Investigation of dynamic Stern layer of liposomes by utilizing the isoelectric point and isoconducting point

Abstract

The electrostatic force between microscopic bodies such as cells and membranes in biological fields is an important factor for the interactions between them, which is determined by the dynamic properties of surface charges and counterions in the electric double layer. If the adsorbed-counterion mobility is small the approximation of the interaction at constant charge is valid, but in the opposite case the charge regulation occurs during their interaction. Therefore, the surface conductivity of counterions, especially Stern layer conductivity on the surface of biological membranes or liposome particles, is an important parameter to be measured. A simple analytical method to estimate the surface diffusivity of adsorbed counterions utilizing isoelectric points from electrophoresis and isoconducting points from the measurements of surface conductivity is proposed. The large surface diffusitivities of certain divalent metal ions adsorbed on negatively-charged liposomes are found by conducting both the measurements of electrophoresis and conductivity.