Ficoll
Ficoll is a neutral, highly branched, high-mass, hydrophilic polysaccharide which dissolves readily in aqueous solutions. Ficoll radii range from 2-7 nm. It is prepared by reaction of the polysaccharide with epichlorohydrin. Ficoll is a registered trademark owned by GE Healthcare companies.[1]
Ficoll is part of Ficoll-Paque which is used in biology laboratories to separate blood to its components (erythrocytes, leukocytes etc.) Ficoll-Paque is a registered trademark owned by GE Healthcare companies. Ficoll-Paque is normally placed at the bottom of a conical tube, and blood is then slowly layered above Ficoll-Paque. After being centrifuged, the following layers will be visible in the conical tube, from top to bottom: plasma and other constituents, a layer of mono-nuclear cells called buffy coat (PBMC/MNC), Ficoll-Paque, and erythrocytes & granulocytes which should be present in pellet form. This separation allows easy harvest of PBMC's. Note that some red blood cell trapping (presence of erythrocytes & granulocytes) may occur in the PBMC or Ficoll-Paque layer. Major blood clotting may sometimes occur in the PBMC layer. Ethylene diamine tetra-acetate (EDTA) and heparin are commonly used in conjunction with Ficoll-Paque(TM) to prevent clotting.
Ficoll can also be used to separate islets of Langerhans from pancreatic tissue. The separated islets can then be used for transplantation into patients with type 1 diabetes
Because Ficoll-Paque layering is a very slow process, devices that aid in the most time-consuming step, the overlay, have been developed. One of these devices includes a column containing a porous high-density polyethylene barrier or "frit." This product allows blood to be layered on much more quickly without mixing polysaccharide and blood. An example of such a product is the "Accuspin System Histopaque-1077" sold by Sigma Aldrich. The cost of this product is significantly higher than basic Ficoll and Ficoll-Paque products. Another such device, which was recently developed in 2009, aids significantly in the overlay process without the high cost of a porous high-density polyethylene barrier. By dividing the conical tube into two compartments, it overlays blood by slowly leaking blood from the top compartment to the bottom compartment along the walls of the conical tube. An example of such a device is the "BioSep Overlay System" sold by M Biosciences. It is also possible to have the Ficoll-Paque separating system included in the Vacutainer used to collect the blood. Such vacutainers increase the convenience and safety of collecting blood products, but cost 50 times as much as the basic vacutainer.
[edit] Notes
- ^ "Ficoll". United States Patent and Trademark Office. http://tess2.uspto.gov/bin/showfield?f=doc&state=r67qfq.2.2. Retrieved 2007-02-15.
