Combining imaging and anticancer properties with new heterobimetallic Pt(ii)/M(i) (M = Re, ^99mTc) complexes

In this article, we report on the development of new metal-based anticancer agents with imaging, chemotherapeutic and photosensitizing properties. Hence, a new heterobimetallic complex (Pt-LQ-Re) was prepared by connecting a non-conventional trans-chlorido Pt(ii) complex to a photoactive Re tricarbonyl unit (LQ-Re), which can be replaced by ^99mTc to allow for in vivo imaging. We describe the photophysical and biological properties of the new complexes, in the dark and upon light irradiation (DNA interaction, cellular localization and uptake, and cytotoxicity). Furthermore, planar scintigraphic images of mice injected with Pt-LQ-Tc clearly showed that the radioactive compound is taken up by the excretory system organs, namely liver and kidneys, without significant retention in other tissues. All in all, the strategy of conjugating a chemotherapeutic compound with a PDT photosensitizer endows the resulting complexes with an intrinsic cytotoxic activity in the dark, driven by the non-classical platinum core, and a selective activity upon light irradiation. Most importantly, the possibility of integrating a SPECT imaging radiometal (^99mTc) in the structure of these new heterobimetallic complexes might allow for in vivo non-invasive visualization of their tumoral accumulation, a crucial issue to predict therapeutic outcomes.