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  • Microspheres for Medical Devices – MDDI Magazine – January 2011

    The Microsphere of Influence

    Published: January 2011, MDDI

    Published on MDDI Magazine
    By: Yelena Lipovetskaya

    Find more content on: Feature, Nano and Microtechnology, Technology, Testing and Inspection

    Microspheres come in many different grades and sizes, and are usually solid particles that are composed of polymers, glass, and ceramics. All images courtesy of COSPHERIC LLC

    Microspheres are round microparticles that typically range from 1 to 1000 μm in diameter. In the pharmaceutical and cosmetics industry, microspheres are well known for their ability to deliver active materials. This process usually involves the microencapsulation of a drug or an active cosmetic ingredient to protect it from the deteriorating effects of the environment or for optimal release and performance in the final product. Active ingredients are released by dissolution of the capsule walls, mechanical rupture (rubbing, pressure, or impact), melting, or digestion processes. Solid microspheres are widely used as fillers and spacers in a variety of industries.

    Microspheres used to manufacture and test medical devices are typically solid particles that are made from robust and stable raw materials such as polymers, glass, and in some cases, ceramics. Different types and grades of microspheres are available and selected based on specific application requirements.

    They are often used as tracers and challenge particles in medical devices. In these situations, it is beneficial to use larger microspheres with sphere diameters greater than 50 μm that are vividly colored (red, blue, black, yellow, or green), since they provide contrast with the background material and visibility to the naked eye in daylight. Colored microspheres are typically used in the testing of filtration media and systems, vial and container cleaning evaluations, flow tracing and fluid mechanics, centrifugation and sedimentation processes, pharmaceutical manufacturing, and contamination control.

    Fluorescent microspheres are recommended for applications that require the use of particles that emit distinctive colors when illuminated by UV light and offer additional sensitivity for observation through the use of microscopes, lasers, and other analytical methods. Examples include microcirculation and biological research, imaging, and flow cytometry. Fluorescent microspheres can be excited and detected by a wide range of methods and are useful as experimental particles for acoustical and optical analytical systems.

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  • ParaMagnetic Microspheres

    Paramagnetic microspheres have the ability to increase in magnetization with an applied magnetic field and loose their magnetism when the field is removed. Neither hysteresis nor residual magnetization is observed and that provides the end use two very practical advantages:

    • When the filed is removed, the microspheres demagnetize and re-disperse easily. This property allows efficient washing steps, low background and good reproducibility.
    • The behavior of the microspheres is always the same whatever the magnetization cycles may be. Such behavior is a key point for automated instrument.
    Black Paramagnetic Microspheres

    106-125um Magnetic Microspheres

    Recently black paramagnetic microspheres have been produced in larger sizes of 10 micron to 1mm (1000um) and in dry form enabling scientists to leverage the benefits of paramagnetic particles in new applications. These highly spherical polyethylene microspheres offer the flow-ability of standard microspheres, with the ability to be separated from other materials for re-use and cleanup.

    One use of paramagnetic microspheres as large as 1mm in diameter to simulate salmon eggs, Scientists are able to place them in a natural habitat, observe how they move with the water currents and then use their magnetic properties to clean them up.

    SuperParamagnetic microspheres, sometimes just called magnetic microspheres or paramagnetic microspheres have become widely used in the life sciences industry (<10um diameters) for applications such as:

    • Solid Phase Immunoassays
    • Bacteria Detection
    • High Throughput screening
    • Rapid Tests
    • Cell Sorting
    • Biosensors
    • Nucleic Acids Technology
    • Microfluidics1

    Super paramagnetic microspheres used in the life science industry are supplied in solution form.

    1. Merck Estapor Super Paramagnetic Microspheres Brochure