Active Coordinatively Unsaturated Manganese Monoxide-Containing Mesoporous Carbon Catalyst in Wet Peroxide Oxidation

A novel heterogeneous coordinatively unsaturated manganese monoxide-containing mesoporous carbon catalyst (C-MnO) is reported here. The catalysts exhibit high catalytic activity in wet oxidation of phenol (almost complete mineralization with an initial concentration of 50 mg/L at atmospheric pressure) and stability (reused 20 times without obvious activity loss or metal leaching), and they take more advantages than most developed heterogeneous Fenton catalysts. The one-pot surfactant self-assembly approach is used for the synthesis of the mesoporous C-MnO catalysts. Small-angle X-ray diffraction (XRD), N₂ sorption, and transmission electron microscopy results reveal that the catalysts have the ordered two-dimensional hexagonal mesostructure, large surface areas (530–552 m²/g), uniform pore sizes (3.3–5.4 nm), and large pore volumes (0.34–0.44 cm³/g); MnO nanoparticles (<12 nm) are well dispersed inside carbon mesopore systems with high crystallinity. The wide-angle XRD pattern reveals the presence of cubic rock salt structure MnO, and the Mn K-edge X-ray absorption fine structure spectra confirms the low chemical valence and the coordination unsaturated state of Mn. The high activity and stability of C-MnO catalysts might be related to the mesostructure, carbon pore wall, and, more importantly, the confined undercoordinative MnO nanoparticles

Effect of Microelectrode Structure on Electrocatalysis at Nucleic Acid-Modified Sensors

The electrochemical detection of nucleic acids using an electrocatalytic reporter system and nanostructured microelectrodes is a powerful approach to ultrasensitive biosensing. In this report we systematically study for the first time the behavior of an electrocatalytic reporter system at nucleic acid-modified electrodes with varying structures and sizes. [Ru­(NH₃)₆]³⁺ is used as a primary electron acceptor that is electrostatically attracted to nucleic acid-modified electrodes, and [Fe­(CN)₆]^3– is introduced into the redox system as a secondary electron acceptor to regenerate Ru³⁺ after electrochemical reduction. We found that the electrode structure has strong impact on mass transport and electron-transfer kinetics, with structures of specific dimensions yielding much higher electrochemical signals and catalytic efficiencies. The electrocatalytic signals obtained when gold sensors were electrodeposited in both circular and linear apertures were studied, and the smallest structures plated in linear apertures were found to exhibit the best performance with high current densities and turnover rates. This study provides important information for optimal assay performance and insights for the future design and fabrication of high performance biomolecular assays

Enantioselective Construction of Cyclopenta[<i>b</i>]indole Scaffolds via the Catalytic Asymmetric [3 + 2] Cycloaddition of 2‑Indolylmethanols with <i>p</i>‑Hydroxystyrenes

The catalytic asymmetric [3 + 2] cycloaddition of 2-indolylmethanols to <i>p</i>-hydroxystyrenes was established in the presence of a chiral phosphoramide, and this reaction provided chiral cyclopenta­[<i>b</i>]­indole scaffolds in generally high yields and with good enantioselectivities (up to 98% yield, 99:1 er). The control experiments demonstrated that the dual hydrogen-bonding activation mode of the chiral catalyst toward the two substrates played an important role in the reaction. In addition, the large-scale reaction indicated that this catalytic asymmetric [3 + 2] cycloaddition could be scaled up for the synthesis of chiral cyclopenta­[<i>b</i>]­indole derivatives

Activation of Aryl Chlorides in Water under Phase-Transfer Agent-Free and Ligand-Free Suzuki Coupling by Heterogeneous Palladium Supported on Hybrid Mesoporous Carbon

In this study, heterogeneous palladium catalysts supported on ordered mesoporous cobalt oxide–carbon nanocomposites were applied to the water-mediated Suzuki coupling reaction of chlorobenzene and phenylboronic acid and exhibited a high yield of biphenyl (49%) under mild reaction conditions free of phase-transfer agents and ligands. Product yields in the reaction of aryl chlorides containing electron-withdrawing groups attached to their benzene ring can reach approximately 90%. Thiol-functionalized mesoporous silica, which can trap soluble Pd species, was used to confirm the negligible leaching in solution and therefore heterogeneous reaction. This heterogeneous catalyst is stable, showing unobvious activity loss after 10 catalytic runs. Characterization by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption fine structure analysis, and N₂ sorption techniques revealed intercalated CoO nanoparticles inside a carbon matrix with uniform mesopore sizes (∼3 nm), high surface area (∼504 m²/g), and large pore volumes (∼0.38 cm³/g). Additionally, very small Pd clusters consisting of approximately three atoms and Pd–O bonds formed on the interface between CoO and Pd nanoparticles. The unsaturated coordinative Pd may be responsible for the activation of chlorobenzene in the absence of any additives or ligands. Uniform mesopores and the hydrophobic nature of the carbon support may also facilitate the mass transfer of the reactant molecules and enrichment inside pores. For comparison, the catalytic activities of Pd catalysts supported on pristine mesoporous carbon and carbon embedded with nickel oxide nanoparticles were also tested

Enhancing Doxorubicin Delivery toward Tumor by Hydroxyethyl Starch‑<i>g</i>‑Polylactide Partner Nanocarriers

