Microparticles GmbH, Volmerstr. 9A, UTZ, Geb.3.5.1, D-12489 Berlin, Phone: +49 30-6392 2565 Fax: +49 30-6392 2555

News/Short Communications

Monodisperse Silica Particles from microParticles GmbH up to 25 µm

FlowCyto_combined

SEM pictures of 15 µm monodisperse Silica-Particles
By courtesy
of Dr. L. Dähne
Surflay Nanotec GmbH

Monodisperse Silica Particles from microParticles GmbH up to 25 µm

Silica particles in the nanometer as well as micrometer diameter range find an increasing use in medical diagnostics, in the pharmaceutical industry, in biotechnology and molecular biology, sensor technique, materials sciences, colloid research, and others. Sol-gel processes that were established already at the end of the 1960s by Stöber and coworkers allow for the rather convenient preparation of monodisperse silica particles in the size range from 100 nm to 3µm. So far, attempts that were made to utilize these processes for the manufacture of silica particles in the micrometer diameter range above 3 µm failed. This was mainly due to the barely controllable balance between nucleation and growth on one hand and reduced colloidal stability on the other. As a consequence, often dumbbells, irregularly-shaped particles, and heavily broadened particle size distribution are yielded. In the market, monodisperse silica particles in the micrometer diameter range above 3 µm are either rarely found or the offered materials show broad size distribution with CV values of about 20-30 %.
Recently, we have successfully developed a modified sol-gel strategy for the preparation of monodisperse silica particles in the diameter range up to 8 µm. By further developments of this process, a considerably extended range of high-quality silica particles above 8 µm up to 25 µm could be achieved.
The manufactured particles possess the following properties:

  • Narrow particle size distributions (CV < 5 %).
  • Spherical shape.
  • Non-porous.
  • Smooth surface.
  • High optical tranparency.
  • High mechanical and thermal stability.
  • Hydrophilic surface properties.
  • Density: 1,85 g/cm3.
  • Refractive index: 1,42.
  • Available in a wide diameter range up to 25 µm

The Silica-particles come as 5 wt.-% aqueous dispersions or in dry powder form. They can be used in a number of applications, such as isolation of nucleic acids, purification of biomolecules, preparation of hollow capsules, or in particle-based immunoassays.

New superparamagnetic fluorescent particles for flow-cytometric multiplex analyses

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PS-MAG-Fluo-COOH particles; 7 µm diameter, 12 fluorescence intensities, excitation: 488 nm, detection: > 675 nm (Partec-flow cytometer)

New superparamagnetic fluorescent particles for flow-cytometric multiplex analyses

For the simultaneous detection of different analytes, multiplex analyses with flow cytometers have proven a very efficient method in quite a number of sample types. The process relies on highly monodisperse polymer particles with distinctively graded fluorescence intensities as well as particle diameters. In order to achieve a high sample throughput, the automatization of the technology is desireable. To date, this challenge is not solved in a satisfactory manner by any of the competitors in the market. A smart way toward the automation of particle-based methods is the usage of paramagnetic beads that can be moved and directed by external magnetic fields and thus are suited for computer-aided process sequences. microParticles GmbH’s scientists now succeeded in the manufacture of 7 µm diameter superparamagnetic polymer particles with up to 12 fluorescent intensities that are distinct from each other. In combination with analogous 5 µm diameter beads, a whole range of up to 20 distinguishable superparamagnetic fluorescent particles was set up. For the coupling of antibodies to the particles they have been equipped with carboxyl functions (PS-MAG-Fluo-COOH, see figure). Our investigations also yielded a good batch-to-batch reproducibility both with respect to particle diameters and fluorescence intensities.

New superparamagnetic polymer particles with multiple fluorescence

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MAG-red

Fig.: Nominal 10 µm superparamagnetic polymer particles with green and red double fluorescence

New superparamagnetic polymer particles with multiple fluorescence

In the course of our research on paramagnetic polymer particles with fluorescent labels, we recently did succeed in the manufacture of superparamagnetic particles carrying two different coexisting fluorophores. Due to an appropriate design, both emissions can be distinctively observed in one and the same particle. The described particles are of spherical shape and possess a narrow size distribution. Moreover, they show strong superparamagnetism and high fluorescence intensities. Currently, the new superparamagnetic polymer particles can be delivered in the nominal diameter range from 1 through 10 microns. Variations of the applied dye and surface functionalities of the particles are possible within a wide range.

