Search Results (22)

Background/Objectives: Boron neutron capture therapy (BNCT) is a promising, less-invasive anticancer treatment. However, the development of effective boron-based agents (BNCT probes) remains a critical and challenging issue. Previously, we developed a styrene–maleic acid (SMA) copolymer conjugated with glucosamine, encapsulating boronic acid, which exhibited tumor-targeted distribution via the enhanced permeability and retention (EPR) effect. Building upon this approach, in this study, we designed and synthesized a series of SMA-based polymeric probes for BNCT and evaluated their biological activities, with a particular focus on tumor-targeting properties. Methods: Two SMA-based BNCT nanoprobes, SMA–glucosamine conjugated Borax (SG@B) and SMA-conjugated aminophenylboronic acid encapsulating tavaborole (S-APB@TB), were designed and synthesized. The boron content in the conjugates was quantified using inductively coupled plasma mass spectrometry (ICP-MS), while particle sizes were measured via dynamic light scattering (DLS). In vitro cytotoxicity was assessed using the MTT assay in mouse colon cancer C26 cells. The tissue distribution of the conjugates was analyzed in a mouse sarcoma S180 solid tumor model using ICP-MS. Results: Both SG@B and S-APB@TB formed nanoformulations with average particle sizes of 137 nm and 99 nm, respectively. The boron content of SG@B was 2%, whereas S-APB@TB exhibited a significantly higher boron content of 14.4%. Both conjugates demonstrated dose-dependent cytotoxicity against C26 cells, even in the absence of neutron irradiation. Notably, tissue distribution analysis following intravenous injection revealed higher boron concentrations in plasma and tumor tissues compared to most normal tissues, with S-APB@TB showing particularly favorable tumor accumulation. Conclusions: These findings highlight the tumor-targeting potential of SMA-based BNCT nanoprobes. Further investigations are warranted to advance their clinical development as BNCT agents. Full article

In this study, we pioneered the synthesis of nanoflower-shaped TiO₂-supported Au photocatalysts and investigated their properties. Au nanoflowers (Au NFs) were prepared by a Na-citrate and hydroquinone-based preparation method, followed by wet impregnation of the derived Au NFs on the surface of TiO₂ nanorods (TNR). A uniform and homogeneous distribution of Au NFs was observed in the TNR + NF(0.7) sample (lower Na-citrate concentration), while their distribution was heterogeneous in the TNR + NF(1.4) sample (higher Na-citrate concentration). The UV-Vis DR spectra revealed the size- and shape-dependent optical properties of the Au NFs, with the LSPR effect observed in the visible region. The solid-state EPR spectra showed the presence of Ti³⁺, oxygen vacancies and electron interactions with organic compounds on the catalyst surface. In the case of the TNR + NF(0.7) sample, high photocatalytic activity was observed in the H₂-assisted reduction of NO₂ to N₂ at room temperature under visible-light illumination. In contrast, the TNR + NF(1.4) catalyst as well as the heat-treated samples showed no ability to reduce NO₂ under visible light, indicating the presence of deformed Au NFs limiting the LSPR effect. These results emphasized the importance of the choice of synthesis method, as this could strongly influence the photocatalytic activity of the Au NFs. Full article

