Chitosan, also known as chitin, is the only natural cationic polysaccharide because it contains a large amount of amino polysaccharides. It is mainly extracted from the shells of crustaceans or the exoskeletons of insects. Chitin is a polysaccharide formed from N-acetyl-2-amino-2-deoxy-D-glucose through β-1,4 glycosidic bonds, that is, N-acetyl-D-glucosamine. Chitosan is the deacetylation product of the amino group on chitin, and its reactivity and solubility are stronger than those of chitin. Chitosan ranks second in content in nature, only lower than cellulose, and can be recycled, making it an ideal biomedical material. Chitosan has many excellent properties: no pollution to the environment, high biocompatibility and degradability, wide source, mucoadhesiveness, antibacterial activity, etc.
Hydrogel is formed by cross-linking water-soluble polymers. The cross-linked network structure can swell in water but disperse. It can maintain a high-water content but does not contain solvents, and can reach tens or even hundreds of times. Water absorption is a very strong water-absorbent material, in which the liquid water is fixed in the three-dimensional polymer network, and the entire hydrogel system can maintain good stability. The soft texture of hydrogel is similar to that of living tissue. Its good biocompatibility makes it have broad application prospects in the field of biomedicine. For example, it can be used as a drug sustained-release material, protein electrophoresis, contact lenses, artificial plasma and skin, tissue filling materials, tissue engineering scaffolds, etc.
Chitosan hydrogel has low toxicity and high biocompatibility. As a smart hydrogel, it is also pH or temperature sensitive and does not affect the efficacy of the drug itself. It is used as a drug sustained-release material and tissue engineering. It has good application prospects in fields such as stents and medical dressings.
Drug Delivery Systems for Medical Use of Chitosan Hydrogels
The drug release system mainly refers to the process of drug control and drug control. Due to the network effect, the gel can play a better role in the storage and fixation of drugs. At the same time, when the swelling degree changes, it can Intervening and controlling the release rate of drugs can also make the drug degrade and metabolize faster in the body. Therefore, hydrogels have great development potential and practical value whether they are administered directly orally, sprayed into the nose, or vacuum injected.
The main indicators of hydrogels used for drug release include pH and temperature-sensitive hydrogels. As for temperature-sensitive gels, when the human body temperature is 37 degrees Celsius, the gel will expand due to hydrophilicity. When the pH value of the human intestinal tract is high, the gel will expand and release the drug; when the pH value of the human intestinal tract is low, the own gastric environment cannot release the drug to avoid losing the effect of the drug due to the strong acidity of gastric juice.
Researchers have developed a new type of xanthan gum and chitosan composite hydrogel. By compounding it with drugs with an alkaline pH, they can release the drugs in an acidic pH environment. The degree of deacetylation in chitosan molecules is adjusted, thereby intervening in the physical and chemical properties. Some researchers combined the three ingredients of chitosan, pectin and gelatin, and used glutaraldehyde as a cross-linking agent to obtain a chitosan-based gel. This hydrogel is very sensitive to pH and can Used in drug release systems as a control reagent for the treatment of gastrointestinal diseases or antacid tablets, to reduce the toxic side effects produced during the burst release process, and at the same time play a very good role in biocompatibility and retention Effect. In addition, some researchers have combined chitosan fatty acid ester complex with sodium glycerophosphate and developed a hydrogel with good temperature sensitivity, which can be used as a carrier for local injection treatment. Using its own esterification modification to improve the sensitivity and stability of chitosan at different temperatures has great potential for development in overcoming tumor difficulties.
Chitosan Hydrogel Dressing for Medical Use
The hydrogel itself is very soft in texture and has sufficient contact with the wound. At the same time, it can also create a suitable moist environment for the wound, which is conducive to wound healing. Medical dressings developed by using chitosan hydrogel have the advantages of high softness, comfortable use, and full contact with wounds. They can also reduce pain and control bleeding. Some hydrogels can also play an antibacterial and anti-inflammatory role. In addition, during the healing of injured areas and the production of new skin, chitosan hydrogel can degrade itself and be more easily absorbed by the body, which can reduce patients' pain and promote new skin growth, and is more effective in treating high-heat wounds.
Currently, there are medical colloid dressings on the market. The main ingredients of this dressing are highly water-soluble rosacetate and chitin. It can reduce pain, inhibit bacterial growth, eliminate inflammation, promote wound healing, reduce scar hyperplasia, Improves the quality of wound repair and is very effective in treating and repairing surgical wounds, burns, and ulcers.
Tissue Engineering Scaffolds Using Chitosan Hydrogel in Medicine
Hydrogel is a three-dimensional network structure, which contains a lot of water in the grid, and can transport nutrients and metabolic substances, which can better protect the body's cells. In addition, hydrogel can also be injected into the body by injection. The wound caused during the operation is small, and when the internal conditions of the body change, gel can be generated at the injection site. Under a suitable environment, the gelation reaction has less impact on the effect of loaded drugs, and it is a carrier medium suitable for transporting drugs. Therefore, it itself has greater advantages.
Figure 1. The chitosan-based biomimetic materials and the forms of material prepared.(Zhang Z, et al.; 2021)
Chitosan itself is filled with many positive charges because of its own amino component, which attracts the negative charges on the cell wall, allowing cells to attach; after degradation, the products produced are compatible with other organisms. In addition, chitosan can also prevent adhesion, reduce inflammation, sterilize and other functions, which is helpful for repairing body tissues. Therefore, chitosan materials can be used in the field of tissue engineering scaffolds.
References
- Zhang Z, et al.; Research Progress of Chitosan-Based Biomimetic Materials. Mar Drugs. 2021, 19(7):372.
- Wang X, et al.; Chitosan-Based Hydrogels for Infected Wound Treatment. Macromol Biosci. 2023, 23(9): e2300094.
