Preparation and characterization of cross-linked hyaluronan nanoparticles

The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on hyaluronic acid (HA). The diamine, 2,2'(ethylenedioxy)bis(ethylamine) was used for cross-linking of the HA linear chains. The condensation reaction of amino groups and pendant carboxyl groups of HA was performed in aqueous media at room temperature using water-soluble carbodiimide. The prepared nanosystems, aqueous solutions, or dispersions of nanoparticles were stable, transparent, or mildly opalescent systems depending on the ratio of cross-linking, findings consistent with values of transmittance above 77%. The structure of products was determined by nuclear magnetic resonance spectroscopy, and the particle size was identified by laser light scattering (DLS) and transmission electron microscopy (TEM) measurements. Particle size measured by TEM varied less than 130 nm; in the swollen state, the average size of the particles measured by DLS was in the range of 30-140 nm depending on the ratio of cross-linking and the molecular weight of HA. Formation of cross-linked nanoparticles results in a viscosity drop compared to the viscosity of the corresponding solution of the HA, and this trend becomes decreasingly appreciable as the molecular weight of HA decreases.