Photocatalysis based on titanium dioxide (TiO₂) has become a promising method to remediate industrial and municipal effluents in an environmentally friendly manner. However, the efficiency of TiO₂ is hampered by problems such as rapid electron–hole recombination and limited solar spectrum absorption. Furthermore, the sensitization of TiO₂ through heterojunctions with other materials has gained attention. Vanadium, specifically in the form of ammonium vanadate ((NH₄)₂V₃O₈), has shown promise as a photocatalyst due to its ability to effectively absorb visible light. However, its use in photocatalysis remains limited. Herein, we present a novel synthesis method to produce lamellar (NH₄)₂V₃O₈ as a sensitizer in a supramolecular hybrid photocatalyst of TiO₂–stearic acid (SA), contributing to a deeper understanding of its structural and magnetic characteristics, expanding the range of visible light absorption, and improving the efficiency of photogenerated electron–hole separation. Materials, such as TiO₂–SA and (NH₄)₂V₃O₈, were synthesized and characterized. EPR studies of (NH₄)₂V₃O₈ demonstrated their orientation-dependent magnetic properties and, from measurements of the angular variation of g-values, suggest that the VO₂⁺ complexes are in axially distorted octahedral sites. The photocatalytic results indicate that the 2D/2D heterojunction layered TiO₂/vanadate at a ratio (1:0.050) removed 100% of the methylene blue, used as a model contaminant in this study. The study of the degradation mechanism of methylene blue emphasizes the role of reactive species such as hydroxyl radicals (^•OH) and superoxide ions (O₂^•−). These species are crucial for breaking down contaminant molecules, leading to their degradation. The band alignment between ammonium vanadate ((NH₄)₂V₃O₈) and TiO₂–SA, shows effective separation and charge transfer processes at their interface. Furthermore, the study confirms the chemical stability and recyclability of the TiO₂–SA/(NH₄)₂V₃O₈ photocatalyst, demonstrated that it could be used for multiple photocatalytic cycles without a significant loss of activity. This stability, combined with its ability to degrade organic pollutants under solar irradiation, means that the TiO₂–SA/(NH₄)₂V₃O₈ photocatalyst is a promising candidate for practical environmental remediation applications. Full article

Chromium complexes containing a bis(diphenylphosphino) ligand have attracted significant interest over many years due to their potential as active catalysts for ethylene oligomerisation when combined with suitable co-catalysts such as triethylaluminium (TEA) or methylaluminoxane (MAO). While there has been considerable attention devoted to the possible reaction intermediates and the nature of the Cr oxidation states involved, the potential UV photoactivity of the Cr(I) complexes has so far been overlooked. Therefore, to explore the photoinduced transformations of bis(diphenylphosphino) stabilized Cr(I) complexes, we used continuous-wave (CW) EPR to study the effects of UV radiation on a cationic [Cr(CO)₄(dppp)]⁺[Al(OC(CF₃)₃)₄]⁻ complex (1), where dppp represents the 1,3 bis-(diphenylphosphino)propane ligand, Ph₂P(C₃H₆)PPh₂. Our preliminary investigations into the photochemistry of this complex revealed that [Cr(CO)₄(dppp)]⁺ (1) can be readily photo-converted into an intermediate mer-[Cr(CO)₃(κ¹-dppp)(κ²-dppp)]⁺ complex (2) and eventually into a trans-[Cr(CO)₂(dppp)₂]⁺ complex (3) in solution at room temperature under UV-A light. Here, we show that the intermediate species (2) involved in this transformation can be identified by EPR at much lower temperature (140 K) and at a specific wavelength (highlighting the wavelength dependency of the reaction). In addition, small amounts of a ‘piano-stool’-type complex, namely [Cr(CO)₂(dppp-η⁶-arene)]⁺ (4), can also be formed during the photoconversion of [Cr(CO)₄(dppp)]⁺ using UV-A light. There was no evidence for the formation of the [Cr(L-bis-η⁶-arene)]⁺ complex (5) in these UV irradiation experiments. For the first time, we also evidence the formation of a 1-hexene coordinated [Cr(CO)₃(dppp)(1-hexene)]⁺ complex (6) following UV irradiation of [Cr(CO)₄(dppp)]⁺ in the presence of 1-hexene; this result demonstrates the unprecedented opportunity for exploiting light activation during Cr-driven olefin oligomerisation catalysis, instead of expensive, difficult-to-handle, and hazardous chemical activators. Full article

