Fluorescence micrographs of nominal 1 µm Rhodamine B-labelled PS particles in 2 n NaCl dispersion
Top: plain particle surfaces
Bottom: PEG-modified particle surfaces.

In medical research, microfluidics, and other applications, agglomeration of tracer particles or their sticking to the walls of channels, vessels, or tubes often becomes a problem. Namely in electrolyte solutions, aggregation of conventional polymer particles may hinder experiments severely. microParticles GmbH now succeeded in overcoming such difficulties with PS (polystyrene) and PMMA (poly(methyl methacrylate)) particles by PEG (poly(ethylene glycol)) modification. The particles bear a special permanent PEG coating, anchored in the particle surface. They are colloidally stable even in 2 n NaCl solution. The custom-made particles come either untagged as 5 wt.-% or fluorescently labelled as 2,5 wt.-% aqueous dispersions. They possess the following features:

• Available diameter range nominal 300 nm up to 10 microns.
• Narrow particle size distributions (C.V. values < 3 %).
• Spherical shape.
• Untagged or fluorescently labelled, according to customer requirements.
• Material density 1.05 g/cm³ (PS), 1,19 g/cm³ (PMMA).

MicroParticles GmbH has established a DIN EN ISO 9001:2000-conform Quality Management System (QMS) for several years. The QMS serves as a tool to secure all quality-relevant processes in the company and to put into practice our business objectives

• to continually improve the quality of our products and service,
• to permanently ensure customer satisfaction,
• to be a reliable partner for our customers,
• to ensure competitiveness of our products and service throughout the market,
• to increase the economic efficiency and success of the company.

According to the audit scheme, TÜV Rheinland Berlin Brandenburg conducted the DIN EN ISO 9001:2000 reassessment of microParticles GmbH on July 04 and 05, 2006. The reassessment covered all business areas of the company, such as research and development, production, logistics, purchasing, and accounting system. As a result, microParticles GmbH was attested to have an effective Quality Management System in place. The auditing yielded that all relevant measures, meant to meet the quality metrics, have been put into action and are maintained at a high level. It emphasized the implemented Failure-Mode-and-Effects-Analysis (FMEA) for process optimization, risk assessment, and effects analysis being an effective instrument to guarantee high product quality and customer satisfaction in the future. Being confronted with toughened competition and an increasing demand for innovations, we consider FMEA a decisive factor for success and good corporate image.

Magnetic polystyrene particles (nominal diam. 22 µm) without and under the influence of an external magnetic field

MicroParticles GmbH now offers to its customers a series of monodisperse superparamagnetic polymer particles with well defined diameters. In addition to plain magnetic particles and magnetic particles with COOH-modification (COOH >100 µmol/g), we supply magnetic beads with streptavidin coating (binding capacity: 400-1200 pmol FITC-biotin/mg). Outstanding properties of the new magnetic microspheres of microParticles GmbH are:

• Narrow size distribution (CV <5 %) and absolutely spherical shape.
• Superparamagnetic properties.
• Nanoscale iron oxide particles are uniformly dispersed throughout the polystyrene matrix.
• The iron oxide content can be adjusted in a wide range up to 70 wt.-%.
• The magnetic microspheres can be supplied in monodisperse quality with well defined particle diameters in the size range from 1 µm to 50 µm

These particles are excellent tools for separation and purification of DNA, proteins, or other biotinylated biomolecules, and in several immunoassays. Rapid, efficient, and gentle separation from the surrounding media is possible via an external magnetic field which can be applied just by a permanent magnet.

With immediate effect, microParticles GmbH provides high quality services in characterization of particulate materials in the nano- and micrometer size range. Particle characterization in suspensions or powders includes measurements of particle size, particle size distribution, particle number, and particle shape as well as determination of surface chemical properties like surface charge, functional groups, electrophoretic mobility resp. Zeta potential. Techniques and measuring equipment in our newly established analytical lab comprise:

• Photon Correlation Spectroscopy (Coulter^® Nanosizer N4+)
• Electrical Sensing Zone Method (Coulter^® Multisizer III)
• Differential Sedimentation (High resolution CPS disc centrifuge DC 24000)
• Optical Microscopy / Fluorescence Microscopy (Olympus BX 40)
• Microelectrophoresis (Zeta View, Particle Metrix GmbH)
• Potentiometry
• Conductometry
• UV-Vis Spectroscopy (Varian Cary 50 Bio)

Don't hesitate to discuss your questions and problems on particle-related issues with us - We would be pleased suggesting solutions for you.

Mixture of 7 highly monodisperse nanoscale particle size standards measured with a CPS disc centrifuge (DC-24000)

With the beginning of 2006, microParticles GmbH offers its customers a considerably expanded line of NIST-traceable nanoscale particle size standards. Designed especially for quality assurance and calibration purposes in a variety of particle sizing instruments, the nanometer size standards possess the following features:

• Polymer matrix polystyrene (density: 1.05 g/cc; refractive index: 1.59).
• Extremely narrow size distribution (C.V.<3 %).
• High colloidal stability in aqueous dispersions.

The newly available 15 size standards within the diameter range from 100 nm through 1000 nm have been characterized by a high resolution CPS disc centrifuge (DC-24000), photon correlation spectroscopy (PCS), and scanning electron microscopy (SEM). All particle size standards come as 2 % aqueous suspensions in 10 or 15 ml dropper-tipped bottles together with a Certificate of Analysis containing also selected physical data and a graph of the size distribution, and an appropriate Material Safety Data Sheet. Of course our mirometer sized standards remain available to our customers as before.

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

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:

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.

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.

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

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 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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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