Search Results (412)

The potentialities of mechanochemistry trough extrusion have been investigated for the design of nanosized catalysts and their use in C-C bond-forming reactions. The mechanochemical approach proved successful for the synthesis of supported palladium nanoparticles with mean diameter within 6–10 nm, achieved by the reduction of Pd(II) acetate with ethylene glycol, in the absence of any solvent. A mesoporous N-doped carbon derived from chitin as a renewable biopolymer, was used as a support. Thereafter, the resulting nanomaterials were tested as catalysts to implement a second extrusion based-protocol for the Suzuki-Miyaura cross-coupling reaction of iodobenzene and phenylboronic acid. The conversion and the selectivity of the reaction were 81% and >99%, respectively, with a productivity of the desired derivative, biphenyl, of 41 mmol g_cat⁻¹ h⁻¹. Full article

While fluorescent sensors have been developed for monitoring metal ions in health and diseases, they are limited by the requirement of an excitation light source that can lead to photobleaching and a high autofluorescence background. To address these issues, bioluminescence resonance energy transfer (BRET)-based protein or small molecule sensors have been developed; however, most of them are not highly selective nor generalizable to different metal ions. Taking advantage of the high selectivity and generalizability of DNAzymes, we report herein DNAzyme-based ratiometric sensors for Zn²⁺ based on BRET. The 8-17 DNAzyme was labeled with luciferase and Cy3. The proximity between luciferase and Cy3 permitted BRET when coelenterazine, the substrate for luciferase, was introduced. Adding samples containing Zn²⁺ resulted in a cleavage of the substrate strand, causing dehybridization of the DNAzyme construct, thus increasing the distance between Cy3 and luciferase and changing the BRET signals. Using these sensors, we detected Zn²⁺ in serum samples and achieved Zn²⁺ detection with a smartphone camera. Moreover, since the BRET pair is not the component that determines the selectivity of the sensors, this sensing platform has the potential to be adapted for the detection of other metal ions with other metal-dependent DNAzymes. Full article

In this study, a new modified chitosan conjugate (Chito-TZ) was developed via amide coupling between the acid chloride derivative of the methylthio-thidiazole compound and the free primary amino groups of chitosan. The product was characterized using several instrumental investigations, including Fourier-transform infrared spectroscopy (FT-IR), ¹H-Nuclear magnetic resonance, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and X-ray diffraction (XRD). XRD indicated that the crystalline pattern of chitosan was interrupted after chemical modification with the thiadiazole derivative. Broido’s model was used to determine the thermal activation energy E_a, and the results showed that the E_a for the first decomposition region of Chito-TZ is 24.70 KJ mol⁻¹ lower than that required for chitosan (95.57 KJ mol⁻¹), indicating the accelerating effect of the thiadiazole derivative on the thermal decomposition of Chito-TZ. The modified chitosan showed better antibacterial and antifungal activities than the non-modified chitosan; except for seed germination, chitosan was better. The Chito-TZ showed a low MIC value (25–50 µg mL⁻¹) compared to Chito (50–100 µg mL⁻¹). Moreover, the maximum inhibition percentages for plant-pathogenic fungi, Aspergillus niger, Fusarium oxysporum, and Fusarium solani, were attained at a concentration of 300 µg mL⁻¹ with values of 35.4 ± 0.9–39.4 ± 1.7% for Chito and 45.2 ± 1.6–52.1 ± 1.3% for Chito-TZ. The highest germination percentages (%) of broad bean, shoot and root length and weight, and seed vigor index were obtained after Chito treatment with a concentration of 200 µg mL⁻¹ compared to Chito-TZ. Full article

Gene therapy is the ultimate therapeutic technology for diseases related to gene abnormality. However, the use of DNA alone has serious problems, such as poor stability and difficulty in entering target cells. The development of a safe and efficient gene delivery system is the cornerstone of gene therapy. Of particular interest, multifunctional peptides are rationally designed as non-viral vectors for efficient gene delivery. As components of gene delivery vectors, these peptides play critically important roles in skeleton construction, the implementation of targeting strategies, cell membrane penetration, endosome rupture, and nuclear transport. In recent years, the research of functional peptide-based gene delivery vectors has made important progress in improving transfection efficiency. The latest research progress and future development direction of peptide-based gene delivery vectors are reviewed in this paper. Full article

