ARS chemists Sevim Erhan and Zengshe Liu developed the soy-oil-based hydrogels as a biodegradable alternative to the synthetic polymers now used, including polyacrylic acid and polyacrylamide.

Soy oil is an appealing raw material to use because it is chemically versatile, abundant and renewable--meaning the crop can be replanted each year to renew the supply. In 2006, U.S. farmers planted 76 million acres of soybeans, equal to about 38 percent of the world's total oilseed production, notes Erhan. She and Liu both work at ARS' National Center for Agricultural Utilization Research in Peoria.

They first began investigating soy-oil-based hydrogels in 1999 as part of the Peoria center's mission of exploring new, value-added uses for corn, soybeans and other Midwest crops. Using a two-step process--ring-opening polymerization and hydrolysis--they created a squishy but durable hydrogel polymer that expands and contracts in response to changes in temperature and acidity levels.

In tests, they observed that the hydrogel's water-absorbing capacity was lower than that of petroleum-based polymers. But this later proved to be a plus. In collaboration with Erhan and Liu, a University of Toronto scientist successfully formulated the hydrogel into nanoparticles that encapsulate the breast cancer drug doxorubicin. In drug-release experiments, nanoparticle-delivered doxorubicin proved eight times more toxic to cancerous cell lines than when lipid-water solutions were used.

Soy proteins are known allergens, but Erhan doesn't anticipate this posing a problem to the nanoparticles' use as drug-delivery agents. That's because soy oil's chemical structure is completely changed by the two-step manufacturing process used to make the hydrogel.

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