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Fusion Science and Technology
Researchers report fastest purification of astatine-211 needed for targeted cancer therapy
Astatine-211 recovery from bismuth metal using a chromatography system. Unlike bismuth, astatine-211 forms chemical bonds with ketones.
In a recent study, Texas A&M University researchers have described a new process to purify astatine-211, a promising radioactive isotope for targeted cancer treatment. Unlike other elaborate purification methods, their technique can extract astatine-211 from bismuth in minutes rather than hours, which can greatly reduce the time between production and delivery to the patient.
“Astatine-211 is currently under evaluation as a cancer therapeutic in clinical trials. But the problem is that the supply chain for this element is very limited because only a few places worldwide can make it,” said Jonathan Burns, research scientist in the Texas A&M Engineering Experiment Station’s Nuclear Engineering and Science Center. “Texas A&M University is one of a handful of places in the world that can make astatine-211, and we have delineated a rapid astatine-211 separation process that increases the usable quantity of this isotope for research and therapeutic purposes.”
The researchers added that this separation method will bring Texas A&M one step closer to being able to provide astatine-211 for distribution through the Department of Energy’s Isotope Program’s National Isotope Development Center as part of the University Isotope Network.
Details on the chemical reaction to purify astatine-211 are in the journal Separation and Purification Technology.
A. K. Knight, D. R. Harding
Fusion Science and Technology | Volume 49 | Number 4 | May 2006 | Pages 728-736
Technical Paper | Target Fabrication | dx.doi.org/10.13182/FST06-A1193
Articles are hosted by Taylor and Francis Online.
Vapor deposited PMDA-ODA poly(amic acid) and polyimide capsules have been produced with desirable material properties (high tensile strength, permeability, and elastic modulus), but the contributions of the process steps and their dependence on external control variables has not been investigated. We have combined numerical simulations with experimental measurements to model the steps of the vapor deposition process including monomer sublimation, vapor transport to the bounce pan, and poly-condensation on the substrate surfaces. The measured sublimation rates of PMDA and ODA monomer at temperatures that yielded stoichiometric poly(amic acid) (10-6 Torr deposition) are 1.2 × 10-7 gm/s PMDA (at 153° C) and 6.3 × 10-10 gm/s ODA (at 126° C) - a 180:1 PMDA:ODA molar ratio. These provide initial boundary conditions to simulate the thermal environment and vapor transport inside the deposition chamber at 1 × 10-2 Torr. A disproportionate loss of PMDA gas during transport to a stationary mandrel is shown by the numerical model to reduce the monomer stoichiometry to 9:1 PMDA:ODA. The transport-based loss depends strongly on the geometry of the substrate support, as is shown by modifying the substrate to change the flow pattern, which reduces this ratio to 1:1 PMDA:ODA above the mandrel. A separate model of the kinetics of monomer deposition and polymerization reactions was developed to correlate the gas concentrations above the substrate with the elemental concentrations comprising the film. This basic model was tested with rate constants based on reaction probabilities of one and equal deposition rates for two monomers in the absence of measured values and is sensitive to changes in vapor stoichiometry.