The Microsphere of Influence
Why Use Microspheres in Medical Devices?
Microspheres are round microparticles that typically range from 1 to 1000 micron in diameter. Benefits of microspheres in medical devices, pharmaceuticals, and cosmetics are well known due to the microspheres’ ability to encapsulate and deliver active materials. However, there are many other lesser known advantages and functionalities of using micropsheres in medical device design, quality control, manufacturing, and testing.
The typical manufacturing process 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. The resulting particles are often called microcapsules, which are different from solid, non-deformable microspheres.
Solid microspheres are widely used as fillers and spacers in a variety of industries. Microspheres that are 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.
Solid microspheres in medical devices are often used as tracers and challenge particles. In these situations, it is beneficial to use larger microspheres with sphere diameters greater than 50 micron 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.