Biocompatible and biodegradable polymersomes for pH-triggered drug release

Nano-sized biocompatible and biodegradable polymersomes were prepared based on poly(D,L-lactide)block-poly(2-methacryloyloxyethyl phosphorylcholine) (PLA-b-PMPC) diblock copolymers and applied for the release anti-cancer drugs. Hydrophobic doxorubicin (DOX) and hydrophilic doxorubicin hydrochloride (DOX center dot HCl) were successfully loaded into the polymersome membrane and polymersome interior, respectively. The in vitro release studies demonstrated that the release of DOX and DOX center dot HCl from polymersomes was highly pH-dependent, i.e. significantly faster drug release at mildly acidic pH of 5.0 compared to physiological pH 7.4. Furthermore, DOX center dot HCl-loaded polymersomes exhibited faster drug release than DOX-loaded polymersomes under the same pH conditions. The highly pH-depended release behavior was attributed to the hydrolysis of PLA-b-PMPC, which would result in morphological transformation from polymersome to micelle with a triggered release of the encapsulated drugs. The drug-loaded polymersomes were shown to rapidly enter HepG2 cells, localize in their endosome/lysosomes with acidic pH environment and display enhanced intracellular release of the drugs into the cytosol. These biocompatible and acid pH-sensitive polymersomes might have great potential for cancer therapy.