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Nitrogen-Sulfur Polymers Break New Ground

ACS Meeting News: Polymers bearing nitrogen-sulfur groups have potential applications as biodegradable drug-delivery materials

by Stephen K. Ritter
August 21, 2012

In a set of chemical firsts, University of Iowa researchers have created three polymers that incorporate nitrogen-sulfur groups: sulfenamides (–R2NSR–), diaminosulfides (–R2NSNR2–), and diaminodisulfides (–R2NSSNR2–). The members of this new family of polymers, described at the American Chemical Society national meeting in Philadelphia on Monday, fall apart in aqueous solution and appear to be nontoxic—ideal properties for using them as biodegradable drug-delivery materials.

The three nitrogen-sulfur functional groups are found in a modest number of small organic molecules, but they haven’t appeared in macromolecules until now, noted Iowa’s Ned B. Bowden, whose group carried out the research in collaboration with the group of Iowa colleague Aliasger K. Salem. Bowden’s team prepared the polymers by reacting secondary amines with sulfur reagents (Macromolecules, DOI: 10.1021/ma300190b and DOI: 10.1021/ma2023167). For example, the researchers made poly(diaminosulfides) by reacting secondary amines with bis(N-dialkyl) sulfides.

They made microparticles out of the polymers and showed in lab tests that, similar to polyester drug-delivery materials, the particles are absorbed by human embryonic cells and exhibit no measurable toxicity. Once they enter cells’ mildly acidic environment, the polymers degrade rapidly, Bowden explained. He is intrigued by the degradation products, which include sulfur monoxide, hydrogen sulfide, and allicin—a sulfur antioxidant compound found in garlic. The release of these by-products could possibly be controlled for additional therapeutic effects beyond those of a delivered drug, he suggested. Besides drug delivery, the functional groups might also be incorporated into conducting polymers for electronics applications, Bowden added.

“The ability to incorporate N–S linkages into a polymer backbone brings a wealth of opportunities ranging from biomaterials to microelectronics,” commented polymer expert Craig J. Hawker, a former IBM researcher now at the University of California, Santa Barbara. “It’s not often that a new class of polymers is developed that bears little resemblance to current materials—these polymers are really something unique.”


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