(509f) Synthesis, Manipulation and Assembly of Functional Phospholipid Vesicles In AC-Electric Fields

Recently, there has been an emerging interest in exploiting the rich electrokinetic behavior of biomolecular entities for sensing, manipulation and assembly, with broad applications from drug delivery to medical diagnostics. In this work, we examine the dielectrophoresis (DEP) behavior of hybrid phorspholipid vesicles in the presence of AC-electric fields by using confocal laser scanning microscopy. With phospholipid vesicles of 100-400 nm in diameter (liposomes) synthesized with 1,2-Dioleoyl-sn-Glycero-3-Phosphate (DOPA), we focus on their DEP responses with the addition of polystyrene nanoparticles. We observe that liposomes stabilized by opposite charged nanoparticles can be rapidly assembled to form large lipid membranes under positive DEP, where applied frequency is below the crossover frequency of liposomes. However, it is very surprising to observe that the measured crossover frequency of the liposome is independent of the nanoparticle coverage on the lipsome's surface, even though the adsorption of nanoparticles effectively varies the surface charge of the lipsomes. Similar behavior is also explored with liposomes coated with a uniform inorganic conducting layer of 20-50 nm thick. The DEP shell model modified with dynamic double-layer effects by charged nanocolloids accounted for this unusual DEP behavior. Recently, we also exploited the DEP-induced synthesis and encapsulation of giant unilamellar vesicles (GUV). A narrow frequency range is observed to form GUVs from lipid monolayers on a conducting coverslip with applied AC-fields. With increasing AC-field strength, GUVs can be stretched and fuse together near the microelectrodes, which provides a new method for the encapsulation of nanocolloids and macromolecules into the aqueous cores of GUVs.