**6.1 Ether injection method**

Ether injection method is also known as solvent vaporization. A solution of lipids dissolved in diethyl ether or an ether-methanol mixture is injected into an aqueous solution of the drug in order to be encapsulated at 55–65°C or under reduced pressures. The removal of ether under vacuum leads to the formation of liposomes.

#### **6.2 Ethanol injection method**

A lipid solution of ethanol is rapidly injected to a huge buffer excess. Multilamellar vesicles are at once formed. Unfortunately, the population is not homogeneous with this method.

#### **6.3 Reverse-phase evaporation method**

Reverse-phase evaporation method is based on the formation of inverted micelles. These inverted micelles are formed upon the sonication of a mixture of a buffered aqueous phase, which contains the water-soluble molecules to be encapsulated into the liposomes, and an organic phase, in which the amphiphilic molecules

**39**

*Breaking down the Barrier: Topical Liposomes as Nanocarriers for Drug Delivery…*

ing micelles, which results in the formation of liposomes.

phospholipids, and, lastly, they combine to form UVs.

**7.2 Detergent removal of mixed micelle method**

**7.3 Gel permeation chromatography method**

**7.5 Stealth liposomes and conventional liposomes**

beaded organic polystyrene absorbers.

are solubilized. The slow removal of organic solvent leads to the transformation of these inverted micelles into a gel-like, viscous state. After the gel-state collapses, some of the inverted micelles disintegrate, but the excess of phospholipids in the environment contributes to the formation of a complete bilayer around the remain-

As the detergent is detached, the micelles increasingly become better-off in

The absorption method is attained by shaking mixed micelle solution with

In this method, the detergent is depleted through size special chromatography.

The spontaneous transition from polydispersed micelles to vesicles occurs due to the dilution of the aqueous micellar solution of detergent and phospholipids with

Liposomes become known by the mononuclear phagocytic system following contact with plasma proteins. This is solved through the use of synthetic phospholipids, particle coated with amphipathic polyethylene glycol, coating liposomes with chitin derivatives, freeze drying, polymerization, and microencapsulation of gangliosides. A stealth liposome is a sphere-shaped vesicle with a membrane that is composed of a phospholipid bilayer used to deliver drugs or genetic material

Drug loading can be achieved through passive (if the drug is encapsulated during liposome formation) or active methods (after liposome formation). Freeze-dried (lyophilization) liposomes are formed from preformed liposomes at tremendously low pressures. Very high encapsulation efficiencies, even for macromolecules, can be achieved using this method. During dehydration, the lipid bilayers and the drug to be encapsulated into the liposomes are brought into close contact. Upon reswelling, the chances for the encapsulation of the adhered molecules are much higher. Rehydration is a very important step and it should be very carefully done. The aqueous phase should be added in very small portions with a micropipette to the dried materials. After each addition, the tube should be

Liposomes can interact with cells through different mechanisms [129]:

*DOI: http://dx.doi.org/10.5772/intechopen.86601*

**7. Detergent removal method**

**7.1 Dialysis method**

**7.4 Dilution method**

buffer.

to a cell.

thoroughly vortexed.

*7.5.1 Transportation mechanisms*

*Breaking down the Barrier: Topical Liposomes as Nanocarriers for Drug Delivery… DOI: http://dx.doi.org/10.5772/intechopen.86601*

are solubilized. The slow removal of organic solvent leads to the transformation of these inverted micelles into a gel-like, viscous state. After the gel-state collapses, some of the inverted micelles disintegrate, but the excess of phospholipids in the environment contributes to the formation of a complete bilayer around the remaining micelles, which results in the formation of liposomes.
