Hyaluronic Acid HA

HA is used as a diagnostic marker for many diseases including cancer, rheumatoid arthritis, and hver 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 [423, 424]. 

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FIGURE 8.46 Hyaluronic acid has the consistency of a soft gel. It absorbs water easily and bonds with the proteins in the skin, making it useful in the repair of wounds and joint injuries. 

NS AIDS were never able to stop the different processes of inflammation, degradation, and reparation of OA. Intra-articular injection of hyaluronic acid has also not been able to stop the destruction of affected joint cartilage over time. The National Institute of Health (USA) has showed that glucosamine or chondroitin sulfate have comparative efficacy with placebo. 

Chitosan has been shown to increase precorneal drug residence times. The cationic chitosan slows tear drainage by increasing viscosity and by mucoadhesion with the negatively charged mucin. Up to a threefold increase of the corneal residence time has been achieved by the addition of chitosan to topical vehicles [5]. Carbomer gels at 0.3% have also been shown to be effective in prolonging the tear film break-up time [6]. Hyaluronic acid has been reported to... 

Figure 31. Computer-generated projections down the helix axis of the three-fold left-handed helical conformations of Klebsiella K25, Hyaluronic acid, HA, Chon-droitin 4-sulphate, C4-S, and Chondroitin 6-sulphate, C6-S...

Skin retains a large amount of water, and much of the external traumas to which it is constantly subjected, in addition to the normal process of aging, cause loss of moisture. The key molecule involved in skin moisture is hyaluronan (hyaluronic acid HA) with its associated water-of-hydration. Understanding the metabolism of HA, its reactions within skin, and the interactions of HA with other skin components, will facilitate the ability to modulate skin moisture in a rational manner, different from the empirical attempts that have been utilized up to now. 

A further use for self-assembling peptides is as lubricants to reduce joint friction between cartilage surfaces (Bell et al., 2006). The amphiphilc peptide Pn-9 which resembles hyaluronic acid (HA), the natural lubricant in joints, successfully reduced joint friction in simulated experiments. Bell and colleagues suggest that this peptide may be a superior synthetic treatment compared to injection to replace HA, which is not suitable in all osteoar-thritic cases. 

Hyaluronan (hyaluronic acid, HA) is a highly anionic unbranched linear polymer containing a -GlcAfSl,4GlcNAcP 1,4-repeating unit, which plays important roles in modulating cell adhesion, signaling, and motility. Several enzymes responsible for HA synthesis, namely Hyaluronic Acid Synthases, have been cloned from bacteria and mammals (107, 108). 

Hyaluronic acid (HA) Natural polysaccharide from c oa Substituted pyranose cosequences... 

Different glycosaminoglicans are not very different in structure. For example, the repeating unit in chondroitin is - 4)-0-(p-D-glucopyranosyluronic acid)-(1 3)-0-(2-acetamido-2-deoxy-p-D-galactopyranosyl)-(1 ->. The number of units varies but can be in the range of hundreds. Hyaluronic acid has a rather similar structure, - 4)-0-(p-D-glucopyranosyluronic acid)-(1 ->3)-0-(2-acetamido-2-deoxy-p-D-glucopyranosyl)-(1 as shown below ... 

In addition to PEG, certain polysaccharides, such as hyaluronic acid (HA) and dextran, have been used as low protein-adsorption, low cell adhesion surface coatings. Synthetic polymer surfactants consisting of poly(vinyl amine) with dextran and alkanoyl side chains, which mimicks the glycocalyx—negatively charged sugar layer outside cell membrane, are also shown to reduce protein adsorption to hydrophobic graphite surface. ... 

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