Chitin and chitosan are biological polymers derived from the exoskeletons of arthropods and insects, beaks of birds, internal shells of cephalopods, and the cell walls of fungi. Take note that in its unadulterated form, chitin is a translucent, flexible, and tough material. On the other hand, chitosan is a derivative of chitin produced through the process of deacetylation in which chitin is treated with a sodium hydroxide solution.
Shells of shrimps and crabs are the most common sources of chitin. In fact, these shells are waste products of the shrimp canning and crabbing industries. Nonetheless, studies have explored the properties of chitin and chitosan, thus revealing further their potential expansive commercial, industrial, and biomedical applications.
The subsequent discussions enumerate and describe some of the notable applications of chitin and chitosan. Note that these applications are obtained from a review of relevant research or studies from different fields and disciplines.
Agricultural applications of chitin and chitosan: Fertilizer and pesticide
Several studies have explored and identified the possible agricultural applications of chitin and chitosan, particularly as a fertilizer and pesticide. For instance, a study by L. A. Hadwiger revealed that when absorbed by a plant, chitosan activates and improves its natural defense mechanism by influencing the biochemistry of plant cells. The study further showed that the application of this chitosan-based solution enhances seed germination, plant growth, and yields due to the improved defense response.
More specific agricultural applications of chitin and chitosan have been patented to promote commercialization. R. J Stoner and J. C. Linden filed a patent for inventing a chitin-based micronutrient elicitor that can be used as a seed coating, a component of irrigation water, or a part of a foliar spray mixture for treating nematode infestation in field crops. D. E. Freepons successfully secured a patent for a plant growth regulator made of chitosan and non-phytotoxic acid. This regulator promotes plant growth when used as a component of an aqueous solution or dry blend powders.
The aforementioned are some of the notable agricultural uses of chitin and chitosan. Take note that in the United States, the U.S. Environmental Protection Agency and the U.S. Department of Agriculture monitor and regulate the use of chitin and chitosan as components of fertilizers and pesticides.
Industrial of chitin and chitosan: Manufacturing and Food Processing
Chitosan can be used as a non-toxic and biodegradable alternative to plastics. A literature review by S. K. Shukla, A. K. Mishra, O. A. Arotiba, and B. B. Mamba mentioned that this polymer has structures that can be modified chemically and mechanically, thus resulting in the developed of derivative materials with newer properties and applications. The Wyss Institute at Harvard University successful developed a plastic-like material made from chitosan. Researchers used conventional casting and molding techniques, thus demonstrating specific applications in manufacturing plastic-like materials such as bottles and containers, toys, and components of consumer electronic devices.
Another application of chitin and chitosan is in self-healing protective coatings and paints. H. Y. Atay, L. E. Dogan, and E. Celik demonstrated in their study the use of chitosan-reinforced epoxy dye composite coating with self-healing properties. Other studies, such as the separate works of J. Carneiro et al. and M. L. Zheludkevich et al., investigated the use of chitosan as an additive for composite coating material with protective properties against corrosion. These studies mentioned that the chitosan-based coatings are capable of self-repair from surface abrasions.
The food manufacturing and processing industry can take advantage of the beneficial properties of chitin and chitosan. For example, the study of F. Shahidi, J. K. V. Arachci, and Y. J. Jeon demonstrated the use of chitosan as an inexpensive and natural alternative thickening and stabilizing agent in processed foods. Another study by S. Quintela et al. demonstrated the application of chitin and chitosan as a fining agent in winemaking. To be specific, the study showed the effectiveness of these polymers in removing a winemaking byproduct called ochratoxin. Note that an ochratoxin is a group of mycotoxins produced by some species of fungi that could cause acute toxicity in mammalian kidneys coupled with a potential human carcinogenic effect.
Medical applications of chitin and chitosan: Biomedical and Pharmaceutical
The United States and European Union have approved the marketing and application of bandages and hemostatic agents fortified with chitosan. Research has revealed that chitosan has properties that promote wound healing by accelerating blood clotting. A case study by M. A. Brown, M. R. Daya, and J. A. Worley that involved civilian emergency medical services revealed that the use of chitosan-based wound care products improves the survival rate from lethal arterial wounds due to their effects on rapid blood clotting that reduces blood loss.
A review of the literature by F. Khoushab and M. Yamabhai discusses other medicinal properties of chitin and chitosan. Such include reports about the immune-enhancement activity of chitin and its different derivatives, as well as antitumor, anticholesterolemic, antioxidant, antimicrobial properties.
