1. Chitosan molecular chains contain a large number of amino and hydroxyl groups. These polar groups can interact with polar groups (such as carboxyl and hydroxyl groups) on the surface of biological mucous membranes through hydrogen bonds, thus enabling the adhesion of chitosan on the mucous membrane surface.
Hydrogen bonds are a type of intermolecular force. When the amino and hydroxyl groups on chitosan molecules approach the carboxyl and hydroxyl groups on the surface of biological mucous membranes, hydrogen bonds are formed due to the electrostatic attraction between hydrogen atoms and highly electronegative atoms (such as oxygen and nitrogen), causing chitosan to attach to the mucous membrane surface.
2. The positively charged amino groups of chitosan can attract molecules with negative charges (such as glycoproteins and phospholipids) on the surface of biological mucous membranes through electrostatic interactions, promoting the adhesion of chitosan to the mucous membrane surface.
In a physiological environment, the surface of biological mucous membranes usually carries a certain negative charge. The amino groups on chitosan molecules will be protonated and carry a positive charge under appropriate pH conditions. The electrostatic attraction between positive and negative charges causes chitosan to approach and adhere to the mucous membrane surface.
3. Chitosan molecules have a certain degree of flexibility and can undergo conformational changes on the surface of biological mucous membranes. Through the entanglement of molecular chains and the intertwining with biological macromolecules on the mucous membrane surface, the adhesion effect is enhanced.
The molecular chains of chitosan are not rigid. When they come into contact with the surface of biological mucous membranes, they will change their own conformations and entangle with the molecular chains of biological macromolecules (such as proteins and polysaccharides) on the mucous membrane surface, just like ropes entangling together, thereby increasing the stability of adhesion.
4. Chitosan can form complexes with metal ions on the surface of biological mucous membranes. This complexation acts as a bridge between chitosan and the mucous membrane, promoting the occurrence of adhesion.
There are some metal ions on the surface of biological mucous membranes. Groups such as amino and hydroxyl groups on chitosan molecules can act as ligands to undergo complexation reactions with these metal ions, forming stable complexes, which makes chitosan closely connected to the mucous membrane.
5. Chitosan can form a hydrogel layer on the surface of biological mucous membranes. Through its good hydrophilicity and viscosity, it can fill the tiny gaps on the mucous membrane surface and fit closely with the mucous membrane to achieve adhesion.
Chitosan can form a hydrogel under certain conditions. The hydrogel contains a large amount of water and has a certain degree of viscosity. It can flow into the tiny depressions and pores on the mucous membrane surface, increasing the contact area with the mucous membrane, thereby improving the adhesive force.
6. The hydrophobic regions of chitosan molecules and the hydrophobic regions on the surface of biological mucous membranes attract each other through hydrophobic interactions, contributing to the adhesion of chitosan on the mucous membrane surface.
Although chitosan is generally hydrophilic, there are also some hydrophobic regions in its molecules. There are also some hydrophobic regions on the surface of biological mucous membranes. When the two approach, the hydrophobic regions will aggregate with each other to reduce contact with water, thereby generating hydrophobic interactions and promoting adhesion.
7. The amino groups of chitosan can react with aldehyde groups on the surface of biological mucous membranes through Schiff base reactions to form covalent bonds, making chitosan firmly adhere to the mucous membrane.
The Schiff base reaction is a chemical reaction between amino groups and aldehyde groups, generating Schiff base compounds containing carbon – nitrogen double bonds. Through the formation of this covalent bond, the connection between chitosan and the mucous membrane is more stable and not easy to fall off.
8. The presence of chitosan can change the surface tension of the surface of biological mucous membranes, making it easier for chitosan to spread and attach on the mucous membrane surface, enhancing adhesion.
Surface tension affects the spreading of liquids on solid surfaces. The addition of chitosan will reduce the surface tension of the mucous membrane surface, enabling the chitosan solution to better spread on the mucous membrane surface, increasing the contact area with the mucous membrane, and thus improving the adhesion effect.
9. Chitosan molecules can bind to nucleic acid molecules on the surface of biological mucous membranes through base complementary pairing or electrostatic interactions, achieving adhesion.
Nucleic acid molecules have specific base sequences and charge distributions. Groups on chitosan molecules can interact with the bases or charges of nucleic acid molecules, such as electrostatic attraction and hydrogen bonds, so that chitosan can attach to the biological mucous membrane regions containing nucleic acids.
10. The high molecular weight characteristic of chitosan makes it have high viscosity. When in contact with biological mucous membranes, it can form a viscous film layer and adhere to the mucous membrane surface through physical viscous effects.
The molecular chains of high – molecular – weight chitosan are longer, and the intermolecular interactions are stronger, resulting in a higher viscosity of the solution. The viscous film layer formed by this viscous chitosan solution on the mucous membrane surface can tightly adhere to the mucous membrane, playing an adhesive role.
11. Chitosan can achieve adhesion through specific recognition and binding interactions with immunoglobulins on the surface of biological mucous membranes.
Immunoglobulins have specific structures and antigen – binding sites. Certain groups or structures on chitosan molecules may have specific interactions with immunoglobulins, just like the relationship between a key and a lock, so that chitosan can adhere to the mucous membrane regions containing immunoglobulins.
12. During the adsorption process of chitosan on the surface of biological mucous membranes, it will cause changes in the microenvironment on the mucous membrane surface, prompting the rearrangement of biological molecules on the mucous membrane surface, thereby enhancing the interaction and adhesion between chitosan and the mucous membrane.
When chitosan is adsorbed on the mucous membrane surface, it will change local factors such as ion concentration and pH value. These changes will affect the conformation and distribution of biological molecules on the mucous membrane surface, causing them to rearrange to better interact with chitosan and improve the adhesive force.
As a leading manufacturer and supplier of chitosan and its derivatives, Tianya Chemical provides high-quality products that leverage these adhesion mechanisms, meeting diverse application needs in biomedicine, pharmaceuticals, etc.
The article is to be continued. Please refer to the next article Adhesion Mechanisms of Chitosan (2).
