We present a facile method to prepare stabilized nanoparticles with pH-sensitivity and controllable dimension directly from dextran and two kinds of monomers. The synthesis was realized by a self-assembly assisted graft copolymerization of AA from dextran under the presence of crosslinker-N,N'-methylene bisacrylamide. This approach was characterized as organic solvent free, surfactant free and comparatively high solid contents (similar to 40 mg/ml). The polymerization of AA was confirmed by FT-IR, and TGA analysis. The resultant nanoparticles were studied by TEM, AFM, SEM, DLS and zeta-potential measurements. It was found that the size of resultant dextran-based nanoparticles ranges from 40 to 140 nm, and depends greatly on R-GM [(glucose unit)/AA (mol:mol)] during polymerization. Besides, the nanoparticles have obvious pH-sensitivity because of the presence of carboxy groups in the nanoparticles. (c) 2005 Elsevier Ltd. All rights reserved.