The effect of sodium thiosulfate on cytotoxicity of a diimine Re(i) tricarbonyl complex

Abstract

Recently, diimine Re(I) tricarbonyl complexes have attracted great interest due to their promising cytotoxic effects. Here, we compare the cytotoxicity and cellular uptake of two Re(I) compounds fac-[(Re(CO)₃(bpy)(H₂O)](CF₃SO₃) (1) and Na(fac-[(Re(CO)₃(bpy)(S₂O₃)])·H₂O (bpy = 2,2′-bipyridine) (2). The Re-thiosulfate complex in 2 was characterized in two solvated crystal structures {Na(fac-[Re(CO)₃(bpy)(S₂O₃)])·1.75H₂O·C₂H₅OH}₄ (2 + 0.75H₂O + C₂H₅OH)₄ and (fac-[Re(CO)₃(bpy)(H₂O)]) (fac-[Re(CO)₃(bpy)(S₂O₃)])·4H₂O (3). The cytotoxicity of 1 and 2 was tested in the MDA-MB-231 breast cancer cell line and compared with that of cisplatin. The cellular localization of the Re(I) complexes was investigated using synchrotron-based X-ray fluorescence microscopy (XFM). The results show that replacement of the aqua ligand with thiosulfate renders the complex less toxic most likely by distrupting its cellular entry. Therefore, thiosulfate could potentially have a similar chemoprotective effect against diimine fac-Re(CO)₃ complexes as it has against cisplatin.