Ruthenium Photosensitizers Research Articles

In Vitro Encapsulation of Functionally Active Abiotic Photosensitizers Inside a Bacterial Microcompartment Shell.

Bacterial microcompartments (BMCs) are self-assembling, selectively permeable protein shells that encapsulate enzymes to enhance catalytic efficiency of segments of metabolic pathways through means of confinement. The modular nature of BMC shells' structure and assembly enables programming of shell permeability and underscores their promise in biotechnology engineering efforts for applications in industry, medicine, and clean energy. Realizing this potential requires methods for encapsulation of abiotic molecules, which have been developed here for the first time. We report in vitro cargo loading of BMC shells with ruthenium photosensitizers (RuPS) by two approaches─one involving site-specific covalent labeling and the other driven by diffusion, requiring no specific interactions between cargo molecules and shell proteins. The highly stable shells retain encapsulated cargo over 1 week without egress and preserve RuPS photophysical activity. This study is an important foundation for further work that will converge biological BMC architecture with synthetic chemistry to facilitate biohybrid photocatalysis.

Proton-Coupled Electron Transfer upon Oxidation of Tyrosine in a De Novo Protein: Analysis of Proton Acceptor Candidates.

Redox-active residues, such as tyrosine and tryptophan, play important roles in a wide range of biological processes. The α3Y de novo protein, which is composed of three α helices and a tyrosine residue Y32, provides a platform for investigating the redox properties of tyrosine in a well-defined protein environment. Herein, the proton-coupled electron transfer (PCET) reaction that occurs upon oxidation of tyrosine in this model protein by a ruthenium photosensitizer is studied by using a vibronically nonadiabatic PCET theory that includes hydrogen tunneling and excited vibronic states. The input quantities to the analytical nonadiabatic rate constant expression, such as the diabatic proton potential energy curves and associated proton vibrational wave functions, reorganization energy, and proton donor-acceptor distribution functions, are obtained from density functional theory calculations on model systems and molecular dynamics simulations of the solvated α3Y protein. Two possible proton acceptors, namely, water or a glutamate residue in the protein scaffold, are explored. The PCET rate constant is greater when glutamate is the proton acceptor, mainly due to the more favorable driving force and shorter equilibrium proton donor-acceptor distance, although contributions from excited vibronic states mitigate these effects. Nevertheless, water could be the dominant proton acceptor if its equilibrium constant associated with hydrogen bond formation is significantly greater than that for glutamate. Although these calculations do not definitively identify the proton acceptor for this PCET reaction, they elucidate the conditions under which each proton acceptor can be favored. These insights have implications for tyrosine-based PCET in a wide variety of biochemical processes.

Self-assembly of a ruthenium-based cGAS-STING photoactivator for carrier-free cancer immunotherapy

The cGAS (cyclic GMP-AMP synthase)-STING (stimulator of interferon genes) pathway promotes antitumor immune responses by sensing cytosolic DNA fragments leaked from nucleus and mitochondria. Herein, we designed a highly charged ruthenium photosensitizer (Ru1) with a β-carboline alkaloid derivative as the ligand for photo-activating of the cGAS-STING pathway. Due to the formation of multiple non-covalent intermolecular interactions, Ru1 can self-assemble into carrier-free nanoparticles (NPs). By incorporating the triphenylphosphine substituents, Ru1 can target and photo-damage mitochondrial DNA (mtDNA) to cause the cytoplasmic DNA leakage to activate the cGAS-STING pathway. Finally, Ru1 NPs show potent antitumor effects and elicit intense immune responses in vivo. In conclusion, we report the first self-assembling mtDNA-targeted photosensitizer, which can effectively activate the cGAS-STING pathway, thus providing innovations for the design of new photo-immunotherapeutic agents.

Highly Efficient, Noble-Metal-Free, Fully Aqueous CO2 Photoreduction Sensitized by a Robust Organic Dye.

