Spatial and acoustic pressure dependence of microbubble‐mediated gene delivery targeted using focused ultrasound

Abstract

Gene delivery can be targeted using focused ultrasound and microbubbles. Since delivery is dependent on acoustic pressure, the degree of targeting can be determined by appropriate transducer design to modify the ultrasound field. In contrast to other physical gene delivery approaches, the non-invasive targeting ability of ultrasound makes this technology an attractive option for clinical gene therapy.

Gene therapy progress and prospects: Ultrasound for gene transfer

“…The development of ultrasound enhanced gene transfer (UEGT) began when a number of research groups speculated that the physical perturbations induced by an ultrasound beam would encourage plasmid DNA uptake and transgene expression. Although the early results were at best modest, achieving 10-to 30-fold increases in transfection efficiency in vitro, technical refinements have meant that enhancements of up to several thousand fold in vitro are now being observed, [1][2][3][4][5][6][7][8][9] sufficient to encourage studies of UEGT in vivo.…”

Microvascular free tissue transfer for gene delivery: in vivo evaluation of different routes of plasmid and adenoviral delivery

“…[29][30][31] Briefly, signal from a waveform generator (model 33220A, Agilent Technologies Inc., Loveland, CO, USA) was fed into an RF power amplifier (58 dB gain, model BT00500 BETA, Tomco Technologies, Norwood, Australia) and thence to a custom-made 1 MHz ultrasound transducer (Imasonics, Besancon, France). The transducer was spherically focused, of 20 mm diameter and 68% bandwidth, with the focal point of the ultrasound beam 67 mm from the transducer face.…”

“…Dosimetry of the 1 MHz transducer in its focal plane has been previously described. 29,30 To expose the tissue flap at the focal distance, a cylindrical perspex 'stand-off' was made to fit around the transducer: a layer of cling-film was used to retain a column of water in this tube through which the ultrasound was transmitted. The internal diameter of 38 mm was such that there was negligible disturbance of the acoustic field at the focal distance (that is, at the end of the tube).…”

“…The latter was used to prevent reflections and standing wave generation leading to unquantifiable exposure conditions; the effectiveness of this material in eradicating reflections has been demonstrated. 29,30 Before exposure of the tissue flap to ultrasound, a total volume of 0.4 ml of 0.9% (w/v) sodium chloride containing 50 mg p.Luc and 4% (v/v) SonoVue microbubbles (Bracco, High Wycombe, UK) was injected into the tissue flap through the cannulated artery. A further 0.6 ml 0.9% (w/v) sodium chloride was injected and the artery was clamped.…”

“…SonoVue is an ultrasound contrast agent consisting of phospholipid-encapsulated microbubbles (1-12 mm) filled with SF 6 gas. 30,31 SonoVue was prepared according to the manufacturer's protocol to yield a solution containing 2 Â 10 8 -5 Â 10 8 microbubbles per ml.…”