What Are Liposomes?

Liposomes are small artificial sphere-shaped vesicles consisting of one or more phospholipid bilayers, which were first described in the mid-60s. Today, they are a very useful reproduction, reagent, and tool in various scientific disciplines, including mathematics and theoretical physics, biophysics, chemistry, colloid science, biochemistry, and biology. Since then, liposomes have made their way to the market. Due to their size and hydrophobic and hydrophilic character(besides biocompatibility), liposomes are promising systems for drug delivery. Among several talented new drug delivery systems, liposomes characterize an advanced technology to deliver active molecules to the site of action, and at present, several formulations are in clinical use. Research on liposome technology has progressed from conventional vesicles to “second-generation liposomes”, in which long-circulating liposomes are obtained by modulating the lipid composition, size, and charge of the vesicle. Liposomes with modified surfaces have also been developed using several molecules, such as glycolipids or sialic acid. What’s the Function of a Liposome? Liposomes can be filled with drugs, and used to deliver drugs for cancer and other diseases. Membranes are usually made of phospholipids, which are molecules that have a polar head group and two hydrophobic tails. How Are liposomes Manufactured? Solvent dispersion method: A solution of lipids dissolved in diethyl ether or ether-methanol mixture is gradually injected to an aqueous solution of the material to be encapsulated at 55°C to 65°C or under reduced pressure. The consequent removal of ether under vacuum leads to the creation of liposomes. The main disadvantages of the technique are that the population is heterogeneous (70 to 200 nm) and the exposure of compounds to be encapsulated to organic solvents at high temperature. For more methods, please click here. How Are Liposomes Composed? Liposomes are made of physiologically acceptable natural or synthetic phospholipids found in the lipid bilayer membranes of human cells. The most frequently used phospholipids for liposomes preparation are phosphatidylcholines (PC), phosphatidylethanolamines (PE), phosphatidylserines (PS) and phosphatidylglycerols (PG). Are Liposomes Safe? Due to their nature, liposomes are in fact considered safe nanocarriers. However, the addition of nonphysiological additives can induce chemical modifications that are useful to improve efficacy in drug delivery but potentially toxigenic. In addition to being biocompatible, all liposomes have in common a structure that gives them the ability to contain both hydrophilic and hydrophobic drugs. Why Are Liposomes Important? The application of liposomes to assist drug delivery has already had a major impact on many biomedical areas. They have been shown to be beneficial for stabilizing therapeutic compounds, overcoming obstacles to cellular and tissue uptake, and improving biodistribution of compounds to target sites in vivo. This enables effective delivery of encapsulated compounds to target sites while minimizing systemic toxicity. References 1. Akbarzadeh, Abolfazl, et al. Liposome: classification, preparation, and applications. Nanoscale research letters.2013, 1: 1-9.rn2. Daraee, Hadis, et al. Application of liposomes in medicine and drug delivery.Artificial cells, nanomedicine, and biotechnology. 2016, 1: 381-391.rn3.Nkanga, Christian Isalomboto, et al. General perception of liposomes: formation, manufacturing and applications. Liposomes-advances and perspectives.rn4. Sercombe, Lisa, et al. Advances and challenges of liposome assisted drug delivery. Frontiers in pharmacology. 2015,6: 286.rn5.Bozzuto, Giuseppina, and Agnese Molinari. Liposomes as nanomedical devices.International journal of nanomedicine. 2015, 10: 975.