Aminopropyl methacrylamide chloride-graft-poly(N-vinyl pyrrolidone) nanogels (NGs) were designed to exploit the favorable properties of poly(N-vinyl pyrrolidone) (PVP), such as its high affinity to water and complexation ability of ions, molecules and macromolecules, with the availability of primary amino groups for bioconjugation reactions. A thorough structural characterization of the nanoscalar networks was performed via H-1 NMR and solid state C-13 NMR spectroscopies, while solid state NMR relaxation time measurements completed the NGs description in terms of polymer network density. Information on the hydrodynamic size and surface charge densities were sought via dynamic light scattering (DLS) and xi-potential measurements. These measurements, carried out both in water and in buffer and at the variance of pH, temperature and time, support the excellent colloidal stability of the amino-graft PVP nanogels and their redispersability from the dry physical form. The total absence of in vitro toxicity and immunogenicity was ascertained first, and then cell localization studies in cell cultures of fluorescent variants were performed. Furthermore, the possibility of decorating the nanogels with bovine serum albumin (BSA) to obtain a stable bio-hybrid colloidal nanoconstruct was established. All the gathered evidences qualify these materials as potential candidates to be used as nanocarriers for intra-cellular delivery of protein and other biomolecular drugs. (C) 2013 Elsevier Ltd. All rights reserved.