Scientists in France have discovered a way of making longer-lasting bubbles for use in ultrasound imaging. 

Marie-Pierre Krafft at Institut Charles Sadron in Strasbourg and colleagues studied the lifetime of bubbles a few micrometers in diameter. The bubbles were made of fluorinated phospholipids and filled with mixtures of nitrogen and fluorocarbon gases called perfluorocarbons (PFCs).

The team mixed a phosphate buffered saline, a fluorinated phospholipid and a wetting agent under an atmosphere of nitrogen saturated with PFC. They measured the lifetime of the resulting bubbles, finding that they lasted on average 70 minutes (compared to about five minutes for bubbles made from a non-fluorinated phospholipid). 

PFCs make phospholipid microbubbles more stable in an aqueous environment because of their poor solubility in water. Bubbles filled with only nitrogen last less than 100 seconds regardless of which of the two phospholipids are used to make them. 

Krafft said that using a phospholipid that contains fluorine provides a highly effective stabilisation of the microbubbles compared to the non-fluorinated phospholipids. 

She said there was an unexpected cooperation between the fluorocarbon gas and the fluorinated phospholipids to give the very stable bubbles. She added that the increased stability of microbubbles is good news for ultrasound imaging where they are used to provide visual contrast.

Michael J Smith