Could A Nanotube-based Drug Prevent Radiation Injury?

"More than half of those who suffer acute radiation injury die within 30 days, not from the initial radioactive particles themselves but from the devastation they cause in the immune system, the gastrointestinal tract and other parts of the body," said James Tour, Rice's Chao Professor of Chemistry, director of Rice's Carbon Nanotechnology Laboratory (CNL) and principal investigator on the grant. "Ideally, we'd like to develop a drug that can be administered within 12 hours of exposure and prevent deaths from what are currently fatal exposure doses of ionizing radiation."

The Defense Advanced Research Projects Agency (DARPA) has awarded Tour and co-principal investigators J. Conyers and Valerie Moore at the University of Texas Health Science Center at Houston (UT-Houston) and Luka Milas, Kathy Mason and Jeffrey Myers at the University of Texas M.D. Anderson Cancer Center a $540,000 grant for a nine-month study of an experimental drug that the investigators have named Nanovector Trojan Horses (NTH).

NTH is made at Rice's Chemistry Department and Carbon Nanotechnology Laboratory in the Richard E. Smalley Institute for Nanoscale Science and Technology. The drug is based on single-walled carbon nanotubes, hollow cylinders of pure carbon that are about as wide as a strand of DNA. To form NTH, Rice scientists coat nanotubes with two common food preservatives -- the antioxidant compounds butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) -- and derivatives of those compounds.

"The same properties that make BHA and BHT good food preservatives, namely their ability to scavenge free radicals, also make them good candidates for mitigating the biological affects that are induced through the initial ionizing radiation event," Tour said.

In preliminary tests at M.D. Anderson in July 2007, mice showed enhanced protection when exposed to lethal doses of ionizing radiation when they were given first-generation NTH drugs prior to exposure.

"Our preliminary results are remarkable, and that's why DARPA awarded us this grant with a very compressed timeline for delivery: nine months, which is almost unheard of for an academic study of this type," Tour said. "They are very interested in finding out whether this will work in a post-exposure delivery, and they don't want to waste any time."

Ionizing radiation is any form of radioactive particle or energy that converts an atom or molecule into an ion by altering the balance between the number of protons and electrons. In living organisms, ionization often results in the creation of free radicals -- highly reactive molecules that can wreak havoc by disrupting healthy physiological processes. These free radicals induce a cascade of deleterious biological events that cause further destruction to the organism in the days and weeks after initial radiation exposure event. NTH is designed to terminate the destructive biological cascade.

Tour said the researchers are also interested in finding out whether the new drugs can prevent the unwanted side effects that cancer patients suffer after undergoing radiation therapy.