Research on polysaccharides could result in better drug delivery
Picture a tree. Its thick, rough trunk extends upward, gradually tapering as it meets the sky. Powerful branches extend from its sides, covered in gently blowing leaves. The tree seems to ignore the most basic rule of life on earth — gravity. In large part, this phenomenon is due to polysaccharides, which are organic molecules that perform functions as diverse as building strong, flexible trees and delivering nutrients through the bodies of animals.
According to Kevin Edgar, a professor in the College of Natural Resources’ Department of Wood Science and Forest Products, polysaccharides are also the "magic" ingredient to improving medicine. Currently, many medications have poor solubility and bioavailability, meaning that only a small portion of the drug reaches the bloodstream to combat illness. To compensate, patients must take higher doses to get enough of the drug into their bloodstream, leading to higher medical costs and increased risk of side effects from the off-target portion of the drug.
Edgar said he believes that polysaccharides can be used to solve many of these problems. Polysaccharides are naturally safe for use in medicines. Edgar’s students modify them through selective photosynthesis to create safe derivatives with attributes that enable them to help to move the drug from the gastrointestinal tract into the bloodstream and to control release times. This opens the door to extended release medications that allow the patient to take a pill once a day, rather than once every few hours. Edgar said the opportunity to create extended release medications is an important one because that convenience is a vital component of successful treatment.
Improved drug delivery has been Edgar’s goal since before he joined the Virginia Tech faculty in 2007, he said. While a Technology Fellow at Eastman Chemical Company, Edgar and his colleagues conducted research to improve the delivery of saquinavir, an HIV drug, and of tamoxifen, an important therapeutic for the prevention of breast cancer. Their research resulted in drugs that can be more easily absorbed into patients’ bloodstreams, increasing a drug's effectiveness.
In his quest to develop the most effective medications possible, Edgar crosses traditional boundaries, applying many different disciplines to his research. In the journal Cellulose, he wrote, “It is typical of modern scientific inquiry that it is at this multidisciplinary interface, at the intersection of organic chemistry, material science, polysaccharide chemistry, pharmacology, and pharmaceutical science, that rich opportunities for discovery exist.”
Edgar said he pursues these opportunities through the long process of drug creation. Before he can use the polysaccharides, Edgar must first modify them by adding benign chemical groups to enhance their solubility — their ability to dissolve — and to ensure that they remain non-toxic. Next, he must determine the most suitable method to combine the polysaccharide with the drug, a process that can be as simple as mixing the ingredients together and pressing a pill, or as complicated as freeze-drying.
Edgar can further enhance the drug’s solubility by incorporating the drug into a polysaccharide matrix, a process that requires testing many drug-polysaccharide matrices before finding the best combination. If laboratory tests indicate the system should be effective, it is then tested in complex living systems. If these tests are successful, the next step is approval from the Food and Drug Administration. Approval consists of a three-part process in which the drug is tested extensively for safety, efficacy, and uniform response in patients representing a wide spectrum of ages, races, and medical conditions.
Though Edgar spends much of his time dealing with the complicated chemical processes involved in creating new drugs, he said his ultimate goal is to help people. His progress toward this goal recently earned Edgar a place in the inaugural class of the American Chemical Society (ACS) Fellows, an honor given to only 162 of its 154,000 members.
“I hope my work will make drug taking more effective, safer, and more convenient for patients,” Edgar said.
- For more information on this topic, contact Lynn Davis at (540) 231-6157.
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Kevin Edgar's research at Virginia Tech includes working with several components of the university.
- Edgar Research Group: Edgar and his students work together to exploit the opportunity that polysaccharide derivatives present to the field of medicine. The group explores the synthetic development of polysaccharide derivatives as well as the influence of structure on polysaccharides’ properties.
- Macromolecules and Interfaces Institute: Edgar is one of eight associate directors at the Macromolecules and Interfaces Institute. The institute’s Research Initiatives Unit, led in part by Edgar, seeks to identify major funding opportunities for multidisciplinary institute faculty groups in areas of importance to the nation’s economy, security, and energy systems.
- Institute for Critical Technology and Applied Science: This university-wide organization is designed to incorporate engineering, science, and medicine into research collaboration. Edgar serves on the faculty advisory board and is the thrust leader for Renewable Materials research, leading the Bio-based Materials Design and Processing Group.
- Virginia Tech Carilion School of Medicine: Established in January 2007, the school will welcome its charter class of M.D. students in fall 2010. The public-private partnership is designed to address the need for a bridge between scientific research and clinical expertise in medicine. Edgar is currently collaborating with faculty members Drs. Thomas Kerkering and Jayasimha Rao on a project that investigates the use of amorphous drug polymer nanoparticles in the treatment of infectious diseases.
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