page_title: Actinium
section_title: Applications
hierarchical_section_title: Actinium / Applications
caption_attribution_description: English: polyaminocarboxylic acid
context_page_description: Actinium is a chemical element with the symbol Ac and atomic number 89. It was first isolated by French chemist André-Louis Debierne in 1899. Friedrich Oskar Giesel later independently isolated it in 1902 and, unaware that it was already known, gave it the name emanium. Actinium gave the name to the actinide series, a group of 15 similar elements between actinium and lawrencium in the periodic table. It is also sometimes considered the first of the 7th-period transition metals, although lawrencium is less commonly given that position. Together with polonium, radium, and radon, actinium was one of the first non-primordial radioactive elements to be isolated.
  A soft, silvery-white radioactive metal, actinium reacts rapidly with oxygen and moisture in air forming a white coating of actinium oxide that prevents further oxidation. As with most lanthanides and many actinides, actinium assumes oxidation state +3 in nearly all its chemical compounds.
context_section_description: Owing to its scarcity, high price and radioactivity, ²²⁷Ac currently has no significant industrial use, but ²²⁵Ac is currently being studied for use in cancer treatments such as targeted alpha therapies.²²⁷Ac is highly radioactive and was therefore studied for use as an active element of radioisotope thermoelectric generators, for example in spacecraft. The oxide of ²²⁷Ac pressed with beryllium is also an efficient neutron source with the activity exceeding that of the standard americium-beryllium and radium-beryllium pairs. In all those applications, ²²⁷Ac (a beta source) is merely a progenitor which generates alpha-emitting isotopes upon its decay. Beryllium captures alpha particles and emits neutrons owing to its large cross-section for the (α,n) nuclear reaction:
  The ²²⁷AcBe neutron sources can be applied in a neutron probe – a standard device for measuring the quantity of water present in soil, as well as moisture/density for quality control in highway construction. Such probes are also used in well logging applications, in neutron radiography, tomography and other radiochemical investigations.
  ²²⁵Ac is applied in medicine to produce ²¹³Bi in a reusable generator or can be used alone as an agent for radiation therapy, in particular targeted alpha therapy (TAT). This isotope has a half-life of 10 days, making it much more suitable for radiation therapy than ²¹³Bi (half-life 46 minutes). Additionally, ²²⁵Ac decays to nontoxic ²⁰⁹Bi rather than stable but toxic lead, which is the final product in the decay chains of several other candidate isotopes, namely ²²⁷Th, ²²⁸Th, and ²³⁰U. Not only ²²⁵Ac itself, but also its daughters, emit alpha particles which kill cancer cells in the body. The major difficulty with application of ²²⁵Ac was that intravenous injection of simple actinium complexes resulted in their accumulation in the bones and liver for a period of tens of years. As a result, after the cancer cells were quickly killed by alpha particles from ²²⁵Ac, the radiation from the actinium and its daughters might induce new mutations. To solve this problem, ²²⁵Ac was bound to a chelating agent, such as citrate, ethylenediaminetetraacetic acid (EDTA) or diethylene triamine pentaacetic acid (DTPA). This reduced actinium accumulation in the bones, but the excretion from the body remained slow. Much better results were obtained with such chelating agents as HEHA (1,4,7,10,13,16-hexaazacyclohexadecane-N,N′,N″,N‴,N‴′,N‴″-hexaacetic acid) or DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) coupled to trastuzumab, a monoclonal antibody that interferes with the HER2/neu receptor. The latter delivery combination was tested on mice and proved to be effective against leukemia, lymphoma, breast, ovarian, neuroblastoma and prostate cancers.
  The medium half-life of ²²⁷Ac (21.77 years) makes it very convenient radioactive isotope in modeling the slow vertical mixing of oceanic waters. The associated processes cannot be studied with the required accuracy by direct measurements of current velocities (of the order 50 meters per year). However, evaluation of the concentration depth-profiles for different isotopes allows estimating the mixing rates. The physics behind this method is as follows: oceanic waters contain homogeneously dispersed ²³⁵U. Its decay product, ²³¹Pa, gradually precipitates to the bottom, so that its concentration first increases with depth and then stays nearly constant. ²³¹Pa decays to ²²⁷Ac; however, the concentration of the latter isotope does not follow the ²³¹Pa depth profile, but instead increases toward the sea bottom. This occurs because of the mixing processes which raise some additional ²²⁷Ac from the sea bottom. Thus analysis of both ²³¹Pa and ²²⁷Ac depth profiles allows researchers to model the mixing behavior.
  There are theoretical predictions that AcHₓ hydrides (in this case with very high pressure) are a candidate for a near room-temperature superconductor as they have Tc significantly higher than H3S, possibly near 250 K.
caption: Chemical structure of the DOTA carrier for 225Ac in radiation therapy.
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