Polyphenols have gained increasing attention for their therapeutic potential, particularly in conditions like cancer, due to their established antioxidant and anti-inflammatory properties. Recent research highlights their ability to bind to transition metals, such as copper. This is particularly noteworthy given the key role of copper both in the initiation and progression of cancer. Copper can modulate the activity of kinases required for the epithelial–mesenchymal transition (EMT), a process fundamental to tumor cell dissemination. We have previously demonstrated the copper-binding capacity of oleuropein, a secoiridoid found in Olea europaea. In the present study, we investigated the effect of hydroxytyrosol, the primary oleuropein metabolite, on the metastatic potential of three triple-negative breast cancer cell lines (MDA-MB-231, MDA-MB-468, and SUM159). We found that hydroxytyrosol modulated the intracellular copper levels, influencing both the epithelial and mesenchymal markers, by downregulating copper-dependent AKT phosphorylation, a member of the EMT signaling cascade, through Western blot, RT-qPCR, and immunofluorescence. Indeed, by optical spectra, EPR, and in silico approaches, we found that hydroxytyrosol formed a complex with copper, acting as a chelating agent, thus regulating its homeostasis and affecting the copper-dependent signaling cascades. While our results bring to light the copper-chelating properties of hydroxytyrosol capable of countering tumor progression, they also provide further confirmation of the key role of copper in promoting the aggressiveness of triple-negative breast cancer cells. Full article

In vascular plants, the final photosynthetic electron transfer from ferredoxin (Fd) to NADP⁺ is catalyzed by the flavoenzyme ferredoxin:NADP⁺ oxidoreductase (FNR). FNR is recruited to thylakoid membranes via an integral membrane protein TROL (thylakoid rhodanese-like protein) and the membrane associated protein Tic62. We have previously demonstrated that the absence of TROL triggers a very efficient superoxide (O₂^•−) removal mechanism. The dynamic TROL–FNR interaction has been shown to be an apparently overlooked mechanism that maintains linear electron flow before alternative pathway(s) is(are) activated. In this work, we aimed to further test our hypothesis that the FNR–TROL pair could be the source element that triggers various downstream networks of chloroplast ROS scavenging. Tandem affinity purification followed by the MS analysis confirmed the TROL–FNR interaction and revealed possible interaction of TROL with the thylakoid form of the enzyme ascorbate peroxidase (tAPX), which catalyzes the H₂O₂-dependent oxidation of ascorbate and is, therefore, the crucial component of the redox homeostasis system in plants. Further, EPR analyses using superoxide spin trap DMPO showed that, in comparison with the wild type, plants overexpressing TROL (TROL OX) propagate more O₂^•− when exposed to high light stress. This indicates an increased sensitivity to oxidative stress in conditions when there is an excess of membrane-bound FNR and less free FNR is found in the stroma. Finally, immunohistochemical analyses of glutathione in different Arabidopsis leaf cell compartments showed highly elevated glutathione levels in TROL OX, indicating an increased demand for this ROS scavenger in these plants, likely needed to prevent the damage of important cellular components caused by reactive oxygen species. Full article

Graphitic carbon nitride (gCN) materials have been shown to efficiently perform light-induced water splitting, carbon dioxide reduction, and environmental remediation in a cost-effective way. However, gCN suffers from rapid charge-carrier recombination, inefficient light absorption, and poor long-term stability which greatly hinders photocatalytic performance. To determine the underlying catalytic mechanisms and overall contributions that will improve performance, the electronic structure of gCN materials has been investigated using electron paramagnetic resonance (EPR) spectroscopy. Through lineshape analysis and relaxation behavior, evidence of two independent spin species were determined to be present in catalytically active gCN materials. These two contributions to the total lineshape respond independently to light exposure such that the previously established catalytically active spin system remains responsive while the newly observed, superimposed EPR signal is not increased during exposure to light. The time dependence of these two peaks present in gCN EPR spectra recorded sequentially in air over several months demonstrates a steady change in the electronic structure of the gCN framework over time. This light-independent, slowly evolving additional spin center is demonstrated to be the result of oxidative processes occurring as a result of exposure to the environment and is confirmed by forced oxidation experiments. This oxidized gCN exhibits lower H₂ production rates and indicates quenching of the overall gCN catalytic activity over longer reaction times. A general model for the newly generated spin centers is given and strategies for the alleviation of oxidative products within the gCN framework are discussed in the context of improving photocatalytic activity over extended durations as required for future functional photocatalytic device development. Full article

