Gadolinium Complex of DO3A-benzothiazole Aniline (BTA) Conjugate as a Theranostic Agent

A gadolinium complex of 1,4,7,10-tetraazacyclododecane-1,4,7-trisacetic acid (DO3A) and benzothiazole-aniline (BTA) of the type [Gd­(DO3A-BTA)­(H<sub>2</sub>O)] has been prepared for use as a single molecule theranostic agent. The kinetic inertness and <i>r</i><sub>1</sub> relaxivity (= 3.84 mM<sup>–1</sup> s<sup>–1</sup>) of the complex compare well with those of structurally analogous Gd-DOTA. The same complex is not only tumor-specific but also intracellular, enhancing MR images of cytosols and nuclei of tumor cells such as MCF-7, MDA-MB-231, and SK-HEP-1. Both DO3A-BTA and Gd­(DO3A-BTA) reveal antiproliferative activities as demonstrated by GI<sub>50</sub> and TGI values obtainable from the cell counting kit-8 (CCK-8) assays performed on these cell lines. Ex vivo and in vivo monitoring of tumor sizes provide parallel and supportive observations for such antiproliferative activities.