Editing Actinium (section)

==Applications==
Owing to its scarcity, high price and radioactivity, <sup>227</sup>Ac currently has no significant industrial use, but <sup>225</sup>Ac is currently being studied for use in cancer treatments such as targeted alpha therapies.<ref name="CRC" /><ref name="AcNatureChem">{{Cite journal|last1=Deblonde|first1=Gauthier J.-P.|last2=Abergel|first2=Rebecca J.|date=2016-10-21|title=Active actinium|journal=Nature Chemistry|language=en|volume=8|issue=11|pages=1084|doi=10.1038/nchem.2653|doi-access=free|pmid=27768109 |issn=1755-4349|bibcode=2016NatCh...8.1084D|osti=1458479|osti-access=free}}</ref><!--http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=4066566-->
<sup>227</sup>Ac is highly radioactive and was therefore studied for use as an active element of [[radioisotope thermoelectric generator]]s, for example in spacecraft. The oxide of <sup>227</sup>Ac pressed with [[beryllium]] is also an efficient [[neutron source]] with the activity exceeding that of the standard americium-beryllium and radium-beryllium pairs.<ref name="b1">Russell, Alan M. and Lee, Kok Loong (2005) [https://books.google.com/books?id=fIu58uZTE-gC&pg=PA470 ''Structure-property relations in nonferrous metals'']. Wiley. {{ISBN|0-471-64952-X}}, pp. 470–471</ref> In all those applications, <sup>227</sup>Ac (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:

: <chem>^{9}_{4}Be + ^{4}_{2}He -> ^{12}_{6}C + ^{1}_{0}n + \gamma</chem>

The <sup>227</sup>AcBe neutron sources can be applied in a [[neutron probe]]&nbsp;– a standard device for measuring the quantity of water present in soil, as well as moisture/density for quality control in highway construction.<ref>Majumdar, D. K. (2004) [https://books.google.com/books?id=hf1j9v4v3OEC&pg=PA108 ''Irrigation Water Management: Principles and Practice'']. {{ISBN|81-203-1729-7}} p. 108</ref><ref>Chandrasekharan, H. and Gupta, Navindu (2006) [https://books.google.com/books?id=45IDh4Lt8xsC&pg=PA203 ''Fundamentals of Nuclear Science – Application in Agriculture'']. {{ISBN|81-7211-200-9}} pp. 202 ff</ref> Such probes are also used in well logging applications, in [[neutron radiography]], tomography and other radiochemical investigations.<ref>{{cite journal |title = Neutron Spectrum of an Actinium–Beryllium Source |first1 = W. R. |last1 = Dixon |journal = Can. J. Phys. |volume = 35 |issue = 6 |pages = 699–702 |date = 1957 |doi = 10.1139/p57-075 |last2 = Bielesch |first2 = Alice |last3 = Geiger |first3 = K. W.|bibcode = 1957CaJPh..35..699D }}</ref>
[[File:DOTA polyaminocarboxylic acid.png|thumb|upright=0.70|Chemical structure of the [[DOTA (chelator)|DOTA]] carrier for <sup>225</sup>Ac in radiation therapy]]
<sup>225</sup>Ac is applied in medicine to produce {{chem2|^{213}Bi|link=Bismuth-213}} in a reusable generator<ref name="sep">{{cite journal |doi = 10.1016/j.apradiso.2004.12.003 |date = 2005 |volume = 62 |issue = 5 |pages =667–679 |title = Production of actinium-225 for alpha particle mediated radioimmunotherapy |last1 = Bolla |first1 = Rose A. |journal = Applied Radiation and Isotopes |pmid = 15763472 |last2 = Malkemus |first2 = D. |last3 = Mirzadeh |first3 = S.|bibcode = 2005AppRI..62..667B }}</ref> 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 <sup>213</sup>Bi (half-life 46 minutes).<ref name="AcNatureChem" /> Additionally, <sup>225</sup>Ac decays to nontoxic <sup>209</sup>Bi rather than toxic [[lead]], which is the final product in the decay chains of several other candidate isotopes, namely <sup>227</sup>Th, <sup>228</sup>Th, and <sup>230</sup>U.<ref name="AcNatureChem" /> Not only <sup>225</sup>Ac itself, but also its daughters, emit alpha particles which kill cancer cells in the body. The major difficulty with application of <sup>225</sup>Ac 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 <sup>225</sup>Ac, the radiation from the actinium and its daughters might induce new mutations. To solve this problem, <sup>225</sup>Ac was bound to a [[Chelation|chelating]] agent, such as [[citrate]], [[ethylenediaminetetraacetic acid]] (EDTA) or [[pentetic acid|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 ({{nowrap|1,4,7,10,13,16-hexaazacyclohexadecane-N,N′,N″,N‴,N‴′,N‴″-hexaacetic acid}})<ref>{{cite journal |title=Improved in Vivo Stability of Actinium-225 Macrocyclic Complexes|pmid=10425108|journal=J Med Chem |date=1999 |volume=42|issue=15|pages=2988–9|author=Deal K.A.|author2=Davis I.A.|author3=Mirzadeh S.|author4=Kennel S.J.|author5=Brechbiel M.W.|name-list-style=amp |doi=10.1021/jm990141f}}</ref> or [[DOTA (chelator)|DOTA]] ({{nowrap|1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid}}) coupled to [[trastuzumab]], a [[monoclonal antibody]] that interferes with the [[HER2/neu]] [[Receptor (biochemistry)|receptor]]. The latter delivery combination was tested on mice and proved to be effective against [[leukemia]], [[lymphoma]], [[breast cancer|breast]], [[Ovarian cancer|ovarian]], [[neuroblastoma]] and [[prostate cancer]]s.<ref>{{cite journal|last1=McDevitt|first1=Michael R.|last2=Ma|first2=Dangshe|last3=Lai|first3=Lawrence T.|last4=Simon|first4=Jim|last5=Borchardt|first5=Paul|last6=Frank|first6=R. Keith|last7=Wu|first7=Karen|last8=Pellegrini|first8=Virginia|last9=Curcio|first9=Michael J.|last10=Miederer|first10=Matthias|last11=Bander|first11=Neil H.|last12=Scheinberg|first12=David A.|display-authors=3|title=Tumor Therapy with Targeted Atomic Nanogenerators|date=2001|journal=Science|volume=294|issue=5546|pages=1537–1540|doi=10.1126/science.1064126|bibcode=2001Sci...294.1537M|pmid=11711678|s2cid=11782419|url=https://www.researchgate.net/publication/11642922}}</ref><ref>{{cite journal |url=http://cancerres.aacrjournals.org/content/63/16/5084.full.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://cancerres.aacrjournals.org/content/63/16/5084.full.pdf |archive-date=2022-10-09 |url-status=live |title=Targeted Actinium-225 in Vivo Generators for Therapy of Ovarian Cancer |author=Borchardt, Paul E. |journal=Cancer Research |volume=63 |issue=16 |pages= 5084–5090 |date=2003 |pmid=12941838|display-authors=etal}}</ref><ref>{{cite journal |author=Ballangrud, A. M. |title=Alpha-particle emitting atomic generator (Actinium-225)-labeled trastuzumab (herceptin) targeting of breast cancer spheroids: efficacy versus HER2/neu expression |journal=Clinical Cancer Research |volume=10 |issue=13 |pages=4489–97 |date=2004 |pmid=15240541 |doi=10.1158/1078-0432.CCR-03-0800|display-authors=etal|doi-access=free }}</ref>