Superparamagnetic fluorescent polystyrene particles

PSMAG-MG-2a

PSMAG-MR-2a

Optical fluorescence miroscopy of PS-MAG-Fluorescence-S2392 with green and red fluororescent label, resp.

Superparamagnetic fluorescent polystyrene particles

Intensive R&D at microParticles GmbH now led to the manufacture of monodisperse superparamagnetic polymer particles which are labeled with a number of fluorophores. Currently, particle batch PS-MAG-Fluorescence-S2392 (diameter 11.21 ± 0,41 µm, CV: 3,7 %) can be offered. Other diameters are under preparation. The particles are of spherical shape. They have a narrow size distribution, strong paramagnetism, and high fluorescence intensities. From now on, these beads can be delivered in aqueous suspensions.

New large superparamagnetic polymer beads

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Optical microscopy of MP-MAG-S2211 (375 µm)

New large superparamagnetic polymer beads

With our technology to manufacture iron oxide-laden polymer particles, we recently succeeded in entering the diameter range beyond 200 µm with superparamagnetic beads. Currently, one batch of superparamagnetic polymer particles is available: MP-MAG-S2211 (375 µm, C.V. 2,0 %).
The polymer beads possess strong superparamagnetic properties. They show a narrow size distribution and are of spherical shape. With immediate effect, these new polymer particles are available as aqueous suspensions or in dry powder form.

New nanometer scale superparamagnetic polymer particles

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Particle size distribution of PS-MAG-S1702 (400 nm, CV ≤5 %) as determined by Differential Sedimentation (CPS disc centrifuge).

New nanometer scale superparamagnetic polymer particles

Within a BMWi-sponsored R&D project, microParticles GmbH now succeeded in developing monodisperse superparamagnetic polystyrene particles (PS-MAG) with 400 and 600 nm in diameter. The particles are of spherical shape and have C.V. values ≤5 %. Thus, they distinctively differ from competing products currently available in the market. Due to their high iron oxide contents of approx. 50 wt.-%, the particles show an excellent superparamagnetic behavior.
Our magnetic beads are available as plain, non-functionalized species as well as with COOH-modified surfaces. The COOH-surface functionalities are suitable for the coupling of proteins or other NH2-containing molecules. Hence, also streptavidin-modified particles (PS-MAG-SA) do belong to our product portfolio. The binding capacity with this type of beads is in the range of 3000 – 4000 pmol FITC-biotin per mg.
In the near future microParticles GmbH will be able to offer its customers also monodisperse nominal 200 nm and 300 nm superparamagnetic PS particles.

Breakthrough in the development of monodisperse superparamagnetic silica particles in the 1 micron diameter range

magnetische Silica Partikel

magnetische Silica Partikel

Nominal 1µm superparamagnetic silica particles (Scanning Electron Microscopy image, by courtesy of Dr. M. Wagener, Carl Zeiss NTS GmbH.)

Breakthrough in the development of monodisperse superparamagnetic silica particles in the 1 micron diameter range

Magnetic microspheres have found widespread applications in biochemistry, biology, biotech-nology, and medicine. Although a number of magnetic microbeads are commercially available, only few products fulfill the requirements of high magnetizability, narrow size distribution, colloidal stability, minimized nonspecific adsorption, and high bindig capacity for bioligands.
Recently, microParticles GmbH has succeeded in fabricating monodisperse spherical magnetic silica particles in the 1µm diameter range. With the newly developed method, using a modified sol-gel process, it is possible to combine strong magnetic response with high monodispersity, high colloidal stability, and high binding of bioligands. The synthesized superparamagnetic silica microspheres possess the following features:

  • Narrow particle size distribution (C.V. values
  • Spherical shape.
  • High magnetizability due to iron oxide loadings up to 50 wt.-%.
  • Superparamagnetic properties.
  • Homogeneously dispersed iron oxide nanoparticles throughout the silica matrix.
  • Rapid attraction of the suspended particles by a conventional permanent magnet.

