Synthesis and Structure-Activity Relationships of Gadolinium Complexes of DO3A-Benzothiazole Conjugates as Potential Theranostic Agents.

The synthesis of two bifunctional chelates, 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) conjugates of benzothiazoles (H3L3a and H3L3b), and the corresponding gadolinium complexes (GdL3a and GdL3b) was achieved. The intracellular and tumor-specific nature of GdL3a and GdL3b were confirmed by magnetic resonance images of the cytosols and nuclei of various cell lines. The two complexes displayed antitumor activities with varying degrees of growth-inhibition and total-growth-inhibition values depending on the types of tumor cells. They caused morphological changes in tumor cell lines at much lower concentrations of gadolinium ([Gd] ≥ 50 μ M) than their predecessors, DO3A-( p-aniline benzothiazole) conjugates (H3L1), and its GdIII complex (GdL1) required concentrations that were almost four times as high ([Gd] ≥ 200 μ M). [ABSTRACT FROM AUTHOR]