Effect of liposome molecular composition on its ability to carry drugs

Liposomes have become a popular supramolecular structures used to deliver highly toxic drugs. In order to fulfill commercial handling requirements, the lipid-drug aggregate has to form stable and reproducible preparations. When applied as a therapeutic agent, its behavior must ensure proper drug distribution and well controlled release. The aggregate should have such properties built into its structure. Those properties depend mainly on aggregate's lipid composition and current external environmental conditions. It is not possible to precisely predict the behavior of the aggregate, since currently there are no theories sufficiently accurate to describe such complex structures. Nevertheless, some parameters of the lipid-drug aggregate can be elucidated based on simplistic semi-empirical theories. The paper presents general outline of molecular shape approximation and the zone model for the lipid bilayer. These two approximations were used as a starting point in the discussion of the effects of various membrane modifications on global aggregate behavior, as well as their relevance to the ability to carry drugs.