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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

  • Raising Awareness

    Miltenyi Biotec(www.miltenyibiotec.com) is expanding its core product offerings for immunologists. In fact, multiple kits have been released virtually every month for the past year. “We’re a science-driven organization,” points out Kirt Braun, Ph.D., marketing manager. “As scientists tease apart the mechanics of the immune system, they come across cell subtypes of interest,” for which biomagnetic separation makes sense, particularly when viewed against traditional flow cytometry, which can be cumbersome and may have a negative impact on individual cells.

    Biomagnetic separations and their streamlined workflow, however, are new to many researchers outside the world of immunology. “Awareness is the big challenge,” Dr. Braun says. Researchers often are astounded that biomagnetic separations can be used in their own particular fields.

    “Therefore,” Dr. Braun reports, “Miltenyi is extending its reach to new markets. Neural cell isolation, for instance, has undergone a revolution. Researchers are interested in isolating specific cell populations within the brain much faster and more reliably than with selection by culture. So, we offer a complete workflow solution in the form of kits to dissociate the neural tissues and cells into viable, single-cell suspensions.”

    Miltenyi released kits utilizing trypsin or papain, plus the automated gentleMACS™ Dissociator for mouse, rat, and human tissue. The technology can also be used for spleen and liver tissue, with protocols for lung and tumor tissue on the horizon. Miltenyi has also a growing portfolio of MicroBeads to isolate neural cell subsets, such as anti-PSA-NCAM MicroBeads to isolate neuronal restricted precursors and anti-A2B5 MicroBeads and antibodies for the positive selection and analysis of glial-restricted precursor cells.

    The focus in stem cell research is continuing, as the demand for supplies to support it is growing at 10% or more per year, according to Dr. Braun. Miltenyi recently released anti-Prominin-1 MicroBeads and antibodies to isolate and analyze mouse neural stem and progenitor cells and the CD146 MicroBead Kit to isolate human mesenchymal stem cells from lipoaspirates and other tissue sources.

    “An increasing numbers of scientists are focusing on the T-cell regulatory pathways, as this pathway is of great importance to better understanding and modulating autoimmune disease,” Dr. Braun continues. Miltenyi’s portfolio of products for the study of T cells and T regs now includes a kit for the isolation of a new T-cell subset, characterized as CD4+CD25+ and CD127dim, which helps researchers focus their efforts and drill down through the immune system to better understand its regulation and thus certain disease mechanisms.

    The MACS® Cytokine Secretion Assay (CSA) technology will also continue to expand to encompass a greater variety of the cells involved in regulating the immune system. “Miltenyi’s CSA products isolate antigen-specific cells. In the next few months, new CSA kits will be released that will enable researchers to isolate antigen-specific cells based on the secretion of interferon alpha as well as interleukin 17,” Dr. Braun adds.

    At Invitrogen Dynal (www.invitrogen.com/dynal), applications for Dynabeads Protein A and Dynabeads® Protein G have expanded into immunoprecipitation. “As a response to the increased interest in immunoprecipitation (IP), co-IP, chip and other pull-downs, we will be launching dedicated kits for immunoprecipitation this fall,” according to Haege Wetterhus, business segment director, molecular separations.

    “Another hot topic is sample preparation for peptide profiling. Processes for sample collection, preparation, and analysis are being standardized in biomarker discovery and in clinical proteomics. The Dynabeads for magnetic bead-based chromatography were launched to meet the need for pre-massSpec sample prep. We will be expanding this product range even further in the future,” Wetterhus says.

    Invitrogen Dynal is seeing a trend to use primary cells to create studies that more closely resemble in vivo studies. The aim is to remove outside influences. Positive cell isolation allows direct pullout—a benefit of the FlowComp™ product line—thus removing the risk of contamination with iron, dextran, or other potentially harmful structures. Because positive cell isolation has minimal impact on cells, they maintain functional characteristics and are suitable for all downstream applications,” notes Øystein Aamellem, Ph.D., business segment director, cell separation and expansion.

    The FlowComp product line was launched last summer with human and mouse CD4 and CD8 specific cell isolation. The product line has since been extended with Dynabeads FlowComp Flexi and Dynabeads FlowComp Human NKp46, Aamellem says. Two more FlowComp products were slated for launch last month—Dynabeads FlowComp Mouse CD49b (+mouse NK cells) and Dynabeads FlowComp Mouse CD4+CD25+ T reg Cells (+mouse regulatory T cells).

    The Dynabeads negative isolation kits are being rebranded as the Dynabeads Untouched™ line and are being reformatted to double the isolation capacity. The reformatted human CD4 kit launched in March with greater than 90% purity, 70% average recovery, and about 98% viability, Aamellem reports. The CD8 kit launched at the same time and the human T-cells kit launched last month.

    “Dynabeads T-cell expansion products allow activation and/or expansion of naive and memory T cells, T-cell clones, regulatory T cells, NKT cells, and CTLs from mouse and human samples,” Aamellem adds. Originally developed for immunotherapeutics, they are being used in the clinical trial arena and in the clinic to standardize blood cell assays. Blood cell separation has been a major barrier in improving high-throughput screening and developing standardized blood cell assays and other clinical diagnostics.

    Ademtech is optimizing the key parameters of beads for biosensor applications. For example, if the magnetic core’s iron content exceeds 70%, detection is enhanced. A homogenous, smooth surface reduces nonspecific binding and the uniform, nanometric bead size decreases particle sedimentation rates while increasing specific surface area.

    These magnetic nanoparticles range in size from 100 to 500 nm, with surfaces that include COOH, NH2, streptavidin, and silica “to comply with biosensors development requirements,” Godichaud explains. “We have developed magnetic beads that have a specific surface polymer designed for DNA capture by electrostatic interactions and compatible with direct PCR and real-time PCR without the need to perform an elution step.”

    Recent additions to Ademtech’s product family include Bio-Adembeads Streptavidin plus two levels of biotin-binding capacities for 200 and 300 nm particles, and a new streptavidin 100 nm particle.

  • Need Drives Automation

    Dexter Magnetic Technologies (www.dextermag.com) has focused on separation equipment, betting that “future growth is in automated particle separation equipment,” according to Doug Hartl, business manager for medical and LifeSep products. The attention to automation is driven by the “need for high-throughput analysis, the demand for new drug development, and the demand for higher testing volumes in the diagnostic arena,” he says.

    Much of Dexter’s work, Hartl states, is with diagnostic equipment manufacturers, providing custom-engineered design assistance on such aspects as sophisticated magnetic particle separation subsystems. Some requests, for example, are for systems that perform separations at specific rates and for systems in which the magnetic beads are placed at specific positions in a tube or vessel. Depending upon the machine, he explains, flow-through separation may be beneficial, or the client may prefer particles to be placed on a specific position within a vessel.

    “Customers are looking for ways to manipulate magnetic particles to advance innovation,” he adds. Ongoing improvements in magnetic properties make miniaturization possible, so researchers may achieve more efficient results using less magnetic material.

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