Micelles refer to molecularly ordered aggregates that begin to form in large quantities after the surfactant concentration reaches a certain value in an aqueous solution. In micelles, the hydrophobic groups of surfactant molecules aggregate to form the core of the micelle, and the hydrophilic polar groups form the outer layer of the micelle. Liposomes are an artificial membrane. In the water, the hydrophilic head of the phospholipid molecule is inserted into the water, and the hydrophobic tail of the liposome extends into the air. After stirring, a spherical liposome with a double layer of lipid molecules is formed, with a diameter ranging from 25 to 1000 nm.

Micelles and liposomes are both nanoscale carrier systems commonly used to improve drug delivery or cosmetic formulations. From their definitions, we can see that there are certain differences between the two.

Differences in Structure and Composition

Micelles: Micelles are tiny particles made of surfactant molecules (also called surfactants or emulsifiers) that are hydrophilic and lipophilic. When surfactant molecules form micelles, they interact with water through their hydrophilic heads and oil through their hydrophobic tails. The core of the micelle is usually hydrophobic, while the outside is hydrophilic.

Figure 1. Comparison between micelles, liposomes, nanoemulsions and solid lipid nanoparticles.

Liposome: Liposome specifically refers to a bilayer structure composed of phospholipid molecules. Since the phospholipid molecules themselves have a hydrophilic head and a hydrophobic tail, liposomes also show similar characteristics to micelles. Therefore, drugs or active ingredients in liposomes can appear to be embedded between bilayers or wrapped within bilayers depending on their native hydrophilic or hydrophobic properties.

Differences in Loading Medications

Micelles: Micelles are often used to disperse and deliver water-insoluble hydrophobic drugs or active ingredients because these drugs can be encapsulated within the lipophilic core of the micelle.

Liposomes: Liposomes can be used to deliver a variety of drugs, whether they are hydrophobic or hydrophilic, as the drugs can be embedded in the bilayer of the liposomes or inside the liposomes.

Stability and Storage Differences

Micelles: Generally speaking, micelles are relatively easy to prepare, so they may be less stable. Micelles may break down or aggregate when stored for long periods of time or under certain environmental conditions, such as high temperature or low pH.

Liposomes: Liposomes generally have good stability and can store drugs or active ingredients for a long time because the structure of the phospholipid molecules provides good protection. This makes liposomes more advantageous in terms of preparation and long-term storage.

Differences in Application Areas

Micelles: Micelles are commonly used in cosmetics, drug delivery systems, and biochemical research. They are suitable for applications requiring rapid release of drugs or active ingredients.

Liposomes: Liposomes are widely used in areas such as drug delivery, biomedical research, and cosmetics, especially those where stable delivery over long periods of time is required. Liposomes are suitable for controlled release of drugs, increasing drug bioavailability and improving drug stability.

In summary, micelles and liposomes are different nanoscale carrier systems with their own characteristics in structure, drug delivery, stability and application fields. Which system to choose depends on the specific application needs and required performance.