Factors affecting drug release from liposomes.

Liposomes are the most widely used nanocarrier systems in medicine. Common strategies for tumor-specific drug delivery using liposomes include the passive accumulation of liposomes that have an increased circulation half-life, which is possible as a result of the leakiness of tumor neovasculature, as well as the active targeting of liposomes using surface-bound ligands. However, such targeting of the nanocarrier is not effective if the encapsulated drug within the liposome is not released at the intended site. Drug release can be influenced by both the membrane composition of the liposome and the choice of drug. In addition to environmental triggers, such as low pH and the presence of particular enzymes, external stimuli such as heat or ultrasound have gained attention in the clinic. This review provides a summary of the various approaches to modifying drug release from liposomes.