Targeted drug delivery could be transformed by microbubble technology

04 June 2013

Microbubble shells

Until now, researchers have been unable to accurately study the flexibility of microbubble shells, which are injected into the bloodstream as an aid to ultrasound imaging.

This lack of information meant that it was hard to predict exactly how the bubbles would behave under the ultrasound beams.

By adding a glowing molecule just beneath the outer shell of the bubble, researchers at Imperial College London and the University of Oxford were able to study the shells of bubbles in minute detail for the first time using a powerful microscope.

This allowed them to accurately map microbubble shells and determine how flexible they are and could lead to future applications for targeting drug delivery to specific areas that require treatment.

One of the lead researchers, Dr Marina Kuimova, from the Department of Chemistry at Imperial, said: "The new technique can potentially have a big impact on our understanding of how microbubbles interact with living cells and each other in blood vessels.  We can now begin work on how to manipulate or manufacture microbubbles for use in medical treatments."

The researchers  demonstrated that addition of the certain molecules to the bubble shells makes them more stable. In the future, scientists could replace these molecules with drugs, so that the bubbles could deliver medicine in an efficient, targeted way.

Information about the properties and behaviours of microbubbles may also be used to improve how they are created so that bubbles can be designed for specific biomedical purposes, such as enhancing how they are used in ultrasound and for delivering drugs directly to where they are required in the body.

Dr Eleanor Stride, from the University of Oxford, added: "This valuable new method will enable us to understand how the microbubble manufacturing techniques we are developing affect the properties of the microbubbles and hence how we can optimise their response to ultrasound for both imaging and drug delivery applications."

The paper, Mapping microbubble viscosity using fluorescence lifetime imaging of molecular rotors, is published in the Proceedings of the National Academy of Sciences.

  • Scientists at Imperial College London have found a way to illuminate tiny bubbles which are used to track blood flow with medical imaging. In the future such bubbles could also deliver targeted drugs in the body.
  • Microbubbles are sized around 100μm. Their shells are made from lipids (fat molecules) similar to those that make up the outer surfaces of human body cells. They are made by agitating air dissolved in water to separate out the liquid and gas. Lipid molecules in the water form a thin layer around pockets of air, creating round bubbles. The lipids arrange themselves with an outer surface that likes water and an inner surface that hates water; this keeps the bubble's shape stable around the air pocket. 
  • Microbubbles used in medical procedures are created in controlled conditions in labs. They are injected into the blood stream in tiny amounts where they circulate until they are gradually absorbed and eliminated by normal biological processes after about a day.