Chitosan structure properties relationship and biomedical applications

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Cuticle, Ovipositors and Beetle cocoonCrustaceans e. Crab shell and Shrimp shellSquid e. Ommastrephes pen and Loligo stomach wallCentric Diatoms e. Thalassiosira fluviatilis and Algae and Fungi e. Mucor rouxi and Aspergillis nidulans. Chemical structure of chitin [4]. Although chitin is found naturally in large amounts through many sources, chitosan is only found in nature in limited quantities, such as in some fungi. The chitosan used in industrial or research applications is typically derived from chitin through the use of chemical or enzymatic treatments [ 4 ].

Chitosan is a copolymer of N-acetyl-D-glucose amine and D-glucose amine as shown in figure 2. The deacetylation of chitin is conducted by chemical hydrolysis under severe alkaline conditions or by enzymatic hydrolysis in the presence of particular enzymes, among of chitin deacetylase [ 78 ]. After cellulose, chitin is the second most abundant biopolymer [ 6 ] and is commonly found in invertebrates as crustacean shells or insect cuticles but also in some mushrooms envelopes, green algae cell walls, and yeasts [ 9 - 11 ].

At industrial scale, the two main sources of chitosan are crustaceans and fungal mycelia; the animal source shows however some drawbacks as seasonal, of limited supplies and with product variability which can lead to inconsistent physicochemical characteristics [ 12 ].

The mushroom source offers the advantage of a controlled production environment all year round that insures a better reproducibility of the resulting chitosan [ 13 ], chitosan is safe for both healthcare and biomedical application [ 514 ].

The mushroom-extracted chitosan typically presents a narrower molecular mass distribution than the chitosan produced from seafood [ 14 ], and may also differ in terms of molecular mass, DD and distribution of deacetylated groups [ 1315 ].

Chitosan oligomers can be prepared by degradation of chitosan using specific enzyme [ 5 ] or reagent as hydrogen peroxide [ 17 ].

Chitosan as a Biomaterial — Structure, Properties, and Electrospun Nanofibers

After production, many different tools such as pH-potentiometric titration, IR-spectroscopy, viscosimetry, 1H NMR spectroscopy, UV-spectroscopy, and enzymatic degradation can determine chitosan properties [ 5618 ]. In contrast, practical applications of chitin are extremely limited due to its poor solubility, if any [ 19 ].

Interestingly, the aqueous solubility of chitosan is pH dependent allowing processability under mild conditions [ 20 ]. Chitosan with protonated amino groups becomes a polycation that can subsequently form ionic complexes with a wide variety of natural or synthetic anionic species [ 20 ], such as lipids, proteins, DNA and some negatively charged synthetic polymers as poly acrylic acid [ 19 - 22 ].

As a matter of fact, chitosan is the only positively charged, naturally occurring polysaccharide [ 19 ]. Chitosan molecules have both amino and hydroxyl groups so that it can form stable covalent bonds via several reactions such as etherification, esterification and reductive amination reactions [ 56 ]. Chitosan have remarkable antibacterial activity [ 52324 ], along with antifungal [ 11 ], mucoadhesive [ 25 ], analgesic [ 11 ] and haemostatic properties [ 26 ].

Chitosan: Structure-properties relationship and biomedical applications – ScienceOpen

It can be biodegraded into non-toxic residues [ 2728 ] the rate of its degradation being highly related to the molecular mass of the polymer and its deacetylation degree — and has proved to some extent biocompatibility with physiological medium [ 2930 ].

All these singular features make chitosan an outstanding candidate for biomedical applications. Chemical structure chitosan [4]. Chitin and chitosan production Chitosan produced from crustacean shell such as crab and shrimp. Production of chitosan involves four steps: Chitosan production flow scheme [4, 31]. Chitosan as biomaterial Chitosan have several properties to be used in biomedical applications.

It has positive charges in acidic medium, due to protonation of amino groups, and it can bind with negative residues in the mucin, that lead to improve mucoadhesive properties [ 515 ]. Also positive charges on chitosan can bind to negative charges on red blood cells RBC so that chitosan used as haemostatic agent [ 53233 ].

Chitosan has two mechanisms to explain its antimicrobial activity. The first mechanism proposed that positive charges on chitosan could bind with negative charges at the bacterial cell surface, which alter permeability and leaks solutes outside the cells. Indeed, the amino groups of the D-glucosamine residues can protonate in the presence of proton ions that are released in the inflammatory area, resulting in an analgesic effect [ 34 ].

