Poly(l-glutamic acid)-based star-block copolymers as pH-responsive nanocarriers for cationic drugs

Star-block copolymers PEI-g-(PLG-b-PEG), which consist of a hyperbranched polyethylenimine (PEI) core, a poly(l-glutamic acid) (PLG) inner shell, and a poly(ethylene glycol) (PEG) outer shell, were synthesised and evaluated as nanocarriers for cationic drugs. The synthesised star-block copolymers were characterised by 1H NMR, gel permeation chromatography (GPC), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Crystal violet (CV), as a model cationic dye, and doxorubicin hydrochloride (DOX), as a model anticancer drug, could be efficiently entrapped by the synthesised star-block copolymers at physiological pH as a result of electrostatic interactions between the cationic guest molecules and the negatively charged PLG segments in the PEI-g-(PLG-b-PEG) host. The drug–polymer complexes showed relatively high temporal stability at physiological pH and sustained release of the encapsulated drugs was observed. The entrapped model compounds demonstrated accelerated release as the pH was gradually decreased.