The same review also mentioned specific applications in regenerative medicine. For example, chitin and chitosan are ideal scaffolds because they can form a temporary matrix and a porous structure for tissue to grow, as well as their biodegradability and non-toxicity. The mechanical strength of chitin also makes it ideal for use as tubes that could guide nerve regeneration, primarily by supporting nerve adhesion and neurite outgrowth.
Several studies reviewed by Brown et al. also reported cholesterol-lowering effects. In an animal model, chitin supplementation lowers cholesterol level as chitin binds to lipids, thus inhibiting lipid absorption. Another study mentioned that chitosan lowers cholesterol level simply by suppressing food intake. An alternative proposed mechanism explained that chitosan combines bile acids in the digestive tract and allows their excretion through defecation. This phenomenon decreases the resorption of bile acids, thus resulting in decreased cholesterol pool and decreased level of serum cholesterol.
The pharmaceutical applications of chitin and chitosan have also been explored. To be specific, several studies have suggested and demonstrated drug delivery and gene delivery using chitin-based nanostructures. The biocompatibility, biodegradability, and non-toxic properties of chitin and its derivatives, as well as their superior physical and chemical properties, make them ideal for engineering new classes of pharmaceutical delivery systems.
FURTHER READINGS AND REFERENCES
- Atay, H. Y., Dogan, L. E., & Celik, E. (2013). “Investigations of Self-Healing Property of Chitosan-Reinforced Epoxy Dye Composite Coatings.” Journal of Materials. 2013. DOI: 10.1155/2013/613717
- Brown, M. A., Daya, M. R., & Worley, J. A. (2009). “Experience with Chitosan Dressings in a Civilian EMS System.” The Journal of Emergency Medicine. 37(1): 1-7. DOI: 10.1016/j.jemermed.2007.05.043
- Carneiro, J., Tedim, J., Fernandes, S. C. M., Freire, C. S. R., Silvestre, A. J. D., Gandini, A., Ferreira, M. G. S., & Zheludkevich, M. L. (2012). “Chitosan-based Self-Healing Protective Coating Doped with Cerium Nitrate for Corrosion Protection of Aluminum Alloy 2024.” Progress in Organic Coatings. 75(1): 8-13. DOI: 10.1016/j.porgcoat.2012.02.012
- Freepons, D. E. (1989). “Plant Growth Regulator Derived from Chitin.” U.S. Patent US48121591A. Filed 31 March 1986, Granted 14 March 1989
- Hadwiger, L. A. (2013). “Multiple Effects of Chitosan on Plant Systems: Solid Science or Hype.” Plant Science. 208: 42-49. DOI: 10.1016/j.plantsci.2013.03.007
- Harvard Wyss Institute. (2014, May 5). “Promising Solution to Plastic Pollution.” The Harvard Gazette. Retrieved online.
- Khoushab, F. & Yamabhai, M. (2010). “Chitin Research Revisited.” Marine Drugs. 8: 1988-2012. DOI: 10.3390/md8071988
- Quintela, S., Villaran, M. C., De Armentia, I. L., & Elejalde, E. (2012). “Ochratoxin A Removal from Red Wine by Several Oenological Fining Agents: Bentonite, Egg Albumin, Allergen-Free Adsorbents, Chitin and Chitosan.” Food Additives & Contaminants. 29: 1168-1174. DOI: 10.1080/19440049.2012.682166
- Shahidi, F., Arachci, J. K. V., and Jeon, Y. J. (1999). “Food Applications of Chitin and Chitosan.” Trends in Food Science & Technology. 10(2): 37-51. DOI: 10.1016/S0924-2244(99)00017-5
- Shukla, S. K., Mishra, A. K., Arotiba, O. A. & Mamba, B. B. (2013). “Chitosan-based Nanomaterials: A State-of-the-Art Review.” Macromolecules. 59: 46-58. DOI: 10.1016/j.ijbiomac.2013.04.043
- Stoner, R. J. & Linden, J. C. (2008). “Micro Nutrient Elicitor for Treating Nematodes in Field Crops.” U.S. Patent US200800724949A1. Filed 27 March 2008.
- Zheludkevich, M. L., Tedim, J., Freire, C. S. R., Fernandes, S. C. M., Kallip, S., Lisenkov, A., Gandini, A., & Ferreira, M. G. S. “Self-Healing Protective Coating with “Green” Chitosan Based Pre-Layer Reservoir of Corrosion Inhibitor.” Journal of Materials Chemistry. 21: 4805-4812. DOI: 10.1039/C1JM10304K