The medium half-life of <sup>227</sup>Ac (21.77 years) makes it a 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 <sup>235</sup>U. Its decay product, <sup>231</sup>Pa, gradually precipitates to the bottom, so that its concentration first increases with depth and then stays nearly constant. <sup>231</sup>Pa decays to <sup>227</sup>Ac; however, the concentration of the latter isotope does not follow the <sup>231</sup>Pa depth profile, but instead increases toward the sea bottom. This occurs because of the mixing processes which raise some additional <sup>227</sup>Ac from the sea bottom. Thus analysis of both <sup>231</sup>Pa and <sup>227</sup>Ac depth profiles allows researchers to model the mixing behavior.<ref>{{cite journal |last1=Nozaki |first1=Yoshiyuki |title=Excess <sup>227</sup>Ac in deep ocean water |journal=Nature |volume=310 |pages=486–488 |date=1984 |doi=10.1038/310486a0 | issue=5977 | bibcode = 1984Natur.310..486N|s2cid=4344946 }}</ref><ref>{{cite journal |last1=Geibert |first1=W. |last2=Rutgers Van Der Loeff |first2=M. M. |last3=Hanfland |first3=C. |last4=Dauelsberg |first4=H.-J. |title=Actinium-227 as a deep-sea tracer: sources, distribution and applications |journal=Earth and Planetary Science Letters |volume=198 |issue=1–2 |pages=147–165 |date=2002 |doi=10.1016/S0012-821X(02)00512-5 |bibcode=2002E&PSL.198..147G|url=https://doi.pangaea.de/10.1594/PANGAEA.90616 }}</ref>

There are theoretical predictions that AcH<sub>x</sub> hydrides (in this case with very high pressure) are a candidate for a near [[room-temperature superconductor]] as they have T<sub>c</sub> significantly higher than H<sub>3</sub>S, possibly near 250&nbsp;K.<ref>{{Cite journal|last1=Semenok|first1=Dmitrii V.|last2=Kvashnin|first2=Alexander G.|last3=Kruglov|first3=Ivan A.|last4=Oganov|first4=Artem R.|date=2018-04-19|title=Actinium hydrides AcH<sub>10</sub>, AcH<sub>12</sub>, AcH<sub>16</sub> as high-temperature conventional superconductors|journal=The Journal of Physical Chemistry Letters|volume=9|issue=8|pages=1920–1926|doi=10.1021/acs.jpclett.8b00615|pmid=29589444|issn=1948-7185|arxiv=1802.05676|s2cid=4620593}}</ref>