Preparation and physicochemical characteristics of self-assembled nanoparticles of deoxycholic acid modified-carboxymethyl curdlan conjugates

Various deoxycholic acid (DOCA)-modified-carboxymethylated (CM)-curdlan (DCMC) were synthesized and characterized by FTIR, H-1 NMR and XRD. The degree of DOCA substitution (DS), as spectrophotometrically determined, was 2.1, 3.2, 4.1, or 6.3 DOCA groups per hundred sugar residues of CM-curdlan. The physicochemical properties of the self-assembled nanoparticals in aqueous media were investigated using H-1 NMR, dynamic light scattering, zeta potential, transmission electron microscopy (TEM) and fluorescence spectroscopy. DCMC conjugates provided monodispersed self-assembled nanoparticles in water, with mean diameter decreasing from 192 to 347 nm with DOCA DS increasing. Moreover, the mean diameter also increased with decreasing pH in PBS. Zeta potential of DCMC self-assembled nanoparticles exhibited near -60 mV in distilled water and -26 to -36 mV in PBS, indicating these nanoparticles were covered with negatively charged CM-curdlan shells. The critical aggregation concentration (cac) of the DCMC were dependent on the degree of substitution (DS) of DOCA and were slightly lower in PBS than in distilled water. The TEM images demonstrated that these self-assembled nanoparticles were of spherical shape. (c) 2007 Elsevier Ltd. All rights reserved.