**7. Acknowledgements**

The Authors thank Dr. Steven Feinstein and GE Global Research, for their contributions for the ApoA-I-DNA experiments.

#### **8. References**

210 Non-Viral Gene Therapy

Fig. 13. Baseline to peak response measurement in 30 treated rats recorded in raw data values of mg/dL. A statically significant 14% increase was measured (p-value= 0.0001).

possible to repeat treatment, potentially indefinitely.

material scientists, biologists and biopharma.

translation.

**6. Conclusions** 

**7. Acknowledgements** 

the ApoA-I-DNA experiments.

the intact skin or, if need be, via specialized probes. While ultrasound is blocked by air/tissue or air/fluid interfaces, even in the lung, it is possible to create acoustic windows to the bronchi with bronchoscopes and water filled balloons. Ultrasound can be targeted precisely to tissues to treat volumes of tissues ranging to more than 500 ml to less than a ml. Most studies have shown relatively low toxicity due to ultrasound and MBs. It also is

Despite early studies in ultrasound and gene delivery with MBs being performed more than a decade ago, none of the ultrasound gene delivery programs with MBs, at the time of preparation of this chapter, have advanced to clinical trials. The field is still early in its development, but the tolerability, ease of use and high degrees of expression in the target tissue indicate that this technology merits serious consideration for clinical

Ultrasound mediated gene delivery with acoustically active carriers (e.g. microbubbles) is a promising field that affords the potential for high levels of expression in the target tissue without the adverse bioeffects of viral-based carriers. The field is early in its development however as no clinical studies have yet been performed as of the time of preparation of this manuscript. Clinical development of this promising field will require identification of biological targets in areas of medical need and multi-disciplinary collaborations between

The Authors thank Dr. Steven Feinstein and GE Global Research, for their contributions for


**10** 

**Ultrasound-Mediated Gene Delivery** 

*Seattle Children's Research Institute & University of Washington, Seattle WA* 

Human gene therapy holds great promise in treating not only hereditary genetic disorders, but also disease states such as cancer and viral infections, and contingencies such as stroke or myocardial infarctions. It can be achieved by delivery of a correct gene into target cells with genetic deficiency or mutations, or by transfer of a therapeutic agent such as agents targeting a cancer-causing oncogene, growth factor gene, antisense oligonucleotides (ODN), or small interfering RNA (siRNA) to correct the disease state using either viral or nonviral vectors. Viral gene therapy has succeeded in many animal disease models {Snyder 1999}, and has progressed to clinical trials {Hacein-Bey-Abina *et al.* 2002; Kay *et al.* 2000}. However, significant obstacles remain, including immune responses {Manno *et al.* 2006} or tumor genesis {Hacein-Bey-Abina *et al.* 2003}. A nonviral approach would provide a safer strategy. The potential for therapeutic ultrasound (US) to effect minimally invasive nonviral gene transfer has long been recognized, and a growing body of evidence indicates that significant enhancement of transgene expression can be achieved by using high frequency acoustic energy. In addition to its well-known role in providing inexpensive, real-time imaging capability, US has been used therapeutically for years {Herzog *et al.* 1999}. The most common therapeutic application involves low acoustic intensities and is intended to heat deep tissues; *e.g*., as used in sports medicine. At the other 'end' of the acoustic intensity spectrum is HIFU (high intensity focused ultrasound), which can be used to ablate {Fischer *et al.* 2010} or to liquefy tissues {Hall *et al.* 2009}. US of intermediate intensities has been applied to many systems, together with exogenous microbubbles [MBs], to use the acoustically-forced behavior of the MBs to generate desired bioeffects. The latter usually involves changing the permeability of endogenous barriers to otherwise impermeable materials (*e.g*., drugs or macromolecules). Many gene therapies have been attempted by direct intramuscular or intraparenchymal injection of gene vectors; these vectors gain immediate access to the interstitial space and must then traverse the plasma membrane of the targeted cells. US contrast agents are almost always administered intravascularly. When accompanied by a gene vector, the first barrier encountered is the vascular endothelium. The next are other vascular anatomical features (*e.g.*, the basement membrane, smooth muscle layer, *etc.*) and then the outer cell membrane of the cells one hopes to target. Finally, DNA needs to be transferred across the nuclear membrane to enter the nucleus for

This review will focus almost entirely on the use of ultrasound targeted microbubble destruction (UTMD) as a means by which to deliver foreign DNA (or drugs or photo

**1. Introduction** 

efficient gene expression.

Carol H. Miao and Andrew A. Brayman

*United States of America* 

