Functionalized Hydrogels Deliver Insulin Nanomedicine

Researchers in Texas have functionalized hydrogel nanoparticles to improve the delivery of orally-administered drugs to the small intestines, a site where therapeutic compounds are absorbed into the bloodstream .The team grafted methacrylic acid and ethylene glycol together to create a unique polymer hydrogel that can survive the harsh acidic conditions of the stomach. The hydrogel nanoparticles were also decorated with wheat germ agglutinin (WGA) to make them stick to the intestinal tissue.

In vitro tests indicate that functionalized hydrogel nanoparticles, soaked with insulin are very efficient at loading and retaining the drug. This makes them a good delivery vehicle for insulin, a protein drug used to treat diabetes.

When subjected to the pH conditions found in the stomach, the particles retain insulin. On raising the pH to more neutral levels, such as those found in the small intestines, insulin is released. This happens because methacrylic acid contains carboxyl groups which remain protonated at low pH conditions.

Fluorescence microscopy image of cells taking up insulin from functionalized nanoparticles. The insulin has been labeled with a fluorescent compound and the bright green cell perimetry indicates insulin transport.

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At more neutral pH levels, the carboxyl group deprotonates causing the polymer chains to repel each other. As a result, the hydrogel swells, releasing the drug molecules from the nanoparticle and into the system.

Nicholas A. Peppas told Materials Today that the hydrogel spheres are designed to be greater than 200 nm in diameter to prevent their uptake by lymphoid cells called Peyer's patches that are also present in the small intestines. Instead the insulin cargo is released directly into the bloodstream, where it is needed. He also explained the reasoning behind using WGA as anchors. “Functionalization of PEG chains with WGA allows for specific binding to carbohydrate moieties present in the intestinal mucosa to improve residence time of the carrier at the delivery site.”