Keywords: chitin, chitosan, biomaterial, adsorbent, antioxidant, high added value product. Introduction Chitin is considered the second most abundant polysaccharide after cellulose on Earth, being first described by Henri Braconnot in Open in a separate window.
Figure 1. Structural composition and arrangement of chitin in the shell of crustaceans. Table 1 Sources of chitin and chitosan. Figure 2. Table 2 Several characterization methods to evaluate the deacetylation degree and average molecular weight of chitosan. Characterization Methods Chitosan Property Ref. Potenciometric titration Deacetylation degree [ 12 , 13 ] Elemental analysis [ 14 ] Fourier transform infrared FTIR [ 15 , 16 , 17 , 18 ] Nuclear magnetic resonance NMR [ 19 , 20 ] Viscosimetry Molecular weight [ 21 , 22 ] Gel permeation chromatography [ 23 , 24 , 25 ].
Chitosan Chitosan was discovered by Rouget in after heating chitin in an alkaline medium [ 26 ]. Figure 3. Table 3 Main chemical properties of chitosan, according the information reported in [ 28 ]. Linear aminopolysaccharide with a high nitrogen content Rigid d -glucosamine structure: hydrophilicity, crystallinity Weak base pK a : 6. Deprotonated amino group can act as strong nucleophile Enable to form intermolecular hydrogen bonds: high viscosity Existence of reactive groups for chemical activation and cross-linking Insoluble in water and organic solvents, but soluble in dilute aqueous acid solutions.
It forms salts with organic and inorganic acids Complexing and chelating properties Ionic conductivity Polyelectrolytes at acid pH Cationic biopolymer with high charge density one positive charge per glucosamine residue Flocculating agent interacts with negatively charged molecules Entrapment and adsorption properties filtration and separation Film-forming ability adhesive materials for isolation of biomolecules Biological properties biocompatibility bioadhesivity bioactivity non-toxic biodegradable adsorbable antimicrobial activity fungi, bacterial, viruses antiacid, antiulcer and antitumoral properties blood anticoagulants hypolipidermic activity.
Modification of Chitosan by Functionalization The presence of amine and hydroxyl groups provides interesting applications to chitosan, since these can be modified to improve certain properties of this biopolymer.
Figure 4. Chitosan hydrogels obtained by hydrophobic or crosslinking interactions. Graft Copolymerization The graft copolymerization of synthetic polymers with chitosan is of great interest in several fields.
Figure 5. Carboxymethylation As was indicated in the previous sections, one of main disadvantages of chitosan is its low solubility. Figure 6. Etherification Chitosan was also grafted with propylene epoxide under basic conditions to form a hydroxypropylchitosan composite.
Esterification Another alternative to improve certain properties of chitosan is to carry out esterification reactions with the chitosan molecule. Figure 7. Phosphorilation The phosphorylation of chitosan modifies their biological and chemical properties due to this treatment improves its bactericidal and osteoinductive properties. Figure 8. Phosphorylation of chitosan using P 2 O 5.
Sulphatation Both O -sulfated derivative [ 52 ] and N -sulfated chitosan [ 53 ] are of interest in biomedical applications as anticoagulants. Applications of Chitosan Taking into account that chitosan can be modified to improve some of its physical, chemical or biological properties, these chitosan-based materials have been highly tested in a wide range of applications.
Table 4 Some applications of chitosan in biomedical and pharmaceutical material. Uses in Pharmacy and Medicine As was previously described, chitosan is a biopolymer with interesting biomedical applications due to its low toxicity, biodegradability and biocompatibility. Biomaterial Chitosan displays a wide range of applications as a biomaterial due to its good behavior in the human body since it has been reported that this biopolymer displays antimicrobial activity, bioactivity, chemotactic action, immunostimulaion, enzymatic biodegradability, mucoadhesion, or epithelial permeability, favoring its adhesion with different types of cells [ 66 ].
Tissue Engineering Several materials are developed according to the wound type and healing mode. Table 5 Some applications of chitosan in tissue engineering. Figure 9.
