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.#