A study conducted by academics at the University of Gothenburg revealed a method that can change the way medicines are delivered to specific parts of the body.

Until the temperature climbs over 32 degrees, microgels create a thin protective shell around a droplet. The microgels then contract and the droplet dissolves in the surrounding liquid.

Emulsions are made up of many droplets that exist in a liquid without dissolving or combining with it. Milk, for example, is made up of fat droplets that are stabilised by milk proteins and distributed in water.

Many applications, such as drug administration, require not just the ability to retain droplet form but also the ability to control when the droplets dissolve. This is due to the fact that the encapsulated active chemicals in the droplet should be released only after the drug has entered the body.

Researchers from many universities, including the University of Gothenburg, have developed a concept called responsive emulsions, which allows them to control when the droplets dissolve.

"The idea is to stabilise 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," explained Marcel Rey, a researcher in Physics at the University of Gothenburg and lead author of the study published in Nature Communications.

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

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

"The morphological changes in the stabilising microgels, triggered by external stimuli, play a crucial role in influencing the stability of the associated emulsions. This understanding is fundamental to the design of microgels capable of stabilising emulsions at room temperature while facilitating dissolution at body temperature," explained Marcel Rey.

The stabilising 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 the 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 customise 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-stabilised emulsions that respond to the pH of the surrounding fluid," explained Marcel Rey.

Pharmaceutical research focussing on targeted medicines is crucial. The goal is to deliver medication in a higher concentration to specific diseased areas of the body rather than affecting the entire body.

"Responsive emulsions hold great potential as a precise tool for delivering medicine to specific areas in the body. Although additional research is needed, the future looks promising, and advancements can be expected over the next 10 years," said Marcel Rey.