Peptaibols are proteolysis-resistant, membrane-active peptides. Their remarkably stable helical 3D-structures are key for their bioactivity. They can insert themselves into the lipid bilayer as barrel staves, or lay on its surface like carpets, depending on both their length and the thickness of the lipid bilayer. Medium-length peptaibols are of particular interest for studying the peptide–membrane interaction because their length allows them to adopt either orientation as a function of the membrane thickness, which, in turn, might even result in an enhanced selectivity. Electron paramagnetic resonance (EPR) is the election technique used to this aim, but it requires the synthesis of spin-labeled medium-length peptaibols, which, in turn, is hampered by the poor reactivity of the C^α-tetrasubstituted residues featured in their sequences. After several years of trial and error, we are now able to give state-of-the-art advice for a successful synthesis of nitroxide-containing peptaibols, avoiding deleted sequences, side reactions and difficult purification steps. Herein, we describe our strategy and itsapplication to the synthesis of spin-labeled analogs of the recently discovered, natural, medium-length peptaibol pentadecaibin. We studied the antitumor activity of pentadecaibin and its analogs, finding potent cytotoxicity against human triple-negative breast cancer and ovarian cancer. Finally, our analysis of the peptide conformational preferences and membrane interaction proved that pentadecaibinspin-labeling does not alter the biological features of the native sequence and is suitable for further EPR studies. The nitroxide-containing pentadecaibins, and their synthetic strategy described herein, will help to shed light on the mechanism of the peptide–membrane interaction of medium-length peptaibols. Full article

Schiff bases and similar molecules forming metal complexes may cause redox effects, which may also be influenced by light. Anthraquinones such as doxorubicin and idarubicin are widely used antitumor agents, which can generate reactive oxygen species (ROS), stimulated by both the presence of iron and copper ions and also by light. The generated ROS can cause DNA scission, cell membrane oxidation, and many other toxic effects. The redox activity of the quinone-quinoline chelator 2-phenyl-4-(butylamino)naphtho [2,3-h]quinoline-7,12-dione (Q1) was investigated in the presence of iron, copper, and zinc. The influence of light in these interactions was also examined. The chemically induced dynamic nuclear polarization (CIDNP), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) methods were used to elucidate the molecular changes and ROS generation effects of the Q1 metal interactions. A model electron transfer reaction system between 1,4-dihydropyridine and Q1 was utilized to demonstrate that the chelate complexes of Q1 with both Fe(III) and Cu(II) ions were more redox active than Q1 itself. Similarly, CIDNP and NMR data showed that the concentration dependence of the free radicals yield is much higher in the presence of Fe(III) and Cu(II) ions, in comparison to Zn(II), and also that it increased in the presence of light. These findings underline the role of transition metal ions and Q1 in cyclic redox chain reactions and increase the prospect of the development of copper- and iron-based chelating agents, including Q1 and its derivatives, for anticancer therapy. Furthermore, these findings also signify the effect of light on enhancing ROS formation by Q1 and the prospect of utilizing such information for designing target specific anticancer drugs for photodynamic therapy. Full article

Tricalcium phosphate (TCP)-based materials, such as β-Ca₃(PO₄)₂ doped with rare earth ions (RE), have shown applications as biomaterials, lighting emitting materials, scintillating materials, in vivo imaging probes, and thermoluminescent dosimeters. Their properties are found to be dependent on the distribution of RE³⁺ on Ca²⁺ sites that can be controlled by pulsed electron paramagnetic resonance (EPR) and electron spin echo envelop modulation (ESEEM) experiments. The main spectroscopic parameters (spin Hamiltonian values) of Gd³⁺ and nitrogen impurity centers are quantitatively determined (g-factor, the fine structure parameters D and E, the hyperfine constants A) as well as dynamic characteristics: spin–lattice T₁ and spin–spin T₂ relaxation times. Based on the analysis of the EPR datasets, the interatomic distance between Gd³⁺ and ³¹P was estimated in the dipole–dipole approximation. Two structurally nonequivalent Gd³⁺ positions in the β-TCP structure have been identified. The obtained valuable results demonstrate applicability of modern EPR techniques to characterize Gd-TCP systems despite the powder structure of the material and high electron spin S = 7/2 of Gd³⁺ ions. Full article

