Researcher enlists S&T reactor to build better cancer drugs

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On August 16, 2017

Maria Camila Garcia Toro, left, and her faculty mentor Dr. Carlos Henry Castano Giraldo display vials of radioactive gold and silver nanoparticles inside the Missouri S&T nuclear research reactor. The doctoral student in nuclear engineering is working to refine the process used to synthesize the tiny specks in hopes of reducing the complexity and cost of producing specialty drugs for cancer treatment. Photos by Sam O’Keefe/Missouri S&T

Ph.D. student Maria Camila Garcia Toro taps state’s first university research reactor for cancer inquiry

The use of radioactive gold and silver nanoparticles to target certain deadly cells is a promising step in the painstaking process of cancer research and treatment.

Now a Missouri University of Science and Technology doctoral student in nuclear engineering is building on that promise – with the help of the campus’ research reactor − in hopes of refining the process used to synthesize the tiny specks.

Maria Camila Garcia Toro’s research is part of a larger vision by her former advisor, Dr. Carlos Henry Castano Giraldo, of an integrated facility in which radioisotopes created at the Missouri S&T reactor could be tested on laboratory mice colonies maintained by the university’s biological sciences department. The project’s promise led to the award of an Innovation Grant from the university earlier this year.

Rather than separately create the nanoparticles using either gamma radiation or chemical methods before activating them through neutron radiation, Garcia Toro’s work focuses on combining those two disparate processes into a single step that could reduce production costs while also increasing effectiveness.

“The novel part of my process is that we use gamma radiation at the same time as we’re using neutrons,” she says. “So it’s possible to create nanoparticles that are already radioactive in one single step.”

In June, Garcia Toro presented her research findings at the Cancer Nanotechnology Gordon Research Conference in Vermont. The Colombia native earned her master’s degree in nuclear engineering from Missouri S&T in 2016, and a bachelor’s degree in chemical engineering from the National University of Colombia at Medellin, the same campus where her Rolla mentor also studied as an undergraduate.

Castano Giraldo is an associate professor of nuclear engineering and S&T faculty member since 2008. His initial interest in nanoparticles stemmed from earlier work on hydrogen fuel cell storage inside carbon nanotubes created with gamma radiation.

“I later realized we could produce nanoparticles of many materials with radiation,” he says.

How it works

The single-step synthesis involves the irradiation of aqueous solutions at different concentrations of the metallic precursors, which are activated using the nuclear reactor. Controlling the time and dose rate of the irradiation process has allowed Garcia Toro to determine the optimal nanoparticle size for cancer treatment.

“The size distribution of nanoparticles used in cancer treatment is a key element to improve tumor retention, interstitial interaction inside of the body and the cancer cell-killing process,” she explains. “Nanoparticles with approximately 50 nanometers of diameter exhibited greater sensitization and higher cell uptake compared with other sizes.”

Project collaborators include Dr. Joshua Schlegel, an assistant professor of nuclear engineering who plans to study modifications to the irradiated nanostructures and the corresponding biological paths; and Dr. Xin Liu, an assistant professor in the mining and nuclear engineering department who oversees a specialized facility for gamma radiation imaging that will be used to determine the distribution of nano-radioisotopes in mice.

Once a promising treatment is identified, the next step, says Castano Giraldo, is a possible collaboration on human clinical trials with the Mallinckrodt Institute of Radiology at Washington University in St. Louis.

“There is still much work to be done before a new treatment is FDA-approved,” he notes.

The 200-kilowatt nuclear reactor where Garcia Toro is working to streamline the production of irradiated nanoparticles has been in operation since 1961.

In addition to its irradiation facilities, the reactor’s research capabilities include a graphite thermal column, a key source of slow neutrons, and a beam port that can be positioned between the reactor floor and the ground floor for experiments involving high-energy neutrons.

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