New approach on evaluation of liposome release property with electric impedance measuring method

Abstract

The purpose of this study is to develop a novel method for evaluation of the liposomes' release property by detecting the electric impedance change in the liposome solution. Liposomes encapsulating calcein (calcein-liposomes) and de-ionized water (white-liposomes) were prepared and ultrasound was employed as the stimulus in order to release the calcein from liposomes. The impedance change of calcein-liposomes in de-ionized water was measured before and after ultrasound treatment, as well as that of white-liposomes in de-ionized water and in calcein solutions for comparison. Besides, the release of calcein-liposome suspensions was evaluated simultaneously by spectrofluorometer. Results showed that the impedance of white-liposomes would change greatly when it was exposed to ultrasound and it was related to the total ion concentration of the sample. The release rate of calcein calculated with electric impedances showed a good agreement to that calculated with fluorescence intensities. It indicates that the electric impedance measuring method has high potential to estimate the release rate as the fluorescence analysis do, and might be used for non-fluorescent encapsulated liposomes which could not be evaluated by fluorescence method.