Diethylaminoethyl chitosan-hyaluronic acid polyelectrolyte complexes

Polysaccharide-based polyelectrolyte complexes (PECs) are of great interest for the development of drug delivery systems, as they are easily prepared and exhibit a wide range of colloidal properties. The water-soluble diethylaminoethyl chitosan (DEAE-CS) was synthesized with various degrees of substitution (DS), ranging from 26 to 113%. Analysis of the substitution pattern of DEAE-CS by different NMR techniques revealed N- and O-substitution, as well as quaternization of the tertiary amino group of the DEAE substituent; the fraction of quaternary amino groups increased with the DS. Unlike the tertiary amino groups, the quaternary amino groups did not support increases in the ζ-potential of DEAE-CS with the DS and the complexation with hyaluronic acid (HA). The influence of the PEC composition, DS of DEAE-CS, and mixing order on the size and polydispersity of PEC nanoparticles was investigated by dynamic and static light scattering. Internal disordered heterogeneous PEC nanoparticles were formed by the aggregates of several primary PECs. Disordered and structurally heterogeneous spherical complexes were formed (R_g/R_h = 1.0 ± 0.3). The obtained PECs were metastable and their properties were influenced by mixing order. The high molecular weight component (HA), being a minor component, was more exposed on the surface than was the low molecular weight DEAE-CS.