Targeting cancer at the nanoscale

Osaka, Japan – Scientists from the Department of Nuclear Medicine and Tracer Kinetics at Osaka University developed a novel system for targeted cancer radiation therapy that uses gold nanoparticles labeled with astatine-211. Owing to the limited range and half-life of the radiation, along with the localization of the nanoparticles, healthy cells are considerably less likely to be harmed. This work may lead to effective cancer treatments without the side effects of current techniques.

Brachytherapy is a method of treating cancer using a sealed radioactive source called a “seed” implanted directly inside the patient’s body. It has been found to be effective for certain tumors of the prostate, head, neck, and brain, among others. However, like other forms of radiation therapy, brachytherapy can also cause severe side effects, such as vomiting or headaches. More sophisticated methods for targeting radiation are needed to maximize the effectiveness of the treatment while sparing healthy cells.

Now, a team of scientists led by Osaka University has used gold nanoparticle “nanoseeds” containing a radioactive isotope to ensure that radiation was localized only to cancer cells. Astatine-211 is an unstable isotope of the element astatine that contains one extra neutron. This causes it to undergo radioactive decay while emitting alpha particles. Because of their large size, rapidly moving alpha particles can cause fatal double-strand breaks in the DNA of cancer cells while remaining close to the radiation source. In addition, because the half-life of astatine-211 is so short, about 7 hours, it will become inactive long before the nanoparticles can leak into healthy tissues. This allows large therapeutic doses to be administered without causing severe side effects. “We have developed a new safe and powerful cancer treatment using gold nanoparticles with astatine-211, which emits alpha rays that strongly damage target DNA but have a very short range inside the body,” first author Hiroki Kato explains.

Using rat or mouse models, the nanoparticles were injected directly into tumors. The team found that the nanoparticles entered the cancer cells but did not spread to other organs during a time period equivalent to six radioactive half-lives. At the same time, the nanoparticles were highly toxic to the cancer cells.  “We have demonstrated that tumor growth can be strongly suppressed by injecting this nano drug directly into the tumor,” senior author Koichi Fukase says. Because gold nanoparticles can be easily fabricated, and astatine-211 may be produced in cyclotrons without the need for nuclear fuel, this new therapy can be made widely available in hospitals.

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The article, “Intratumoral administration of astatine‑211‑labeled gold nanoparticle for alpha therapy” was published in the Journal of Nanobiotechnology at DOI: https://doi.org/10.1186/s12951-021-00963-9

About Osaka University

Osaka University was founded in 1931 as one of the seven imperial universities of Japan and is now one of Japan's leading comprehensive universities with a broad disciplinary spectrum. This strength is coupled with a singular drive for innovation that extends throughout the scientific process, from fundamental research to the creation of applied technology with positive economic impacts. Its commitment to innovation has been recognized in Japan and around the world, being named Japan's most innovative university in 2015 (Reuters 2015 Top 100) and one of the most innovative institutions in the world in 2017 (Innovative Universities and the Nature Index Innovation 2017). Now, Osaka University is leveraging its role as a Designated National University Corporation selected by the Ministry of Education, Culture, Sports, Science and Technology to contribute to innovation for human welfare, sustainable development of society, and social transformation.

Website: https://resou.osaka-u.ac.jp/en