The development of efficient, selective, and durable CO2 photoreduction systems presents a long-standing challenge in full aqueous solutions owing to the presence of scarce CO2 and the fierce competition against H2 evolution, which is even more challenging when noble metals are not utilized. Herein, we present the facile decorations of four phosphonic acid groups on a donor-acceptor-type organic dye to obtain a water-soluble photosensitizer (4P-DPAIPN), which succeeds the excellent photophysical and photoredox properties of its prototype, exhibiting long-lived delayed fluorescence (>10 μs) in aqueous solutions. Combining 4P-DPAIPN with a cationic cobalt porphyrin catalyst has accomplished record-high apparent quantum yields of 9.4-17.4% at 450 nm for CO2-to-CO photoconversion among the precedented systems (maximum 13%) in fully aqueous solutions. Remarkable selectivity of 82-93% and turnover number of 2700 for CO production can also be achieved with this noble-metal-free system, outperforming a benchmarking ruthenium photosensitizer and a commercial organic dye under parallel conditions. Such high performances of 4P-DPAIPN can be well maintained under real sunlight. More impressively, no significant decomposition of 4P-DPAIPN was detected during the long-term photocatalysis. Eventually, the photoinduced electron transfer pathways were proposed.

Photokatalytische CO2 Reduktion mit CO2‐bindenden Enzymen

AbstractNeuartige Konzepte zur Nutzung von Kohlendioxid sind erforderlich, um eine kreislauforientierte Kohlenstoffwirtschaft zu erreichen und Umweltprobleme zu minimieren. Um diese Ziele zu erreichen, sind Photo‐, Elektro‐, thermische und Biokatalyse die Schlüsselwerkzeuge, die vorzugsweise in wässrigen Lösungen eingesetzt werden. Dennoch gibt es nur wenige katalytische Systeme, die in Wasser effizient arbeiten. Hier stellen wir eine allgemeine Strategie zur Identifizierung von Enzymen vor, die für die CO2‐Reduktion geeignet sind und zwar auf der Grundlage von Strukturanalysen für potenzielle Kohlendioxid‐Bindungsstellen und anschließenden Mutationen. Wir entdeckten, dass die Phenolsäure‐Decarboxylase aus Bacillus subtilis (BsPAD) die wässrige photokatalytische CO2‐Reduktion in Gegenwart eines Ruthenium‐Photosensibilisators und Natriumascorbat selektiv zu Kohlenmonoxid‐Bildung ermöglicht. Mit modifizierten Varianten von BsPAD wurden TONs von bis zu 978 und Selektivitäten von bis zu 93 % (wobei die gewünschte CO‐ gegenüber der H2‐Erzeugung bevorzugt wurde) erreicht. Durch Mutationen im Bereich des aktiven Zentrums von BsPAD wurden die Umsatzzahlen für die CO‐Erzeugung weiter verbessert. Dabei zeigte sich, dass der Elektronentransfer geschwindigkeitsbegrenzend ist und durch mehrstufiges Tunneln erfolgt. Die Allgemeingültigkeit dieses Ansatzes wurde durch die Verwendung von acht anderen Enzymen bewiesen, die alle die gewünschte Aktivität zeigten, was unterstreicht, dass eine Reihe von Proteinen zur photokatalytischen CO2‐Reduktion in der Lage ist.

Photocatalytic CO2 Reduction Using CO2-Binding Enzymes.

Novel concepts to utilize carbon dioxide are required to reach a circular carbon economy and minimize environmental issues. To achieve these goals, photo-, electro-, thermal-, and biocatalysis are key tools to realize this, preferentially in aqueous solutions. Nevertheless, catalytic systems that operate efficiently in water are scarce. Here, we present a general strategy for the identification of enzymes suitable for CO2 reduction based on structural analysis for potential carbon dioxide binding sites and subsequent mutations. We discovered that the phenolic acid decarboxylase from Bacillus subtilis (BsPAD) promotes the aqueous photocatalytic CO2 reduction selectively to carbon monoxide in the presence of a ruthenium photosensitizer and sodium ascorbate. With engineered variants of BsPAD, TONs of up to 978 and selectivities of up to 93 % (favoring the desired CO over H2 generation) were achieved. Mutating the active site region of BsPAD further improved turnover numbers for CO generation. This also revealed that electron transfer is rate-limiting and occurs via multistep tunneling. The generality of this approach was proven by using eight other enzymes, all showing the desired activity underlining that a range of proteins is capable of photocatalytic CO2 reduction.

