HEALTH CARE

Chitin and Chitosan have a wide variety of uses in health care. Most important are wound care, implants, fat and cholesterol-binding drugs, and drug delivery. We also survey other proposed uses.

Wound Healing Ointment : An obvious method of exploiting chitm's wound-healing properties is to use the material in ointments for treating wounds. One example is a salve made by passing powdered chitin through a small-bore hole at high speed and pressure, which causes the chitin to shear. The product that results is lyophilized, ground, suspended in petroleum jelly or other suitable medium and homogenized to produce an ointment. This type of material is already finding use in veterinary medicine, to treat infections in animals. Companies in Japan and Poland are applying the technique, clinical trials for wound-healing and surgical applications are under way in California, and U.S. researchers have plans for further studies. If the veterinary work proves successful, the way will be open to human applications of the technology. The extent of this market remains unclear, however.

Wound Dressing. Several research groups and companies, notably in Japan, have devised methods of making wound dressings from chitin or chitosan. As in the case of wound-healing soil is blended with the material. The nematocides. can be applied to lawns and turf grasses at any time in the growing season, followed by irrigation to ensure that the material penetrates the subsurface

Feed ingredients : Chitin and chitosan offer three main benefits as components of animal feeds: They permit food processors to recycle protein from food processing waste into animal feed; they have beneficial nutritional properties; and they control the release of feed additives in ruminant animals.

The high positive charge of ehitosan enables it to flocculate proteins in waste streams from food processing. Generally, solutions containing up to 1% chitosan are injected into the waste stream. After drying, the flocculated proteins contain about 0.5% to 8% chitosan and 30% to 70% protein.

Recovered proteins containing the chitosan flocculant could be used as diet supplements at level up to 10% of the diet of farm animals. Such a diet would contain about 0.05% to 0.1% chitosan ~ levels at which chitosan and its derivatives are nontoxic. Chitosan has been approved in the United States as a feed ingredient at such levels.

As a feed supplement, chitin offers the advantage of reducing lactose intolerance. Thus, animals that cannot normally metabolize feed supplements that contain lactose could eat a diet that contains whey. Such a move would help to dispose of some of the billion of kilograms of whey produced annually as a byproduct of cheese manufacture.

Chitin operates by stimulating the growth in the gut of bacteria that contain lactase. These bacteria break down the lactose in whey. Experiments in which boiler chickens received feed containing various types of chitin have shown that the substance prevents the diarrhea that normally results from feeding on whey. Studies also have shown similar results in cattle. In addition, chitosan and related substances control the release of feed additives in ruminants. The chitosan allows the additives to pass undigested through the rumen to the abomasum, or fourth stomach, where they are finally digested.

Insecticides : Chitinase enzymes have potential as insecticides or insecticide adjuvants. They work by attacking the chitin that exists in the exoskeletons of insects. What is required is an inexpensive way of producing the enzymes and delivering them to the appropriate location. One possibility, under study by Roger Layne at Louisiana State University, focuses on genetic engineering. The concept is to isolate the gene for chitinase and implant it in a common bacterium, such as E. coli. Once the altered bacteria find their way into the insect targets, they would release the chitinase enzyme to attack the chitin in their exoskeletons.

In addition to chitosan itself, seed treatments can use chitosan oligosaccaride or its particular degradation product. These products are made by treating chitosan with chitin-degrading enzymes or with acid; they are purified using ion-exchange resins. To apply them, seeds are soaked in solutions of the oligosaccharides.