The most recent chemical, biochemical and medical information about the unique characteristics of chitins and chitosans

has been integrated for the first time 

to provide an overview of the performances of chitosan 

in the area of animal and human tissue regeneration. 

Chitins and chitosans for the repair of wounded skin, nerve, cartilage and bone   Riccardo A.A. Muzzarelli

A review article

Carbohydrate Polymers, 76 (2009) 167–182.

Elsevier, Amsterdam.

Chitins and chitosans are not present in the human tissues, but acetylglucosamine and chitobiose are found in glycoproteins and glycosaminoglycans: therefore, the use of chitin and chitosan is safe for the human body, as demonstrated on laboratory animals and in vitro tests. Since chitosan is biodegradable, non-toxic, non-immunogenic and biocompatibile in animal tissues, much research has been directed toward its use in medical applications such as drug delivery, artificial skin and blood anticoagulants.

Upon application of the commercial chitin-based dressings to traumatic and surgical wounds, hemostasis is immediately obtained: platelets are activated by chitin with redundant effects and superior performances compared with known hemostatic materials. To promote angiogenesis, indispensable to support physiologically ordered tissue formation, the production of the vascular endothelial growth factor is strongly up-regulated in wound healing when macrophages are activated by chitin / chitosan. The inhibition of activation and expression of matrix metalloproteinases in primary human dermal fibroblasts by low MW chitosans prevents or solves problems caused by metalloproteinase-2 such as the hydrolysis of the basement membrane collagen IV.

Biocompatible wound dressings derived from chitin are today available in the form of hydrogels, xerogels, powders, composites, films and scaffolds: the latter are easily colonized by human cells in view of the restoration of tissue defects, with the advantage of avoiding retractive scar formation. The growth of nerve tissue has been guided with chitin tubes covalently coated with oligopeptides derived from laminin. The regeneration of cartilage is also feasible because chitosan maintains the correct morphology of chondrocytes and preserves their capacity to synthesize cell-specific extracellular matrix: chitosan scaffolds incorporating growth factors and morphogenetic proteins have been developed. Impressive advances have been made with osteogenic chitosan composites in treating bone defects, particularly with osteoblasts from mesechymal stem cells in porous hydroxyapatite-chitin matrices.

The introduction of azido functions in chitosan has provided photo-sensitive hydrogels that crosslink in a matter of seconds, thus paving the way to cytocompatible hydrogels for surgical use as coatings, scaffolds, drug carriers, and implants capable to deliver cells and growth factors.

The peculiar biochemical properties of chitins and chitosans remain unmatched by other polysaccharides. The cotton-based wound dressing are today obsolete in the light of the performances of chitosan.

Some commercial chitin- and chitosan-based bandages and wound dressings.

Chitin-based:

Beschitin^® Unitika. Non-woven material manufactured from chitin. Available in Japan since 1982. Favours early granulation, no retractive scar formation. For traumatic wounds, surgical tissue defects.

Syvek Patch^® Marine Polymer Technologies. Made of chitin microfibrils from the centric diatom Thalassiosira fluviatilis grown under aseptic conditions. It is claimed to be 7 times faster in achieving hemostasis than fibrin glue, because it agglutinates red blood cells, activates platelets whose pseudopodia make a robust contact with chitin, and promotes fibrin gel formation within the patch, thus acting in a redundant way even on heparinized patients.

Chitipack S^® Eisai Co. Sponge-like chitin from squid. For traumatic wounds and surgical tissue defects. Favours early granulation, no retractive scar formation.

Chitipack P^® Eisai Co. Dispersed and swollen chitin supported on poly(ethylene therephthalate). For the treatment of large skin defects. Favours early granulation. Suitable for defects difficult to suture.

Chitosan-based:

Chitodine^® IMS. Chitosan powder with adsorbed elementary iodine, for the disinfection and cleaning of wounded skin and for surgical dressing.

Chitoflex^®. HemCon. Antibacterial, biocompatible wound dressing designed to be stuffed into a wound track to control moderate to severe bleeding. It adheres strongly to tissue surfaces forming a flexible barrier that seals and stabilizes the wound surface. Easily removed with saline or water.

Chitopack C^®. Eisai. Cotton-like chitosan obtained by spinning chitosan acetate salt into a coagulating bath of ethylene glycol, ice and NaOH; fibers washed with water and methanol. Complete reconstruction of body tissue, re-building of normal subcutaneous tissue, and regular regeneration of skin.

Chitopoly^® Fuji Spinning. Chitosan and Polynosic Junlon poly(acrylate) for the manufacture of antimicrobial wears, suitable to prevent dermatitis.

Chitosan Skin^® Hainan Xinlong Nonwovens. A chitosan-based skin substitute.

Chitoseal^® Abbott, based on chitosan, for bleeding wounds.

Clo-Sur^® Scion. A non-woven.

Crabyon^® Ohmikenshi. Made of cellulose viscose and chitosan mainly for comfortable sportwear.

HemCon^® HemCon. Freeze-dried chitosan acetate salt, for emergency use to stop bleeding. Used on battlefields since the time of the Desert Storm expedition in Iraq.

Tegasorb^® 3M. The dressing contains chitosan particles that swell while absorbing exudate and producing a soft gel. A layer of waterproof Tegaderm^® film dressing covers the hydrocolloid. For leg ulcers, sacral wounds, chronic wounds. Reportedly superior to Comfeel^® and Granuflex^®.

Vulnosorb^® Tesla-Pharma. Freeze-dried sponge of collagen and chitosan, on the European market since 1996.