polyaminocarboxylates

Polyaminocarboxylates are a class of multidentate ligands that contain multiple amine nitrogen atoms and carboxylate groups. They form stable, often kinetically inert complexes with a broad range of metal ions and are used in chemistry, medicine, and environmental applications. The ligands are typically charged at physiological pH and can be acyclic (for example EDTA, DTPA) or macrocyclic (for example DOTA, NOTA).

Structure and denticity: These ligands combine an amino backbone with several pendant carboxylate arms, providing several donor sites for metal coordination. The number of donor atoms (denticity) can vary from hexadentate to octadentate or higher, depending on the ligand and metal. The macrocyclic version generally offers greater kinetic inertness and overall stability compared with acyclic analogues.

Applications: In chelation therapy, polyaminocarboxylates bind toxic metals to promote their excretion; classic example is calcium disodium EDTA for lead poisoning. In radiopharmacy and nuclear medicine, they chelate radiometals for imaging and therapy, with DOTA- and NOTA-based chelators widely used for gadolinium or radioactive metals. In MRI, gadolinium complexes such as Gd-DOTA derivatives are common. They are also used in analytical separations and environmental cleanup to remove metals from solutions.

Safety and considerations: The choice of chelator, metal, and administration conditions influences stability, selectivity, and safety. Some gadolinium chelates carry risks in patients with kidney impairment, and excessive chelation can deplete essential metals. Ongoing development focuses on improving stability and reducing toxicity while maintaining strong binding to targeted metals.