Gold Nanoparticles to Deliver Powerful Radioactive Particles Directly to Tumors for Treatment

The study’s findings were published in February 2012 in the journal PLOS ONE. Typically, when radiation treatment is recommended for cancer patients, doctors are able to choose from several radiopharmaceuticals that use low-energy radiation particles, known as beta particles. For quite a while, scientists have been examining how to use alpha particles, which are radioactive particles that contain a large amount of energy, in cancer treatments. The challenges to using alpha particles, which are more than 7,000 times heavier than beta particles, include confining the powerful alpha particles in a selected location inside the body while preventing radiation from wandering to healthy organs and tissues.

“If you think of beta particles as slingshots or arrows, alpha particles would be similar to cannon balls,” said J. David Robertson, director of research at the University of Missouri (MU; Columbia, USA) research reactor and professor of chemistry in the College of Arts and Science. “Scientists have had some successes using alpha particles recently, but nothing that can battle different cancers. For example, a current study using radium-223 chloride, which emits alpha particles, has been fast-tracked by the US Food and Drug Administration because it has been shown to be effective in treating bone cancer. However, it only works for bone cancer because the element, radium, is attracted to the bone and stays there. We believe we have found a solution that will allow us to target alpha particles to other cancer sites in the body in an effective manner.”

Dr. Robertson and researchers from Oak Ridge National Laboratory (Oak Ridge, TN, USA) and the School of Medicine at the University of Tennessee (Knoxville, USA) used the element actinium, which is an element known as an alpha emitter because it generates alpha particles. As it decays, actinium creates three additional elements that produce alpha particles. Because of the strength of these particles, keeping the elements positioned at cancer sites was not possible, until the investigators designed a gold-plated nanoparticle that serves as a holding cell for the elements, keeping them in place at the cancer site.

Dr. Robertson’s nanoparticle is a layered device. At the core is the original element, actinium. The researchers then added four layers of material and then coated the nanoparticle with gold. This made the nanoparticle strong enough to hold the actinium—and the other alpha emitters that are ultimately created—long enough for any alpha particles to destroy nearby cancer cells. “Holding these alpha emitters in place is a technical challenge that researchers have been trying to overcome for 15 years,” Dr. Robertson said. “With our nanoparticle design, we are able to keep more than 80% of the element inside the nanoparticle 24 hours after it is created.”

Whereas alpha particles are very powerful, they do not travel very far, so when the nanoparticles get close to cancer cells, the alpha particles move out and destroy the cell more successfully than current radiation therapy options, according to Dr. Robertson. “Previously, basic research had established that scientists can attach antibodies onto gold nanoparticles that help drive the nanoparticles to the tumor sites in the body,” Dr. Robertson said. “Without that groundbreaking work, we would not have been able to put this puzzle together.”

The preliminary results of this research are promising. If additional studies are successful within the next few years, MU officials will request authority from the federal government to begin human drug development (referred to as the investigative new drug [IND] status). After this status has been granted, researchers may conduct human clinical trials with the potential of developing new cancer therapies.

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