For many of us, caffeine is a "catalyst" that turns us from sleepy zombies into functioning members of society, but now that may be more literal. Researchers from MIT and Brigham and Women's Hospital have used caffeine to replace the metal catalysts normally used in creating polymer materials, opening the door for drug delivery via chewable gels.
Normally, polymer gels are synthesized using metal catalysts, which can be dangerous if they remain in the final product and are not things you'd really want to be ingesting. While they are already used in biomedical applications, plenty of post-processing needs to be done beforehand to remove any traces of the metal. So, the MIT/Brigham team set out to remove that final step by finding edible equivalents.
"Most synthetic approaches for synthesizing and cross-linking polymeric gels and other materials use catalysts or conditions that can damage sensitive substances such as biologic drugs," says Robert Langer, senior author of the study. "In contrast, here we used green chemistry and common food ingredients. We believe these new materials could be useful in creating new medical devices and drug delivery systems."
Caffeine was a clear catalyst candidate, thanks to its ability to act as a weak base – a substance that can gently remove protons from other molecules. Structurally, it's also fairly similar to other weak bases that have been used for the same types of chemical reaction needed here – namely, the ability to form polyesters.
"Polyesters allow for the intentional design of ingestible materials made from bioderived resources," says Angela DiCiccio, lead author of the study. "However, there didn't exist any catalysts that were mild enough to enchain these molecules without causing unwanted reactions or requiring super high heat. Our new platform provides an elegant solution to this problem using inexpensive materials and broadly accessible chemistries."
To make their new polymer gel, the researchers combine citric acid with polyethylene glycol (PEG) – the former is a common plant product, and the latter is a biocompatible polymer that's long been used in everyday products like toothpaste. When caffeine is added to the mix and mildly heated, it catalyzes the other ingredients to form a polymer network.
The resulting gel is safe enough to swallow, and can be loaded with drugs to make medication. In their tests, the researchers successfully demonstrated the latter with two malaria drugs, known as artesunate and piperaquine. The gel's strength, surface structure and rate of drug release can also be controlled by changing the combination and ratio of the polymers used.
The team says the new ingestible gel simplifies the manufacturing of these materials, making medication based on them more affordable. They can be loaded with a range of drugs to fight different diseases, and the softer texture makes them easier to swallow or even chewable, which could help kids or other people who may have trouble swallowing pills. While the gel obviously contains caffeine, the researchers say it's only a small amount – about as much as a cup of tea.
The research was published in the journal Biomaterials.
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