In recent years new promising opportunities for targeted drug and gene delivery have been discovered using ultrasound contrast agents. Ultrasound contrast agents consisting of micron-sized encapsulated gas bubbles are used to increase the contrast between blood and tissue during an ultrasonic examination and thereby improving the image quality and diagnostic confidence. More recently, it has been shown that gaseous microbubbles offer a new dimension for therapeutic applications with ultrasound for an efficient local drug and gene delivery. Indeed, it has been reported that microbubbles and ultrasound increase the permeability of biological barriers (cell membrane, endothelial layer) transiently, allowing thus a higher extravasation of molecules. In this way drugs and genes can be delivered locally without serious consequences for the cell viability of neighboring tissue. The ultrasound triggered action of microbubbles known as sonoporation provides unprecedented possibilities for a highly selective therapeutic action. Moreover, the microbubbles can act as a drug carrier for a targeted release with ultrasound. We will show in this review different examples of therapeutic applications with microbubbles including sonothrombolysis, blood brain barrier opening and local drug and gene delivery. Moreover the different hypothesized mechanisms of sonoporation will be further discussed.
Keywords: ultrasound, microbubbles, drug delivery, sonoporation
