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Polymer particles protect micronutrients to fortify food

A pH-sensitive polymer that keeps iron and vitamins from degrading during storage or cooking may help fight malnutrition

by Alla Katsnelson, special to C&EN
November 13, 2019


An image shows particles about 200 micrometers in diameter made from a polymer called BMC encapsulate micronutrients.
Credit: Science Translational Medicine
Particles about 200 micrometers in diameter made from a polymer called BMC encapsulate micronutrients (dark spots) and protect them from degradation caused by heat, moisture and chemical exposure until they reach the stomach.

A pH-sensitive polymer that encapsulates vitamins and minerals and protects them from degrading during storage or cooking may become a powerful tool for fighting malnutrition in the developing world (Sci. Transl. Med. 2019, DOI: 10.1126/scitranslmed.aaw3680).

About 2 billion people worldwide don’t get enough iron, zinc, vitamin A or other vitamins, and are at risk for brain damage, stunted growth, blindness, birth defects, and, particularly for children, even death. The most effective way to counter nutritional deficiencies on a public-health scale is to fortify staple foods in a shelf-stable way. For example, fortifying salt with iodine has made goiter—an enlargement of the thyroid—virtually obsolete.

But supplementing vitamins and minerals in the developing world—where people often can’t walk into a pharmacy and purchase them—has been challenging because micronutrients can degrade when cooked or when exposed to light or moisture. They can also change the taste or color of foods, making them unpalatable. Ana Jaklenec and her colleagues in Robert Langer’s lab at MIT set out to find a better alternative. With funding from the Bill and Melinda Gates Foundation, they worked to develop a material that would essentially serve as a barrier between micronutrients and their surroundings—until the micronutrients reach the stomach.

“We were looking for a coating or cover that could help sequester the micronutrients but also prevent some of the water and moisture penetration to just slow down all these chemical reactions” that affect micronutrient stability, says Jaklenec.

The researchers tested about 50 different materials and settled on a polymer called BMC (poly(butylmethacrylate-co-(2-dimethylaminoethyl)methacrylate-co-methylmethacrylate)(1:2:1)). BMC is safe to consume, and is already used in dietary supplements. Some nutrients could be embedded in BMC in a single mixing step, but others that are water soluble, such as iron, worked better when first complexed to hyaluronic acid and then embedded in the polymer. Micronutrients embedded in BMC particles about 200 micrometers in diameter were unaffected by exposure to UV light, oxidizing chemicals—such as polyphenols, which are present in fruits and vegetables—or two hours of boiling. BMC also readily dissolves at a pH of 1.5—equivalent to the acidic conditions of the stomach. Tests in mice showed the polymer particles released their micronutrient payloads in the gastrointestinal tract within an hour, and that they were absorbed into the body.

The researchers then tested the micronutrient particles in humans. In the first trial, people who ate a maize stew containing iron encapsulated by BMC absorbed only about 40% of the mineral. Based on the trial, the researchers then reformulated the particles to contain less polymer and more micronutrients. In a second trial using fortified bread they achieved more than 80% absorption, which is equivalent to fortification with unencapsulated iron. Combinations of different micronutrients, embedded into separate particles, worked just as well as those delivered on their own.

“There has been a revolution in the design of food-grade microparticle and nanoparticle delivery systems,” says D. Julian McClements, a food scientist at the University of Massachusetts, Amherst. “What is particularly noteworthy about the recent Langer paper is that the delivery system is designed to contain a broad range of different bioactive agents that are targeted to a specific population”—in this case, people in developing countries at risk of malnutrition, he says.

The team is now working with a contract research organization to manufacture the encapsulated micronutrients in large quantities. They are also working with the Gates Foundation to target a specific geographical region where micronutrient deficiencies are prevalent and determine what staple food to fortify.

One possibility is bouillon, a salty, flavorful, reduced broth, says Jaklenec. Just a handful of companies make bouillon, and many people in West Africa use it, so distributing it widely would be easy. Fortifying flour is another good option, though mills tend to distribute locally or regionally.


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