Radiotherapy is widely used to fight cancers. Today, only beta particles are approved by health regulators, such as the U.S. FDA. Beta particles are small and travel fast, but it takes thousands of them to kill a cancer cell. Now, U.S. researchers have found a way to use alpha particles to destroy cancer tumors by encapsulating them inside carbon nanotubes. These alpha particles, which are 4,000 times bigger than beta particles, are much slower but are more efficient. According to the researchers, 'cancer cells can be destroyed with just one direct hit from an alpha particle on a cell nucleus.' But major issues need to be overcome before future treatments become possible by using them.
This research work has been led by Lon Wilson, professor of chemistry at Rice University, the members of his research group, and other researchers at the University of Washington (UW). On the left is an artist vision of how the alpha radioactive particles could be packaged inside DNA-sized carbon nanotubes. (Credit: Rice University)
This research work has been published online on July 31, 2007 by the scientific journal Small under the name "211AtCl@US-Tube Nanocapsules: A New Concept in Radiotherapeutic-Agent Design." The article is available here (sorry, no abstract!).
According to Rice University News, in their study, the researchers "developed and tested a process to load astatine atoms inside short sections of carbon nanotubes. Because astatine is the rarest naturally occurring element on Earth -- with less than a teaspoon estimated to exist in the Earth's crust at any given time -- the research was conducted using astatine created in a UW cyclotron."
Why did they use such a rare element? "Astatine, like radium and uranium, emits alpha particles via radioactive decay. Alpha particles, which contain two protons and two neutrons, are the most massive particles emitted as radiation. They are about 4,000 times more massive than the electrons emitted by beta decay -- the type of radiation most commonly used to treat cancer."
So these encapsulated alpha particles could be very efficient. On the other hand, as they are slow, they have very little penetrating power and can be stopped. And there is another issue. "One complicating factor in any astatine-based cancer therapy will be the element's short, 7.5-hour half-life. In radioactive decay, the term half-life refers to the time required for any quantity of a substance to decay by half its initial mass. Due to astatine's brief half-life, any treatment must be delivered in a timely way, before the particles lose their potency."
In other words, this potential treatment for cancer needs to be given in a location close to a cyclotron. This doesn't look too promising...
Sources: Jade Boyd, Rice University News, via EurekAlert!,August 23, 2007; and various websites
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