# Polymers and Polymer Nanocomposites for Cancer Therapy +
## 6 Polymersomes and Liposomes
Polymersomes along with a series of copolymers employed for their preparation and potential applications as drug carriers were recently reviewed [125]. To achieve simultaneity in the case of liposome delivery, as in other carriers, the contents must be protected from possible degradation, and premature release must be prevented [70]. There are spherical lipid vehicles composed of one or more phospholipid bilayers and an aqueous internal cavity. They can be classified as uni-, oligo-, or multilamellar vesicles depending on the number of membrane bilayers, and they are formed through the self-assembly of phospholipids in contact with hydrophilic medium. This behavior increases their solubility in the medium and decreases their surface-to-volume ratio. Liposomes can be prepared through reverse-phase evaporation, the injection of phospholipids dissolved in an organic phase into a drug-containing aqueous phase, detergent dialysis, microfluidic hydrodynamic focus, supercritical reverse-phase evaporation, electroformation, microfluid liposome formation, and thin lipid film formation [126]. Liposomes as carrier systems have been explored more than other systems as a result of their various forms. Phospholipid bilayer membranes can generate spherical structures with an internal hydrophilic compartment through the introduction of phospholipids in water solution. They are biocompatible and biodegradable, and they are able to encapsulate and deliver both hydrophilic and hydrophobic agents in an afflictive way [127]. Their platforms have attracted considerable attention from academic and clinical areas and have become the most studied biomaterial nanoparticles due to the fact that they can improve the efficiency of a drug by increasing its solubility, overcoming resistance, controlling its targeted release, and modifying its biocompatibility, bioavailability, and safety profile [128]. Phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine are the components of different liposomes. The drug Carboplatin was encapsulated into a liposome made of lecithin, cholesterol, and PEG through a reverse-phase evaporation technique, and its efficacy on lung cancer in vitro was evaluated. The study indicated that liposomes can be used for carboplatin delivery in lung cancer [129]. The same technique was used to prepare cis-platin-loaded PEGylated liposomes targeted with FA and evaluate their efficacy in a liver cancer cell line. The results of this research confirmed the potency of targeted PEGylated liposomal nanoparticles [130]. Liposomes consist of a region of aqueous solution inside a hydrophobic membrane. Hydrophobic chemicals can be easily dissolved into the lipid membranes: in this way, liposomes are able to carry both hydrophilic and hydrophobic molecules, while the location of the drug depends upon its physiochemical characteristics and the composition of the lipid. For the delivery of necessary drugs to the site of the tumor, the lipid bilayers fuse with other bilayers of the cell (cell membrane) to release the liposomal content. The steps involved in liposome drug delivery are adsorption, endocytosis, fusion, and lipid exchange. Once the anticancer drugs are released, the cancer cells are killed [131]. Although polymersomes and liposomes possess amphiphilic characteristics, they are different from a properties point of view. Polymersomes are tougher, malleable, and more stable: liposomes, on the other hand, are closer mimics of natural cell membranes, and they are more difficult to handle and use. Table 2 shown below presents other carrier and drugs for cancer therapies.