Exploiting Orthogonal C-C Cross-Coupling Reactions for Chemistry-on-the-Complex: Modular Assembly of 2,6-Di(quinolin-8-yl)pyridine Ruthenium(II) Photosensitizer Triads.

In this work, we present a concise modular assembly strategy using one universal heteroleptic 2,6-di(quinolin-8-yl)pyridine-based ruthenium(II) complex as a starting building block. Extending the concept from established ligand modifications and subsequent complexation (classical route), the later appearing chemistry-on-the-complex methodology was used for late-stage syntheses, i.e., assembling discrete building blocks to molecular architectures (here: dyad and triads). We focused on Suzuki-Miyaura and Sonogashira cross-couplings as two of the best-known C-C bond forming reactions. Both were performed on one building block complex bearing a bromine and TIPS-protected alkyne for functional group interconversion (bromine to TMS-protected alkyne, a benzyl azide, or a boronic acid pinacol ester moiety with ≥95% isolated yield and simple purification) as well as building block assemblies using both a triarylamine-based donor and a naphthalene diimide-based acceptor in up to 86% isolated yield. Additionally, the developed purification via automated flash chromatography is simple compared to tedious manual chromatography for ruthenium(II)-based substrates in the classical route. Based on the preliminary characterization by steady-state spectroscopy, the observed emission quenching in the triad (55%) serves as an entry to rationally optimize the modular units via chemistry-on-the-complex to elucidate energy and electron transfer.

Anchor Group Effects in Ruthenium (II) Photosensitizers Bearing N-Heterocyclic Carbene and Polypyridyl Ligands for DSSCs: A Computational Evaluation

In this work, we evaluate the bonding characteristics and interfacial electron transfer dynamics of three heteroleptic ruthenium photosensitizers featuring different terpyridine (tpy) acceptor end configurations through quantum-chemical calculations. These photosensitizers...

Enhancing the stability of photocatalytic systems for hydrogen evolution in water by using a tris-phenyl-phenanthroline sulfonate ruthenium photosensitizer

Using the water-soluble Ru-tris-phenyl phenanthroline sulfonate photosensitizer versus regular Ru-tris-bipyridine improves the efficiency of H2 production in water.

Metal cluster/ruthenium photosensitizer/cobalt phthalocyanine synergistic photocatalytic cycloaddition of carbon dioxide and propylene oxide

The cycloaddition of CO2 and propylene oxide (PO) is of great significance to green chemistry and resource utilization. Here, two new metal clusters and four ruthenium photosensitizers were synthesized, and a series of composite catalysts were prepared by combining them with cobalt phthalocyanine. Light was introduced into the reaction system and it was found that TON increased from 550 (0 W) to 990 (200 W) at 60 °C. At 120 °C, 200 W, the TON was as high as 4616. The electron paramagnetic resonance (EPR) experiments showed that for the Cat13, electrons were generated by light irradiation. After the system was injected into PO, the photogenerated electrons quickly transferred to PO. Gibbs free energy calculations also indicate that by introducing light, the system is more likely to promote PO ring opening and exhibits excellent catalytic performance for CO2 ring addition. In addition, the recycled catalyst can still catalyze the formation of propylene carbonate from CO2 and PO.

Recent Investigations on the Use of Copper Complexes as Molecular Materials for Dye-Sensitized Solar Cells.