The combined use of di-2-pyridyl ketone ((py)₂CO) with various diols in Mn cluster chemistry has afforded five new compounds, namely, [Mn₁₁O₂(OH)₂{(py)₂CO₂}₅(pd)(MeCO₂)₃(N₃)₃(NO₃)₂(DMF)₄](NO₃)∙2DMF∙H₂O (1∙2DMF∙H₂O), [Mn₁₁O₂(OH)₂{(py)₂CO₂}₅(mpd)(MeCO₂)₃(N₃)₃(NO₃)₂(DMF)₄](NO₃) (2), [Mn₁₂O₄(OH)₂{(py)₂CO₂}₄(mpd)₂(Me₃CCO₂)₄(NO₃)₄(H₂O)₆](NO₃)₂∙2MeCN (3∙2MeCN), [Mn₄(OMe)₂{(py)₂C(OMe)O}₂(2-hp)₂(NO₃)₂(DMF)₂] (4), and [Mn₇{(py)₂CO₂}₄(2-hp)₄(NO₃)₂(DMF)₂](ClO₄)∙DMF (5∙DMF) ((py)₂CO₂²⁻ and (py)₂C(OMe)O⁻ = gem-diol and hemiketal derivatives of di-2-pyridyl ketone, pdH₂ = 1,3-propanediol, mpdH₂ = 2-metly-1,3-propanediol, 2-hpH₂ = 2-(hydroxymethyl)phenol). Complexes 1 and 2 are isostructural, possessing an asymmetric [Mn^III₅Mn^II₆(μ₄-O)(μ₃-O)(μ₃-OH)(μ-OH)(μ₃-OR)₂(μ-OR)₁₀(μ-N₃)]⁸⁺ core. Compound 3 is based on a multilayer [Mn^III₈Mn^II₄(μ₄-O)₂(μ₃-O)₂(μ₃-OH)₂(μ-OR)₁₂]¹⁰⁺ core, while complex 4 comprises a defective dicubane core. The crystal structure of 5 reveals that it is based on an unusual non-planar [Mn^III₅Mn^II₂(μ-OR)₁₂]⁷⁺ core with a serpentine-like topology. Direct current (dc) magnetic susceptibility studies revealed the presence of dominant antiferromagnetic exchange interactions in complex 3, while ferromagnetic coupling between the Mn ions was detected in the case of compound 5. Fitting of the magnetic data for complex 4 revealed weak antiferromagnetic interactions along the peripheral Mn^II∙∙∙Mn^III ions (J_wb = −0.33 (1) cm⁻¹) and ferromagnetic interactions between the central Mn^III∙∙∙Mn^III ions (J_bb = 6.28 (1) cm⁻¹). Full article

Aptamers are artificial oligonucleotides with excellent molecule-targeting ability. Compared with monoclonal antibodies, aptamers have the advantages of low cost, no batch effect, and negligible immunogenicity, making them promising candidates for cancer immunotherapy. To date, a series of aptamer agonists/antagonists have been discovered and directly used to activate immune response, such as immune checkpoint blockade, immune costimulation, and cytokine regulation. By incorporating both tumor- and immune cell-targeting aptamers, multivalent bispecific aptamers were designed to pursue high tumor affinity and enhanced immune efficacy. More importantly, benefiting from feasible chemical modification and programmability, aptamers can be engineered with diverse nanomaterials (e.g., liposomes, hydrogels) and even living immune cells (e.g., NK cells, T cells). These aptamer-based assemblies exhibit powerful capabilities in targeted cargo delivery, regulation of cell–cell interactions, tumor immunogenicity activation, tumor microenvironment remodeling, etc., holding huge potential in boosting immunotherapeutic efficacy. In this review, we focus on the recent advances in aptamer-based immune drug systems (AptIDCs) and highlight their advantages in cancer immunotherapy. The current challenges and future prospects of this field are also pointed out in this paper. Full article

The demand for synthetic bone grafts has increased in recent years. Hydroxyapatite (HA) is one of the highly suitable candidates as a bone graft material due to its excellent biocompatibility and high osteoconductive properties with low toxicity. HA has disadvantageous mechanical strength showing relatively fragile and brittle behavior due to its high hygroscopic properties. This leads to improper mechanical properties for such grafting applications. Therefore, HA should be combined with another material with similar biocompatibility and high hardness, such as SiO₂. In this work, HA/SiO₂ (HAS) composite material was prepared via a hydrothermal method to obtain the high purities of HA with a particle size of approximately 35 nm and around 50% crystallinity. It was found that the addition of SiO₂ stimulated the composite system by forming an orthosilicic acid complex that can reduce the overall solution’s pH, thus contributing to the integrity and stability of the HAS composite. Therefore, higher SiO₂ contents in the HAS composite can enhance its mechanical stability when immersed in simulated body fluid (SBF). Our work demonstrated that HAS can highly improve HA material’s hardness and mechanical stability under immersion of SBF. The Vickers test showed that the 0.05 GPa hardness in 10% SiO₂ increased to 0.35 GPa hardness with the addition of 20% SiO₂. The crystal structures of HAS were analyzed using X-ray diffraction, and the morphology of the HAS composites was observed under electron microscopy. Full article