Figure Different methodologies to synthesize three-dimensional chitosan scaffolds. Wounds and Burns The healing of wound and burns is a biological process related with growth and tissue regeneration. The wound healing process has five important steps [ 84 ]: Homeostasis Inflammation Migration Proliferation Maturation Several studies have reported the use of chitosan membranes to facilitate wound healing with potential application in patients with severe burns or wounds.
Drug Delivery The development of drugs in the clinical field is a great challenge due to the fact most drugs do not achieve desired clinical effects as a result of their inability to reach the target site of action. Table 6 Chitosan-based drug delivery systems.
Artificial Kidney Membrane Commercially both cuprophan and cellulose are used as semipermeable artificial kidneys due to their mechanical strength and good permeability. Blood Vessel Vascular diseases are one of the highest causes of mortality worldwide. Ophthalmology Chitosan has also interesting applications in the field of ophthalmology due to its mechanical stability, optical clarity, gas permeability-partially towards oxygen, immunologically compatibility, wettability, tear strength, tensile strength, elongation capacity and biodegradability, making this biopolymer a potential material to be used for the perfect contact lens [ ].
Cosmetics Chitosan is the only natural cationic polymer that turns viscous on being neutralized with acid. Agricultural Applications The use of both chitin and chitosan in agriculture is focused on four directions: Plant protection against diseases and plagues pre- and post-harvest. Support of beneficial microorganism-plant symbiotic relationships.
Enhancing biological control and antagonist microorganism action. Plant growth development and regulation. Food and Nutrition Applications N -Acetylglucosamine coming from human milk improves the growth of bifidobacteria, which inhibit the growth of other microorganisms and produce lactase that is necessary for milk digestion.
Table 7 Applications of chitosan in the field of food and nutrition. Chitosan Application Example Additive Clarification and deacilification of fruits and beverages Color stabilization Emusifying agent Food mimetic Natural flavor extender Texture controlling agent Thickening and stabilizing agent Antimicrobial agent Bactericidal Fungicidal Measure of mold contamination in agricultural commodities Edible film industry Controlled release of antimicrobial substances Controlled release of antioxidants Controlled release of nutrients, flavors and drugs Controlled moisture transfer between foo and surrounding environment Nutritional quality Antigastritis agent Dietary fiber Hypocholesterolemic effect Infant feed ingredient Livestock and fish feed additive Production of single cell protein.
Antioxidant and Antimicrobial Properties Chitosan is a polysaccharide with antimicrobial properties. Table 8 Some microbial applications of chitosan and chitosan derivatives.
Chitosan Streptococcus Dental materials [ ] Listeria monocytogenes, Pseudomonas aeruginosa and S. Adsorption of Pigments, Dyes and Metals As chitosan displays a polycationic structure, this biopolymer has been used as a flocculating agent but also as a chelating agent and to trap metals.
Table 9 Chitosan-based composites used in the adsorption of dyes. Table 10 Chitosan-based composites used in the adsorption of cations.
Pervaporation Pervaporation is a separation method where a liquid is transported through a non-porous liophilic membrane Figure Table 11 Chitosan-based composites and its uses in separation processes. Application Membrane Ref. Catalytic Applications Chitosan can be used for both homogeneous and heterogeneous catalysis. Preparation of 4 H -pyrimido [2,1-b] benzothiazole derivatives.
Synthesis of 1,4-dihydropyridines from the Hantzsch reaction. Carbon-Carbon Coupling Reactions Carbon-carbon coupling reactions enable the construction of organic molecules with a wide range of applications. Suzuki couplings using catalysts modified with 6-carboxymethylchitosan. Suzuki reaction with Pd 0 -chitosan based catalysts. Chitosan-based catalysts loaded with Ni 0 used in C-C.
Carbon-Nitrogen Coupling Reactions The most important and frequently used method to form C-N bonds via is the coupling of haloarenes. Carbon-Sulfur Coupling Reactions Recently, Cu-based catalysts have been employed in the carbon-sulfur coupling reactions.
