In the past 30 years, significant progress has been made in research in the field of liposomes. Various types of liposomes, such as different particle sizes, phospholipid composition, suitable additives to meet clinical needs, and unique surface morphology, have been applied in various treatments.
(1) Protecting drugs from degradation
Liposomes are used to protect encapsulated drugs from enzymatic degradation in circulation. Thanks to the action of the matrix, the lipids used in the formulation are sufficiently resistant to enzymatic degradation, allowing liposomes to protect encapsulated drugs during systemic or extracellular fluid circulation. When liposomes enter cells, the encapsulated drugs are released through membrane diffusion or lysosomal enzyme degradation of the lipid membrane. They can protect β- Antibiotics sensitive to lactamases such as cephalosporins and penicillin should be avoided β- The degradation effect of lactamases enhances drug efficacy. Similarly, liposomes can also protect the drugs they encapsulate in the gastrointestinal environment and promote the gastrointestinal transport of various substances. Drugs encapsulated in liposomes can induce humoral and cell-mediated immunity when administered orally. Due to their biodegradability and non toxicity, liposomes can be used as vaccine delivery carriers. Proteins and insulin used as vaccines are degraded when taken orally. The protective effect on the loaded content makes liposomes a good candidate carrier for oral protein and insulin. Liposomes, as oral vaccine carriers, can now be administered with various vaccines, such as the hepatitis A vaccine.
(2) Oral administration
The study of liposome drug delivery for oral administration is extensive and has been extensively reported. Previous studies have shown that the main factors affecting the stability of oral medications include bile, pH, and pancreatic enzymes in the gastrointestinal tract. In order to protect liposomes and their loaded drugs from the influence of the gastrointestinal environment, several membrane surface polymerization chemical methods have been studied. However, the inability to completely remove toxic reagents and their derivatives hinders the full utilization of these technologies. This issue can be addressed by using liposomes as suspensions or solubilizers of highly insoluble or lipophilic drugs to prepare microemulsions, which can then be further developed into soft capsules for oral delivery. The research results of encapsulating cyclosporine using this method indicate that the formulation can improve reproducibility and oral bioavailability of the drug. As for stimulating the immune response of the mucosa, oral liposome antigen preparations can also enhance the delivery of antigens to antigen-presenting cells. The targeting of antigens to antigen-presenting cells, antigen protection, and ineffective stimulation of the immune response by oral delivery of soluble antigens can also be achieved through the application of liposomes.
(3) Local administration
As a unique application, liposomes can promote drug transdermal penetration. Liposomes can reduce the side effects of local application of drugs, as they only require small doses when used as local preparations. In addition, they increase the permeability of the skin to load drugs. Liposomes are also very important in skin care and cosmetic applications. Therefore, liposomes are often prepared into cosmetic dispersions or hydrogels. Hydrophilic polymers are suitable thickeners for gel. However, liposomes may be coated in the polymer network structure of hydrogel in some cases, thus reducing the bioavailability of transdermal drug delivery
