The use of the biocompatible amphiphilic diblock copolymer poly(ethylene glycol-b-propylene sulfide) (PEG(44)PPS(20)) allows a tuned loading of doxorubicin onto the surface of non-functionalized multi-walled carbon nanotubes and an efficient cell internalization. The obtained multi-walled carbon nanotube-based systems show enhanced cytotoxic activity with respect to non-vehicled doxorubicin.