Interpolyelectrolyte complexes based on hyaluronic acid-block-poly(ethylene glycol) and poly-l-lysine

Abstract

The preparation of spherical, nanosized interpolyelectrolyte complexes by the interaction of hyaluronic acid-block-poly(ethylene glycol) (HA-b-PEG) with poly-l-lysine (PLL) at a stoichiometric charge-to-charge ratio is described. The complexation was studied by dynamic light scattering and cryogenic transmission electron microscopy for HA-b-PEG with different lengths of the HA and PEG blocks. A minimal molecular weight of the HA block (ca. 9 kDa) is necessary for efficient complexation, while a minimal molecular weight of the PEG block (ca. 5 kDa) is needed to prevent macroscopic aggregation. The formed nanoassemblies have hydrodynamic radii ranging from 45 to 150 nm with very low dispersity indices (D.I. = 0.02-0.05). They appear as soft objects with a nanogel structure and pronouncedly swell on addition of NaCl. The increasing ionic strength leads to disruption of the complexes above ca. 120-160 mM of NaCl. Decreasing the ionic strength by dialysis reforms the nanogels, demonstrating the reversibility of nanogel formation. Crosslinking with carbodiimide leads to nanoassemblies with a very well defined structure and high stability against ionic strength. © 2013 The Royal Society of Chemistry.