pH-sensitive Liposomes in Drug Delivery
The pH-sensitive liposomes have been extensively studied in recent years as an advantageous alternative to conventional liposomes in effective targeting and accumulation of anticancer drugs in tumors. pH-sensitive liposomes usually contain phosphatidylethanolamine and stabilizing amphiphiles and can destabilize under acidic conditions of the endocytotic pathway. The drug loaded is thought to be delivered into the cytoplasm, probably through destabilization of or fusion with the endosome membrane. This fusogenic property makes the pH-sensitive liposomes more efficient in delivering anticancer drugs than conventional liposomes. The intra-cellular release of drug/gene/diagnostic agents can be achieved without altering their therapeutic efficacy by means of the endosomal escape phenomenon. Cell surface targeting ligands, including antibodies, can be appended on the surface of pH-sensitive liposomes to target specific receptors on tumor cells. This chapter provides an introduction to pH-sensitive liposomes and examples of their therapeutic interest as smart drug-delivery systems.