Natural polyampholyte-based core-shell nanoparticles with N-carboxyethylchitosan-containing core and polyoxyethylene shell

For the first time, core-shell nanoparticles were prepared from the natural polyampholyte N-carboxyethylchitosan (CECh). This was triggered by polyelectrolyte complex (PEC) formation between CECh and strong polyelectrolyte-containing double hydrophilic block copolymers. Quaternized poly[2-(dimethylamino)ethyl methacrylate]-b-poly(ethylene oxide) (quaternized PDMAEMA-b-PEO) and sodium poly(2-acrylamido-2-methylpropane sulfonate)-b-poly(ethylene oxide) (PAMPSNa-b-PEO) were used as polycation and polyanion, respectively. Based on the proper choice of partners and medium conditions, spherical core-shell nanoparticles with PEO shell were obtained both in basic and in acidic medium. The size of the particles was in the range 230-450 nm and depended on the partner nature, the polyelectrolyte molar mass, the pH, and the ionic strength. The obtained structures were studied by dynamic light scattering (DLS), atomic force microscopy (AFM), cryogenic transmission electron microscopy (cryo-TEM), and X-ray photoelectron spectroscopy (XPS). The results were explained in terms of the polyampholytic nature of CECh and the host-guest concept.