Imagine if doctors could track exactly where cancer medicine goes inside your body, how long it stays, and whether it effectively reaches the tumor. This level of precision could make cancer treatments safer and more targeted, improving outcomes for patients. Now, scientists in Japan have developed a groundbreaking method to do just that, using tiny gold particles and a special technique called neutron activation.

Conventional imaging methods often rely on external tracers, like fluorescent dyes and radioisotopes, to track nanoparticles inside the body. While these methods can be useful, they often fall short because the tracers can detach from the nanoparticles during circulation. This detachment leads to inaccurate results and limits the ability to visualize the nanoparticles’ full journey.

To address this issue, researchers at Waseda University have modified gold nanoparticles (AuNPs) to make them directly detectable via X-rays and gamma rays, without needing external tracers. This new technique involves exposing stable gold nanoparticles (197Au) to neutron radiation, transforming them into a radioactive form (198Au). The 198Au emits gamma rays, which can be detected outside the body, offering a precise and continuous tracking method.

Professor Jun Kataoka of Waseda University, one of the lead researchers, explains that this technique alters the gold nanoparticles at an atomic level without changing their chemical properties. This allows the nanoparticles to retain their effectiveness while being tracked seamlessly in real-time. The result is an accurate, non-invasive way to monitor the distribution of cancer drugs inside the body.

To validate their approach, the research team injected neutron-activated AuNPs into tumor-bearing mice. Using a specialized imaging system, the team successfully tracked the nanoparticles, demonstrating the ability to monitor drug distribution over extended periods. This breakthrough technique allows for long-term monitoring, providing valuable insights into how cancer treatments are distributed and how effectively they target tumors.

In addition to tracking the nanoparticles themselves, the researchers explored the potential of this method to monitor a cancer treatment drug called astatine-211 (211At). This radio-therapeutic drug emits alpha particles and X-rays, but its short half-life of just 7.2 hours limits its tracking and effectiveness. To extend the tracking ability of 211At, the team labeled the drug with neutron-activated AuNPs, forming 211At-labeled (198Au) AuNPs.

Thanks to the longer half-life of 198Au (2.7 days), the researchers were able to extend the tracking window of 211At up to five days, significantly improving the ability to monitor the drug’s movement through the body. This development could help enhance the safety and efficacy of cancer therapies that rely on short-lived radioisotopes.

Real-time tracking of cancer drug delivery represents a significant leap forward in medical imaging. The researchers believe their neutron activation technique could be applied to various nanoparticle-based drug delivery systems, opening up new possibilities for more personalized and precise cancer treatments.

Assistant Professor Yuichiro Kadonaga from Osaka University, another key member of the team, envisions refining the imaging resolution and expanding the application of this technology to other biomedical fields. With further improvements, this innovative imaging approach has the potential to become a standard clinical tool, enabling more accurate drug monitoring and helping to optimize targeted cancer therapies.

Published in Applied Physics Express, the research highlights the immense potential of neutron activation technology in transforming cancer treatment. By providing a way to monitor therapeutic nanoparticles more accurately and for longer periods, this breakthrough paves the way for safer and more effective cancer treatments in the future.

By Impact Lab