Preparation, complexation mechanism and properties of nano-complexes of Astragalus polysaccharide and amphiphilic chitosan derivatives.

•Chitosan derivatives bearing deoxycholic acid/vitamin B12 residues were synthesized.•Nano-complexes of chitosan derivatives and Astragalus polysaccharides were prepared.•Fluorescence and resonance light scattering spectroscopy confirmed formation of complexes.•The nano-complexes exhibited high permeation through intestinal enterocytes.