Study Of Electroformation Of Oleic Acid-based Vesicles And Their Drug Release Behavior

Vesicles have been of great interest to the scientific community as they have the similar membrane structure as cells. They are not only widely used in the fields of food, drug delivery and cosmetics, but also important tools for the study of the origin of life and protocell models. In contrast with lipid vesicle, the building block of fatty acid vesicle is a kind of surfactants which has only one hydrophobic chain. This simple structure makes fatty acid more possible to exist in the prehistorical period than phospholipid. Therefore fatty acid vesicle has always been regarded as a more appropriate model for protocell from the perspective of origin of life. Many works have been accomplished so far about fatty acid vesicle and they are mainly focus on two aspects. One is the p H dependency which allows reversible transformations from non-vesicular to vesicular aggregates and the other is its applications on protocell models. However its application on drug delivery system has not been developed widely because of its instability and the study on electroformation of fatty acid vesicle is rarely seen.In this work we successfully employed the method of electroformation onto the synthesis of oleic fatty vesicle. Then we designed a systematic experiment to find the optimized conditions for vesicle growth such as temperature and solution. The results show that oleic acid vesicle could grow very well at a temperature range of 25 to 45℃ and saline solution is more suitable than alkaline solution to gain a higher yield. A rich AC-frequency and voltage phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar oleic acid vesicles which shows vesicles could only be formed within a limited range of voltage and frequency. By using the Comsol software we also did simulations based on the theories of electrohydrodynamic effect and Newton fluid. Together with the observation of vesicle growth we could understand the mechanism of eletromation more thorough. The results of simulation explain why vesicle growth occurs more frequently at the edge of the whole device. Furthermore we added another surfactant into the system to form oleic acid-based vesicle, which aim to improve the stability of the vesicle formed by electroformation. Zeta potential test and changes of the vesicle morphology proved that mixture vesicle has been successf ully formed. ACfrequency and voltage phase diagrams were also obtained in these works and showed similar results as pure oleic acid vesicle. Finally we conducted experiments to test the drug release behaviour of such oleic acid-based vesicles. The results show that the addition of another surfactant do have effects on the p ermeability property of the vesicles.The successful synthesis of oleic acid-based vesicles provides a new method to form giant fatty acid vesicles. It could not only make the forming pr ocess more controllable, but also increase the level of observation of that process. By forming mixture vesicles we expand the family of oleic acid-based vesicles. The effects on the permeability property of those vesicles may be helpful in employing oleic acidbased vesicles to the field of drug delivery system.