Separation of chondroitin sulfate and hyaluronic acid fragments by centrifugal precipitation chromatography

Isolation and characterization of hyaluronic acid from marine organisms

Hyaluronic acid (HA) being a viscous slippery substance is a multifunctional glue with immense therapeutic applications such as ophthalmic surgery, orthopedic surgery and rheumatology, drug delivery systems, pulmonary pathology, joint pathologies, and tissue engineering. Although HA has been isolated from terrestrial origin (human umbilical cord, rooster comb, bacterial sources, etc.) so far, the increasing interest on this polysaccharide significantly aroused the alternative search from marine sources since it is at the preliminary level. Enthrallingly, marine environments are considered more biologically diverse than terrestrial environments. Although numerous methods have been described for the extraction and purification of HA, the hitch on the isolation methods which greatly influences the yield as well as the molecular weight of the polymer still exists. Adaptation of suitable method is essential in this venture. Stimulated by the developed technology, to sketch the steps involved in isolation and analytical techniques for characterization of this polymer, a brief report on the concerned approach has been reviewed.

Centrifugal precipitation chromatography

Centrifugal precipitation chromatography separates analytes according their solubility in ammonium sulfate (AS) solution and other precipitants. The separation column is made from a pair of long spiral channels partitioned with a semipermeable membrane. In a typical separation, concentrated ammonium sulfate is eluted through one channel while water is eluted through the other channel in the opposite direction. This countercurrent process forms an exponential AS concentration gradient through the water channel. Consequently, protein samples injected into the water channel is subjected to a steadily increasing AS concentration and at the critical AS concentration they are precipitated and deposited in the channel bed by the centrifugal force. Then the chromatographic separation is started by gradually reducing the AS concentration in the AS channel which lowers the AS gradient concentration in the water channel. This results in dissolution of deposited proteins which are again precipitated at an advanced critical point as they move through the channel. Consequently, proteins repeat precipitation and dissolution through a long channel and finally eluted out from the column in the order of their solubility in the AS solution. The present method has been successfully applied to a number of analytes including human serum proteins, recombinant ketosteroid isomerase, carotenoid cleavage enzymes, plasmid DNA, polysaccharide, polymerized pigments, PEG-protein conjugates, etc. The method is capable to single out the target species of proteins by affinity ligand or immunoaffinity separation.

Immunoaffinity centrifugal precipitation chromatography

Purification of proteins based on immunoaffinity has been performed using a solid support coated with antibody against the target proteins. The method requires immobilizing the antibody onto the solid support using protein A or G, and has a risk of adsorptive loss of target proteins onto the solid support. Centrifugal precipitation chromatography has been successfully used to purify enzymes, such as ketosteroid isomerase and hyaluronidase without the use of solid support. The purpose of this study is to demonstrate that immunoaffinity centrifugal precipitation chromatography is capable of isolating an antigen by exploiting antigen-antibody binding. The separation was initiated by filling both channels with 40% saturated ammonium sulfate (AS) of pH 4-4.5 followed by loading 20 microl of human plasma (National Institutes of Health blood bank) mixed with 2 mg of rabbit anti-HSA (human serum protein) antibody (Sigma). Then, the sample channel was eluted with water at 0.03 ml/min and AS channel with 40% AS solution of pH 4-4.5 at 1 ml/min until all non-binding components were eluted. Then, the releasing reagent (50% AS solution containing 0.5 M glycine and 10% ammonium hydroxide at pH 10) was introduced through the AS channel to release the target protein (HSA). The retained antibody was recovered by eluting the sample channel with water at 1 ml/min. A hollow fiber membrane device at the outlet (MicroKros, Spectrum, New Brunswick, NJ, USA) was provided on-line dialysis of the eluent before fractions were collected, so that the fractions could be analyzed by SDS-PAGE (sodium dodecyl sulfate - polyacrylamide gel electrophoresis) without further dialysis. The current method does not require immobilizing the antibody onto a matrix, which is used by the conventional immunoaffinity chromatography. This method ensures full recovery of the antigen and antibody, and it may be applied to purification of other proteins.

Hyaluronic acid: separation and biological implications

Hyaluronic acid (hyaluronan) is a ubiquitous extracellular matrix component, and present at high concentrations in skin, joints and cornea. In the skin, it is synthesized primarily by dermal fibroblasts and by epidermal keratinocytes. Hyaluronic acid usually exists as a high molecular mass (600,000-1,000,000) and non-sulfated glycosaminoglycan composed of a disaccharide unit of [bond]3GlcNAc beta 1[bond]4GlcA beta 1[bond]. Hyaluronic acid has been widely used not only for osteoarthritis and ophthalmology but also for cosmetics for skin care. To examine the biological activities of hyaluronic acid, we have to accurately determine the quantity and molecular masses in biological samples. We review recent development in the analysis of hyaluronic acid having various molecular sizes using electrophoretic and chromatographic techniques. Recently, interactions between hyaluronic acid oligomers and hyaluronic acid-binding proteins have attracted the interest for understanding the biological functions. We show some interesting reports on biological interactions of hyaluronic acid and its oligomers with some proteins.

Method for the fractionation of dextran by centrifugal precipitation chromatography

Recent advances in biotechnology and biochemistry have been facilitated by efficient separation methods for biopolymers, such as proteins and nucleic acids. On the other hand, research on polysaccharides is hindered by problems in their fractionation. For many decades, polysaccharides have been fractionated by stepwise ethanol precipitation, and even at the present time, almost all of their purification protocols include at least one such step, although it is tedious and inefficient. This paper describes a novel approach for chromatographic fractionation of polysaccharides by ethanol gradient precipitation using an open column under a centrifugal force field. Using a unique column design, chromatographic separation of polymers is achieved by subjecting the sample to a repetitive process of precipitation and dissolution along a long, spiral channel. In this article, we fully describe the principle, design of the prototype, and basic studies on various parameters for optimization of chromatographic conditions, using dextran as an example.