Towards Ruthenium(II)-Rhenium(I) Binuclear Complexes as Photosensitizers for Photodynamic Therapy

The search for new metal-based photosensitizers (PSs) for anticancer photodynamic therapy (PDT) is a fast-developing field of research. Knowing that polymetallic complexes bear a high potential as PDT PSs, in this study, we aimed at combining the known photophysical properties of a rhenium(I) tricarbonyl complex and a ruthenium(II) polypyridyl complex to prepare a ruthenium-rhenium binuclear complex that could act as a PS for anticancer PDT. Herein, we present the synthesis and characterization of such a system and discuss its stability in aqueous solution. In addition, one of our complexes prepared, which localized in mitochondria, was found to have some degree of selectivity towards two types of cancerous cells: human lung carcinoma A549 and human colon colorectal adenocarcinoma HT29, with interesting photo-index (PI) values of 135.1 and 256.4, respectively, compared to noncancerous retinal pigment epithelium RPE1 cells (22.4).

A ruthenium-oligonucleotide bioconjugated photosensitizing aptamer for cancer cell specific photodynamic therapy

Ruthenium complexes have emerged as a promising class of compounds for use as photosensitizers (PSs) in photodynamic therapy (PDT) due to their attractive photophysical properties and relative ease of chemical alteration. While promising, they generally are not inherently targeting to disease sites and may therefore be prone to side effects and require higher doses. Aptamers are short oligonucleotides that bind specific targets with high affinity. One such aptamer is AS1411, a nucleolin targeting, G-quadruplex forming, DNA aptamer. Here we present the first example of direct conjugation of a Ru(ii) polypyridyl complex-based PS to an aptamer and an assessment of its in vitro cancer cell specific photosensitization including discussion of the challenges faced.