The membrane material of liposomes is divided into:
Neutral phospholipids: Phosphatidylcholine (PC) is the most common neutral phospholipid and is a major component of lecithin and soy phospholipids. Among them, the synthesis of phosphatidylcholine includes: dipalmitoylcholine (DPPC), distearoylcholine (DSPC), dimyrist phosphatidylcholine (DMPC), etc.
Negatively charged phospholipids: also known as acid phospholipids, including: phosphatidic acid (PA), phosphatidylglycerol (PG), phosphatidylinositol (PI), etc.
Positively charged phospholipids: all are synthetic, including stearamide (sa) cholesterol derivatives, etc.
Cholesterol (CLS): As an amphiphilic *** lipid, cholesterol can penetrate into the phospholipid membrane in a high concentration.
Preparation method: solvent injection method: solvent injection method is a more commonly used method for preparing liposomes, generally the membrane can be dispersed in ethanol or ether, and then the solution is injected into the aqueous solution of the drug, and the liposomes can be obtained by homogenization or ultrasound after the solvent is exhausted. Compared with other methods, this method can avoid the use of toxic solvents such as chloroform, and the use of safe and inexpensive ethanol as a solvent is also more conducive to large-scale promotion. However, there are still problems in this method that solvent residues are difficult to remove.
Thin film dispersion method: The thin film dispersion method is simple and easy to operate, generally after dissolving the drug in an organic solvent, removing the solvent under reduced pressure, so that the lipid forms a thin film on the container wall, and then adding a buffer solution containing water-soluble drugs, and fully shaking to obtain liposomes. However, this method uses a large amount of organic solvent and takes a long time.