Encapsulating nanoemulsions inside eLiposomes for ultrasonic drug delivery.

An eLiposome is a liposome encapsulating an emulsion nanodroplet and can be used for drug delivery. For example, therapeutic agents are encapsulated inside the eLiposomes, and the application of ultrasound can cause the emulsion droplet to change from liquid to gas, thus increasing the volume inside the vesicle and causing rupture and the release of the drug. In this research, two different methods were used to prepare eLiposomes. In the first method, emulsion droplets were made of perfluorohexane or perfluoropentane and stabilized with 1,2-dipalmitoyl-sn-glycero-3-phosphate. A layer of 1,2-dimyristoyl-sn-glycero-3-phosphocholine was dried in a round-bottomed flask. Then the emulsion suspension was added to the flask. As the suspension hydrated the phospholipids, they formed liposomes around the emulsions. In the second method, emulsions and liposomes were made separately, and then they were mixed using ultrasound. The advantage of this second method compared to the previous one is that eLiposomes can be made with fewer restrictions because of incompatible combinations of surfactants. Dynamic light scattering and transmission electron microscopy were used to measure the size of the emulsions, liposomes, and eLiposomes. The size of eLiposomes is appropriate for extravasation into tumors with malformed capillary beds. We hypothesize that ultrasound breaks open these eLiposomes. Both types of eLiposomes were constructed with folate attached via a poly(ethylene glycol) tether to induce endocytosis of the eLiposome. The latter eLiposomes were successfully used to deliver calcein as a model drug to HeLa cells.

Ultrasonic gene and drug delivery using eLiposomes.

eLiposomes are liposomes encapsulating emulsions and therapeutics for targeted delivery. By applying ultrasound to eLiposomes, emulsion droplets can transform from liquid to gas and rupture the lipid bilayer of the eLiposome to release a drug or plasmid. In this study, perfluoropentane (PFC5) emulsions were encapsulated inside folated eLiposomes carrying a model drug (calcein) or a model GFP plasmid to examine the effects of a folate ligand, PFC5 emulsion and various ultrasonic acoustic parameters in drug delivery and gene transfection into HeLa cells. Confocal microscopy was used to quantify drug delivery and the level of plasmid transfection into HeLa cells. The results showed that drug delivery or transfection was minimal without incorporation of internal PFC5 emulsions and folate ligand on the eLiposome surface. It was also shown that application of ultrasound greatly enhanced the drug delivery and plasmid transfection. Delivery of these therapeutics appears to be to the cytosol, indicating that the expansion of the emulsion droplets disrupted both the eLiposomes and the endosomes.