Interleukin-12 (IL-12) gene therapy is expected to be effective against cancers because it primes the immune system for cancer cells. In this therapy, it is important to induce IL-12 gene expression in the tumor tissue. Sonoporation is an attractive technique for developing non-invasive and non-viral gene delivery systems, but simple sonoporation using only ultrasound is not an effective cancer gene therapy because of the low efficiency of gene delivery. We addressed this problem by combining ultrasound and novel ultrasound-sensitive liposomes (Bubble liposomes) which contain the ultrasound imaging gas perfluoropropane. Our previous work showed that this is an effective gene delivery system, and that Bubble liposome collapse (cavitation) is induced by ultrasound exposure. In this study, we assessed the utility of this system in cancer gene therapy using IL-12 corded plasmid DNA. The combination of Bubble liposomes and ultrasound dramatically suppressed tumor growth. This therapeutic effect was T-cell dependent, requiring mainly CD8(+) T lymphocytes in the effector phase, as confirmed by a mouse in vivo depletion assay. In addition, migration of CD8(+) T cells was observed in the mice, indicating that the combination of Bubble liposomes and ultrasound is a good non-viral vector system in IL-12 cancer gene therapy.
"URDDS include microbubbles,8–10 nanobubbles,11,12 nanodroplets,13 liposomes,14,15 emulsion,16 and micelles.17–19 A combination of two or more formulations can be used as URDDS, such as liposomal bubbles20,21 and microemulsions.22 The drugs loaded can include inorganic substances, eg, titanium dioxide,23 small molecules (curcumin,24 doxorubicin,25 cisplatin,5 epirubicin hydrochloride,26 10-hydroxycamptothecin27), proteins,28,29 small interfering RNA,8,21 DNA,30 and antisense oligodeoxynucleotides.31,32 "
[Show abstract][Hide abstract] ABSTRACT: Ultrasound is an important local stimulus for triggering drug release at the target tissue. Ultrasound-responsive drug delivery systems (URDDS) have become an important research focus in targeted therapy. URDDS include many different formulations, such as microbubbles, nanobubbles, nanodroplets, liposomes, emulsions, and micelles. Drugs that can be loaded into URDDS include small molecules, biomacromolecules, and inorganic substances. Fields of clinical application include anticancer therapy, treatment of ischemic myocardium, induction of an immune response, cartilage tissue engineering, transdermal drug delivery, treatment of Huntington's disease, thrombolysis, and disruption of the blood-brain barrier. This review focuses on recent advances in URDDS, and discusses their formulations, clinical application, and problems, as well as a perspective on their potential use in the future.
International Journal of Nanomedicine 04/2013; 8:1621-33. DOI:10.2147/IJN.S43589 · 4.38 Impact Factor
"To solve this problem, several papers report on the so-called nanobubbles  , also named 'bubble liposomes' , which are smaller than 1 μm, combining the benefits of a liposome (small size, long circulation time) with ultrasound responsiveness. These small bubbles are generally prepared by sonicating liposomes in the presence of fluorinated gases. "
[Show abstract][Hide abstract] ABSTRACT: Time and space controlled drug delivery still remains a huge challenge in medicine. A novel approach that could offer a solution is ultrasound guided drug delivery. “Ultrasonic drug delivery” is often based on the use of small gas bubbles (so-called microbubbles) that oscillate and cavitate upon exposure to ultrasound waves. Some microbubbles are FDA approved contrast agents for ultrasound imaging and are nowadays widely investigated as promising drug carriers. Indeed, it has been observed that upon exposure to ultrasound waves, microbubbles may (a) release the encapsulated drugs and (b) simultaneously change the structure of the cell membranes in contact with the microbubbles which may facilitate drug entrance into cells. This review aims to highlight (a) major factors known so far which affect ultrasonic drug delivery (like the structure of the microbubbles, acoustic settings, etc.) and (b) summarizes the recent preclinical progress in this field together with a number of promising new concepts and applications.
"For example, the transgene expression of luciferase plasmid in the posterior heart after US-mediated transfection peaked at Day 4 but dropped to less than one tenth of the peak value at Day 14 . In one case, the half period of luciferase expression after gene transfection with bubble liposomes and US in mice was only 0.54 days and the luciferase activity was less than 1% at Day 7 . Previous research has shown that cationic polymers such as polyethylenimine (PEI) could enhance the efficiency (and potentially also the expression duration) of both in vitro and in vivo gene transfection. "
[Show abstract][Hide abstract] ABSTRACT: Ultrasound (US) irradiation has been found to facilitate the inward transport of genetic materials across cell membranes (sonoporation). However, its transfection efficiency is generally low, and the expression duration of transfected gene is short. Polyethylenimine (PEI), a cationic polymer, has been shown to aggregate plasmid DNA and facilitate its internalization. The purpose of this study is to determine whether PEI can also prolong the expression duration after US-mediated transfection. A mixture of pCMViLUC and 22-kDa linear PEI was transfected to cultured cells or mouse muscle by exposure to 1-MHz pulsed US. The duration of expression was assessed periodically following US treatment. As expected, strong expression of luciferase could be found 30days after the treatment of DNA-PEI complex with US exposure, both in vitro and in vivo. However, without US, only very low transfection level could be obtained in vivo. The DNA/PEI complex showed protective effect against digestion of DNase I enzymes as compared with groups without PEI or to which PEI was added following the mixing of plasmid DNA with DNase I. PEI enhanced the US transfection efficiency by increasing both the intracellular uptake of plasmid DNA and the percentage of transfected cells. Most of the DNA uptake occurred at 3h after US exposure, suggesting that endocytosis took place. Moreover, the PEI-facilitated US gene transfection depended on the ratio of PEI and DNA (N/P ratio), which was different for in-vitro and in-vivo conditions. This system could be applied in future human gene therapies.
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