A review on recent advancements of iridium (III) complexes as antiproliferative and photodynamic therapy agents

Controlled cell death (CCD) is becoming a focus as a successful practice in cancer therapy, especially when triggered specifically by light-based therapies, including photodynamic therapy (PDT) and photoactivated chemotherapy (PACT). Photosensitizers (PSs) made of metal are of particular interest in this respect since the excited-state behaviour of these complexes can be rationally designed, depending on the rational design of the metal centre, ligand and oxidation state. Despite extensive literature on CCD induced by PDT, little work has given a cohesive view on metal-based PSs as inducers of particular CCD pathways. This review will highlight the decade progress in Iridium metal-based PSs that induce ferroptosis, immunogenic cell death, and pyroptosis with focus on its characteristics, mechanisms and commonalities among Iridium systems. Moreover, methods of improving biological selectivity, especially by bioconjugation of Iridium polypyridyl complexes are described. On the whole, this review is intended to gain an understanding of the logical construction of metal-based PSs to induce RCD in a controlled fashion and to stimulate the future introduction of photoactivating metal complexes to treat cancer.