Physico-chemical characterization of polysaccharide-coated nanoparticles

A series of amphiphilic copolymers (PCL-DEX) made of poly(epsilon-caprolactone) (PCL) side chains grafted onto a dextran (DEX) backbone, was used to modify the surface of PCL nanoparticles. PCL-DEX nanoparticles were prepared by a technique derived from emulsion-solvent evaporation. The purpose of the present study was to investigate the DEX coating (quantification, conformation, mobility) in order to better understand particle surface-protein interactions. The DEX coating was deeply examined using different complementary methods: zeta potential measurement, specific degradation of the DEX shell by dextranase, energy-filtering transmission electron microscopy coupled to image-spectrum electron energy-loss spectroscopy, electronic paramagnetic resonance, high performance size exclusion chromatography as well as nonspecific bovine serum albumin adsorption. All our data together supported a core-shell structure of the nanoparticles, DEX moieties constituting the external coating. The amount of DEX located on the nanoparticle surface was estimated to 70%. The organisation of the shell including chains density and mobility was found to be dramatically influenced by DEX molar mass. The steric repulsion conferred by the presence of DEX at the surface of the nanoparticles decreased the adsorption of albumin. The nanoparticle-protein interaction was, however, greatly influenced by the polysaccharide conformation onto the surface.