A new study by researchers at Kyoto University’s Institute for Integrated Cell-Material Sciences (iCeMS) and collaborators in Japan and the United States demonstrates that enhancing radiation therapy using novel iodine nanoparticles can destroy cancer cells.
The findings were published in the journal Scientific Reports in a paper titled, “Iodine containing porous organosilica nanoparticles trigger tumor spheroids destruction upon monochromatic X-ray irradiation: DNA breaks and K-edge energy X-ray.”
“X-ray irradiation of high Z elements causes photoelectric effects that include the release of Auger electrons that can induce localized DNA breaks,” wrote the researchers. “We have previously established a tumor spheroid-based assay that used gadolinium containing mesoporous silica nanoparticles and synchrotron-generated monochromatic X-rays. In this work, we focused on iodine and synthesized iodine-containing porous organosilica (IPO) nanoparticles.”
“Exposing a metal to light leads to the release of electrons, a phenomenon called the photoelectric effect. An explanation of this phenomenon by Albert Einstein in 1905 heralded the birth of quantum physics,” said iCeMS molecular biologist Fuyuhiko Tamanoi, PhD, who led the study. “Our research provides evidence that suggests it is possible to reproduce this effect inside cancer cells.”
The researchers sought to overcome the challenge of effective radiation therapy at the center of tumors where oxygen levels are low due to the lack of blood vessels penetrating deeply into the tissue.
They designed porous, iodine-carrying organosilica nanoparticles. Then the researchers dispersed their nanoparticles through tumor spheroids.
The researchers demonstrated that the nanoparticles destroyed tumor spheroids upon irradiation with monochromatic X-ray. By systematically changing energy levels, they were able to demonstrate that the optimum effect of tumor destruction occurs with 33.2 keV X-ray.
Further observation revealed that the nanoparticles were taken up by the tumor cells, localizing just outside their nuclei.
“Our study represents an important example of employing a quantum physics phenomenon inside a cancer cell,” said Matsumoto. “It appears that a cloud of low-energy electrons is generated close to DNA, causing double strand breaks that are difficult to repair, eventually leading to programmed cell death.”
Looking toward the future, the researchers want to further their studies to understand how electrons are released from iodine atoms when they are exposed to X-rays. They are also working on placing iodine on DNA rather than near it to increase efficacy, and to test the nanoparticles on mouse models of cancer.