Microbubbles as ultrasound triggered drug carriers.

Originally developed as contrast agents for ultrasound imaging and diagnostics, in the past years, microbubbles have made their way back from the patients' bedside to the researcher's laboratory. Microbubbles are currently believed to have great potential as carriers for drugs, small molecules, nucleic acids, and proteins. This review provides insight into this intriguing new frontier from the perspective of the pharmaceutical scientist. First, basic aspects on the application of ultrasound-targeted microbubble destruction for drug delivery will be presented. Next, we will review the recently applied approaches for manufacturing and drug-loading microbubbles. Important quality issues and characterization techniques for advanced microbubble formulation will be discussed. Finally, we will provide an assessment of the prospects for microbubbles in drug and gene therapy, illustrating the problems and requirements for their future development.