PEGylated Molybdenum-Iodine Nanocluster as a Promising Radiodynamic Agent against Prostatic Adenocarcinoma.

The combination of photodynamic therapy and radiotherapy has given rise to a modality called radiodynamic therapy (RDT), based on reactive oxygen species-producing radiosensitizers. The production of singlet oxygen, O2(1Δg), by octahedral molybdenum (Mo6) clusters upon X-ray irradiation allows for simplification of the architecture of radiosensitizing systems. In this context, we prepared a radiosensitizing system using copper-free click chemistry between a Mo6 cluster bearing azido ligands and the homo-bifunctional linker bis-dPEG11-DBCO. The resulting compound formed nanoparticles, which featured production of O2(1Δg) and efficient cellular uptake, leading to remarkable photo- and radiotoxic effects against the prostatic adenocarcinoma TRAMP-C2 cell line. Spheroids of TRAMP-C2 cells were also used for evaluation of toxicity and phototoxicity. In vivo experiments on a mouse model demonstrated that subcutaneous injection of the nanoparticles is a safe administration mode at a dose of up to 0.08 g kg-1. The reported results confirm the relevancy of Mo6-based radiosensitizing nanosystems for RDT.

Expanding Luminescence Horizons in Macropolyhedral Heteroboranes.

Luminescence is observed in three novel macropolyhedral nineteen- and eighteen-vertex chalcogenaboranes: Se2B17H17 (1), SeB17H19 (3) and SeB18H20 (4). This led us to the recognition that previously published macropolyhedral heteroborane species might also exhibit luminescence. Thus, the known nineteen- and eighteen-vertex dithiaboranes S2B17H17 (2), n-S2B16H16 (5) and i-S2B16H16 (6) were synthesised and also found to exhibit a range of luminescent properties. These macropolyhedral species are very different from the previously unique fluorescent binary borane B18H22 in terms of their structural architectures, by the presence of borane cluster hetero atoms, and, as in the cases of 5 and 6, that their synthetic origins are not derived simply through the modification of B18H22 itself. They consequently greatly expand the possibilities of finding new luminescent inorganic borane species.

Subphthalocyanines as fluorescence sensors for metal cations.

Subphthalocyanines (SubPcs) and their aza-analogues (SubTPyzPzs) are fluorophores with strong orange fluorescence emission; however, their sensing ability towards metal cations remains uncharted. To fill this gap, we have developed an efficient method for introducing aza-crown moieties at the axial position of SubPcs and SubTPyzPzs to investigate the structure-activity relationship for sensing alkali (Li+, Na+, K+) and alkaline earth metal (Ca2+, Mg2+, Ba2+) cations. SubPcs showed better photostability than SubTPyzPzs and even a commonly utilized dye, 6-carboxyfluorescein. Selectivity toward metal cations was driven by the size of the aza-crown, irrespective of the counter anion. The stoichiometry of binding was found to be 1 : 1 in all cases, and the interaction between SubPcs and cations was characterized by the corresponding apparent binding constants (Ka). Notably, an unusually strong interaction of all sensoric SubPcs with Ba2+ compared to other studied cations was demonstrated. The role of the surrounding environment, i.e. the addition of water or methanol, in sensing cations is shown in detail as well. Selectivity towards K+ over Na+ was demonstrated in aqueous media with SubPcs bearing the 1-aza-6-crown-18 moiety in Tween 80 micelles. In this case, a 5-fold increase of the fluorescence quantum yield was observed upon binding K+ ions. The high brightness, photostability, and sensing activity in aqueous media make SubPc macrocycles promising fluorophores for metal cation sensing.