Protected Droplets: A New Transport Route for Medicines

Microgels form a thin protective shell around a droplet until the temperature rises above 32 degrees. Then the microgels shrink and the droplet dissolves in the surrounding liquid. A study now reveals the underlying mechanism behind this process. The discovery could revolutionize methods of targeting medicines to specific locations within the body.

Emulsions consist of numerous droplets that are present in a liquid without dissolving and mixing with the liquid.

In many applications such as medicine delivery, it is important to not only maintain the droplet structure but also to be able to control when the droplets dissolve.

This is because the encapsulated active ingredients in the droplet should only be released once the medicine has entered the body.

Researchers from several universities have introduced a concept of responsive emulsions to control when the droplets dissolve.

“The idea is to stabilize emulsions using temperature-sensitive microgel particles that adapt their shape to the ambient temperature. At room temperature, they swell in water, but above 32°C, they shrink and contract,” explains Marcel Rey, lead author of the study.

What happens when the temperature rises above 32°C is that the droplets dissolve in the surrounding liquid as they are no longer sufficiently stabilized by the protective microgel shell.

While this phenomenon has been known in science for an extended period, the researchers have now uncovered that the fundamental mechanism driving stimuli-responsive emulsions involves morphological changes in the stabilizing microgels.

The stabilizing microgels can be regarded as both particles and polymers.

The particle character leads to a high stability of the emulsion, while the polymer character makes the microgels responsive to external influences leading to dissolution of the droplets.

Achieving temperature-sensitive emulsions necessitates a delicate balance, requiring a minimal particle character for stability and a substantial polymer character for rapid and reliable dissolution of the droplets.

“Now that we understand how responsive emulsions function, we can customize them to specific requirements. While our current efforts have been confined to laboratory experiments with temperature dependence, we are actively exploring the development of microgel-stabilized emulsions that respond to the pH of the surrounding fluid,” explains Marcel Rey.

The goal is to deliver medication in a higher concentration to specific diseased areas of the body rather than affecting the entire body.

Sources:

Materials provided by University of Gothenburg. Note: Content may be edited for style and length.

Marcel Rey, Jannis Kolker, James A. Richards, Isha Malhotra, Thomas S. Glen, N. Y. Denise Li, Fraser H. J. Laidlaw, Damian Renggli, Jan Vermant, Andrew B. Schofield, Syuji Fujii, Hartmut Löwen, Paul S. Clegg. Interactions between interfaces dictate stimuli-responsive emulsion behaviour. Nature Communications, 2023; 14 (1) DOI: 10.1038/s41467-023-42379-z

University of Gothenburg. “Protected droplets a new transport route for medicines.” ScienceDaily. ScienceDaily, 30 November 2023. <www.sciencedaily.com/releases/2023/11/231130113236.htm>.

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