Cell‐Membrane Staining Properties and Photocytotoxicity of a Ruthenium(II) Photosensitizer

Abstract

Organelle‐targeting photosensitizers have attracted increasing attention in the development of drugs for photodynamic therapy because they can efficiently induce cellular functional disorder upon light irradiation. In this work, we reported a ruthenium(II) complex bearing two lipophilic carbon chains which specifically binds to the cell membrane. Light irradiation on the complex‐treated cells caused an increase of intracellular reactive oxygen species. The photocytotoxicity of the complex toward HeLa cells were evaluated via the 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide (MTT) assay. A high dose (3 µm) of the complex induced apoptotic cell death by photogeneration of intracellular reactive oxygen species. A low dose (0.25 µm) of the complex did not cause noticeable cell death but increased the permeability of the cell membrane upon light irradiation.

Shining New Light on Biological Systems: Luminescent Transition Metal Complexes for Bioimaging and Biosensing Applications

“…Zhao and co-workers have developed a ruthenium(II) complex featuring two nonyl chains (306) for targeting the plasma membrane. 552 Interestingly, the complex exhibits selective staining of the plasma membrane of cancer cells (A549) over noncancerous cells (human skin fibroblast and 3T3), indicating that the complex can distinguish cancer cells that are characterized by negative surface charges from normal cells. Li, Tian, Li, and co-workers have developed a platinum(II) complex bearing two long alkyl chains (307) as a two-photon probe for the plasma membrane.…”

“…The complex is readily taken up by HepG2 cells and reacts with intracellular esterases, resulting in a change in the emission color from blue to red. Qiao, Zhang, and co-workers have developed an iridium(III) complex (552) for specific detection and imaging of hCE2 in live cells. 1031 Upon cleavage of the ester bond by hCE2, the emission lifetime of the complex increases from 338 to 625 ns due to a reduction in nonradiative decay pathways associated with intramolecular vibrational relaxation.…”

“…The differential staining further supports the importance of a long alkyl chain in facilitating the accumulation of the complexes in the plasma membrane. Zhao and co-workers have developed a ruthenium(II) complex featuring two nonyl chains ( 306 ) for targeting the plasma membrane . Interestingly, the complex exhibits selective staining of the plasma membrane of cancer cells (A549) over noncancerous cells (human skin fibroblast and 3T3), indicating that the complex can distinguish cancer cells that are characterized by negative surface charges from normal cells.…”