Zeta potentials of human salivary micelle-like particles

Abstract

Zeta potential determinations of recently demonstrated salivary micelle-like structures may provide information about their adsorption potentials to enamel surfaces. The aim of this study was to determine the zeta potentials of the salivary micelle-like structures at different pH levels and to determine their isoelectric points (IEPs). The zeta potentials were determined by measuring the electrophoretic mobilities of the salivary particles in an electric field using an electrophoretic light scattering method. Parotid saliva was collected from four individuals and analyzed separately. The zeta potentials were measured at different pH by acidification with lactic acid. Zeta potential determinations of casein micelles in milk were included as a control. The zeta potential measurements showed an overall net negative surface charge of the micelle-like structures of about −9 mV at physiological pH. On acidification of the saliva the zeta potential gradually increased from pH 5 and at pH 3 the particles became positive. The IEPs ranged from pH 2.9 to pH 3.1. The zeta potential determinations in the present study are consistent with the assumption that the salivary particles exhibit a micelle-like structure which may interact electrostatically with enamel surfaces.