Recent advances on thermosensitive and pH-sensitive liposomes employed in controlled release

Nanotechnology has recently gained lots of interest in drug delivery due to its potential to improve the therapeutic outcomes of various diseases. Particularly, a wide range of different nano-sized vesicles has been investigated for drug delivery. Among them, one of the most attractive and well-investigated nanocarriers are liposomes. Although liposomes have several advantages such as low toxicity, biodegradability and biocompatibility as well as accumulate in tumor site via enhanced permeability and retention (EPR) effect, inefficient drug delivery to the target cells could affect the therapeutic purpose of most of conventional liposomal formulations. Therefore, new systems of drug release including stimuli-responsive liposomal have been introduced for the improvement of the efficacy and release payloads in a site-specific manner. Stimuli-responsive liposomes stay stable in blood stream circulation but are activated in response to internal or external stimuli. This review highlights the development of thermosensitive and pH-sensitive liposomes, focusing on liposomal compositions and the effects of the synthetic polymers on their drug release behavior. Furthermore, in vitro and in vivo applications of these formulations will be discussed.