DU researchers are using electron paramagnetic resonance to examine diseases at the molecular level. Thermal image: James Doss/Shutterstock
In Isaac Asimov’s 1966 sci-fi classic Fantastic Voyage, a team of physicians is shrunk to the size of a molecule and injected into a patient to diagnose and treat.
Asimov’s idea is likely to remain fantasy, but scientists have come up with the next best thing — electron paramagnetic resonance (EPR), which can be used to examine diseases at the molecular level.
In fact, University of Denver researchers have found that using EPR to peer inside living creatures — in vivo studies — can boost the effectiveness of radiation therapy for cancer, help treat circulatory problems and help determine whether medications are safe.
All that from a technique most people have never heard of.
The research
You probably have heard of EPR’s famous cousin, MRI (magnetic resonance imaging), which creates images of internal tissues by detecting the spin of an atom’s nucleus.
EPR, however, detects the spin of electrons — negatively charged particles that whirl around the nucleus of an atom at great speed. The ways that electrons spin reveal information about the identity of molecules, their arrangement and their environment within a sample, such as tissue. And, EPR has the unique power to detect oxygen concentrations and identify free radicals — molecules that contain unpaired electrons.
Although groundbreaking, EPR isn’t a brand new discovery. Dutch scientists discovered its basic principles some 80 years ago, and EPR instrumentation has been around for more than 60 years.
For the past three decades, DU has been a world leader in EPR research. In 2001, DU received a five-year, $1 million grant from the National Institutes of Health (NIH) to establish the Center for EPR Imaging for In Vivo Physiology in partnership with the University of Maryland and the University of Chicago, where the actual in vivo research takes place. The center is one of only a handful capable of using EPR to detect molecules in small animals and human extremities.
“The center grant puts DU in division one in this research area,” says chemistry Professor Gareth Eaton.
Eaton and his wife, chemistry Professor Sandra Eaton, founded DU’s EPR program and focus their research on the development of EPR methodologies and instruments. They are joined on the EPR vanguard by chemistry department Professor and Chair Lawrence Berliner, who joined the University in 2000. More than 25 DU undergraduates and 25 graduate students have contributed to published papers on EPR, as have DU engineers Richard Quine and George Rinard.
The scientific process can be drawn out and unpredictable, Gareth Eaton says, noting that his and Sandra’s EPR techniques were initially limited to the study of isolated proteins.
Now they’re developing ways to use EPR to determine oxygen concentrations in the body, Sandra Eaton says. Oxygen concentrations are especially important in cancer radiation therapy, where high-energy rays are used to kill cancer cells.
“Radiation treatment is only effective when the rays are directed into tissue regions that contain high concentrations of oxygen,” she explains.
While MRI can indirectly measure oxygen concentrations, EPR can generate detailed maps that show varying oxygen levels in tissue, thus enabling physicians to direct radiation precisely into oxygen-rich cancerous areas, Sandra Eaton says. The radiation initiates chemical reactions that destroy the tumor tissue, consuming all oxygen in the process. Because EPR can follow the oxygen concentration over time, it tells the physician exactly when enough oxygen is regenerated to send the next dose.
“This application really has the potential of making clinical treatment much more effective,” Sandra Eaton adds.
EPR’s ability to detect oxygen levels in tissue also could be used to diagnose and treat circulatory problems, like those that can lead to amputation in diabetic patients.
“There are a number of potential applications of EPR that could be very significant additions to clinical medicine, resulting in the systematic incorporation of in vivo EPR into most clinical settings,” says Harold Swartz, professor of radiology and physiology at Dartmouth Medical School.
It will be another five or 10 years before the application of in vivo EPR for cancer treatment becomes available in a clinical setting, Gareth Eaton says. But, EPR already is providing insight into the interaction between neighboring molecules and the shape of complex molecules such as proteins and enzymes. The Eatons have developed several methods for measuring proteins to determine whether they’re in the correct conformation.
Proteins are indispensable for life and are the building blocks for everything from hair and skin to the molecules produced by our immune system. But a protein only does its job when it is assembled correctly, and diseases such as Alzheimer’s and cystic fibrosis result when proteins are misshapen.
“The EPR spectrum can tell you whether the protein is sick or not,” says Berliner, who, in addition to studying proteins, has been using EPR to research free radicals — molecules that can damage healthy DNA and have been linked to ailments such as cancer and heart disease.
Berliner has used EPR to test whether certain drugs cause harmful side effects by producing free radicals. He demonstrated that the liver can convert the blood-pressure medication Nipedifine into a free-radical producing compound, potentially increasing the risk of heart attack; Berliner and second-year master’s student Maria Parkin are studying the biochemistry and biology of this phenomenon on mice.
Berliner also hopes to study the effects of free-radical reactions that diesel fuel particulates induce on lung tissue. He suspects that reactive oxygen radicals play a role in diseases such as asthma and emphysema.
Awards and recognition
DU’s EPR studies have garnered national and international attention and, over the past 33 years, have been funded by more than $14 million in grants from the NIH and others. Currently, the Eatons’ research group accounts for five grants totaling more than $3 million.
Sandra and Gareth Eaton have authored or edited seven books and published more than 270 peer-reviewed papers. In 1997, they were jointly named DU John Evans Professors. And in 2002, they received the Royal Society of Chemistry’s Bruker Prize, one of the most prestigious awards in the field of EPR.
In 2000, Berliner received the International EPR Society’s Silver Medal for Biology/Medicine. Last year, he received the Lifetime Achievement Award in Biological EPR from Ohio State University. He has published 190 scientific papers and edited 27 books.
DU engineers Rinard and Quine received the International EPR Society’s Silver Medal for Instrumentation in 2002. And for the past 28 years, the University has hosted the International EPR Symposium.
“In a way, this is a real success story for DU’s investment in faculty research,” says Gareth Eaton. The University went out on a limb to provide the instrumentation, equipment and lab space he and Sandra needed when they joined DU as junior scientists, he says.
“Today, we have a team of chemists, engineers and even an oncologist at the University of Chicago working together to transform basic research into instruments and procedures that ultimately will be used to help people,” Gareth Eaton adds. “It is important that universities support curiosity-driven research because there is almost no way to predict what comes out of fundamental research. We couldn’t have guessed that we could be where we are today.”