Nanoparticles with iodine against cancer
Quantum physics helps destroy cancer cells
Anna Yudina, "Scientific Russia"
Researchers have found a way to improve radiation therapy using porous nanoparticles containing iodine molecules, according to a press release from Quantum physics helps destroy cancer cells.
Cancer cell death is triggered within three days when X-rays hit tumor tissue containing nanoparticles carrying iodine. Iodine releases electrons that destroy the DNA of the tumor, which leads to cell death. The findings of scientists from the Institute for Integrated Cellular Materials Research (iCeMS) at Kyoto University and colleagues from Japan and the USA were published in the journal Scientific Reports (Higashi et al., Iodine containing porous organosilica nanoparticles trigger tumor spheroids destruction upon monochromatic X-ray irradiation: DNA breaks and K-edge energy X-ray).
"The effect of light on metal leads to the release of electrons – a phenomenon called the photoelectric effect. Albert Einstein's explanation of this phenomenon in 1905 heralded the birth of quantum physics," says iCeMS molecular biologist Fuuhiko Tamanoy, who led the research. "Our study provides evidence to suggest that this effect can be replicated inside cancer cells."
A long-standing problem with cancer radiation therapy is that it is ineffective in the center of tumors, where oxygen levels are low due to the lack of blood vessels penetrating deeply into the tissues. For X-ray irradiation, oxygen is needed to generate reactive oxygen that damages DNA when the rays hit molecules inside the cell.
Tamanoi, along with Kotaro Matsumoto and his colleagues, tried to solve this problem by finding more direct ways to damage cancer DNA. In earlier work, they showed that gadolinium-containing nanoparticles can kill cancer cells when irradiated with synchrotron-generated X-rays with a voltage of 50.25 kiloelectronvolts (keV).
In the current study, they developed porous, iodine-containing organosilicon nanoparticles. Iodine is cheaper than gadolinium and releases electrons with a lower energy level.
The researchers dispersed their nanoparticles through tumor spheroids, a three–dimensional tissue containing many cancer cells. Irradiation of spheroids with 33.2 keV X-rays for 30 minutes led to their complete destruction within three days. By systematically changing the energy levels, they were able to demonstrate that the optimal effect of tumor destruction is achieved using 33.2 keV X-rays.
Further analyses showed that the nanoparticles were captured by tumor cells, localized outside their nuclei. Illuminating the tissue with the right amount of X-ray energy prompts iodine to release electrons, which then cause double-stranded breaks in the nuclear DNA, causing cell death.
"Our study is an important example of using the phenomenon of quantum physics inside a cancer cell," says Matsumoto. "It looks like a cloud of low–energy electrons is generated next to DNA, causing double-stranded breaks that are difficult to repair, which ultimately leads to programmed cell death."
The team then wants 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 next to it, to increase efficiency and test nanoparticles on mouse models of cancer.
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