They can be used in a variety of applications like nucleic acid isolation, biomolecule purification, and particle-based immunoassays. As from now, these superparamagnetic silica particles are available with carboxylic groups (5 wt.-% aq. suspensions) or streptavidin-modified surfaces (1 wt.-% aq. suspensions). Currently, research is underway at microParticles GmbH to develop monodisperse magnetic silica miroparticles in the submicron-size range from 200 through 1000 nm, too.

microParticles GmbH offers electrolyte-stable research particles

PS_RhB_1

PS_RhB_PEG_1

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.

microParticles GmbH offers electrolyte-stable research particles

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).

Successful reassessment of microParticles GmbH according to DIN EN ISO 9001:2000

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Successful reassessment of microParticles GmbH according to DIN EN ISO 9001:2000

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.

Multifunctional superparamagnetic polystyrene particles

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psmags1202_b

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

Multifunctional superparamagnetic polystyrene particles

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
  • 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.

New analytical service of microParticles GmbH

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New analytical service of microParticles GmbH

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.

Expanded Line of NIST-traceable Particle Size Standards

PSmix

Gemisch aus 7 hochmonodispersen nanoskaligen Partikelgrößenstandards, vermessen mittels CPS-Scheibenzentrifuge (DC-24000)

Expanded Line of NIST-traceable Particle Size Standards

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.
  • 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.

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

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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.

microParticles GmbH guarantees high quality standards to its customers

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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.

New Monodisperse Streptavidin-coated Melamine Resin Particles

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

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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.

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

 

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

  • 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.

Acid-dissolvable Melamine Resin Particles

MF_shells

FITC-labelled polyelectrolyte layers, templated on acid-dissolvable melamine resin beads of 7 µm diameter
(Confocal Laser Scanning micrograph, by courtesy of L.Dähne/Capsulution NanoScience AG)

Acid-dissolvable Melamine Resin Particles

microParticles GmbH has been sucessfully marketing acid-dissolvable melamine resin particles. As a result of recent efforts, the accessible size range could be significantly extended. Currently, monodisperse soluble melamine resin beads are available from nominal 500 nm up to 7 µm in diameter. Contrary to our stock-held highly crosslinked melamine resin research grade beads, these specialty particles are weakly crosslinked and soluble in hydrochloric acid as well as in some organic solvents. They are characterized by excellent monodispersity and highly uniform spherical shape. The particles possess a pH-dependent surface charge and are the most suitable choice for polyelectrolyte coatings or as templates for the preparation of hollow capsules.

New funktionalized melamine resin particles (MF-particles)

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New funktionalized melamine resin particles (MF-particles)

microParticles GmbH has successfully developed a series of novel functionalized melamine resin particles for stable, permanent attachment of biomolecules. Using innovative strategies of polymer chemistry and synthesis for surface modification, melamine resin particles with the following surface functionalities and polymer coatings are available:

  • Melamine resin particles with carboxyl groups (group density controllable in a wide range up to 1000 µmole/g).
  • Amino-modified melamine resin particles.
  • Melamine resin particles with sulfonic acid groups, epoxy- and aldehyde functions as well as thiol und hydroxyl groups on the particle surface.
  • Monodisperse melamine resin particles with maleimide-functionalization for the directed immobilization of thiol-containing compounds (e.g. HS-DNA).
  • Melamine resine particles with covalently fixed polymer coatings like amino dextrane, poly(ethylene imine), poly(vinyl alcohol), etc.

These new MF particles not only combine excellent monodispersity and high mechanical and chemical stability, but also low unspecific protein adsorption, variable surface chemistry as well as high colloidal stability in a wide range of pH and electrolyte concentrations. The new products are designed for applications in medical diagnostics and in pharmaceutical and biotech industry. They can be delivered in the diameter range from 300 nm up to 12 µm.

