University of Leeds: Improved Microbubble generation may Enhance Pre-clinical Ultra-sound

ResizedImage400265 Sally.170942The properties and methods of production of micron sized, lipid stabilized bubbles of gas, known as 'microbubbles' (MBs) are being studied in detail using microfluidics by Sally Peyman (Photo above) and colleagues at the University of Leeds. The work was presented at the annual Izon Science research symposium held at Oxford University earlier last month.

MBs are in medical use as contrast agents for ultra-sound imaging. Due to their compressibility and gas/liquid interface they reflect and echo sound waves more efficiently than liquid/liquid interfaces thus enhancing diagnostic ultra-sound imaging.

More recently there has been an increase in interest for using MBs as vehicles for targeted drug delivery by functionalising the MB shell with a drug payload and targeting ligands. By combining the imaging and delivery properties of the MBs they can be traced in real time as they accumulate around a tumour, then using a high frequency ultra-sound pulse the MB can be destroyed, thus releasing its drug payload directly to the tumour.

Microfluidic technology provides a reproducible means for MB production and surface functionalisation using flow-focussing microfluidic devices that combine streams of gas and liquid through a nozzle a few microns wide and then subjecting the two phases to a downstream pressure drop. Microfluidics has also been used to surface functionalise MBs with liposomes loaded with drugs. The size and concentration of drugs needs to be accurately measured to understand their loading onto MBs.

Dr. Peyman and colleagues recently demonstrated a microspray regime for the production of sub-micron bubbles at high concentrations (10^10 bub / mL) which show potential as high resolution contrast enhancers for pre-clinical ultra-sound. Due to their small size they cannot be counted with traditional optical techniques, and TRPS has been used to characterise these Ultra-fine bubbles in terms of size and concentration.

Image Below: Adam Churchman, qNano user (PhD student in Microbubbles and Ultrasound at Uni. of Leeds (CDT Molecular-Scale-Engineering, Uni. of Leeds & Sheffield)