From Photoinduced to Dark Cytotoxicity through an Octahedral Cluster Hydrolysis

Abstract

Octahedral molybdenum and tungsten clusters have potential biological applications in photodynamic therapy and bioimaging. However, poor solubility and hydrolysis stability of these compounds hinder their application. The first water-soluble photoluminescent octahedral tungsten cluster [{W I }(DMSO) ](NO ) was synthesised and demonstrated to be at least one order of magnitude more stable towards hydrolysis than its molybdenum analogue. Biological studies of the compound on larynx carcinoma cells suggest that it has a significant photoinduced toxicity, while the dark toxicity increases with the increase of the degree of hydrolysis. The increase of the dark toxicity is associated with the in situ generation of nanoparticles that clog up the cisternae of rough endoplasmic reticulum.

Hexasubstituted Iodide Tungsten Cluster Complexes with Azide and Isothiocyanate Ligands

“…As for (Bu 4 N) 2 [{M 6 I 8 }(NCS) 6 ] (M = Mo, W), the M–N distances are shorter (and the bonds are stronger) for the tungsten complex (Bu 4 N) 2 [{M 6 I 8 }(N 3 ) 6 ] than for molybdenum. Stronger metal‐ligand bonds provide higher stability of tungsten clusters toward hydrolysis or solvolysis, as demonstrated in, .…”

“…), which explains much attention of the researchers to this class of compounds . Moreover, the ability of the clusters to photosensitize the process of singlet oxygen generation expands the area of possible applications from wastewater treatment to photodynamic therapy,, which determines the importance of further development of cluster chemistry. However, despite structural and physicochemical similarities of molybdenum and tungsten cluster complexes, coordination chemistry of W 6 ‐clusters has been much less studied.…”

Molybdenum Iodides – from Obscurity to Bright Luminescence

“…This salt is water soluble, but undergoes aquation (at 37 °C half of the complex loses its DMSO in 52 min). The process can be monitored by ESI‐MS and proceeds as stepwise substitution of coordinated DMSO with H 2 O and OH – , and [W 6 I 8 (DMSO) 6 ](NO 3 ) 4 were prepared.…”

“…By similar routes, (Bu 4 N) 2 [{W 6 I 8 }(NO 3 ) 6 ], (Bu 4 N) 2 [{W 6 I 8 }(OTs) 6 ],, and [W 6 I 8 (DMSO) 6 ](NO 3 ) 4 were prepared. The [W 6 I 8 (DMSO) 6 ] 4+ complex is more robust towards hydrolysis: its half‐life time in water at 37 °C 34 h …”

“…In particular, studies on Hep‐2 cells suggest that [{W 6 I 8 }(DMSO) 6 ](NO 3 ) 4 has significant photoinduced toxicity, while the dark cytotoxicity increases with the increased degree of hydrolysis. This is associated with the in situ generation of nanoparticles that clog up the cisternae of rough endoplasmic reticulum …”