Melamine resin nanoparticles

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SEM image of MF nanoparticles, diameter 540 nm

Melamine resin nanoparticles

microParticles GmbH presents new monodisperse melamine resin (MF) nanometer particles. These research beads are currently available in the size range from 300 to 1000 nm. They are manufactured as either non-modified or fluorescently-labeled species. Other product characteristics are:

  • Narrow particle size distribution.
  • Spherical particles with smooth surface.
  • High thermal, chemical and mechanical stability.
  • Absolutely stable in all solvents, no swelling or shrinking upon contact with organic media.

Upon request, the new particles can be carboxyl-modified and are suitable that way for covalent coupling of proteins and other ligands.

New silica research beadsl

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Optical micrograph of 4.6 µm silica beads

New silica research beads

microParticles GmbH has expanded its product line of dense silica research beads. With optimized Sol-Gel procedures particle diameters of up to 5 microns are achieved. The particles come as 5 wt.-% aqueous dispersions or in dry powder form. The main product characteristics are:

  • Particle diameters above 1 micron up to 5 microns.
  • Narrow size distribution (CV 6 – 7 %).
  • Spherical particles with smooth surface.
  • Surface functionalities (carboxyl, amino groups) available on request.

microParticles GmbH receives DIN EN ISO 9001:2000 certification

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microParticles GmbH receives DIN EN ISO 9001:2000 certification:

In April 2003 microParticles GmbH has been certified under the globally approved ISO 9001:2000 Quality System. Certification validates that microParticles GmbH has implemented and maintains a quality management system (QMS) and establishes microParticles GmbH as a world-class company that continues to be customer and quality focused. For us, being a technology-oriented R&D laboratory, customer satisfaction, management responsibility, and organizational performance are major goals of our company’s philosophy. The ISO 9001:2000 standard delivers excellent means to evaluate and measure those quality metrics.
Our competent partner during the process of establishing QMS was EuroNorm GmbH (www.euronorm.de).

Monodisperse colored nano- and microparticles

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Optical micrographs of colored beads, assembled at the air/water interface on foam bubbles
(blue: PS 4 µm, red: PS/PMMA 5.5 µm; diameter of the bubbles approx. 300 µm).

Monodisperse colored nano- and microparticles

microParticles GmbH introduces a new product line of intensely dyed monodisperse microspheres for use in applications like filter testing, flow tracing, medical diagnostics, and biotechnology. The particles, based on polystyrene and polystyrene copolymers, are produced with microParticles’ own technology platform and come in a wide variety of sizes, dyes, and functionalities. Using specifically designed dyeing processes, intensely colored particles with complete dye retention are obtained. The new particles come as 5 wt.-% aqueous dispersions. With larger beads also dry powders are available. The main product characteristics include:

  • Size range from 500 nm to 1000 ТЕm.
  • Dark blue, dark red and black colors available.
  • Narrow size distribution (CV < 3 %).
  • High lot-to-lot reproducibility.
  • Spherical particles with smooth surface.
  • Surface functionalities (carboxyl, amino, and epoxy groups) available on request.

CARBOXYL-FUNCTIONALIZED MELAMINE RESIN BEADS (white or fluorescent)
Recently, microParticles has developed a new generation of carboxyl-functionalized monodisperse melamine resin (MF) microspheres. Using innovative surface polymerization techniques, functionalized beads with low, medium, or high density of carboxyl groups with up to 1000 ТЕmole/g can be obtained. The new product line can be supplied with diameters from 1 to 12 ТЕm. Combining advantageous material properties of MF with the newly achieved functionalization, these particles enter completely new applications, e.g. in Life Sciences. Main features of these carboxyl-modified microspheres are:

  • Excellent chemical resistance and thermal stability.
  • High density (1.5 g/cm3).
  • Good solvent stability.
  • High mechanical strength.
  • Narrow particle size distribution.
  • High colloidal stability.
  • Covalent coupling of biologands, e.g. streptavidin, possible.
  • Can be handled in dry powder form.

