The
most effective approach to mitigate the toxic effects of internal
exposure of radiometals to humans is metal–ligand (ML) chelation
therapy. Thorium (Th)-induced carcinogenesis as well as other health
hazards to humans as a result of chronic internal exposure necessitates
the development of efficient Th-decorporating agents. In this regard,
chemical and biological studies were carried out to evaluate N-(2-Acetamido)iminodiacetic acid (ADA), a comparatively
cost-effective, readily available, and biologically safe complexing
agent for Th decorporation. In the present work, detailed thermodynamic
studies for complexation of ADA with Th(IV) have been carried out
to understand Th-ADA interaction, using potentiometry, calorimetry,
electrospray ionization mass spectrometry, and theoretical studies,
followed by its biological assessment for Th decorporation. Thermodynamic
studies revealed the formation of strong Th-ADA complexes, which are
enthalpically as well as entropically favored. Interestingly, density
functional theory calculations, to obtain a thermodynamically favored
mode of coordination, showed the uncommon trend of lower denticity
of ADA in ML than in ML2, which has been explained on the
basis of stabilization of ML by hydrogen bonding. The same was also
reflected in the unusual trend of enthalpy for Th-ADA complexes. Biological
experiments using human erythrocytes, whole human blood, and lung
cells showed good cytocompatibility and ability of ADA to significantly
prevent Th-induced hemolysis. Th removal of ADA from erythrocytes,
human blood, and normal lung cells was found to be comparable with
that of diethylenetriamine pentaacetate (DTPA), an FDA approved decorporating
agent. The present study contributed significant data about Th complexation
chemistry of ADA and its Th decorporation efficacy from human erythrocytes,
blood, and lung cells.