Study of the mechanism of formation of hyaluronan putty at pH 2.5: Part I. Experimental measurements

This paper reports on the elucidation of the possible mechanism for forming the putty structure of hyaluronan (HA) at low pH (2.5) using rheological methods. Oscillation and stress relaxation tests on a series HA putty samples containing various concentrations of salt indicated that ionic forces were not the driving force for their formation, but hydrogen bonds were responsible for driving two or more HA molecular chains together to form a three dimensional network. Our results indicated/confirmed that the carboxyl group of the glucuronic acid and acetamido group of N-acetylglucosamine moieties on two neighboring HA chains are involved in the formation of the intermolecular hydrogen bonding, which lead to the formation of the putty at pH 2.5.