Recent Advancements of Stimuli-Responsive Targeted Liposomal Formulations for Cancer Drug Delivery

Liposomes have gained attention as a well-accepted nanocarrier for several chemotherapeutic drugs and are considered a drug delivery system of choice for a wide range of products. These amphipathic spherical vesicles primarily consist of one or more phospholipid bilayers, showing promise for drug delivery of both hydrophilic and hydrophobic components in addition to unique properties, such as biocompatibility, biodegradability, low toxicity, and nonimmunogenicity. Recent advances in liposomes are mainly centered on chemical and structural modification with the multifunctional approach to target the cancer cells activating the offensive mechanisms within the proximity of the tumors. Stimuli-responsive liposomes are a precisive approach to deliver and release chemotherapeutic drugs in the tumor site in a controlled fashion, thus reducing damage to normal tissues and preventing the side effects of the conventional chemotherapy regimen. The unique characteristics of the tumor microenvironment facilitate applying an endogenous stimulus (pH, redox potential, or enzymatic activity) to trigger the release of the drug or the application of an external stimulus (heat or light) to tailor the drug release from liposomes. This review focuses on newer developments in stimuli-sensitive liposomal drug delivery systems designed to implement either exogenous (temperature, light, and magnetic field) or endogenous (pH changes, enzymatic triggers, or redox potential) approaches.