput platforms will make sample processing easier and could open the way for scientists to detect multiple low-abundance biomarkers in small volumes of biological samples.


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