Nano-scaled pH-responsive polymeric vesicles for intracellular release of doxorubicin

Polymeric vesicles produced by spontaneous self-association of poly(acrylic acid-co-distearin acrylate) (poly(AAc-co-DSA)) with varying ratios of AAc and DSA units in aqueous solution of pH 5.0 exhibit the pH-regulated drug release behavior. Through the electrostatic interaction with ionized AAc residues, doxorubicin (DOX) molecules can be highly accommodated onto either the inner or outer surfaces of vesicles when the pH is adjusted from 5.0 to 7.4. The extent of DOX encapsulation is dependent largely on the structural transition of vesicles in response to the pH change. While the pH-evolved drug release profile varies to some extent with the distribution of DOX molecules within vesicles, the drug release from vesicles is accelerated significantly via the disruption of the electrostatic interaction of DOX species with ionized AAc moieties at pH 5.0. The DOX-loaded polymeric vesicles show promoted cellular uptake and cytotoxicity comparable to free DOX for HeLa cells. This indicates that they are probably taken up by the cells via the lipid raft-mediated endocytosis.