The strength of concrete elements under shear is a complex phenomenon, which is induced by several effective variables and governing mechanisms. Thus, each parameter’s importance depends on the values of the effective parameters and the governing mechanism. In addition, the new concrete types, including lightweight concrete and fibered concrete, add to the complexity, which is why machine learning (ML) techniques are ideal to simulate this behavior due to their ability to handle fuzzy, inaccurate, and even incomplete data. Thus, this study aims to predict the shear strength of both normal-weight and light-weight concrete beams using three well-known machine learning approaches, namely evolutionary polynomial regression (EPR), artificial neural network (ANN) and genetic programming (GP). The methodology started with collecting a dataset of about 1700 shear test results and dividing it into training and testing subsets. Then, the three considered (ML) approaches were trained using the training subset to develop three predictive models. The prediction accuracy of each developed model was evaluated using the testing subset. Finally, the accuracies of the developed models were compared with the current international design codes (ACI, EC2 & JSCE) to evaluate the success of this research in terms of enhancing the prediction accuracy. The results showed that the prediction accuracies of the developed models were 68%, 83% & 76.5% for GP, ANN & EPR, respectively, and 56%, 40% & 62% for ACI, EC2 & JSCE, in that order. Hence, the results indicated that the accuracy of the worst (ML) model is better than those of design codes, and the ANN model is the most accurate one. Full article

Materials with ferroelectric properties, low bandgap energies, high polarization, low loss, and thermal stability are essential for future solar-cell applications. Researchers have attempted to obtain such materials by using several approaches. In this vein, a novel approach is reported in this work using gamma ray irradiation. The effect of gamma radiation on the structural, optical, and ferroelectric characterizations of bismuth (Bi)-doped barium titanate (BaTiO₃ (BT)), namely Ba_0.95Bi_0.05TiO₃ ceramics (abbreviated as (Bi:BT)), was investigated. X-ray diffraction, structure refinement, and Raman study revealed the presence of a perovskite structure with a tetragonal phase in all investigated samples. Morphological study revealed a nonuniform grain size and some porosity. Gamma irradiation-induced combined effects were proved by a detailed analysis of bond lengths, bond angles, octahedral distortions, oxygen vacancies, and charge compensations. Electron paramagnetic resonance (EPR) study gave direct evidence of oxygen vacancies in the irradiated samples. After gamma irradiation, UV–vis study indicated a decrease in the bandgap from 3.14 to 2.80 eV and a significant increase in visible light absorption. Cole–Cole plots confirm as an increase in gamma-ray dose results in higher levels of electron hopping. Study of the P–E hysteresis loop demonstrated that ferroelectric properties could be maintained after gamma irradiation, with a slight decrease in remnant polarization. The behaviour of the P–E was correlated with increasing gamma dose in the investigated ceramics, demonstrating a strong gamma dependence in the loops’ profile. We guess that the present approach may be a promising technique for enhancing the multifunctionality of electronic devices. Full article

Targeted therapy by using nanomedicines based on the enhanced permeability and retention (EPR) effect is becoming a promising anticancer strategy. Many nano-designed photosensitizers (PSs) for photodynamic therapy (PDT) have been developed which show superior therapeutic potentials than free PS. To further understand the advantages of nano-designed PS, in this study, we used styrene-co-maleyl telomer (SMA) as a polymer platform to prepare a micellar type of PS with two well-characterized PSs—rose bengal (RB) and methylene blue (MB)—and evaluated the outmatching benefits of SMA-PS micelles, especially focusing on the singlet oxygen (¹O₂) generation capacity and intracellular uptake profiles. In aqueous solutions, SMA-PS self-assembles to form micelles by non-covalent interactions between PS and SMA. SMA-PS micelles showed discrete distributions by dynamic light scattering having a mean particle size of 18–30 nm depending on the types of SMA and different PSs. The hydrodynamic size of SMA-PS was evaluated by Sephadex chromatography and it found to be 30–50 kDa. In the presence of human serum albumin, the sizes of SMA-PS remarkably increased, suggesting the albumin-binding property. ¹O₂ generation from the SMA-PS micelle was determined by electron spin resonance, in which the SMA-PS micelle showed comparatively more photo-stable, and consequently a more durable and constant, ¹O₂ generation capability than free PS. Moreover, intracellular uptake of SMA-PS micelles was extensively faster and higher than free PS, especially in tumor cells. Taken together, SMA-PS micelles appear highly advantageous for photodynamic therapy in addition to its capacity in utilizing the EPR effect for tumor targeted delivery. Full article