Oxidation Reactions Chitosan-based metal catalysts have also been employed in oxidation reactions. Hydrogenation Reactions In this section, chitosan-based metal catalysts involved in hydrogenation of C-C and C-X are summarized. Chitosan-based catalysts loaded with Ru used in transfer hydrogenation reactions. Hydrogenolysis Reactions Likewise, a slurry containing chitosan with PdCl 2 adsorbed in ethanolic solution was reduced with NaBH 4 at room temperature, being active in the transformation of 2-phenyloxirane to 2-phenyl-ethanol, which is used in the fragrance industry [ ].
Catalytic Processes to Valorize Chitosan into Valuable Products In recent years, the scientific community is developing processes to valorize lignocellulosic biomass to obtain high-added value products.
Conclusions Chitosan is a natural polymer with tremendous biological properties such as biocompatibility, biodegradability and anti-infective activity, among others, due its high charge density, the existence of reactive hydroxyl and amine groups or its capacity of interact with other polymeric fractions through hydrogen bonds. Acknowledgments J. Author Contributions Conceptualization: J. Conflicts of Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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In this case, these films prepared from CF1 were too weak to maintain the acids can be added freely without any precipitation of film form. However, all alkali-treated or untreated cellulose, once cellulose has been dissolved in pure cellulose and cellulose-chitosan blends prepared from TFA. After casting the solution on a glass plate, the MPa.
These values are quite high and exceed solvents were removed by natural evaporation at room those of commercial cellophane.
Table 1 shows the temperature. Transparent films can be obtained by degrees of polymerization DPv of the original and peeling them off from the glass plate. Films prepared in regenerated celluloses. Clearly, acid hydrolysis occurred this manner have the amino groups protonated and in all the cellulose samples upon dissolution in TFA.
In However, a D P v higher than was found to be order to obtain the films with free amino groups, the sufficient for the films to have adequate physical films were soaked in 1 N N a O H at room temperature strength. TFA is a volatile cellulose solvent, and this for 1 day while still on the glass plate to remove the unique property may be the key to formation of strong acids.
The films separated spontaneously from the films. They were then washed Figure 2 shows X-ray diffraction patterns of untreated with water, and dried by being placed between a metal and alkali-treated cellulose and cellulose-chitosan plate and a filter paper at room temperature, for blend films.
Table 1. Preparation of cellulose-chitosan polymer blends 27 films, reflecting the high degree of similarity of both primary and secondary structures in these two linear polysaccharides.
Since many factors contribute to development of the patterns of aggregation of the beta- 1,inked polysaccharides, it is difficult to identify a particular element of the structure of chitosan as the dominant factor in its interaction with cellulose.
Some Fig. Scanning electron micrograph of cellulose-chitosan of the special characteristics and uses ofchitosan, such blend film by weight, alkali-treated. A method for the analysis of sugars in plant cell-wall polysaccharides by gas-liquid chromatography. Pathway of chitosan formation in Mucor rouxii. Enzymatic deacetylation of chitin. I Fig. X-ray diffraction patterns ofcellulose-chitosan blend Biochem. Weight ratios between cellulose and chitosan were: 1 Fengel, D.
Holzforschung, 31, treatment followed by washing with water. Isogai, A. Dissolution mechanism of cellulose in SO2-amine-dimethylsulfoxide. Molecular rearrangement of cellulose and chitosan J. Yet it is also clear that the Noguchi, J. Studies presence of the chitosan limits the crystallinity of the on chitin fibers and cellulose fibers blended with chitin.
It is interesting that the tensile strengths were Kobunshi Kagaku Japan , 30, Patel, D. Lyotropic mesomorphic formation of cellulose in trifluoroacetic acid-chlorinated The results, including X-ray diffraction data, SEM alkane solvent mixtures at room temperature. Atalla and Chitosan , eds S. Japan Soc. Smith, D. Solvent system for cellulose, US Pat.
ProcessDesign Develop. Related Papers. By Derval dos Santos Rosa. A review of cellulose and cellulose blends for preparation of bio-derived and conventional membranes, nanostructured thin films and composites. By Manal A. El-Sheikh , Hassan Ibrahim , and A.
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