Shelbie Harris
Staff Writer
Researchers at the Idaho State University Idaho Accelerator Center (IAC) are using high-energy photons to extract isotope copper-67 from zinc for medical and cancer research purposes.
Copper is made up of both stable isotopes as well as isotope copper-67, which is a radioactive isotope.
“These radioactive isotopes have to be made or they have to occur from the decay of some other isotope,” said Jon Stoner, IAC director of technical operations. “In the case of copper-67 we have to make it, and we make it by taking zinc-68 and knocking a proton out of the isotope of zinc, and what’s left is what makes copper-67.”
One isotope of zinc-68 weighing 40 grams, or three to four tablespoons, costs about $20,000 to $30,000.
When one gram of isotope copper-67 has a product quality, or specific activity, of 10,000 curies per gram this correlates to roughly 100,000 doses of isotope copper-67.
Copper-67’s high value is attributed to the fact that in medicine there are a number of different isotopes that can be used not only to diagnose but also to treat things in the human body.
For diagnosing medical concerns, the process usually involves taking pictures of occlusions or areas that might be disease stricken due to plaque buildup or other factors.
Decaying isotopes release energy that can be harnessed and used to hit and kill particular cancer cells within the body.
“In the case of copper-67 you can both diagnose and you can treat as long as you can combine it with the antibody directed to the right kind of tumor and then inject it into the body,” said, Stoner.
He continued, “Medical therapists attach the copper-67 isotope to [an antibody] then they inject it into your blood. It goes through your body until it finds just the antigen it wants. It sticks to that antigen and then when this little suicide packet explodes, or decays basically, it does two things. It sends off a particle that will kill that cell and it also sends off a photon that we can see with a camera.”
Copper-67 has been researched and developed sporadically and in limited quantity by the U.S government going back about 30 years. However, due to its half-life of only two and a half days it was never popularly implemented for medicinal research.
The radioactive isotope is decaying constantly, according to senior scientist at the IAC Frank Harman. In a matter of days it decays away into something that’s stable and then it’s gone.
Certain diffused cancers such as lymphoma and leukemia as well as ovarian, breast and colorectal cancers have utilized copper-67 for research of treatment and diagnosis opportunities.
Stoner said Harman began research that utilized copper-67 nearly 10 years ago by looking for applications of accelerators into particular science related fields.
“We have the largest installed base of accelerators out of any university in the United States,” Stoner said of ISU. “We started looking at a number of different isotopes and then over the last three and half years roughly, we decided to focus on copper-67 because we’ve done enough research to know we could make it and nobody else had been successfully making it.”
With the half-life being only two and a half days, the copper-67 isotope must be sent to researchers virtually the same day, or at the very latest, the next day in order for it to be put to use.
In order to be delivered, the copper-67 isotope must be refined and purified by chemically extracting it from the other materials found within the zinc element.
This process involves taking the small portion of isotope copper-67 derived from the zinc-68 target that has been ‘zapped’ by the accelerator, and placing it into a furnace that is heated until the copper-67 and zinc-68 separate.
“Based on the thermodynamic differences of zinc and copper, the zinc particles evaporate and the copper stays behind,” said radio chemist Tim Gardner. “We can then melt the zinc back down and recycle it into a new target, and the copper we take and dissolve it in acid.”
Gardner continued, “We then use an ion exchange column which allows us to essentially separate the impurities from the copper-67 based on the pH of the acid. What we are left with is pure copper-67 at the end of the process.”
The only problem keeping researchers from continuing this process indefinitely using the same isotope of zinc-68 is that a slight amount is lost through the evaporation process.
The IAC partners with a private Idaho Falls-based company, International Isotopes, which is in the business of delivering isotopes for various medical and clinical applications.
International Isotopes works to set up particular entities such as City of Hope Cancer Research to receive the copper-67 isotope directly from the IAC.
“[The IAC] is developing the method to make the radioactive element and then to chemically separate that from the other materials in the mix of the target, but we really play two roles in this situation,” said President and CEO of International Isotopes Steve Laflin. “One is that when the quantities hopefully grow to a significant level we have some larger shielded processing facilities that can be used to remotely process the materials to do the chemical extractions. The next thing is we have expertise in delivering products that meet [FDA] standards for both bulk drug chemical substance, and the manufacturing requirements that the FDA requires for facilities to have to supply chemicals as a research drug.”
The project, which has been constantly developed over the last 10 years, has been made possible through federal and state grants, including grants from Department of Energy and support from the Higher Education Research Council and Idaho Global Entrepreneurial Mission (IGEM).
For information on obtaining samples or receiving delivery of the IAC’s copper-67 isotope, contact International Isotopes at (208) 524-5300 and moc.diositninull@nimda, or contact Stoner at (208) 282-5875 or ude.usinull@nojnots.
