New polymer could enable gastrointestinal transit monitoring without ionizing radiation

Scientists have developed a new fluorine-based tracer that can be tracked using magnetic resonance imaging (MRI) to monitor how quickly food moves through the gastrointestinal tract. The new method has so far been successfully tested in rats in a preclinical study, but it could eventually help diagnose gastrointestinal motility disorders or monitor treatment response. The study was published in Advanced Healthcare Materials.

The rate at which food moves through the stomach and intestines (gastrointestinal transit) provides important information about the health of the digestive system. Gastrointestinal transit is commonly assessed using methods that involve ionizing radiation, such as contrast X-ray imaging or scintigraphy. However, the associated radiation exposure makes these methods less suitable for frequent monitoring and limits their use in certain groups of patients, including pregnant women and children.

A team of researchers from IOCB Prague, the First Faculty of Medicine of Charles University, and Ghent University has developed a new way to monitor gastrointestinal transit using MRI, which does not involve ionizing radiation. The method relies on water-soluble, fluorinated polymer tracers that remain in the gastrointestinal tract and can be detected using fluorine-19 magnetic resonance imaging (¹⁹F MRI).

“The advantage of fluorine is that it is naturally present in the human body only in negligible amounts. This means that when we track the fluorine signal, there is virtually no background interference. We see only our tracer and can determine where it is in the gastrointestinal tract,” explains Ondřej Groborz of IOCB Prague, first author of the study.

Less fluorine, more suitable properties

The new method combines conventional MRI, which shows the anatomy of the gastrointestinal tract, with ¹⁹F MRI, which reveals the polymer tracer itself. Overlaying the two images enables the researchers to pinpoint the tracer’s location, while comparing images taken at different times shows how food moves through the gastrointestinal tract.

Fluorinated compounds have been investigated for gastrointestinal imaging before. However, many are extremely hydrophobic and do not mix well with chyme, the semifluid contents of the digestive tract. Instead, they can form separate layers, resulting in imaging artifacts. The newly developed polymers, by contrast, are hydrophilic and water-soluble, allowing them to remain evenly mixed with the chyme and enabling researchers to track its movement through the digestive system.

Polymer chemist Kristýna Kolouchová of Ghent University in Belgium explains that developing such a tracer was not straightforward. “We needed to strike the right balance in the fluorine content of our tracer. For ¹⁹F MRI, we want the fluorine content to be as high as possible, but too much fluorine adversely affected the tracer’s properties. In the end, we found the right balance: the polymer remained highly soluble while providing a stable signal.”

Next-generation polymer headed for patent protection

The researchers tested the method in rats by administering the polymer tracer directly into their stomachs and using MRI to track its passage through the gastrointestinal tract until it was excreted. They found no evidence of systemic uptake or damage to the tissues examined.

The research is still at the preclinical stage and represents an initial proof of concept in an animal model. Before the method can be used in clinical practice, its safety and reliability will need to be demonstrated in humans, a process that could take several years. The researchers are already working on the next generation of the polymer, which they plan to patent and develop further for practical applications.

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Lisa Lock

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Andrew Zinin

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