Our group uses the unique spectroscopic and chemical properties of organometallic complexes as such or in metal-bioconjugates for biomedical applications. In particular, Au compounds have received increasing attention as promising anti-tumor agents recently.[1, 2] The proposed mode of action involves anti-mitochondrial activity, leading to redox stress and finally apoptosis. While it is usually assumed that Au compounds in the +I oxidation state are biologically active, Au(III) compounds receive considerable attention as prodrugs. The exact pathway of reduction of these Au(III) prodrugs under biological conditions remains elusive as yet. In earlier work, we have made Au compounds tumor-specific by conjugating them to targeting peptides.[3, 4]
Recently, we extended our studies on Au bioconjugates towards Au-based theranostics and the study of binuclear complexes as theranostics containing combinations such as Au/Ir, Au/Re and Au/Ru.[5] Cellular visualization makes use of the unique properties of the metal cores, including inter alia the use of X-ray fluorescence microscopy. This research has led us to discover a pathway how the Au(III) Au(I) reduction might occur under biological conditions. These results will be presented here for the first time, including the identification and characterization of Au-hydrides as intermediates in aqueous solutions. Finally, encapsulation of active Au complexes in liposomes is explored as a means to make such conjugates specific for cancer tissues.
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