Views: 10 Author: Site Editor Publish Time: 2021-10-29 Origin: Site
Liposomes are self-assembled gel-packed particles that exist naturally or can be prepared artificially. They are liposomes (hollow) made of lecithin and ceramide. They have the same bilayer structure as the skin cell membrane structure. It has excellent moisturizing effect on the skin, especially liposomes coated with moisturizing substances such as hyaluronic acid and polyglucoside are more excellent moisturizing substances. Phospholipids are dispersed in water to form closed multi-layer vesicles, each layer is a bilayer of lipids, and the center of the vesicle and the layers are separated by the water phase. Its size ranges from 20nm to tens of microns. In addition to the common spherical and ellipsoidal shapes, there will also be long tubular structures, and structures of various sizes and shapes can coexist. According to its structure, it can be divided into unilamellar liposomes, multilamellar liposomes and multivesicular liposomes. Because its structure is similar to biofilm, it is also called artificial biofilm. Now liposomes can also be prepared from artificially synthesized phospholipid compounds. It is also more and more widely used in the medicine, cosmetics and food industries.
1. Phospholipids: including natural phospholipids and synthetic phospholipids. The structure of phospholipids is characterized by a hydrophilic group composed of a phosphoric acid group and a quaternary ammonium salt group, and a lipophilic group composed of two longer hydrocarbon groups.
The natural phospholipids are mainly lecithin (phosphatidylcholine, PC), which is derived from egg yolk and soybeans, and is neutral.
Synthetic phospholipids mainly include DPPC (dipalmitoylphosphatidylcholine), DPPE (dipalmitoylphosphatidylethanolamine), DSPC (distearoylphosphatidylcholine), etc., all of which are hydrogenated phospholipids, with stable properties and resistance to It has strong oxidizing properties and stable finished products, and it is the first choice for auxiliary materials abroad.
2. Cholesterol: Cholesterol and phospholipids are the basic substances that together constitute cell membranes and liposomes. Cholesterol has the effect of regulating membrane fluidity, so it can be called liposome "fluidity buffer".
Liposomes can encapsulate both fat-soluble and water-soluble substances. After being encapsulated by liposomes, the substance will have different characteristics from its own. Due to its unique molecular structure and physical and chemical properties, liposomes have the following characteristics:
1. Targeting and lymphatic targeting: passive targeting of the reticuloendothelial system of the liver and spleen.
2. Slow-release effect: slow release, delay renal excretion and metabolism, thereby prolonging the action time.
3. Reduce drug toxicity: Liposome membrane material is similar to mammalian cells and is composed of phospholipids. It is not a foreign body to the body, does not cause local tissue damage, does not induce allergic reactions, and can be used for many times and is non-toxic to humans.
4. Improve stability: For example, insulin liposomes, vaccines, etc. can improve the stability of the main drug.
5. Affinity with cells: As the structure of liposomes is similar to cell membranes, liposomes have a strong affinity with cell membranes, which can increase the ability to penetrate cell membranes and play a role in enhancing treatment.
6. Long-lasting: Under the protection of liposome bilayer, the drug can avoid oxidation, degradation, or damage by acids or enzymes in the human body, thereby prolonging the time of action of the drug.
7. Controllability of the drug distribution in the tissue: During the preparation process, the surface properties such as particle size, surface charge, etc. can be changed to improve the selectivity and orientation of the liposome drug to the target area, and to control the drug in the tissue In the distribution, thereby reducing toxicity and reducing side effects.