Chitosan is actually degraded in vivo by several proteases, and mainly lysozyme [ 113536 ]. Till now, eight human chitinases have been identified, three of them possessing enzymatic activity on chitosan [ 37 ]. The biodegradation of chitosan leads to the formation of non-toxic oligosaccharides of variable length.

These oligosaccharides can be incorporated in metabolic pathways or be further excreted [ 38 ]. The degradation rate of chitosan is mainly related to its degree of deacetylation, but also to the distribution of N-acetyl D-glucosamine residues and the molecular mass of chitosan [ 39 - 41 ]. Chitosan shows biocompatibility in biomedical applications such as sutures and artificial skins [ 561034 ] and was notably approved by the Food and Drug Administration FDA for use in wound dressings [ 42 ].

However, the compatibility of chitosan with physiological medium depends on the preparation method residual proteins could indeed cause allergic reactions and on the DD — biocompatibility increases with DD increase. Chitosan actually proved to be more cytocompatible in vitro than chitin.

Indeed, while the number of positive charges increases the interaction between cells and chitosan increases as well, which tends to improve biocompatibility [ 43 ]. Besides, some chemical modifications of chitosan structure could induce toxicity [ 35 ]. Production process of chitosan has great effect on chitosan properties because these processes control the degree of acetylation of chitosan, i. Chitosan has several biological properties that make it an attractive material for use in medical applications.

Chitosan: An Update on Potential Biomedical and Pharmaceutical Applications

Agricultural applications The abundance, biodegradability, nontoxic, and natural origin of chitosan allow it to be safely used in agricultural applications because it can be used without concerns of pollution, disposal, or harm to consumers if ingested.

Seed coating, leaf coating, fertilizer, and time released drug or fertilizer responses are some of the applications within agricultural where chitosan is utilized. The use of chitosan in these areas has shown to increase the amount of crops produced by improving germination, rooting, leaf growth, seed yield, and soil moisture retention, while reducing the occurrence of fungal infections and diseases [ 47 ].

It can also be utilized to breakdown food particles that contain protein and remove dyes and other negatively charged solids from wastewater streams and processing outlets [ 47 ]. The antibacterial and antifungal properties found in chitosan can also be used during the storage and preservation of food [ 44647 ].

Tissue engineering [ 444547 - 49 ], Wound Healing [ 44455051 ] and Drug Delivery [ 5253 ]. Some examples of biomedical applications of are artificial skin, surgical sutures, artificial blood vessels, controlled drug release, contact lens, eye humor fluid, bandages, sponges, burn dressings, blood cholesterol control, anti-inflammatory, tumor inhibition, anti-viral, dental plaque inhibition, bone healing treatment, wound healing accelerator, hemostatic agent, antibacterial agent, antifungal agent, weight loss effect [ 44 ].

Electrospinning of chitosan Electrospinning is a process that utilizes a strong electrostatic field to obtain ultrafine fibers from a polymer solution accelerated towards the grounded collector due to the motion of charge carriers present in the solution in order to complete the electrical circuit.

Chitin is the structural element in the exoskeleton of insects, crustaceans mainly shrimps and crabs and cell walls of fungi, and the second most abundant natural polysaccharide after cellulose. The complexity of the chitin structure, difficulty in its extraction and insolubility in aqueous solution limited the research on this polymer until s. The cationic nature of chitosan is rather special, as the majority of polysaccharides are usually either neutral or negatively charged in an acidic environment.

This property allows it to form electrostatic complexes or multilayer structures with other negatively charged synthetic or natural polymers [ 2 ]. The interesting characteristics of chitosan such as biocompatibility, non-toxicity, low allergenicity and biodegradability allow it to be used in various applications [ 3 ]. Besides, chitosan is reported to have other biological properties, such as antitumor [ 4 ], antimicrobial [ 5 ], and antioxidant [ 6 ] activities.

The degree of deacetylation, which is described by the molar fraction of deacetylated units or percentage of deacetylation, and the molecular weight of chitosan, were found to affect these properties [ 7 ].

Chitosan has been widely used for different biological and biomedical applications recently due to its unique properties. For instance, it can be used in water treatment [ 8 ], wound-healing materials [ 1 ], pharmaceutical excipient or drug carrier [ 9 ], obesity treatment [ 10 ] and as a scaffold for tissue engineering [ 11 ]. There is increased interest in pharmaceutical as well as biomedical applications of chitosan and its derivatives and significant development has been achieved.

It can be reflected in the increasing number of related publications throughout the years.