Much of modern cell and molecular biology relies on the isolation of pure, functionally intact populations of cells, subcellular organelles and macromolecules in high yield and both research and clinical applications provide an impetus for the development of improved separation technology.
The most commonly used method of separating suspensions of mixed populations of biological particles is centrifugation in density gradients - and the choice of medium used to form the gradients is critical for the retention of particles function. Since the early sixties Nycomed have been developing and producing iodinated compounds as X-ray imaging agents. It was recognized early on that these compounds were also well suited to the formation of density gradients and offered new opportunities for improved methods of separating biological particles, especially osmotically-sensitive cells and subcellular organelles. Nycomed has therefore been avtively involved over the last 30 years in the research and development of density gradient media.
Recently, a new chapter opened in Nycomed's history, when in 2000, Axis-Shield took over responsibility for these products. Today, Alere Technologies AS (Axis-Shield is a trading name of Alere Technologies AS) offers a range of iodinated density gradient media, produced in compliance with EU cGMP standards and regulatory requirements, which can be used for the purification not only of cells and organelles, but also membrane vesicles, viruses, proteins, nucleic acids and lipoproteins. The use of these compounds as contrast media demanded that they be rigorously tested to ensure their safety and suitability for clinical use. Axis-Shield density gradient media are therefore proven to be non-toxic; have a low osmolality and are sufficiently dense to permit the purification of all types of biological particles.
No other density gradient media conform to such strict clinical criteria.
Lymphoprep is a ready-made, sterile and endotoxin tested solution for the isolation of human mononuclear cells.
Polymorphprep is a ready-made, sterile and endotoxin tested solution for the isolation of human polymorphonuclear leucocytes (granulocytes).
OptiPrep is a sterile and endotoxin tested multi-purpose medium based on iodixanol. Unlike any of these other gradient media, iodixanol (as an X-ray imaging agent) has been clinically tested and is manufactured under strict and EU cGMP compliance.
is a general purpose medium, available as a powder. Nycodenz® is freely soluble in water.
Polysucrose 400 is a synthetic high molecular weight polymer made by co-polymerization of sucrose and epichlorohydrin. The molecules have branced structure with a high content of hydroxyl groups giving a good solubility in aqueous media. The product is similar to Ficoll 400® from GE Biosciences. Polysucrose 400 is readily soluble in aqueous solutions when added slowly with stirring. Concentrtations up to 50% (w/v) can easily be prepared.