Practical aspects related to application of chitin and its derivatives in wound management

Corresponding author: Karolina SKOŁUCKA-SZARY – M.Sc., e-mail: [email protected] Introduction Chitin (from the Greek word chiton – covering) is the second most widespread natural polysaccharide after cellulose. It was first isolated from fungi in 1811 by H. Braconnot [1], and its chemical structure was described for the first time in the doctoral dissertation of a Swiss researcher A. Hofmann in 1930 [2]. Chitin is a linear polysaccharide consists of 2-(acetylamino)-2deoxy-D-glucose monomers linked with β-glycosidic bonds at 1 and 4 positions. Chemical structure of chitin differs from that of cellulose due to presence of an acetylamino group –NHCOCH3 (at 2 position of N-acetylglucosamine unit) instead of one hydroxyl group [3]. The annual worldwide biosynthesis of chitin is estimated at 1010 to 1012 tons [4]. Chitin is a component of the cell walls of fungi [5], exoskeletons of arthropods (crustaceans, insects and arachnids) [6–8]; it can be also found in sponges [6] and anthozoans [9]. Chitin used in laboratory research and for industrial purposes is obtained primarily from marine invertebrates, such as crabs, shrimps, lobsters and krill. The process of chitin extraction is not complex but it is time consuming. It consists of grinding of crustacean exoskeletons, removal of CaCO3 (usually with concentrated HCl) and protein (with NaOHaq.), and finally decolorization [10–12]. Specific conditions for chitin extraction are adjusted for its biological source. In recent years, it is observed a growing scientific attention to chitin. The search in the PubMed database, which contains medical and biological articles published in English, produced more than 19 thousand records related to chitin [13]. The first research paper about chitin, authored by S. Morgulis, was published in Science as early as in 1916 [14]. Many previous studies showed that chitin does not exert a cytotoxic effect in vitro. It is physiologically inert and biodegradable. It has antibacterial properties and shows affinity to proteins [15]. Due to its specific physicochemical properties, processing of chitin is difficult, and therefore this biopolymer is rarely used for industrial purposes. Usually, chitin is processed into forms of gels, membranes, fibers, polymer films [15], or as a component of polymer blends [16]. Chitin is used in chromatography, food industry (immobilization of enzymes), manufacturing of biosensors and cosmetics, as well as for processing of industrial pollutants (water treatment) [15]. However, in recent years the most attention was focused on its biomedical applications. It is used especially for wound dressing materials (active dressings) [17], active compounds delivery systems (medications and growth factors), in tissue engineering (cellular scaffolds, primarily in orthopedics) [18] and in regenerative medicine (differentiation of stem cells) [19]. Many previous experiments and clinical trials showed that chitin and its chemical modifications are promising biomaterials that may constitute a breakthrough in wound product industry. It was proved that chitin is able to accelerate wound healing due to the beneficial effects it exerts on various processes, such as angiogenesis, granulation, epithelization and scar formation [20]. All these processes play a key role in physiological wound healing [21]. Biodegradation of chitin within the wound environment results in a release of its oligomers and monomers [22]. Chitin activates macrophages, stimulates fibroblasts proliferation and influences processes of vascularization within the wound [23]. Those properties distinguish chitin from an array of available natural and synthetic polymers used in wound dressing materials. The problem of poorly healing wounds affects millions of patients worldwide and can be potentially solved by the application of dressings containing chitin and its derivatives. According to literature, chronic wounds occur in 1–2% of population in developed countries [24, 25] and represent not only a serious therapeutic challenge (variable etiology, chronic inflammation, dynamic character of the process which is modulated by both systemic and local factors, the long-term and multidirectional treatment), but also a huge economic burden. The management of chronic wounds is estimated to contribute to ca. 2% of global healthcare costs in Europe [24].