A stringent DNA probe to profile microRNA (miRNA) expression within a specific cell remains a key challenge in biology. To address this issue, an intracellular ATP-activated Y-DNA probe for accurate imaging of miRNA in living cells was designed. Y-DNA was based on the fabrication of tripartite function modules, which consisted of a folate (FA)-modified targeting module, an ATP aptamer-sealed driver, and a miRNA sensing module. The Y-DNA probe could be specifically activated by ATP after it efficiently internalized into FA-receptor-overexpressed cells based on caveolar-mediated endocytosis, leading to the activation of the miRNA sensing module. The activated Y-DNA probe allowed for the imaging of miRNA in living cells with high sensitivity. The design of the ATP-activated Y-DNA sensor opens the door for bioorthogonal miRNA imaging and promotes the development of various responsive DNA molecular probes with enhanced anti-interference ability for clinical diagnosis. Full article

The pursuit of operational advancements in direct formic acid fuel cells (DFAFCs) necessitates the development of high-performance platinum (Pt)-based catalysts for formic acid electrooxidation (FAOR). However, FAOR on Pt-based catalysts follows a dual pathway mechanism, in which the direct pathway is a preferred route due to its efficient dehydrogenation process. Conversely, the indirect pathway results in the generation of adsorbed CO species, a process that deleteriously poisons the active sites of the catalyst, with CO species only being oxidizable at higher potentials, causing a significant compromise in catalyst performance. Herein, we have successfully synthesized Pt-C₃N₄@CNT, where three Pt clusters are precisely dispersed in a triplet form within the C₃N₄ by virtue of the unique structure of C₃N₄. The mass activity for the direct pathway (0.44 V) delivered a current density of 1.91 A ${\mathrm{mg}}_{\mathrm{Pt}}^{-1}$, while the indirect pathway (0.86 V) had no obvious oxidation peak. The selectivity of Pt-C₃N₄@CNT catalysts for the direct pathway of FAOR was improved due to the special structure of C₃N₄, which facilitates the dispersion of Pt tri-atoms in the structure and the electronic interaction with Pt. In this study, we provide a new strategy for the development of highly active and selective catalysts for DFAFCs. Full article

The synthesis, crystal structure, and magnetic characterization are reported for three new structurally related iron(III) compounds (NHEt₃)[Fe₈O₅(OH)₅(O₂PPh₂)₁₀] (1), [Fe₁₂ Ca₄O₁₀(O₂CPh)₁₀(hmp)₄] (2), and [Fe₁₂La₄O₁₀(OH)₄(tbb)₂₄] (3), where hmpH is 2-(hydroxymethyl)pyridine and tbbH is 4-^tBu-benzoic acid. 1 was obtained from the reaction of Fe(NO₃)₃·9H₂O, diphenylphosphinic acid (Ph₂PO₂H), and NEt₃ in a 1:4:16 molar ratio in MeCN at 50 °C; 2 was obtained from the reaction of [Fe₃O(O₂CPh)₆(H₂O)₃](NO₃), Ca(NO₃)₂, and NEt₃ in a 1:1:4:2 ratio at 130 °C; and 3 was obtained from the reaction of Fe(NO₃)₃·9H₂O, La(NO₃)₃·6H₂O, 4-^tBu-benzoic acid, and NEt₃ in a 1:1:4:4 ratio in PhCN at 140 °C. The core of 1 consists of two {Fe₄(µ₃-O)₂}⁸⁺ butterfly units stacked on top of each other and bridged by O²⁻ and HO⁻ ions. The cores of 2 and 3 also contain two stacked butterfly units, plus four additional Fe atoms, two at each end, and four M atoms (M = Ca²⁺ (2); La³⁺ (3)) on the sides. Variable-temperature (T) and solid-state dc and ac magnetization (M) data collected in the 1.8–300 K range revealed that 1 has an S = 0 ground state, 2 has a χ_MT value at low T consistent with the central Fe₈ in a local S = 0 ground state and the two Fe³⁺ ions in each end-pair to be non-interacting, whereas 3 has a χ_MT value at low T consistent with these end-pairs each being ferromagnetically coupled with S = 5 ground states, plus intermolecular ferromagnetic interactions. These conclusions were reached from complementing the experimental studies with the calculation of the various Fe₂ pairwise J_ij exchange couplings by DFT computations and by using a magnetostructural correlation (MSC) for polynuclear Fe³⁺/O complexes, as well as a structural analysis of the intermolecular contacts in the crystal packing of 3. Full article

