How do ultrasonically driven bubbles interact with cells?

Amongst the several exciting applications of microbubbles, their promise in the medical industry for use in diagnostics, therapy and medicine is striking to many particularly because of its implications for cancer treatment.

In order to increase the lifetime of these bubbles and prevent their clustering in the body, these bubbles are often coated with lipids and polymers. Such coatings alter their dynamics and modify the oscillation behaviour.

I have recently stumbled upon an informative review by Lohse, in which he summarises various applications of bubbles. I was particularly fascinated by the following pictures, published by C. D. Ohl et al.

Ultrahigh-speed imaging facilities enable a closer study of the interaction of ultrasonically driven bubble with cells. On the left is a HeLa cell culture growing on a glass plate, soon after a bubble collapses close to it. The strong shear forces exerted by the bubble on collapse, cause some cells to detach from the glass plate. Cells at the centre of the cell colony where the bubble imploded took up fluorescein, only possible through holes in the cell membrane.  These holes can be visualized through electron microscopy, as shown on the right. It is through such holes that drugs or genes invade the cells.