For Cancer Research, Radioactive Decay is Observed by Scientists For the First Time

by Monica Joshi

We know about radiation. Some talk about its uses, such as treating cancer, killing germs and producing electricity, while others talk about its side effects and poisoning. Never have we seen an atom emitting radiation - until now. For the first time, scientists have observed atoms of one chemical element, iodine-125, radioactively decay and morph into another element, tellurium – 125.

The process isn't simple. You can't just stick it under a microscope and see the molecule decay. Iodine-125 atoms, a radioactive isotope of iodine frequently used in the treatment of cancer, can take up to 59 days to decay into tellurium-125 and there's no guarantee which atom will decay when. The team used a scanning tunneling microscope that can create images of individual atoms. Yes, it is that sensitive.

With the team spending up to 18 hours a day for several weeks in a lab to see the transformation, you'd think they'd be hallucinating the morphing, but they have pictures to prove it.

Insanely cool? There's more. Being able to study this process in more detail could help scientists understand how to safely treat cancer with radiation. In fact, the possibilities for new cancer therapies are interesting, to say the least.

It turns out that iodine-125 has quite a few expensive demands. Prior to the experiment, the iodine-125 had to be infused onto a bed of gold so that it could rest well. The scientists mixed the iodine-125 with a single drop of water and then deposited this onto a thin layer of gold. When the water had evaporated and the iodine-125 was comfortably bonded with the gold, the sample was scrutinized under the microscope.

The successful images, where iodine-125 had decayed into tellurium-125, showed little spots all over the surface of the gold. These dots were identified by researchers as tellurium-125 atoms.

The researchers have good reason to think there might be a very promising future for gold-plated cancer therapy because in recording the radiation coming from the gold-infused iodine sample, the team specifically monitored the low-energy electron emissions, as they have been very successful in radiation oncology. These emissions can travel a minuscule distance and help to break up the cancer cells' DNA into pieces. This centralized eradication of cancerous cells means nearby organs and tissues are unaffected.

E. Charles H. Sykes, senior author of the paper, says:

"[The gold] was acting like a reflector and an amplifier. Every surface scientist knows that if you shine any kind of radiation on a metal, you get this big flux of low-energy electrons coming out."

The researchers' prediction for the future of radiation oncology is very exciting. Cancer patients might be able to take an injection containing tumor-targeting antibodies studded with gold nanoparticles that have iodine-125 atoms attached to the surface. This ensemble would then attach itself to the tumor, release low-energy electrons that destroy cancer cells and leave healthy tissue unharmed. There is also the added bonus of safety as the gold particles, with the iodine still attached, could be flushed safely out of the patient's system. The iodine-125, under normal circumstances, would accumulate in the thyroid gland and could potentially give rise to cancer or even regenerate cancer in someone already treated. The gold particles, instead, act as a safety net that can escort the iodine-125 safely out of the body.