Electroformation of double vesicles using an amplitude modulated electric field

Double vesicles are a promising model to mimic eukaryotic cells, yet effective preparation methods with high yields and stable double vesicles are scarce. Previously reported electroformation methods were mainly based on sinusoidal AC fields. Using a combination of sinusoidal and amplitude modulated (AM) electric fields lipid double vesicles could be produced for the first time by a simple electroformation process. First lipid domes formed in a sinusoidal AC field. The domes grew into tubes during the subsequent application of an AM field. These tubes deformed into double vesicles to minimize their free energy in accordance with the area-difference-elasticity model. Two forces are involved to explain the mechanism behind tube formation. The pulling force (F) is responsible to drag the domes into tubular vesicles, but has to overcome a critical force (F_c). The most important parameters of the electrical field were explored systematically. In our work, a maximum yield for double vesicles of 63% was achieved. These vesicles proved to be stable for one week at least. Hence our method could provide a way to fabricate novel cell models.