Chitin is the most abundant natural amino polysaccharide and estimated to be produced annually almost as, much as cellulose. It has become of great interest not only as an underutilized resource but also as a new functional material of high potential in various fields and the recent progress in chitin chemistry is quite noteworthy.
The purpose of this review is to take a closer look at fibres made of chitin and its derivatives. Based on the current research and existing products, some new and futuristic approaches, in the development of novel fibres and their applications have been thoroughly discussed.
Introduction To Chitin And Chitosan
Chitosan is a sugar that is obtained from the hard outer skeleton of shellfish, including crab, lobster, and shrimp. It is used for medicine. Chitosan is used to treat obesity, high cholesterol, and Crohn’s disease. Chitosan is a natural, tough, cationic, biodegradable, and biocompatible polymer obtained from chitin by deacetylation.
Chitin is a polysaccharide obtained from exoskeletons of crustaceans and sea insects such as crab, krill, shrimp, and crawfish etc. Chitin is a naturally occurring polymeric material with a structure Similar to cellulose and was originally found to be present in fungi and later in the skeletons of insects and shellfish.
Chitin is insoluble in water but when it gets modified with boiling potassium hydroxide solution it became soluble in weaker acids. Chitosan is biocompatible, biodegradable and non-toxic with excellent antibacterial properties.
These qualities make it suitable for the use in many medical applications. It is versatile material, which is able to use as fibre, films, beads, gels and support matrices or blended with the other materials. This fibres and films are suitable for use in wound care whereas the beads are used as the vehicle for drug delivery.
When this chitosan is used as a food supplement with an improvement in the HDL cholesterol or say total cholesterol ratio. Chitosan has a wide range of uses in pharmaceutical, dietary and water treatment industries.
Chitosan has a number of commercial and possible biomedical uses. It can be used in agriculture as a seed treatment and biopesticide, helping plants to fight off fungal infections.
In winemaking, it can be used as a fining agent, also helping to prevent spoilage. In industry, it can be used in a self-healing coating. In medical, it may be useful In bandages to reduce bleeding and as an antibacterial agent.
Chitosan has been having used in limiting fat absorption, which would make it useful for dieting. Chitosan has a biomaterial of the future with biocompatibility, antibacterial and biodegradable properties that can enhance the properties of many different materials for use within the medical textile world.
Other uses of chitosan that have been researched include use as a soluble dietary fiber. Forming chitosan by partial deacetylation of chitin Commercial chitosan is derived from the shells of shrimp and other sea insects.
Chitosan is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crabs and shrimp and cell walls of fungi. On average, the molecular weight of commercially produced chitosan is between 3800 and 20,000 Daltons.
A common method for the synthesis of chitosan is the deacetylation of chitin. Chitosan of linear unbranched structure exhibits an excellent viscosity. Because the viscosity of chitosan significantly influences its properties especially the biological properties and degradation, the effect of different parameters. The temperature on viscosity has been extensively explored.
It was also found that the viscosity of chitosan is changed along with changing the deacetylation conditions. Therefore, the deacetylation conditions should be precisely controlled during the preparation process. The degradation rate of chitosan is also dependent on weight and the distribution and arrangement of acetyl groups.
It was revealed that degradation rate of chitosan is found to be inversely proportional to weight. Studies revealed that high weight chitosan exhibits very low degradation rate, while low weight chitosan exhibits faster degradation rate. Chitosan comprises three reactive sites; one amino group and two hydroxyl groups in each glucosidic residue.
The amino group of chitosan is very important because it is pH sensitive, which is responsible for cationic nature of chitosan as well as governs different physicochemical properties of chitosan such as solubility and biological properties the solubility of chitosan is dependent on the pH-sensitive amino groups, which have pKa of 6.3.
At low pH, amino groups become protonated allowing chitosan to dissolve the forming soluble cationic polysaccharides. Above pH 6, an amino group is deprotonated rendering chitosan insoluble. In addition to pH, the solubility of chitosan is also dependent on the used deacetylation method, ionic strength, and distribution of acetyl group along the chain.
Recently, water-soluble chitosan was obtained in the presence of glycerol-2-phosphate. Stable chitosan solution was obtained at pH 7 Schematic illustration of the solubility of chitosan A Review on Bionanocomposites Based on Chitosan … 175 and room temperature, while gel was formed upon heating to around 40 °C.
The sol-gel transition was partially reversible based on the gelation temperature and experimental conditions. One successful example of chitosan gel has been clinically used for cartilage repair is chitosan-glycerol phosphate gel, which is exemplified in the market by BST-CarGel.
The amino groups also provide a reactive site allowing ease functionalization of chitosan, for example, amino groups facilitates the adsorption and/or chelation of metal cations. The ease functionalization of chitosan allows altering and tailoring its properties such as cationic nature and acidic solubility.
For instance, by sulfating the amino group of chitosan, chitosan became anionic, water-soluble, and acquired anticoagulant property.[1,5,6] Biodegradation can be regarded as a process in which the degradation results from the action of microorganisms such as bacteria, fungi, or algae. Biodegradation can be generally divided into two steps.
