Graft copolymer nanoparticles prepared from chitosan (CS) and methyl methacrylate (MMA) monomer were synthesized in aqueous solution by using potassium diperiodatocuprate [Cu(III)] as an initiator and characterized in terms of particle size, zeta potential, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, thermal stability, and X-ray diffraction spectrometry. The results indicated that CS was covalently linked to poly(methyl methacrylate) (PMMA), and the resulting copolymers formed nanoparticles. These nanoparticles [prepared at 35 degrees C, in a weight ratio of MMA/CS of 5 : 1 and with a Cu(III) concentration of 1.5 x 10(-3) mol/L] were 54-350 nm in size, with a mean hydrodynamic diameter of 183 +/- 3 nm and were highly uniform in particle-size distribution, with a rather spherical shape and an obvious positive charge surface. The effect of reaction conditions such as Cu(III) concentration, reaction temperature, and the weight ratio of MMA/CS on the mean particle size was also investigated. Insulin-loaded nanoparticles were prepared, and their maximal association efficiency was up to 85.41%. The experiment of release in vitro showed that the nanoparticles gave an initial burst release followed by a slowly sustained one. VC 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 2707-2715, 2011