Interaction of bovine serum albumin with self-assembled nanoparticles of 6-O-cholesterol modified chitosan

In order to understand the nanomedicine and nanotoxicological effects of self-assembled nanoparticles of 6-O-cholesterol modified chitosan (O-CHCS NPs) as a carrier for drug delivery systems, the interaction between O-CHCS NPs and bovine serum albumin (BSA) was studied by spectroscopy and calorimetric methods. The morphology of the complex between O-CHCS NPs and BSA observed by transmission electron microscope (TEM) was almost spherical shape. The size and the zeta potential of the complex increased with the concentration of O-CHCS NPs increasing. The fluorescence spectroscopy indicated that the micro-environment around the tryptophan (Trp) residues in BSA had slight change due to only partially exposure of the Trp residues to water in the interaction process. Compared with free BSA, the addition of O-CHCS NPs led to the decrease of α-helical content of BSA and the increase of β-strand content. Isothermal titration calorimeter (ITC) results showed that the binding reaction between O-CHCS NPs and BSA was exothermic and enthalpically driven. Therefore, it could be concluded that hydrogen bonding, hydrophobic and electrostatic interactions played a key role in the complex formation, and the formation mechanism was proposed accordingly. In addition, cytotoxicity assay implied that O-CHCS NPs were non-cytotoxic and biocompatible up to 200 μg mL−1. These data demonstrated the potential application of O-CHCS NPs for drug delivery.