Preparation and characterization of self-aggregated nanoparticles of cholesterol-modified O-carboxymethyl chitosan conjugates

A series of cholesterol-modified O-carboxymethyl chitosan (CCMC) conjugates with different degrees of substitution (DS) of cholesterol moiety were synthesized by the succinyl linkages and characterized by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (H-1 NMR) and elemental analysis. CCMC conjugates were amphiphilic in nature and their self-aggregation behavior in aqueous media was evaluated by the fluorescence probe technique. CCMC self-aggregated nanoparticles were prepared by probe sonication in water and analyzed by dynamic laser light-scattering (DLLS), zeta potential and transmission electron microscopy (TEM) technologies. These novel nanoparticles were almost spherical in shape, and their size, ranging from 234.9 to 100. 1 nm, could be controlled by DS of cholesterol moiety. The zeta potentials of CCMC self-aggregated nanoparticles were negative, and the absolute values decreased with increasing DS of the cholesterol moiety. This study also compared the morphology and the stability of self-aggregated nanoparticles between CCMC and cholesterol-modified chitosan (CHCS). The results showed that the negatively charged carboxymethyl groups are advantageous for the formation of well-shaped and stable self-aggregated nanoparticles. (C) 2007 Published by Elsevier Ltd.