Synthesis and evaluation of novel 1,4,7-triazacyclononane derivatives as Cu2+ and Ga3+ chelators

Sheng Wang, Yongkang Gai, Lingyi Sun, Xiaoli Lan, Dexing Zeng, Guangya Xiang, Xiang Ma

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Abstract

Advances in chelator design are the cornerstone for the development of metals like copper and gallium based biomedical agents and radiopharmaceuticals. To develop optimal chelating ligands, we explored the synthesis and chelating properties of azaheterocycle pendant armed 1,4,7-triazacyclononane (TACN) dimethylcarboxylate derivatives and dimethylphosphonate derivatives. In the complexation kinetics test, dicarboxylate pendant armed TACN derivatives 2,2′-(7-((1H-imidazol-2-yl)methyl)-1,4,7-triazonane-1,4-diyl)diacetic acid (NODA-Im), 2,2′-(7-((1-methyl-1H-imidazol-2-yl)methyl)-1,4,7-triazonane-1,4-diyl)diacetic acid (NODA-MeIm), and 2,2′-(7-(thiazol-2-ylmethyl)-1,4,7-triazonane-1,4-diyl)diacetic acid (NODA-Thia) exhibited fast complexation kinetics towards Cu (II) cations, which were comparable to the frequently explored ligand 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). And the diphosphonate pendant armed TACN derivative ((7-(thiazol-2-ylmethyl)-1,4,7-triazonane-1,4-diyl)bis(methylene))bis(phosphonic acid) (NODP-Thia) bound with Ga (III) cations at a much faster rate than NOTA. Density functional theory studies confirmed that the better complexation kinetics and metal chelating efficiency of NODA-Im, NODA-MeIm, NODA-Thia, and NODP-Thia could be ascribed to the lower Gibbs energies of corresponding chelator-metal complexes than NOTA-metal complexes. The kinetic inertness of the Cu (II) complex with NODA-Im, NODA-MeIm, and NODA-Thia was also demonstrated by cyclic voltammetry studies. Subsequently radiolabeling experiment demonstrated that these metal chelators could efficiently labeled with 64Cu or 68Ga in good radiochemical purities. These preliminary findings support NODA-Im, NODA-MeIm, NODA-Thia, and NODP-Thia as promising leading chelating agents for the development of bifunctional Cu2+ and Ga3+ chelators in biomedical applications.

Original languageEnglish (US)
Article number111719
JournalJournal of Inorganic Biochemistry
Volume229
DOIs
StatePublished - Apr 2022

Keywords

  • 1,4,7-Triazacyclononane
  • Chelators
  • Cupric ion
  • Gallium ion
  • Metal complexes
  • Positron emission tomography

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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