Rheological Properties of Hyaluronic Acid and Its Effects on Salivary Enzymes and Candida

Objective: To investigate the viscosity and wettability of hyaluronic acid (HA), its effects on lysozyme and peroxidase activities, and its candidacidal activity.

Materials And Methods: Human whole saliva, HA, hen egg-white lysozyme (HEWL), and bovine lactoperoxidase (bLPO) were used. Viscosity was measured with a cone-and-plate digital viscometer, while wettability was determined by measuring the contact angle. Lysozyme activity was determined by the turbidimetric method. Peroxidase activity was determined with NbsSCN assay. Candidacidal activity was determined by comparing colony forming units.

Results: The viscosity of HA solutions was proportional to its concentration, with 0.05 mg ml(-1) of HA in distilled water or 0.5 mg ml(-1) in simulated salivary buffer displaying similar viscosity values to stimulated whole saliva. The contact angle of HA solutions showed no significant differences according to the tested materials and tested HA concentrations. Contact angles of HA solutions on acrylic resin were higher than those of human saliva. HA did not affect lysozyme or peroxidase activities of whole saliva as well as HEWL or bLPO activities. HA also showed no candidacidal activity.

Conclusions: The viscoelastic properties of HA compared with human saliva were objectively confirmed, indicating a vital role for HA in the development of effective salivary substitutes.