Core-shell products

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Cofocal Laser Scanning Micrograph of a fluorescently coded particle library (Layer-by-Layer technique)

MONODISPERSE NANO- and MICROSPHERES with POLYELECTROLYTE MULTILAYERS,

a new product line of microParticles GmbH, are especially designed for applications in Life Sciences. Using proprietary Layer-by-Layer technology monodisperse particles of different core materials, e.g. polystyrene, melamine resin, or silica in the size range between 300 nm and 50µm, are coated by layers of alternately charged polyelectrolytes.
This technology has the advantage over known particle modifications that due to the layering technique several functionalities can be combined without cross-reactions. The following functions are offered

  • positive or negative surface charge,
  • high concentration of reactive binding sites e.g. amino or carboxyl groups,
  • photo-reactive surface groups,
  • covalently coupled fluorescent dyes,
  • superparamagnetic properties.

For example, various combinations of fluorescent colour labels can be deposited on particle surfaces. Due to the LbL technology the dyes are located in spatially separated layers which avoids undesired interactions between them. Using 4 dyes with selected fluorescence wavelengths, a library of 15 differently tagged particles is available. The particles can be delivered as aqueous suspensions in 2 or 10 ml packages. The concentration varies in dependence on the particle size from 5 x 108 particles/ml for 0.5 -2 µm, 2 x 107 particles/ml for 2-10 µm to 5 x 105 particles/ml for 10 – 50 µm.

MONODISPERSE, HOLLOW LBL-CAPSULES® with CONTROLLED PERMEABILITY are designed by means of the patented Layer-by-Layer technology. Their preparation is based on the coating of monodisperse soluble colloidal core particles with polyelectrolytes. After the layering procedure the core particles are removed from the interior. The surface and wall properties of the remaining capsules can be taylor-made as outlined above. The permeability can be varied from low permeability for molecules above 500 g/mol to high permeability for macromolecules with a molecular weight up to 50 kD. Capsule diameters between 500 nm and 10 µm are available. Our new capsules have some outstanding advantages:

  • their interior can be used as container for uptake, transport, and release of different materials,
  • they are stable in most inorganic and organic solvents,
  • the thin wall (15-30 nm) results in very low weight avoiding fast precipitation,
  • capsule walls cause only small light refraction or turbidity of the suspension,
  • our broad label program offers the opportunity to use the capsules in combinatorial libraries, as sensors in different environments, or as photochemically reactive species.

The capsules can be delivered as aqueous suspensions in 1-10 ml packages. The concentration varies in dependence on the capsule size from 5 x 108 particles/ml for 0.5 -2 µm, 2 x 107 particles/ml for 2-10 µm to 5 x 105 particles/ml for 10 – 50 µm.#

New NIST-traceable particle size standards

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Optical micrograph of particle size standard spheres (PS/Q-ST-B743, 244 µm; scale bar 500 µm)

New NIST-traceable particle size standards

of 3 µm, 20 µm, 40 µm, 60 µm, 200 µm, and 250 µm nominal diameter are now available from microParticles GmbH. The new size standards may be used in industrial, pharmaceutical, clinical, and scientific laboratories for quality control and calibration of particle sizing instruments. The particle size standards are monodisperse polystyrene microspheres produced by microParticles’ innovative polymerization technologies. Product characteristics are:

  • Most accurate size standards available, traceable to primary reference materials from the National Institute of Standards and Technology (NIST) and the Community Bureau of Reference (BCR).
  • Extremely narrow size distribution.
  • CV (Coefficient of Variation) <1,5 %.
  • Absolutely spherical shape and smooth particle surface.

Particle sizes and size distributions are determined by Optical Microscopy and Electrical Sensing Zone method (COULTER® Multisizer III). Particle size standards are supplied as aqueous suspensions at 2 wt.-% solids in dropper tipped bottles. The rather high solids concentration facilitates dilution of the standards for use in calibration of many different particle analyzers. Diameters larger than 160 microns are packaged as dry powders in screw-capped bottles. All particles come with Certificate of Analysis and MSDS.