Scientists are developing a localised drug delivery system based on
ultrasound and microbubbles that are partially filled
with cancer drugs. As the drugs are only released at the site of the tumour, the patient’s total body exposure to them could be limited, which could help to reduce the side-effects of chemotherapy for certain types of cancer
Research scientists are developing new drug-delivery technology, based on
ultrasound and microbubbles, which is designed to increase the effectiveness and reduce the side effects of chemotherapy treatment for certain types of cancer.
The use of microbubbles in conjunction with medical ultrasound imaging is not new. However, at the moment, they are only used as contrast agents in applications such as highlighting blood in ultrasound images – which relies on the fact that they reflect ultrasound much better than blood or soft tissue.
The new drug-delivery technology, developed by the research arm of electronic giant Philips, continues to utilise the contrast-enhancing capabilities of microbubbles to help ultrasound operators in locating cancerous tumours.
What’s new is that it then shatters the shells of the microbubbles in these blood vessels using a focused high-energy ultrasound pulse. As a result, the drugs contained in the microbubbles are released directly inside the tumour.
Philips’ system employs the use of drug-loaded microbubbles – no larger than red blood cells – that can be injected into the patient’s bloodstream.
These microbubbles are then 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, such as chemotherapy for breast cancer, this could help to reduce unpleasant side effects.
Focused ultrasound
The scientists at Philips Research have also developed a new computer-controlled ultrasound device that can steer and focus the microbubble-rupturing ultrasound pulses.
To deliver the drug where it is required, these microbubble-rupturing ultrasound pulses must be accurately targeted at the site of the disease.
To achieve this, the researchers developed a special transducer that can focus ultrasound pulses deep in the target tissue.
Microbubble-rupturing also generates its own characteristic acoustic signal to estimate how many microbubbles have ruptured. This might be used to quantify and control drug dosage, according to the boffins.
International Collaborations
Philips is working with several academic partners, including the University of Virginia (USA) and the University of Muenster (Germany), to refine the technology.
Clinical institutions, such as The Methodist Hospital in Houston (USA), are also actively researching this field of ultrasound-mediated drug delivery.
“More and more, patients are demanding treatment options that allow them to maintain their quality of life during the regime, without sacrificing treatment efficacy,” said King Li, MD, Chair of the Department of
Radiology at the Methodist Hospital in Houston and Professor of Radiology, Weill Cornell Medical College.
“The non-invasive nature of ultrasound-mediated delivery is a step in this direction,” he added. “Work at our and other institutions using ultrasound for drug delivery and treatment guidance has shown the potential of this technology in pre-clinical studies.”