Chitin

Chitin is a nitrogenous polysaccharide found in the exoskeleton of the tarantula. It's a tough semitransparent horny substance; the principal component of the exoskeletons of arthropods and the cell walls of certain fungi. The dense substance forming the indigestible outer skeleton of insects, and the material from which the walls of the mycelia are made. This product can be found in crustaceans, such as crabs, lobsters, and shrimp. It can also be found in insects, worms, and fungus, or mushrooms. The thing about chitin is that it is a natural polymer, which means that it is found in nature. In the creatures where chitin is found, it is in different percentages depending on the place.

Chitin is the second most abundant polysaccharide in nature (after cellulose). At least 10 gigatons of chitin are synthesised and degraded each year in the biosphere. Chitin mainly consists of the aminosugar N-acetylglucosamine, which is partially deacetylated. The mostly deacetylated form of chitin is called chitosan. Chitin is present in nature usually complexed with other polysaccharides and with proteins. It is a renewable resource and is isolated from crab and shrimp waste. It is used for waste water clearing, for cosmetics and for medical and verterinary applications.

Chitin is one of the most abundant polysaccharides found in nature. It is often considered a cellulose derivative, although it does not occur in organisms producing cellulose. The difference between cellulose and chitosan is that the 2-hydroxy group of the cellulose has been replaced with an acetamide group. This results in several Beta-(1 -> 4)-2-acetamido-2-deoxy-D- glucopyrnaose structural units (GlcNAc). Chitin has been found to have an acceleratory effect on the wound healing process. Regenerated chitin fibers, non-woven mats, sponges, and films show an increase in wound healing by over 30%. Chitin can also be used as a coating on normal biomedical materials. Standard silk and catgut sutures coated with regenerated chitin or chitosan show wound-healing activities only slightly lower than the all-chitin fibers. Surgical gauze coated with regenerated chitin demonstrates a substantially greater amount of activity than an uncoated control group.

Chitins are polymers of glucosamine, with an acetyl group attached to a variable number of the individual glucosamine molecules (making them acetylglucosamine). A polymer composed totally of acetylglucosamine is called chitin, and one composed totally of glucosamine is called chitosan. These polymers and those made up of a mixture of glucosamine and acetylglucosamine are known collectively as glucoaminoglycans. Chitin and chitosan have the same chemical structure. Chitin is made up of a linear chain of acethylglucosamine groups. Chitosan is obtained by removing enough acethyl groups (CH3-CO) for the molecule to be soluble in most diluted acids. This process, called deacetylation, releases amine groups (NH) and gives the chitosan a cationic characteristic. This is especially interesting in an acid environment where the majority of polysaccharides are usaually neutral or negatively charged.

One of the more important things that chitin, and its products, could be used for is in treating burn patients. It has a remarkable compatibility with living tissue, and has been looked at for its ability to increase the healing of wounds. There is also evidence that chitosan can reduce serum cholesterol levels. More research has also indicated that chitosan can increase crop yields, and clean and clear up pools.

Chitin, the main constituent of the crustacean shells, is an excellent cosmetic product that is remarkably well tolerated by the skin. The chemical structure of chitin, a natural polymer, is very close to that of mucopolysaccharides (heparin and hyaluronic acid), whose biological tolerance has been demonstrated for a long time. In addition, it is an efficient trapper of heavy metals that are responsible for very many contact allergies; therefore it is really interesting for skin allergies. Chitin is a particularly effective hydrating agent. It has two advantages: it supplies water and it avoids dehydration. In addition, the great advantage of chitin and its derivatives is the lasting quality of their hydrating effect. Chitosan forms a protective tensor film on the skin's surface that can fix other active principles for the skin. Thus other hydrating agents, solar filters, organic acids or other active principles can be combined with the derivatives of chitin. Chitin facilitates their effects. Chitin and its derivatives allow active principles to be placed in close contact with the skin by means of a medium that is not only a film-forming tensor but is especially hydrating. This is a new double advantage that makes chitosan of great interest in cosmetics. Chitin and its derivatives have two major properties that are of interest for industry and for nature conservation: they are remarkable chelation agents and heavy metal traps.

Employed as a chelation agent, chitin and its derivatives are used for treating drinking water by separating organic compounds and heavy metals, and for treating sewage by precipitating certain anionic wastes and capturing pollutants such as DDT and PCBs (polychlorobenzene). The Environmental Protection Agency (EPA) has already approved the use of chitosan in water at concentrations of up to 10 mg per litre. For sewage treatment, chitosan can be used at up to 5 ppm. It reduces the oxygen demand by 80 to 85% and reduces the phosphates level to less than 5 ppm.

It is in medicine that the bacteriostatic, immunologic, antitumoral, cicatrizant, hemostatic and anticoagulant properties of chitin and its derivatives have been of the greatest use. Due to its biocompatibility with human body tissue, the cicatrizant properties of chitin and chitosan have demonstrated their effectiveness for all forms of dressings - artificial skin, corneal bandages and suture thread in surgery - as well as for implants or gum cicatrization in bone repair or dental surgery. The many applications include artificial skin and suture thread that are absorbed naturally after cicatrization, and contact lenses that are well tolerated. Betschitib W, an artificial skin based on chitin, has been made in Japan since 1987. This skin is in the form of a tissue that is applied to the wound in one single operation: the dressing does not have to be changed.Betschitib W is gradually biodegraded until a new epidermis is formed. In dental creams, it keeps the paste healthy and regenerates gums that are in poor condition.

Deacyletylated chitin, or chitosan, has been shown to aggressively bind to a variety of mammalian and microbial cells. This property of chitosan may lead to a variety of biomedical applications. These possible applications will use chitosan as a hemostatic, bacteriostatic, and spermicidal agent. Chitin and its derivatives show promise for the future. Products produced using chitin have been shown to increase wound healing in animals and humans. Chitin has also demonstrated a physiological compatibility with living tissues. Chitin's ability to form sulfate esters which are non-thrombogenic appears to make it a promising candidate for prosthetic structural devices of any shape or size. Therefore, chitin could serve as replacements for bone, cartilage, arteries, veins, and musculo-fascial replacements. The uses of chitin and chitosan are only limited by the creativity of the biomedical engineer.