Georgetown College. Georgetown University.

By Theodora Danylevich

Driven by environmental concerns, Dr. Sarah Stoll and her colleagues in Georgetown’s Department of Chemistry are hard at work generating a rival contrast agent to the one currently used in Magnetic Resonance Imaging (MRI). Their work is fundamental, and begins at the level of molecules, focused on the thorough understanding of magnetic clusters and nanoparticles.

Prior to an MRI scan, patients are frequently injected with a solution of a gadolinium-based compound, which enhances contrast and allows doctors to better discern images. Gadolinium is highly toxic, but for this application the metal has been encapsulated by an organic shell rendering it benign. However, no research has yet been done on how the compound later decomposes in the environment.

Dr. Stoll and her colleagues are wary of the toxic potential of gadolinium, and for good reason.

“There are now certain classes of people for whom gadolinium compounds are toxic, although the majority of people are unaffected,” she explains. “More importantly, it is unclear how other species will deal with the compound once it is released into the environment. It is possible that after it is excreted it may become converted, removing the part of the molecule that has been designed to make it safe for humans, and what is safe for humans is not necessarily safe for all organisms.”

Dr. Stoll and her researchers do not believe that this kind of risk is necessary for the purposes of enhancing MRI. As an alternative to gadolinium, they are pursuing the development of a far less risky manganese oxide cluster.

“Manganese is much less toxic in the environment than gadolinium and can also be tailored to control,” says Dr. Stoll. An important feature of the manganese cluster is that the multiple unpaired electrons effectively interact to form a single-molecule magnet. The unpaired electrons are important for the mechanism which causes contrast in MRI. She and her colleagues and students in her lab are currently rigorously working with and studying this cluster to understand its magnetic properties in hopes of further enhancing them for MRI contrast capabilities. For more on this and other research being done in Dr. Stoll’s lab, please refer to the related video.

Dr. Stoll was trained as a solid-state chemist. Solid-state materials with magnetic, optical, or electronic properties are of interest for a variety of applications. She has a passion for studying the unique properties of nanoparticles “because they have intermediate properties between molecules and solid state materials.”

Dr. Stoll and her students target fundamental research, with an eye toward applications. Though their approach, which she calls “basic science,” does not receive much immediate visibility, the rigorous understanding of fundamental properties of nanoparticles for which they aim enables other scientists to use their work in a multitude of valuable applications.

For instance, magnetic nanoparticles have potential applications in magnetic data storage (for example, the hard disk drive in the computer) and separations (for example, in protein synthesis and isolation), as well as biomedicine. While the target application for the work in Dr. Stoll's lab involves the use of magnetic clusters and nanoparticles for contrast in MRI.

Dr. Stoll and her students are also studying lanthanide sulfide nanoparticles to learn about quantum effects in magnetic semiconductors.

“These materials have potential applications in ‘spintronics,’ which are electronic materials that use the spin (or magnetic moment) for coding additional information,” she explains.

Dr. Stoll began her work in the sciences thinking she might end up in medicine, but her love for and fascination with chemistry, as well as the inspiration of a wonderful teacher, led her to her current career.

“When I decided to focus on chemistry, I never thought it would lead me back to the medical field. But, you follow the science and it takes you all over the place. Frequently, scientists with a particular research goal in mind will enable a completely unrelated innovation through their work,” she says.

A professor at Georgetown since 2002, Dr. Stoll is proud of the achievements of her colleagues in the Chemistry Department, pointing out five National Science Foundation (NSF)-funded CAREER five-year grant recipients among junior faculty alone.

“Our department has really had a revolution and is poised for continued progress,” says Dr. Stoll. She is highly pleased with the support that Georgetown provides through the Georgetown Undergraduate Research Opportunities Program, as well as through the new science building project.

Having taught at Oberlin College for six years prior to coming to Georgetown, Dr. Stoll cites the synergy between teaching and research as one of her main passions.

“I love to participate in someone’s learning,” she says. Having done her undergraduate work at Smith College, an all-female school, Dr. Stoll feels strongly about encouraging women’s education in the sciences. Dr. Stoll and her colleagues in the department are actively involved in supporting Project SEED, a program for high school students, sponsored by the American Chemical Society, and the NSF-sponsored Research Experiences for Undergraduate Students, both of which fund students to do summer research in the department.

She has also been involved with an environmental chemistry course, which led her to participate in last year’s Global Environment Leadership Conference, organized by Newsweek magazine and hosted by the university, with a special visit by California Governor Arnold Schwarzenegger.

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