Synopsis

Sound-Induced Bubbles for Drug Delivery

Physics 12, s55
Ultrasound-induced bubble formation, which may benefit drug delivery and other medical procedures, is affected by transitions in surrounding lipid membranes.
S. Shrivastava and R. O. Cleveland, Phys. Rev. Materials (2019)

Ultrasound has long been an important tool for medical imaging. Recently, medical researchers have demonstrated that focused ultrasound waves can also improve the delivery of therapeutic agents such as drugs and genetic material. The intense waves trigger the rapid formation of bubbles that make cell membranes—as well as synthetic membranes enclosing drug-carrying vesicles—more permeable. However, the bubble-membrane interaction is not well understood. New experiments by Shamit Shrivastava and Robin Cleveland from the University of Oxford, UK, show that bubbles form more easily when membranes are at a “melting” transition.

Shrivastava and Cleveland performed ultrasound experiments on an aqueous solution containing a variety of lipid membranes, which are similar to cellular membranes. By varying the temperature of the solution, the duo investigated how the physical state of the membranes affected bubble formation. Fluorescent markers provided information about the molecular ordering within the membranes. When the researchers fired ultrasound pulses into the solution, bubbles formed near the membranes. The bubbles formed at lower acoustic energy when the temperature was near the point where the membranes were transitioning from a gel state to a more liquid-like state. The team also found that bubbles lasted longer when the membranes were in this liquid-like state.

The researchers explained these observed effects with a model that, unlike previous models, accounted for the entropy of the bubble surfaces. Future work may be able to use this model of the system’s thermodynamics to optimize drug-carrying vesicles with membranes that go through a phase transition at the desired moment during an ultrasound procedure.

This research is published in Physical Review Materials.

–Michael Schirber

Michael Schirber is a Corresponding Editor for Physics based in Lyon, France.


Subject Areas

AcousticsBiological Physics

Related Articles

Optimizing Flow Speed is Essential for the Gut
Biological Physics

Optimizing Flow Speed is Essential for the Gut

Fluid dynamics simulations suggest that the varying flow speed inside the small intestine maximizes nutrient absorption while minimizing excess bacteria. Read More »

How Cells Move through Narrow Spaces
Biological Physics

How Cells Move through Narrow Spaces

Experiments demonstrate that biological cells actively change shape to respond to their surroundings when moving in confined regions. Read More »

Disordered Systems Mimic Genetic Evolution
Biological Physics

Disordered Systems Mimic Genetic Evolution

A bacterial genome’s evolution under changing drug concentrations displays effects of memory formation and mimics how disordered solids respond to external forces. Read More »

More Articles