Sodium-ion batteries are a promising class of secondary power sources that can replace some of the lithium-ion, lead–acid, and other types of batteries in large-scale applications. One of the critical parameters for their potential use is high efficiency in a wide temperature range, particularly below 0 °C. This article analyzes the phase equilibria and electrochemical properties of sodium-ion battery electrolytes that are based on NaPF₆ solutions in solvent mixtures of ethylene carbonate and diethyl carbonate (EC:DEC), dimethyl carbonate (EC:DMC), and 1,2-dimethoxyethane (EC:DME). All studied electrolytes demonstrate a decrease in conductivity at lower temperatures and transition to a quasi-solid state resembling “wet snow” at certain temperatures: EC:DEC at −8 °C, EC:DMC at −13 °C, and EC:DME at −21 °C for 1 M NaPF₆ solutions. This phase transition affects their conductivity to a different degree. The impact is minimal in the case of EC:DEC, although it partially freezes at a higher temperature than other electrolytes. The EC:DMC-based electrolyte demonstrates the best efficiency at temperatures down to −20 °C. However, upon further cooling, 1 M NaPF₆ in EC:DEC retains a higher conductivity and lower resistivity in symmetrical Na₃V₂(PO₄)₃-based cells. The temperature range from −20 to −40 °C is characterized by the strongest deterioration in the electrochemical properties of electrolytes: for 1 M NaPF₆ in EC:DMC, the charge transfer resistance increased 36 times, and for 1 M NaPF₆ in EC:DME, 450 times. For 1 M NaPF₆ in EC:DEC, the growth of this parameter is much more modest and amounts to only 1.7 times. This allows us to consider the EC:DEC-based electrolyte as a promising basis for the further development of low-temperature sodium-ion batteries. Full article

Exploring affordable and efficient platform for innovative DNA computing is of great significance. Herein, by coupling 2-aminopurine (2AP) with DNA copper nanoparticles (CuNPs) as two universal opposite outputs, we, for the first time, fabricated a rapid and enzyme-free system for operating DNA contrary logic pairs (D-CLPs). Notably, derived from the rapid and concomitant response of both fluorescent probes, different D-CLPs can be achieved via a “double-results-half-efforts” manner in less than 20 min with low-cost. Moreover, based on the same system, the smart ratiometric analysis of target DNA was realized by employing the high reliability and accuracy of D-CLPs, providing a robust and typical paradigm for the exploration of smart nucleic acid sensors. Full article

Acetone-stabilized Au- and Sn-solvated metal atoms (SMAs) were used as to obtain Au- and AuSn-supported catalysts by simple impregnation on a reducible (TiO₂) and a non-reducible (Al₂O₃) metal-oxide. Their catalytic behaviour was investigated for cyclohexane oxidation to cyclohexanol and cyclohexanone (KA oil), and their morphological and physical properties were studied by TEM, STEM-EDS and ¹¹⁹Sn-Mössbauer spectroscopy. The catalytic results firstly demonstrated that the bare supports played a role on the reaction mechanism, slowing down the formation of the oxidation products and directing the radical formation. Hereinafter, the comparison between the monometallic Au-supported catalysts and the corresponding bimetallic Au-Sn catalysts allowed for the understanding of the potential role of Sn. ¹¹⁹Sn-Mössbauer characterization analyses showed the presence of SnO_2, which was recognized to favour the electrons’ exchange to form radicals, interacting with oxygen. Such interaction, in particular, could be favoured by the co-presence of Au. Moreover, the same metal composition on the catalyst surface resulted in a different catalytic behaviour depending on the support. Full article

Cells constantly experience mechanical forces during growth and development. Increasing evidence suggests that mechanical forces can regulate cellular processes such as proliferation, migration, and differentiation. Therefore, developing new tools to measure and manipulate cellular mechanical forces is essential. DNA nanostructures, due to their simple design and high programmability, have been utilized to create various mechanical sensors and have become a key tool for studying mechanical information in both cellular and non-cellular systems. In this article, we review the development of DNA-based mechanical sensors and their applications in measuring mechanical forces in the extracellular matrix and cell–cell interactions and summarize the latest advances in monitoring and manipulating cellular morphology and function. We hope that this review can provide insights for the development of new mechanical nanodevices. Full article