Three decades ago, dye-sensitized solar cells (DSSCs) emerged as a route for harnessing the sun's energy and converting it into electricity. Since then, an impressive amount of work has been devoted to improving the global photovoltaic efficiency of DSSCs, trying to optimize all components of the device. Up to now, the best efficiencies have usually been reached with ruthenium(II) photosensitizers, even if in the last few years many classes of organic compounds have shown record efficiencies. However, the future of DSSCs is stringently connected to the research and development of cheaper materials; in particular, the replacement of rare metals with abundant ones is an important topic in view of the long-term sustainability of DSSCs intended to replace the consolidated fossil-based technology. In this context, copper is a valid candidate, being both an alternative to ruthenium in the fabrication of photosensitizers and a material able to replace the common triiodide/iodide redox couple. Thus, recently, some research papers have confirmed the great potential of copper(I) coordination complexes as a cheap and convenient alternative to ruthenium dyes. Similarly, the use of copper compounds as electron transfer mediators for DSSCs can be an excellent way to solve the problems related to the more common I3-/I- redox couple. The goal of this mini-review is to report on the latest research devoted to the use of versatile copper complexes as photosensitizers and electron shuttles in DSSCs. The coverage, from 2022 up to now, illustrates the most recent studies on dye-sensitized solar cells based on copper complexes as molecular materials.

A Combination of Ruthenium Complexes and Photosensitizers to Treat Colorectal Cancer

Treatment regimens are regularly evolving alongside novel therapies and drugs. Such evolution is necessary to circumvent resistance mechanisms and to give patients the best possible health care. When dealing with cancer, most regimens involve multiple treatments (surgery, radiation therapy, chemotherapy, immunotherapy, etc.). The purpose of this study was to associate in a single compound metal-based drugs and photosensitizers to combine chemotherapy and photodynamic therapy. Two arene–ruthenium tetrapyridylporphyrin compounds (2H-TPyP-arene-Ru and Zn-TPyP-arene-Ru) have been synthesized and evaluated on two colorectal cancer cell lines (HCT116 and HT-29). Their cytotoxicity and phototoxicity have been evaluated. In addition, the anticancer mechanism and the cell death process mediated by the two compounds were studied. The results showed that the two arene–ruthenium photosensitizer-containing complexes have a strong phototoxic effect after photoactivation. The 2H-TPyP-arene-Ru complex induced outstanding cytotoxicity when compared to the Zn-TPyP-arene-Ru analogue. Moreover, under light, these two arene–ruthenium photosensitizers induce an apoptotic process in human colorectal cancer cell lines.

Surface photosterilization of implantable silicone biomaterials: structural and functional characterization

Hospital-acquired infections (HAIs) remain one of the major challenges faced by the global healthcare system. The increasing rate of pathogenic resistance against antibiotics suggests that alternative treatments are needed to control recurrent infections. Catheter-associated urinary tract infections (CAUTIs) are the third most common type of HAI worldwide, and this is mainly due to indwelling devices being excellent substrates for bacterial adhesion and growth. Subsequent biofilm formation on the implant surface acts as a constant nidus of bacteria and infection, thereby contributing to increased rates of patient morbidity and mortality. Here, we propose a simple and cost-effective method to sterilize silicone-based implant surfaces and prevent initial bacterial colonization, using Polydimethylsiloxane (PDMS) and an embedded ruthenium photosensitizer (PS). Exposure to LED light triggers potent photokilling action, resulting in significant bactericidal activity as evidenced by the number of adherent bacteria being below the level of detection (<10 CFU/mL) after 24 h. Live/dead staining studies using fluorescence microscopy indicated significant reduction in surface-adhered bacterial growth and biofilm formation. This potent antibacterial activity was verified in vivo, with exposure of contaminated PDMS coupons containing PS to LED prior to implantation resulting in over 99.5% reduction in adherent bacteria compared to controls over the 3-day implantation period. Histological analysis of the implantation site of PDMS+PS samples, in the absence of bacteria, revealed no adverse reactions. This was also confirmed using in vitro cytotoxicity studies. Tensile strength, surface roughness, hydrophobicity, and the development of encrustation of surface-treated groups exhibit comparable or improved properties to bare PDMS.

Mesoporous Mixed-Metal-Organic Framework Incorporating a [Ru(Phen)3]2+ Photosensitizer for Highly Efficient Aerobic Photocatalytic Oxidative Coupling of Amines.

