الفهرس 
GENERAL INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Transdermal drug delivery is a non-invasive approach that can be utilized to bypass the variables of drugs oral absorption and the pain and side effects associated with injections. The major challenge with dermal or transdermal drug delivery is the barrier nature of skin that limits the entry of most of the drugs. Several approaches and delivery systems have been investigated and utilized to overcome the barrier of stratum corneum (SC) to attain higher dermal penetration and transdermal permeability. Among explored systems, phospholipid based nanostructured systems offer captivating properties for transdermal delivery due to their biocompatibility and ease of mixing with the skin lipids. There has been considerable interest on the use of liposomes for skin delivery. However, it was proved that conventional liposomes are of little value for transdermal delivery, due to their lower ability to deeply penetrate the skin. They were rather remaining confined to the upper layers of the stratum corneum.
It was reported that flexibility of liposomes could result in enhancing their skin penetration. Furthermore, vesicles with high flexible membranes could deliver macromolecules to deeper layers of skin as compared to rigid liposomes. Being flexible, they were capable of adapting their shape and volume when passing through the SC. Modulating vesicles composition; sequences of new vesicles with flexible membranes were developed in order to improve the dermal or transdermal delivery of drugs. These modified vesicles include transfersomes, ethosomes, and most recently transethosomes.
The most recent approach in liposomal systems that has not so far been employed in transdermal drug delivery is the gel-core liposomes. They are phospholipid bilayered vesicles entrapping hydrogel polymer inside their core. Therefore, they gather the advantages of both phospholipids and hydrogels. In addition, the polymer incorporated inside the core supports the lipid bilayer preventing their rapid degradation in the body and early drug release.