The first step is DE polymerization or chain cleavage where the longer polymer chain undergoes backbone scission into smaller oligomeric fragments with the help of enzymes secreted by microorganisms. The second step is mineralization, which occurs inside the cell in which small oligomeric fragments are converted to biomass, minerals and salts, water, and gaseous substances such as carbon dioxide under aerobic environments and methane under anaerobic environments.
Bio-based and biodegradable polymers (e.g., chitosan) and their composites may be broken down by the enzymes secreted by microorganisms. Once broken down to monomeric level, the polymer is used as the carbon source for the microorganism metabolism. Chitosan can be degraded by enzymes. During a degradation period of 160 days, the compost moisture content was maintained at 48–50 % and the pH at 7.8–8.5 to ensure favorable conditions for the compost microorganisms involved in the biodegradation process.[2,3,4]
Chitosan can be degraded by enzymes. During a degradation period of 160 days, the compost moisture content was maintained at 48–50 % and the pH at 7.8–8.5 to ensure favorable conditions for the compost microorganisms involved in the biodegradation process.[2,3,4]
Equipment- Knauer HPLC Pump 64, Waters 712 WISP autoinjection, Knauer column oven & control unit (set to 30C), Knauer differential refract meter (DRI) and Dionex UI 20 Universal interface (PC Link)
Columns- Progel –TSK PWxl guard, Progel-TMK G6000 PW xl, Progel TSK G4000 PWxl and Progel –TSK G2500PWxl, linked in series
Eluent- Acetic Acid (AcOH, 0.5M) containing sodium acetate (NaOAc, 0.2M)
He degassed immediately prior to use.
Flow Rate- 0.5mL/minute
Calibrants- Pollutant polysaccharides (MP 853, 380, 186, 100, 48, 23, 7, 12.2 & 5.8 kDa) dissolved overnight in eluent (1 mg/mL, 100mL injections)
Data – Data collected by PC using Dionex Chromeleon software (v. 6.11) Connection to the DRI detector via the UI20 Interface. Collected data were analyzed using Polymer Laboratories PL Caliber Reanalysis software (v. 7.04).
All solutions were filtered (Titan nylon membrane filters, 0.20nano meter) prior to injection.
Applications of Chitosan
Due to the unique properties of chitosan as mentioned in previous sections, they have many potential applications in various fields such as environment, food packaging, drug delivery, tissue engineering, and other biomedical applications which are here discussed.
Conclusion and Future Perspective
Present chapter reviewed chitosan bio-Nano composites studies. Making a truly eco-friendly product keeps both environment and human safety in mind. At a minimum, the product is nontoxic. Other eco-friendly attributes include the use of sustainable ingredients, produced in ways that will not deplete the ecosystem.
A naturally occurring polysaccharide, chitosan, shows promise for safe use in healthcare products being a non-toxic, biocompatible material. However, care must be taken to ensure that it is pure, as protein, metal or other contaminants could potentially cause many effects both in the derivative synthesis and in dosage forms.
After derivatization (or cross-linking), unreacted reagents should be thoroughly removed to prevent confounding results as many reagents are cytotoxic uncoupled. It was shown that for special applications like biomedical, packaging, the mechanical and thermal properties of pure chitosan were not sufficient.
Furthermore, many research studies focused on systems with chitosan preferred to synthesize chitosan derivatives at Nanoscale level using various methods. The addition of a few clay nanoparticles enhanced mechanical and thermal properties reducing the limitations of simple chitosan system to be applied in a field which requires a certain strength and thermal stability. By combination of chitosan
By combination of chitosan Nanocomposites with other different polymeric systems, good results were obtained regarding the antimicrobial activity, solubility, drug release efficiency, enzyme immobilization, increased biocompatibility and cytotoxicity, barrier properties offering a wide range of applications (e.g., food packaging, biomedical and pharmaceutical, tissue engineering) which will be likely involved in our future lives.
- Domard A, Domard M (2001) Chitosan: structure–properties relationship and biomedical applications. Polymeric biomaterials. Marcel Decker Incorporated, New York
- Mater. Sci., Vol. 22, No. 5, August 1999, pp. 905-915. © Indian Academy of Sciences. M N V RAVIKUMAR Department of Chemistry, University of Roorkee, Roorkee 247 667, India
- Eco-Friendly Chitosan-Based Nanocomposites: Chemistry and Applications Catalina Natalia Cheaburu-Yilmaz, Onur Yilmaz and Cornelia Vasile
- ISBN 978-81-322-2473-0 (eBook)
- DOI 10.1007/978-81-322-2473-0 Library of Congress Control Number: 2015940723 Springer New Delhi Heidelberg New York Dordrecht London © Springer India 2015
- Medical Textiles and Biomaterials for Healthcare edited by Professor S C Anand, Professor J F Kennedy, Dr M Miraftab, Dr.S Rajendran ISBN-10: 0-8493-1780-0