Microbubbles

Title	:	Microbubbles
Description	:	Ultrasound microbubble technology targets localized drug delivery The future of surgery lies in minimally invasive procedures. By avoiding the trauma associated with traditional surgery, minimally invasive interventions reduce patient risk, increase patient comfort and result in faster recovery. They also help to reduce the cost of treatment, as well as increasing patient throughput. As a result, they are typically win-win solutions for physicians, hospitals, healthcare systems, and patients. However, one challenge of minimally invasive interventions is that physicians can no longer see ‘with their own eyes’ what they are doing. They therefore need additional information, such as real-time images from medical scanners, to see what is going on. As a result, many of today’s minimally invasive interventions – for example, heart catheterizations and needle biopsies – are image-guided by imaging techniques such as low-dose X-ray fluoroscopy or ultrasound imaging.  Although ultrasound is already used to image what is going on inside the patient during some minimally invasive procedures, it may also be able to play a role in the localized delivery of drugs or other therapeutic molecules to specific areas of tissue. Drug loaded microbubbles One evolving technology, for example, proposes the use of drug-loaded microbubbles, no larger than red blood cells, that can be injected into the patient’s bloodstream, tracked via ultrasound imaging, and then ruptured by a focused ultrasound pulse to release their drug payload when they reach the desired spot. Because the drugs would only be released at the site of the diseased tissue, the patient’s total body exposure to them could be limited. For certain types of treatment – for example, chemotherapy for breast cancer – this could help to reduce unpleasant side effects. Gas-filled microbubbles are already in clinical use as contrast agents for enhancing the images obtained during certain ultrasound examinations (for example to highlight the blood in blood vessels) – an application that relies on the fact that the gas in the microbubbles reflects ultrasound much better than blood or soft tissue. However, microbubbles are not yet used clinically for drug delivery. Philips Research is at the forefront of research into the drug delivery potential of microbubbles, by adapting existing microbubble technology so that microbubbles can deliver precise doses of drugs exactly where they might be needed in the body. If this research is brought to a successful conclusion, it could make ultrasound a powerful tool for combining traditional imaging modalities with this novel therapeutic approach. One envisioned application is the delivery of localized chemotherapy for certain types of cancer – for example, breast cancer. The two major challenges that scientists at Philips Research have successfully addressed are the construction of the drug-filled microbubbles and the accurate focusing of microbubble rupturing pulses into living tissue. These are both key enablers to bringing the technology one step closer to reality. Microbubble synthesis Microbubbles are typically less than 5 microns (millionths of a meter) in diameter, which makes them no bigger than red blood cells. As a result, they can pass through even the smallest of blood vessels. When used as contrast agents, their shell is normally manufactured from albumin or a biodegradable material such as polylactic acid or galactose, and their interior is filled with air or an inert gas such as perfluorocarbon or nitrogen. Scientists at Philips Research have now found a way to synthesize microbubbles that are partially filled with drugs and partially filled with gas. This allows the microbubbles to retain their contrast-enhancing ultrasound properties while also making them vehicles for drug delivery. Philips Research’s process also allows accurate control of the size and shell thickness of the bubbles and the amount of drug loaded into them. In particular, the bubble size and shell thickness must be accurately controlled so that they rupture at the appropriate ultrasound frequencies and energies.
Date	:	Sept. 30, 2008
Credit	:	Video Credit: Philips Research Flash Conversion: Scientific Frontline
Source	:	Philips Research
File Type	:	SWF
File Size	:	13.5MB