[Ru(Phen)3]2+ (phen = phenanthroline) as a very classical photosensitizer possesses strong absorption in the visible range and facilitates photoinduced electron transfer, which plays a vital role in regulating photochemical reactions. However, it remains a significant challenge to utilize more adequately and exploit more efficiently the ruthenium-based materials due to the uniqueness, scarcity, and nonrenewal of the noble metal. Here, we integrate the intrinsic advantages of the ruthenium-based photosensitizer and mesoporous metal-organic frameworks (meso-MOFs) into a [Ru(Phen)3]2+ photosensitizer-embedded heterometallic Ni(II)/Ru(II) meso-MOF (LTG-NiRu) via the metalloligand approach. LTG-NiRu, with an extremely robust framework and a large one-dimensional (1D) channel, not only makes ruthenium photosensitizer units anchored in the inner wall of meso-MOF tubes to circumvent the problem of product/catalyst separation and recycling of catalysts in heterogeneous systems but also exhibits exceptional activities for the aerobic photocatalytic oxidative coupling of amine derivatives as a general photocatalyst. The conversion of the light-induced oxidative coupling reaction for various benzylamines is ∼100% in 1 h, and more than 20 chemical products generated by photocatalytic oxidative cycloaddition of N-substituted maleimides and N,N-dimethylaniline can be synthesized easily in the presence of LTG-NiRu upon visible light irradiation. Moreover, recycling experiments demonstrate that LTG-NiRu is an excellent heterogeneous photocatalyst with high stability and excellent reusability. LTG-NiRu represents a great potential photosensitizer-based meso-MOF platform with an efficient aerobic photocatalytic oxidation function that is convenient for gram-scale synthesis.

Specific discrimination and efficient elimination of gram-positive bacteria by an aggregation-induced emission-active ruthenium (II) photosensitizer.

The infections caused by Gram-positive bacteria (G+) have seriously endangered public heath due to their high morbidity and mortality. Therefore, it is urgent to develop a multifunctional system for selective recognition, imaging and efficient eradication of G+. Aggregation-induced emission materials have shown great promise for microbial detection and antimicrobial therapy. In this paper, a multifunctional ruthenium (II) polypyridine complex Ru2 with aggregation-induced emission (AIE) characteristic, was developed and used for selective discrimination and efficient extermination of G+ from other bacteria with unique selectivity. The selective G+ recognition benefited from the interaction between lipoteichoic acids (LTA) and Ru2. Accumulation of Ru2 on the G+ membrane turned on its AIE luminescence and allowed specific G+ staining. Meanwhile, Ru2 under light irradiation also possessed robust antibacterial activity for G+in vitro and in vivo antibacterial experiments. To the best of our knowledge, Ru2 is the first Ru-based AIEgen photosensitizer for simultaneous dual applications of G+ detection and treatment, and inspires the development of promising antibacterial agents in the future.

Visible-light-harvesting basolite-A520 metal organic framework for photocatalytic hydrogen evolution

A heterogeneous photosensitizer Ru@dpdhpzBASF-A520 has been successfully synthesized following an unprecedented strategy based on the incorporation of surface dipyridyl-dihydropyridazine adducts by Diels–Alder reaction on the aluminum fumarate units of the highly porous metal-organic framework (MOF) BASF-A520 and their further coordination to ruthenium metal centers. The characterization of the resulting metal-organic framework, including the ruthenium bipyridine-like photosensitizer moieties attached to its linkers, has been carried out by a wide variety of techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (13C CP/MAS NMR), X-ray photoelectron spectroscopy (XPS) and ultraviolet–visible (UV–vis) spectroscopy. The light absorption in the visible region shown by the resulting material, Ru@dpdhpzBASF-A520, has allowed its application as a single-site solid photosensitizer for photochemical reactions of hydrogen evolution in conjunction with Pt nanoparticles as catalyst, EDTA as sacrificial electron donor and MV as electron carrier. A remarkable photocatalytic activity after 72 h was achieved, with a TON of 1157 based on the heterogeneous ruthenium photosensitizer, in aqueous solution at pH 5.0, which confirmed the effective stabilization of the ruthenium dipyridyl-dihydropyridazine adducts on the MOF surface and the efficient electron injection from the photoexcited Ru@dpdhpzBASF-A520 to Pt nanoparticles mediated by MV electron carrier for hydrogen generation from water.

