Bubble liposomes

Effective In Vitro and In Vivo Gene Delivery by the Combination of Liposomal Bubbles (Bubble Liposomes) and Ultrasound Exposure... 

Fig. 4. In vivo gene delivery into mouse ascites tumor cells with Bubble liposomes. S-180 cells (1x10 cells) were i.p. injected into ddY mice. After 8 days, the mice were anaesthetized, then injected with 510 p.L of pCMV-Luc (10 p.g) and Bubble liposomes (500 pg) in PBS. Ultrasound (frequency 1 MHz, duty 50% intensity 1.0 W/cm, time 1 min) was transdermally applied to the abdominal area. In another experiment, pCMV-Luc (10 pg) - Lipofectin (50 pg) or Lipofectamine 2000 (50 pg) complex was suspended in PBS (510 pL) and injected into the peritoneal cavity of mice. After 2 days, S-180 cells were recovered from the abdomens of the mice. Luciferase activity was determined, as described in Materials and Methods. Each bar represents the mean S.D. (/j=3-6). P<0.01 compared to the group treated with plasmid DNA, Bubble liposomes, ultrasound exposure or lipofection with Lipofectin or Lipofectamine 2000. LF, Lipofectin. LF2000, Lipofectamine 2000. <10 BLU/mg protein...

Then, perfluoropropane was entrapped within lipids like micelles. In addition, the lipid nanobubbles were encapsulated within liposomes. To confirm the structure of BLs, we observed BLs with transmission electron microscope. Interestingly, BLs had nanobubbles into lipid bilayer. Therefore, we called this Bubble liposome because of this structure. This structure of BLs was different from that of conventional microbubbles and nanobubbles which had lipid monolayer. 

In addition, Suzuki et al. [102] achieved tumor-specific ultrasound-enhanced gene transfer with novel liposomal bubbles, which entrapped an ultrasound imaging gas. Extraordinarily, the bubble liposomes healthy transferred genes, only at the site of ultrasound exposure, into tumor cells and solid tnmor tissne [103-106]. 

Prepare a liposome suspension, containing PE, at a total-lipid concentration of 5mg/ml in 0.1M sodium phosphate, 0.15M NaCl, pH 6.8. Maintain all lipid-containing solutions under an inert gas atmosphere. Degas all buffers and bubble them with nitrogen or argon prior to use. 

Aseptic Lltration is necessary for parenteral formulations. Because both lipids and the structure of liposomes are unstable at high temperatures, conventional terminal steam sterilization is not suitable for liposome formulations. Thus, the membrane aseptic Lltration is the most reliable method for sterilizing liposome formulations. Since the possibility exists for the membrane being defective, it is advisable to test the integrity of the assembled unit by carrying out a bubble-point test. This test... 

Talsma, H., Van Steenbergen, M. J., Borchert, J. C. H., Crommelin, D. J. A. (1994), A novel technique for the one-step preparation of liposomes and nonionic surfactant vesicles without the use of organic solvents. Liposome formation in a continuous gas stream The bubble method,/. Pharm. Sci., 83, 276-280. 

Cavitation caused by ultrasound-triggered destruction of gas pockets in ultrasound-responsive liposomes bubbles increases the permeability of cells and tissues, thus facilitating the transport of the drug or gene into the targeted cells and tissues. 

The formation of liposomes [or better arsonoliposomes (ARSL)], composed solely of arsonolipids (Ars with R=lauric acid (C12) myristic acid (C14) palmitic acid (C16) and stearic acid (C18) (Fig. 1) have been used for ARSL construction), mixed or not with cholesterol (Choi) (plain ARSL), or composed of mixtures of Ars and phospholipids (as phosphatidylcholine [PC] or l,2-distearoyl- -glyceroyl-PC [DSPC]) and containing or not Choi (mixed ARSL), was not an easy task. Several liposome preparation techniques (thin-film hydration, sonication, reversed phase evaporation, etc.) were initially tested, but were not successful to form vesicles. Thereby a modification of the so called one step or bubble technique (8), in which the lipids (in powder form) are mixed at high temperature with the aqueous medium, for an extended period of time, was developed. This technique was successfiil for the preparation of arsonoliposomes (plain and mixed) (9). If followed by probe sonication, smaller vesicles (compared to those formed without any sonication [non-sonicated]) could be formed [sonicated ARSL] (9). Additionally, sonicated PEGylated ARSL (ARSL that contain polyethyleneglycol [PEG]-conjugated phospholipids in their lipid bilayers) were prepared by the same modified one-step technique followed by sonication (10). 

Suzuki R, Takizawa T, Negisbi Y, Utoguchi N, Maruyama K (2007) Effective gene delivery with liposomal bubbles and ultrasound as novel non-viral system. J Drug Target 15 531-537... 

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