pH sensitive nano-gels based on polyaspartamide graft copolymers are prepared by UV crosslinking the self-assembled nano-aggregates in the presence of a series of hydrophobic and hydrophilic grafting segments. While the physical nano-aggregates dissociate via ionization of the pH sensitive moiety, the nano-gels synthesized in this study swell instead. The chemical structure and morphology of the resulting nano-gels were analyzed using FTIR, H-1 FTNMR, and TEM. The pH dependence of the particle size, 120-250 nm, was investigated using a light scattering analyzer. The swelling behavior of the nano-cores under acidic conditions triggered abrupt release of the drug; this pH dependence occurs reversibly and quickly. The nano-gels prepared may have endosomal rupturing characteristics, as their buffering capacity is as strong as that of uncrosslinked nano-aggregates. The nano-gels synthesized as such possess potential application as sustained releasing drug carriers for intracellular delivery. (C) 2011 Elsevier Inc. All rights reserved.