An Overview of Liposomes for Antimicrobial Drug Delivery

Antibacterial drugs generally refer to drugs with bactericidal or antibacterial activity, including different kinds of synthetic drugs such as antibiotics, sulfonamides, imidazoles, nitroimidazoles, quinolones, etc. Antibacterial drugs can inhibit and kill pathogens at a certain concentration. Certain products obtained by culturing microorganisms such as bacteria, actinomycetes, and fungi, or same or similar substances produced by chemical semi-synthetic methods, can also be fully chemically synthesized.

• Brief Introduction of Antibacterial drugs and Liposomes

Antibacterial drugs are mainly divided into eight categories, including?-lactams such as penicillins, cephalosporins, carbapenems,?-lactams containing enzyme inhibitors and monocyclic amides, etc.; aminoglycosides; tetracyclines; fluoroquinolones; folate pathway inhibitors; chloramphenicol; glycopeptide packages; macrolides.

Some antibiotics, due to their own toxicity, as well as the effect of drug biological distribution and pharmacokinetics, have limited clinical application. Although some antibiotics may have good antibacterial activity, they cannot be used as first-line drugs due to serious adverse reactions unless other drugs are proved to be ineffective.

Therefore, according to the pharmacokinetics and curative effect of the required drugs, they can be made into drug-loaded liposomes, which can effectively avoid the above problems. Liposomes, as antibiotic carriers, can improve the pharmacokinetics and biological distribution of drugs, reduce drug toxicity, enhance targeted selectivity to lesions, increase the drug's antibacterial activity against intracellular and extracellular pathogens, and reduce the occurrence of drug resistance.

• Distribution Characteristics of Liposomes in Vivo

As a carrier of antibiotics, liposomes can slowly and continuously release drugs in the body and maintain effective concentration for a long time. Compared with free antibiotics, there is no need to repeatedly use drugs in a short period of time. Being encapsulated by liposomes, the drug can not only improve its pharmacokinetics and biological distribution, but also avoid hydrolysis by various enzymes.

After conventional intravenous injection of liposomes, they are captured and recognized by the body’s immune system as foreign antigens, thus activate the non-specific defense mechanism of macrophages in the body, and are swallowed by macrophages, making the liposomes accumulate in the organs with abandunt macrophages, such as liver, spleen, lung, kidney, etc., which can shorten the time that the drug stays in the blood circulation. The proportion of liposomes engulfed by the mononuclear phagocyte system depends on their properties, such as the size, whether charged and the amount of charge, and the fluidity. Small liposomes with a diameter of