A series of dual stimuli-responsive block copolymers comprising temperature-responsive poly(N-vinyl-caprolactam) (PVCL) and biodegradable pH-responsive poly(L-lysine) (PLL) of varying chain length were syn-thesized by a combination of free radical polymerization and ring opening polymerization. The block copolymers formed micelles and vesicles (polymersomes) in response to temperature and pH, respectively, in aqueous so-lution. The nanoassemblies were characterized by transmission electron microscopy and dynamic light scattering techniques. Encapsulation of both hydrophobic and hydrophilic dyes in the polymersomes was shown. Doxo-rubicin (DOX) was loaded in the polymersomes and its controlled release in response to the two stimuli, inde-pendently and jointly, was studied. The drug was found to be released due to stimuli-induced increased permeability without disassembly of the polymersomes. A significant increase in the cellular uptake of the drug-loaded polymersomes at hyperthermia conditions was demonstrated at 41 degrees C and release of the drug upon localization in lysosomes was observed. Cellular internalization pathway of the polymersomes was investigated by competitive inhibition assay and a combination of endocytic pathways dominated by caveolae-mediated mechanism was found to be operative.

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