Viscosities of mixtures of hyaluronic acids with different molecular weights and their effects on enzymatic activities of lysozyme and peroxidase.

Abstract

To investigate the viscosity values of mixtures of hyaluronic acids with different molecular weights and the effects of these mixtures on the enzymatic activities of lysozyme and peroxidase. Mixtures of high molecular weight (1 or 2MDa) and low molecular weight (10 or 100kDa) hyaluronic acids at different concentrations were used for viscosity measurements. Hyaluronic acid mixtures showing viscosity values similar to those of human whole saliva were used for enzyme experiments in solution and on hydroxyapatite surface. Hen egg-white lysozyme, bovine lactoperoxidase, and human whole saliva were used as enzyme sources. Lysozyme activity was measured by hydrolysis of fluorescein-labeled Micrococcus lysodeikticus. Peroxidase activity was measured by oxidation of fluorogenic 2',7'-dichlorofluorescein to fluorescing 2',7'-dichlorofluorescein. The mixtures of 1MDa (0.5mg/mL) or 2MDa (0.2mg/mL) hyaluronic acid with 10kDa (2.0mg/mL) or 100kDa (0.1mg/mL) hyaluronic acid had viscosity values similar to those of human whole saliva at shear rates, reflecting normal oral functions. Compared with single molecular weight hyaluronic acids, these mixtures showed viscosity values more similar to those of human whole saliva. The mixtures inhibited lysozyme and peroxidase activities on the hydroxyapatite surfaces; however, the degree of inhibition did not differ from that of hyaluronic acid of 1 or 2MDa only. Compared with single molecular weight hyaluronic acids, hyaluronic acid mixtures showed viscosity values more similar to those of human whole saliva, without additional inhibitory effects on lysozyme and peroxidase activities. Hyaluronic acid mixtures offer distinct advantages for the development of saliva substitutes.