Self-assembled discrete coordination architectures toward biological applications

Abstract

An upsurge of the drug-resistant cancerous genes and pathogens in humans has made it imperative to develop alternative strategies. Reactive oxygen species (ROS) are significant for biological applications due to their target-specific anti-proliferative effect on damaged cells or pathogens. Singlet-oxygen ( 1 O 2 ) has immense applications in the specified cellular damage, fluorescence aided cellular imaging and localization, photodynamic therapy (PDT), and in the cure of bacterial, viral, or fungal infections. Conjugated aromatic moieties are well-known photosensitizers that can be effectively used in PDT. However, due to their less solubility in the aqueous medium, their direct application in the biological medium is limited. On the other hand, supramolecular coordination complexes (SCCs) are fascinating because of the prospect of solution process ability due to their highly charged nature and counter ion-effect, which have found intense applications in the biological field. SCCs have well-defined cavities that can act as a vessel to encapsulate and deliver drug molecules at the desired locations. Further, with a wide choice of its components, these architectures can amalgamate the chemotherapeutic effects of the metals like Palladium, Platinum, and Ruthenium, and the 1 O 2 mediated cytotoxicity using ligands with photosensitizing ability. Here, in this chapter we will mainly focus on the aspects of ROS generation, singlet-oxygen mediated PDT, and SCCs based on Palladium, Platinum, and Ruthenium metals for applications in cellular imaging, drug delivery, and PDT. At last, a brief discussion about the recently applied two-photon absorption-driven 1 O 2 generation is provided due to its exceptional utility in PDT.