Hyaluronic acid (hyaluronan, HA) is a linear polysaccharide formed from disaccharide units containing N-acetyl-D-glucosamine and glucuronic acid. It has a high molecular mass, usually in the order of millions of Daltons, and interesting viscoelastic properties influenced by its polymeric and polyelectrolyte characteristics. HA is present in almost all biological fluids and tissues. In clinical medicine, it is used as a diagnostic marker for many diseases including cancer, rheumatoid arthritis and liver pathologies, as well as for supplementation of impaired synovial fluid in arthritic patients by means of intra-articular injections. It is also used in certain ophthalmological and otological surgeries and cosmetic regeneration and reconstruction of soft tissue. Herein we present an overview of the occurrence and physiological properties of HA, as well as of the recent advances in production biotechnology and preparation of the HA-based materials for medical application.

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Hyaluronan (hyaluronic acid, HA) is a linear naturally occurring polysaccharide formed from repeating disaccharide units of N-acetyl-D-glucosamine and D-glucuronate. Despite its relatively simple structure, HA is an extraordinarily versatile glycosaminoglycan currently receiving attention across a wide front of research areas. It has a very high molar mass, usually in the order of millions of Daltons, and possesses interesting visco-elastic properties based on its polymeric and polyelectrolyte characteristics. HA is omnipresent in the human body and in other vertebrates, occurring in almost all biological fluids and tissues, although the highest amounts of HA are found in the extracellular matrix of soft connective tissues. HA is involved in several key processes, including cell signaling, wound repair and regeneration, morphogenesis, matrix organization and pathobiology. Clinically, it is used as a diagnostic marker for many disease states including cancer, rheumatoid arthritis, liver pathologies, and as an early marker for impending rejection following organ transplantation. It is also used for supplementation of impaired synovial fluid in arthritic patients, following cataract surgery, as a filler in cosmetic and soft tissue surgery, as a device in several surgical procedures, particularly as an anti-adhesive following abdominal procedures, and also in tissue engineering. This review will provide an overview of the structure and physiological role of HA, as well as of its biomedical and industrial applications. Recent advances in biotechnological approaches for the preparation of HA-based materials, and as a component of tissue scaffolding for artificial organs will also be presented.

Many human diseases are associated with harmful action of reactive oxygen species (ROS). These species are involved in the degradation of essential tissue or related components. One of such components is synovial fluid that contains a high-molecular-weight polymer--hyaluronan (HA). Uninhibited and/or inhibited hyaluronan degradation by the action of various ROS has been studied in many in vitro models. In these studies, the change of the molecular weight of HA or a related parameter, such as HA solution viscosity, has been used as a marker of inflicted damage. The aim of the presented review is to briefly summarize the available data. Their correct interpretation could contribute to the implementation of modern methods of evaluation of the antioxidative capacity of natural and synthetic substances and prospective drugs--potential inflammatory disease modifying agents. Another focus of this review is to evaluate briefly the impact of different available analytical techniques currently used to investigate the structure of native high-molecular-weight hyaluronan and/or of its fragments.

Nine hyaluronan (HA) samples were fractionated by size-exclusion chromatography, and molar mass (M), radius of gyration (Rg), and intrinsic viscosity ([eta]) were measured in 0.15 M NaCl at 37 degrees C by on-line multiangle light scattering and viscometer detectors. Using such method, we investigated the Rg and [eta] molar mass dependence for HA over a very wide range of molar masses: M ranging from 4 x 10(4) to 5.5 x 10(6) g/mol. The Rg and the [eta] molar mass dependence found for HA showed a meaningful difference. The Rg = f(M) power law was substantially linear in the whole range of molar masses explored with a constant slope of 0.6. In contrast, the [eta] = f(M) power law (Mark-Houwink-Sakurada plot) showed a marked curve shape, and a linear regression over the whole range of molar masses does not make sense. Also the persistence length (stiffness) for HA was estimated. The persistence length derived by using both the Odijk's model (7.5 nm from Rg vs M data) and the Bohdanecky's plot (6.8 nm from [eta] vs M data) were quite similar. These persistence length values are congruent with a semistiff conformation of HA macromolecules.