The human skin is exposed to various environmental factors including solar radiation and ambient air pollutants. Although, due to its physical and biological properties, the skin efficiently protects the body against the harm of environmental factors, their excessive levels and possible synergistic action may lead to harmful effects. Among particulate matter present in ambient air pollutants, PM_2.5 is of particular importance for it can penetrate both disrupted and intact skin, causing adverse effects to skin tissue. Although certain components of PM_2.5 can exhibit photochemical activity, only a limited amount of data regarding the interaction of PM_2.5 with light and its effect on skin tissue are available. This study focused on light-induced toxicity in cultured human keratinocytes, which was mediated by PM_2.5 obtained in different seasons. Dynamic Light Scattering (DLS) and Atomic Force Microscopy (AFM) were employed to determine sizes of the particles. The ability of PM_2.5 to photogenerate free radicals and singlet oxygen was studied using EPR spin-trapping and time-resolved singlet oxygen phosphorescence, respectively. Solar simulator with selected filters was used as light source for cell treatment to model environmental lightning conditions. Cytotoxicity of photoexcited PM_2.5 was analyzed using MTT assay, PI staining and flow cytometry, and the apoptotic pathway was further examined using Caspase-3/7 assay and RT-PCR. Iodometric assay and JC-10 assay were used to investigate damage to cell lipids and mitochondria. Light-excited PM_2.5 were found to generate free radicals and singlet oxygen in season-dependent manner. HaCaT cells containing PM_2.5 and irradiated with UV-Vis exhibited oxidative stress features–increased peroxidation of intracellular lipids, decrease of mitochondrial membrane potential, enhanced expression of oxidative stress related genes and apoptotic cell death. The data indicate that sunlight can significantly increase PM_2.5-mediated toxicity in skin cells. Full article

The rational design of direct Z-scheme heterostructural photocatalysts using solar energy is promising for energy conversion and environmental remediation, which depends on the precise regulation of redox active sites, rapid spatial separation and transport of photoexcited charge and a broad visible light response. The Bi₂WO₆ materials have been paid more and more attention because of their unique photochemical properties. In this study, S²⁻ doped Bi₂WO_6-x coupled with twin crystal ZnIn₂S₄ nanosheets (Sov−BWO/T−ZIS) were prepared as an efficient photocatalyst by a simple hydrothermal method for the removal of tetracycline hydrochloride (TCH). Multiple methods (XRD, TEM, XPS, EPR, UV vis DRS, PL etc.) were employed to systematically investigate the morphology, structure, composition and photochemical properties of the as-prepared samples. The XRD spectrum indicated that the S²⁻ ions were successfully doped into the Sov−BWO component. XPS spectra and photoelectrochemical analysis proved that S²⁻ served as electronic bridge and promoted captured electrons of surface oxygen vacancies transfer to the valence band of T−ZIS. Through both experimental and in situ electron paramagnetic resonance (in situ EPR) characterizations, a defined direct Z-scheme heterojunction in S-BWO/T−ZIS was confirmed. The improved photocatalytic capability of S-BWO/T−ZIS results ascribed that broadened wavelength range of light absorption, rapid separation and interfacial transport of photoexcited charge, precisely regulated redox centers by optimizing the interfacial transport mode. Particularly, the Sov−50BWO/T−ZIS Z-scheme heterojunction exhibited the highest photodegradation rate was 95% under visible light irradiation. Moreover, this heterojunction exhibited a robust adsorption and degradation capacity, providing a promising photocatalyst for an organic pollutant synergistic removal strategy. Full article