Liposomes have been developed for the delivery and buffering of drugs in the body. In recent years stealth liposomes have been used to prevent uptake of the liposomes by the reticuloendothelial system and increase their period of circulation. Stealth liposomes have also been found to accumulate preferentially in the interstitium of tumor sites due to the increased permeability of the vasculature there.

For different applications different membrane properties of the liposomes are needed: these range from stable membranes that do not release their contents for ultrasound contrast agents to membranes that allow for a constant, slow release or a sudden, complete release upon a signal for drug delivery. Drug release characteristics of stealth liposomes can be controlled by manipulating the phase behavior of these complex lipid mixtures or by polymerizing the lipid membranes. Both phase behavior and membrane polymerization will be discussed in detail. Effective membrane properties for drug delivery and ultrasound contrast agent applications, as well as other applications from the relevant literature, will also be described.