Preparation and characterization of self-assembled nanoparticles of 6-O-cholesterol-modified chitosan for drug delivery

6-O-Cholesterol modified chitosan (O-CHCS) conjugates with succinyl linkages were synthesized through a protection-graft-deprotection method with phthaloylchitosan as an intermediate. O-CHCS conjugates were characterized by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H NMR), and the degrees of substitution (DS) of the cholesterol moiety determined by elemental analysis were 1.7%, 4.0% or 5.9%. O-CHCS self-assembled nanoparticles prepared by the dialysis method displayed the classic “core–shell” structures and their sizes were in the range of 100–240 nm. All-trans retinoic acid (ATRA), as a model drug, was physically entrapped inside O-CHCS self-assembled nanoparticles by the dialysis method. With increasing initial levels of the drug, the drug loading content increased, but the encapsulation efficiency and the particle size decreased. The release profiles in vitro demonstrated that ATRA showed slow sustained released over 72 h, which indicated that O-CHCS self-assembled nanoparticles had the potential to be used as a carrier for hydrophobic drugs.