Hyaluronic acid-poly(lactic-co-glycolic acid) nanoparticles with a ruthenium photosensitizer cargo for photokilling of oral cancer cells

• Enhanced photodynamic effect by Ru(II) complex through both Type I and II mechanisms. • Synthesis of Ru(II) complex with 2,2’-biimidazole for PDT of oral cancer. • Ru(II) complex encapsulation in HA-PLGA NPs for improved solubility and selectivity. • High intracellular uptake of Ru(II) complex mediated by HA targeting of CD44. • Preferential accumulation of Ru(II) complex in the mitochondria. Photodynamic therapy (PDT), a combination of light, molecular oxygen and a photosensitizing dye, has gained attention as a promising technique to treat various types of cancers. Among all the photosensitizers reported so far, ruthenium(II) polypyridyl complexes exhibit unique photophysical and photobiological features owing to their photostability, μs triplet excited states, and ability to undergo both ‘type I’ and ‘type II’ reactions in their photodynamic action. We report the synthesis of a novel Ru(II) complex containing one 2,2'-biimidazole (bim) and two tetramethylphenanthroline (tmp) ligands that sensitizes the simultaneous production of superoxide anion (O 2 • - ) and singlet oxygen ( 1 O 2 ) upon irradiation with blue-green light. To improve its solubility and bioavailability, a zero-order degradation-controlled release formulation based on self-assembled hyaluronic acid (HA)–poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) was prepared for its topical application in oral cancer cells (TR146 cell line). These NPs (152 nm diameter) showed 70% Ru-complex encapsulation efficiency, high physiological stability, low polydispersity index (0.12), and a sensitizer release enhanced by the hyaluronidase enzyme overexpressed in many cancer cells. Both the free complex and its nanocarrier are internalized by the TR146 cells, displaying >90% in vitro cytotoxicity under 470 nm activation (50 J cm -2 ), highlighting their potential as PDT agents. The Ru(II) complex loaded nanocarrier developed in this study can be potentially effective in the treatment of oral cancers.

Block copolymer micelles as efficient colloidal photosensitizers in the light-driven hydrogen evolution reaction

We herein demonstrate the use of block copolymer micelles as highly efficient colloidal photosensitizers in light-driven HER.

Visible Light Driven Degradation of Tetracycline Hydrochloride in the Presence of Ruthenium Photosensitizer

Visible Light Driven Degradation of Tetracycline Hydrochloride in the Presence of Ruthenium Photosensitizer

Scanning Electrochemical Cell Microscopy: A Tool for Nanoscopic Deposition of Light-Driven Photocatalysts

Single and multi-barrel nanopipettes and nanopipette-based scanning electrochemical probe microscopy techniques like scanning electrochemical cell microscopy (SECCM) have gained significant attention as tools for localized, maskless, three-dimensional surface modifications [1,2]. The nanometer-sized orifices of nanopipettes allow delivering molecules to solution inducing concentration-confined electrodepositions. Also, electroless nanoscale depositions like the fountain pen technique [3] can be achieved by this technique.In this study, we present the deposition of various cobaloxime-based earth-abundant Co catalysts for light-driven hydrogen evolution reaction (HER) [4]. Arrays of different cobalt(III) complexes were deposited via SECCM and investigated in respect with their HER activity using scanning electrochemical microscopy (SECM) in combination of Pd-microsensors [5] for in situ hydrogen (H2) measurements under illumination. In addition, AFM studies revealed possible degradation of the commercially available neutral benchmark complex [Co(dmgH)2(py)Cl] in these studies. First results will also be presented in respect with the deposition of nanowires via co-deposition of HER catalyst and Ruthenium photosensitizer. First spatially resolved photocatalytic studies at such nanowires, which are characterized by high surface area, will be presented. Also, the influence of the substrate will also be discussed.