Micelle encapsulated luminescent iridium(III)(ppy)2L complexes: Photophysics, photocytotoxic activity in HeLa cells and morphological confocal microscopy imaging in C. flavicans M. larva and L. sativum L. plant

Abstract

Luminescent cyclometallated Ir(III) complexes are multi-modal tools for biological applications. Unfortunately, their potential as imaging and therapeutic agents is often limited by their very low solubility in water and most biological media. Especially the “solubility problem” of Ir(III) complexes influence the imaging of live multicellular animal and plant species in their natural water-abundant habitats. Herein we bypass this difficulty by encapsulation of the two brightly luminescent iridium(III)(ppy)2L1 or L2 (ppy = 2-phenylpyridine, L1 = 2-phenylpyridine-4-amine, L2 = 2-phenylpyridine-4-dimethylamine) complexes into pluronic F-127 block copolymer to form water soluble Ir-loaded micelles. These dye-loaded micelles are indeed rapidly internalized by the cells and no antiproliferative activity is observed in darkness. In contrast, 430 nm light irradiation of the same cells triggered singlet oxygen generation and oxidative stress what resulted in strong lethal effects. The water-soluble Ir-containing micelles could also be used as luminescent probes for studing complex multicellular organisms such as alive water-living phantom midge larva of Chaoborus flavicans M. and Lepidium sativum L. plant which elude of imaging with poorly-water soluble Ir(III) complexes. Iridium-containing micelles localized inside the digestive system and hydrostatic organs of larvae as well as in water-conducting tissues of the plant. Furthermore, although to a lesser extent, this new strategy of encapsulation of the Ir complexes allowed to circumvent the bacterial cell wall barrier and, thus, to penetrate inside S. aureus and E. coli cells. These results provide a reliable strategy for development of new theranostic agents and imaging probes.