Luminescent Hydrogel Particles Prepared by Self-Assembly of β‑Cyclodextrin Polymer and Octahedral Molybdenum Cluster Complexes

A series of luminescent octahedral molybdenum cluster complexes were obtained by treating Na₂[Mo₆I₈(OMe)₆] with icosahedral <i>closo</i>-dicarbaborane C-carboxylic acids in refluxing tetrahydrofuran. The study of the photophysical properties of Na₂[Mo₆I₈(1-OOC-1,2-<i>closo</i>-C₂B₁₀H₁₁)₆] (<b>1</b>), Na₂[Mo₆I₈(1-OOC-1,7-<i>closo</i>-C₂B₁₀H₁₁)₆] (<b>2</b>), and Na₂[Mo₆I₈(1-OOC-1,12-<i>closo</i>-C₂B₁₀H₁₁)₆] (<b>3</b>) in acetonitrile revealed a red luminescence with high quantum yields up to 0.93 for <b>2</b>, an efficient quenching of the luminescence by oxygen, and high quantum yields of singlet oxygen formation of approximately 0.7. Self-assembly between compound <b>2</b> and β-cyclodextrin polymer led to monodisperse hydrogel particles with a diameter of approximately 200 nm and unchanged luminescence spectra and kinetics features over 14 days. In contrast, bare cluster complex <b>2</b> in water formed aggregates and hydrolyzed over the time as indicated by a progressive red shift of the luminescence maxima. The invariance of key photophysical parameters of the hydrogel particles coupled with a high oxygen sensitivity of the luminescence are attractive features for long-term biological experiments involving optical oxygen probing. In addition, this hydrogel is a singlet oxygen sensitizer in water with promising properties for photodynamic therapy

X‑ray Inducible Luminescence and Singlet Oxygen Sensitization by an Octahedral Molybdenum Cluster Compound: A New Class of Nanoscintillators

Newly synthesized octahedral molybdenum cluster compound (<i>n</i>-Bu₄N)₂­[Mo₆I₈(OOC-1-adamantane)₆] revealed uncharted features applicable for the development of X-ray inducible luminescent materials and sensitizers of singlet oxygen, O₂(¹Δ_g). The compound exhibits a red-NIR luminescence in the solid state and in solution (e.g., quantum yield of 0.76 in tetrahydrofuran) upon excitation by UV–vis light. The luminescence originating from the excited triplet states is quenched by molecular oxygen to produce O₂(¹Δ_g) with a high quantum yield. Irradiation of the compound by X-rays generated a radioluminescence with the same emission spectrum as that obtained by UV–vis excitation. It proves the formation of the same excited triplet states regardless of the excitation source. By virtue of the described behavior, the compound is suggested as an efficient sensitizer of O₂(¹Δ_g) upon X-ray excitation. The luminescence and radioluminescence properties were maintained upon embedding the compound in polystyrene films. In addition, polystyrene induced an enhancement of the radioluminescence intensity via energy transfer from the scintillating polymeric matrix. Sulfonated polystyrene nanofibers were used for the preparation of nanoparticles which form stable dispersions in water, while keeping intact the luminescence properties of the embedded compound over a long time period. Due to their small size and high oxygen diffusivity, these nanoparticles are suitable carriers of sensitizers of O₂(¹Δ_g). The presented results define a new class of nanoscintillators with promising properties for X-ray inducible photodynamic therapy

Antibacterial, Antiviral, and Oxygen-Sensing Nanoparticles Prepared from Electrospun Materials

A simple nanoprecipitation method was used for preparation of stable photoactive polystyrene nanoparticles (NPs, diameter 30 ± 10 nm) from sulfonated electrospun polystyrene nanofiber membranes with encapsulated 5,10,15,20-tetraphenylporphyrin (TPP) or platinum octaethylporphyrin (Pt-OEP). The NPs prepared with TPP have strong antibacterial and antiviral properties and can be applied to the photooxidation of external substrates based on photogenerated singlet oxygen. In contrast to nanofiber membranes, which have limited photooxidation ability near the surface, NPs are able to travel toward target species/structures. NPs with Pt-OEP were used for oxygen sensing in aqueous media, and they presented strong linear responses to a broad range of oxygen concentrations. The nanofiber membranes can be applied not only as a source of NPs but also as an effective filter for their removal from solution

X‑ray Inducible Luminescence and Singlet Oxygen Sensitization by an Octahedral Molybdenum Cluster Compound: A New Class of Nanoscintillators

Newly synthesized octahedral molybdenum cluster compound (<i>n</i>-Bu₄N)₂­[Mo₆I₈(OOC-1-adamantane)₆] revealed uncharted features applicable for the development of X-ray inducible luminescent materials and sensitizers of singlet oxygen, O₂(¹Δ_g). The compound exhibits a red-NIR luminescence in the solid state and in solution (e.g., quantum yield of 0.76 in tetrahydrofuran) upon excitation by UV–vis light. The luminescence originating from the excited triplet states is quenched by molecular oxygen to produce O₂(¹Δ_g) with a high quantum yield. Irradiation of the compound by X-rays generated a radioluminescence with the same emission spectrum as that obtained by UV–vis excitation. It proves the formation of the same excited triplet states regardless of the excitation source. By virtue of the described behavior, the compound is suggested as an efficient sensitizer of O₂(¹Δ_g) upon X-ray excitation. The luminescence and radioluminescence properties were maintained upon embedding the compound in polystyrene films. In addition, polystyrene induced an enhancement of the radioluminescence intensity via energy transfer from the scintillating polymeric matrix. Sulfonated polystyrene nanofibers were used for the preparation of nanoparticles which form stable dispersions in water, while keeping intact the luminescence properties of the embedded compound over a long time period. Due to their small size and high oxygen diffusivity, these nanoparticles are suitable carriers of sensitizers of O₂(¹Δ_g). The presented results define a new class of nanoscintillators with promising properties for X-ray inducible photodynamic therapy

Singlet Oxygen Production and Biological Activity of Hexanuclear Chalcocyanide Rhenium Cluster Complexes [{Re₆Q₈}(CN)₆]^4– (Q = S, Se, Te)

Octahedral rhenium cluster complexes have recently emerged as relevant building blocks for the design of singlet oxygen photosensitizing materials toward biological applications such as blue-light photodynamic therapy. However, their singlet oxygen generation ability as well as biological properties have been studied only superficially. Herein we investigate in detail the singlet oxygen photogeneration, dark and photoinduced cytotoxicity, cellular uptake kinetics, cellular localization and in vitro photoinduced oxidative stress, and photodynamic cytotoxicity of the series of octahedral rhenium cluster complexes [{Re₆Q₈}­(CN)₆]^4–, where Q = S, Se, Te. Our results demonstrate that the selenium-containing complex possesses optimal properties in terms of absorption and singlet oxygen productivity. These features coupled with the cellular internalization and low dark toxicity lead to the first photoinduced cytotoxic effect observed for a molecular [{M₆Q₈}­L₆] complex, making it a promising object for further study in terms of blue-light PDT