Acoustic properties of antibubbles

Abstract

Antibubbles are gas bubbles with incompressible liquid cores. When stabilised, antibubbles may have specific acoustic properties that allow for localised drug delivery. The aim of this research was to investigate these acoustic properties. Footage of three types of antibubble-containing media under the influence of ultrasound were analysed. Of the media, two contained antibubbles with different amounts of stabilising endoskeletal content, and the third contained reference bubbles which comprised of core-less antibubbles. Image segmentation and processing was used to analyse the footage and quantify the changes in individual antibubble and bubble size throughout sonication. Antibubble oscillation was found to be symmetric at a low acoustic amplitude of 200 kPa and highly asymmetric at a high, but still clinically safe, acoustic amplitude of 1 MPa. This was a result of the presence of their liquid droplet cores hampering negative excursion under high amplitude sonication. It was also found that under low amplitude sonication, micron-sized antibubbles oscillate more reliably and stably than their bubble counterparts. Additionally, it was observed that only a single pulse of high amplitude ultrasound was enough to cause an antibubble to rupture. This indicates that at lower acoustic amplitudes antibubbles can be carefully controlled and used in diagnostics, and at higher acoustic amplitudes they can be made to rupture and release their therapeutic contents