Astatine's Interactions with Ion Exchange and Chromatography Resins

[Astronuc]

Astatine (Z=85) is one of those elements without a stable isotope, which makes it difficult to study. It is a halide like bromine and iodine.
https://www.azom.com/news.aspx?newsID=63119

²¹⁰At is the most stable isotope with a half-life of 8.1 hrs, while ²¹¹At has a half-life of 7.216 hrs.

Abstract
Astatine is one of the least-studied elements of the Periodic Table, because all isotopes of astatine are unstable, with the longest half-life barely exceeding 8 hours. Thus, only radiochemists at the production facilities (limited worldwide) can have access to this element to study its properties in a timely manner. Most of these isotopes undergo alpha decay. This type of radioactive decay releases alpha particles, which consist of two protons and two neutrons. These alpha particles can target and destroy diseased cells in the body. One isotope, astatine-211 (At-211, which has a 7.2-hour half-life), is among the most promising alpha emitters for cancer therapy. In this research, scientists investigated and explained astatine's behavior when interacting with ion exchange and extraction chromatography resins. Ion exchange and extraction resins are able to selectively isolate and purify radioactive isotopes to make them available for use as cancer therapies. The research examined a variety of different resins to optimize At-211 separation and purification and determined fundamental chemical parameters responsible for the strength of At-211 bonding to various extraction and ion exchange resins.

Targeted Alpha Therapy (TAT) is one of the most powerful cancer treatments. It takes advantage of alpha particles' ability to cause large amounts of damage near a tumor cell while keeping the surrounding tissues practically intact. Alpha therapy is also efficient: one short-range alpha particle can cause as much damage to tumor cells as 10,000 longer-range beta particles. At-211 is currently a promising radionuclide choice for TAT. One of the challenges for TAT is how to selectively deliver the radioactive material to a tumor site. Since astatine exhibits some metal and some nonmetal properties, it can have different behavior than other related halogens on the periodic table, reacting more like a radiometal depending on the oxidation state. The new discovery on At-211's chemical properties in this research helps scientists understand how it binds to a targeting molecule and therefore allows for the optimization of its radiolabeling for TAT.

 

[Borek]

Intriguing. I wonder how long it takes to deliver the radiopharmaceutical to target. If it is in hours range (in terms of half life of the substance in blood, before it settles where we want it), comparable with the half-time for these At isotopes, therapy won't be that much targeted (most alphas being emitted around the body during the delivery phase). But if the delivery is in tens of minutes range it makes much more sense.