Molecular characterization of two host-guest associating Hyaluronan derivatives

The association of two high-molecular-weight hyaluronan (HA) derivatives, namely B-cyclodextrin (HA-B-CD) and an N-acylurea (EDC-HA), dissolved in aqueous NaCl was studied. The weight average of the molecular weights (Mw) of HA-B-CD and EDC-HA was 185.3 and 86.8 (91.2) kDa, respectively. However the Mw value determined for the equimolar mixture of the two biopolymers equaled 556.0 kDa. Similarly, the z-average of the root-mean-square radius of gyration of the above equimolar mixture - Rg = 80.6 nm - was significantly greater than the values found for the single macromolecules, i.e. 40.2 nm for HA-B-CD and 23.8 (25.2) nm for EDC-HA. These data indicate that the two kinds of substituents, borne by the HA polymeric chains, form host-guest/inclusion complexes resulting in polymacromolecular associates/aggregates.