Echogenic liposome as a carrier of siRNA for sonoporation: An alternative microbubble for sonoporation

Ultrasound contrast agents (UCAs), which are groups of engineered microbubbles, have been recently studied for drug delivery applications since cavitation of bubbles can increase the temporary permeability of nearby cells. However, the internal volume of UCAs is generally filled with gas, hence loading drug molecules into UCAs is limited. In this presentation, one type of echogenic liposome having a liquid and gas core is proposed as an alternative carrier of genetic material for ultrasound-mediated drug delivery, which is known as sonoporation. The structure of the synthesized echogenic liposome was analyzed via transmission electron microscopy (TEM) and confocal microscopy with fluorescent labels. The protection of siRNA by echogenic liposomes was also verified by exposure to RNase. The results indicate that at least 20% of the total siRNA used in experiment was successfully protected by the proposed echogenic liposome. Additionally, release of siRNA from the liposomes could be successfully achieved by ultrasound sonication with a treatment of 1-W/cm2 intensity at 1 MHz; parameters low enough to be used in generic ultrasound therapeutic systems. Although further studies to clarify the responses to incident ultrasound fields and to quantitatively analyze the internal liquid volume for drug loading are required, the proposed echogenic liposome seems to have great potential for ultrasound-mediated gene delivery.