The design, sysnthesis and evaluation of sequestering agents specific for Plutonium(IV)

This paper deals with the development of elements which are very specific in their ability to sequester plutonium IV, and to remove it from biologic systems. Early on it was recognized that chemical agents were needed to accelerate excretion of contaminating radionuclides and reduce radiation dosage to the target tissues of contaminated workers. Early research led to the use of diethylenetriaminepentaacetic acid (DTPA) which as the calcium or zinc salt remains the drug of choice in treating actinide contamination. However, DTPA is a non-specific metal complexing agent (like its smaller and much more widely used predecessor EDTA) and the need for better and more specific sequestering agents has been brought up on a number of occasions. Siderophore are low-molecular-weight complexing agents produced by bacteria and other microorganisms to complex iron. These are all very strong ferric ion complexing agents, and they are both powerful and highly specific sequestering agents for this metal ion. The entrainment of plutonium into the mammalian iron transport and storage system represents the major basis for the biological hazard of plutonium. The authors have reasoned that the synthesis of plutonium specific complexing agents could be based on the siderophores, since the same functional groups found in the siderophores should also be good plutonium complexing agents. Plutonium, being larger than iron, has motivated the development of large complexes to encapsulate and bind plutonium. The first of these ligands developed were based on catecholates. The synthesis and characterization of many of the newer ligands is described, with a focus on the biological efficacy of plutonium removal by these agents