Characterization of chitosan hydrochloride-mucin interaction by means of viscosimetric and turbidimetric measurements

In the present work the interaction between chitosan hydrochloride (HCS) an d two different types of mucin - one obtained from bovine submaxillary glan ds and the other from porcine stomach - was investigated. Two hydration med ia were tested: distilled water and 0.1 M HCl. Intrinsic viscosity, which p rovides information about polymeric chain conformation, was assessed in bot h media for HCS and bovine submaxillary mucin. Changes in the specific visc osity of HCS-mucin mixtures were observed as a function of the polymer:muci n weight ratio. The formation of interaction products was indicated by a mi nimum in the specific viscosity. Such a minimum occurred at different polym er:mucin weight ratios depending on the hydration medium and mucin type. Th is suggested a different stoichiometry of interaction. Turbidimetric measur ements were also effected in order to evidentiate the eventual precipitatio n of the polymer-mucin interaction products. While in distilled water the p recipitation of the interaction product did occur, in acidic medium, althou gh a minimum in specific viscosity was observed, no precipitate was formed. The two techniques employed, viscosimetric and turbidimetric, allowed us t o investigate for both mucins the influence of hydration medium on the form ation of the HCS-mucin interaction products and to conclude that a slightly acid-neutral pH favours the interaction between HCS and mucins. (C) 2000 E lsevier Science B.V. All rights reserved.