Breakthrough in the development of monodisperse silica particles in the micrometer size range
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June 2005

Size distribution of nominal 6µm silica particles (5.7µm, C.V. 5 %; Coulter Multisizer II)

Breakthrough in the development of monodisperse silica particles in the micrometer size range

The present difficulties in synthesis of monodisperse silica particles in the size region above 1.5 µm are dumbbell formation, irregular particle morphology, broad size distributions, low yields, and process complexity. Scientists at microParticles GmbH succeeded in developing high-quality silica particles with particle diameters from 2 µm up to currently nominal 7 µm. The new processes are based on a modified sol-gel technique. The yielded particles possess the following features:

  • Narrow particle size distributions (C.V. values ca. 5 %).
  • Absolutely spherical shape (no formation of dumbbells or irregular particles).
  • Non-porous, smooth surfaces.
  • Density 1,85 g/cm3.
  • Refractive index 1,42.

    The Silica-particles come as 5 wt.-% aqueous dispersions or in dry powder form. They can be used in a variety of applications like nucleic acid isolation, biomolecule purification, and particle-based immunoassays.

    • April 2005

    microParticles GmbH guarantees high quality standards to its customers

    Quality and customer satisfaction take a central place within microParticles' GmbH policy. They ensure competitiveness of products and service as well as the continued economic success of our firm.
    This was confirmed by TÜV Rheinland Berlin Brandenburg after completing the second control audit according to DIN EN ISO 9001:2000.
    During this year's audit, again the effectiveness of our implemented quality management was evaluated in terms of customer satisfaction, management responsibility, and organizational performance. microParticles GmbH was certified of having established an effective quality management system. The audit arrived at the conclusion, that all relevant measures, meant to meet the quality metrics, have been put into action and are maintained at a high level.
    We regard the appreciation of our quality policy as motivation to further improve customer satisfaction and to fully achieve our quality objectives, formulated for 2005.

    March 2005

    Fig. 1: Streptavidin-biotin system: Binding of biomolecules to the particle surface

    Fig. 2: Nominal 5 µm streptavidin-coated melamine resin particles, labelled with FITC-biotin

    New Monodisperse Streptavidin-coated Melamine Resin Particles

    Intensive resarch activities of microParticles GmbH led to new monodisperse melamine resin particles functionalized with streptavidin. The introduced particles are meant to be used in streptavidin-biotin technology (see Fig. 1). Main features of our monodisperse melamine resin particles are high sphericity and colloidal stability in an wide pH range. Additionally, the particles possess a hydrophilic surface and high mechanical stability. The covalent binding of streptavidin to the particles is accomplished via COOH groups, located on the particle surface (carbodiimide procedure). The sucessful streptavidin functionalization of the particle surfaces was shown by labelling with FITC-biotin (see Fig. 2). Currently, we offer nominal 1 µm and 5 µm streptavidin-coated melamine resin particles. Other particle diameters within the range of 0.5-10 µm can be prepared upon request. Furthermore, we investigate streptavidin labelling of other polymer beads, such as polystyrene (PS), polymethylmethacrylate (PMMA), or silica particles. These products will be available soon.

    January 2005

    Nanometer-sized Poly(methyl methacrylate) Particles (PMMA particles)

    MicroParticles GmbH successfully completed R&D activities which lead to the manufacture of monodisperse PMMA particles in the nanometer size range. Hence, our customers can choose from the widest assortment of PMMA particles in the range from 100 nm up to 200 µm for immediate delivery. The PMMA particles have an extremely narrow size distribution (C.V.values<3 %) and an absolutely spherical shape. Compared to poly(styrene) particles, PMMA has a number of advantages:

  • The material has a higher density (1,19 g/cm3), so the beads are easier to centrifuge,
  • the particles are less hydrophobic, and
  • they possess a reduced non-specific protein binding activity.

    The new PMMA nanoparticles have been characterized with Dynamic Light Scattering Technique (Coulter®-Nanosizer) and Differential Sedimentation (CPS Disc Centrifuge). The particles come as 10 % aqueous dispersions. They can be modified with a number of functional groups, such as carboxy-, amino-, or epoxy-functions, dyes, or fluorochromes.

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    • News Archives 2003/2004

    Research- and Development Laboratory
    Volmerstr. 9A, UTZ, Geb.3.5.1, D-12489 Berlin
    Phone: +49 30-6392 2565 Fax: +49 30-6392 2555
    info@microparticles.de