Protected droplets create a new transport route for medicines

Researchers from several universities have completed an innovative study which firmly links the structure of microgels to the controlled release of liquid droplets coated in these particles. The discovery could revolutionise methods of targeting medicines to specific locations within the body.

7 December 2023

Emulsions consist of numerous droplets that are present in a liquid without dissolving and mixing with the liquid. For example, milk consists of fat droplets stabilised by milk proteins that are dispersed in water. 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 release their contents. This is because the encapsulated active ingredients in the droplet should only be released once the medicine has entered the body.

An oil droplet (yellow) stabilised by temperature-sensitive microgels (green) in water (blue). The microgels maintain the stability of the oil droplets at room temperature but when heated, their shape flattens and the droplets are released. This image was captured using the cryo-SEM facility at Edinburgh.


In this study, researchers stabilised emulsions using temperature-sensitive microgel particles which form a thin protective shell around a droplet and adapt their shape to the ambient temperature (see the image above). At room temperature, the microgel particles swell in water, but above 32°C, they shrink and the droplet is released into the surrounding liquid. Researchers have now revealed the underlying mechanism behind this process.

Understanding the mechanism

The team, which includes researchers from ECFP and the University of Edinburgh, University of Gothenburg, Heinrich-Heine University Düsseldorf, ETH Zürich and the Osaka Institute of Technology, have revealed that the fundamental mechanism behind stimuli-responsive emulsions are morphological changes of the stabilizing microgels.

The stabilising microgels can be regarded as both particles and polymers. The particle character leads to high stability of the emulsion, while the polymer character makes the microgels responsive to external influences leading to controlled release 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 release of the droplets.

Tailored emulsions

Pharmaceutical research on targeted medicines focuses on delivering medication in a higher concentration to specific diseased areas of the body rather than affecting the entire body, and responsive emulsions hold great potential for this.


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