Liposomes are composed of small vesicles of a bilayer of phospholipid encapsulating an aqueous space ranging from about 0.03 to 10 μm in diameter.
They are composed of one or many lipid membranes enclosing discrete aqueous compartments. The enclosed vesicles can encapsulate water-soluble drugs in the aqueous spaces, and lipid-soluble drugs can be incorporated into the membranes.
Liposomes can be administered parenterally, topically, by inhalation, and possibly by other routes of administration.
Liposomes can trap both hydrophobic and hydrophilic compounds, avoid decomposition of the entrapped combinations, and release the entrapped at designated targets.
Because of their biocompatibility, biodegradability, low toxicity, and aptitude to trap both hydrophilic and lipophilic drugs and simplify sitespecific drug delivery to tumor tissues, liposomes have increased rate both as an investigational system and commercially as a drug delivery system.
Many studies have been conducted on liposomes with the goal of decreasing drug toxicity and/ or targeting specific cells.