Doxorubicin (DOX), a kind of wide-spectrum chemotherapeutic drug, can cause severe side effects in clinical use. To enhance its antitumor efficacy while reducing the side effects, two kinds of nanoparticles with desirable compositions and properties were assembled using optimally synthesized hydroxyethyl starch-grafted-polylactide (HES-<i>g</i>-PLA) copolymers and utilized as partner nanocarriers. The large empty HES-<i>g</i>-PLA nanoparticles (mean size, <i>ca.</i> 700 nm), at an optimized dose of 400 mg/kg, were used to block up the reticuloendothelial system in tumor-bearing mice 1.5 h in advance, and the small DOX-loaded HES-<i>g</i>-PLA nanoparticles (mean size, <i>ca.</i> 130 nm) were subsequently applied to the mice. When these partner nanocarriers were administered in this sequential mode, the released DOX had a significantly prolonged plasma half-life time and much slower clearance rate as well as a largely enhanced intratumoral accumulation as compared to free DOX. <i>In vivo</i> antitumor studies demonstrated that the DOX-loaded HES-<i>g</i>-PLA nanoparticles working together with their partner exhibited remarkably enhanced antitumor efficacy in comparison to free DOX. In addition, these HES-<i>g</i>-PLA partner nanocarriers showed negligible damage to the normal organs of the treated mice. Considering safe and efficient antitumor performance of DOX-loaded HES-<i>g</i>-PLA nanoparticles, the newly developed partner nanocarriers in combination with their administration mode have promising potential in clinical cancer chemotherapy

α‑Amylase- and Redox-Responsive Nanoparticles for Tumor-Targeted Drug Delivery

Paclitaxel (PTX) is an effective antineoplastic agent and shows potent antitumor activity against a wide spectrum of cancers. Yet, the wide clinical use of PTX is limited by its poor aqueous solubility and the side effects associated with its current therapeutic formulation. To tackle these obstacles, we report, for the first time, α-amylase- and redox-responsive nanoparticles based on hydroxyethyl starch (HES) for the tumor-targeted delivery of PTX. PTX is conjugated onto HES by a redox-sensitive disulfide bond to form HES–SS-PTX, which was confirmed by results from NMR, high-performance liquid chromatography-mass spectrometry, and Fourier transform infrared spectrometry. The HES–SS-PTX conjugates assemble into stable and monodispersed nanoparticles (NPs), as characterized with Dynamic light scattering, transmission electron microscopy, and atomic force microscopy. In blood, α-amylase will degrade the HES shell and thus decrease the size of the HES–SS-PTX NPs, facilitating NP extravasation and penetration into the tumor. A pharmacokinetic study demonstrated that the HES–SS-PTX NPs have a longer half-life than that of the commercial PTX formulation (Taxol). As a consequence, HES–SS-PTX NPs accumulate more in the tumor compared with the extent of Taxol, as shown in an in vivo imaging study. Under reductive conditions, the HES–SS-PTX NPs could disassemble quickly as evidenced by their triggered collapse, burst drug release, and enhanced cytotoxicity against 4T1 tumor cells in the presence of a reducing agent. Collectively, the HES–SS-PTX NPs show improved in vivo antitumor efficacy (63.6 vs 52.4%) and reduced toxicity in 4T1 tumor-bearing mice compared with those of Taxol. These results highlight the advantages of HES-based α-amylase- and redox-responsive NPs, showing their great clinical translation potential for cancer chemotherapy

Redox-Sensitive Hydroxyethyl Starch–Doxorubicin Conjugate for Tumor Targeted Drug Delivery

Doxorubicin (DOX) is one of the most potent anticancer agents in cancer chemotherapy, but the clinical use of DOX is restricted by its severe side effects caused by nonspecific delivery. To alleviate the side effects and improve the antitumor efficacy of DOX, a novel redox-sensitive hydroxyethyl starch–doxorubicin conjugate, HES-SS-DOX, with diameter of 19.9 ± 0.4 nm was successfully prepared for tumor targeted drug delivery and GSH-mediated intracellular drug release. HES-SS-DOX was relatively stable under extracellular GSH level (∼2 μM) but released DOX quickly under intracellular GSH level (2–10 mM). In vitro cell study confirmed the GSH-mediated cytotoxicity of HES-SS-DOX. HES-SS-DOX exhibited prolonged plasma half-life time and enhanced tumor accumulation in comparison to free DOX. As a consequence, HES-SS-DOX exhibited better antitumor efficacy and reduced toxicity as compared to free DOX in the in vivo antitumor activity study. The redox-sensitive HES-SS-DOX was proved to be a promising prodrug of DOX, with clinical potentials, to achieve tumor targeted drug delivery and timely intracellular drug release for effective and safe cancer chemotherapy

Point-of-Care Diagnosis on Selenium Nutrition Based on Time-Resolved Fluorometric Glycoaffinity Chromatography

Given the lack of timely evaluation of the well-received selenium fortification, a neat lateral-flow chromatographic solution was constructed here by using the recently identified urinary selenosugar (Sel) as a strongly indicative marker. As there are no ready-made receptors for this synthetic standard, phenylboronic acid (PBA) esterification and Dolichos biflorus agglutinin (DBA) affinity joined up to pinch and pin down the analyte into a sandwich-type glycol complex. Pilot lectin screening on homemade glycan microarrays verified such a new pairing between dual recognizers as PBA-Sel-DBA with a firm monosaccharide-binding constant. To quell the sample autofluorescence, europium nanoparticles with efficient long-life afterglow were employed as conjugating probes under 1 μs excitation. After systematic process optimizations, the prepared Sel-dipstick achieved swift and sensitive fluorometry over the physiological level of the target from 0.1 to 10 μM with a detection limit down to 0.06 μM. Further efforts were made to eliminate matrix effects from both temperature and pH via an approximate formula. Upon completion, the test strips managed to quantify the presence of Sel in not just imitated but real human urine, with comparable results to those in the references. As far as we know, this would be the first in-house prototype for user-friendly and facile diagnosis of Se nutrition with fair accuracy as well as selectivity. Future endeavors will be invested to model a more traceable Se-supplementary plan based on the rhythmic feedback of Sel excretion

Aggregation-Free Gold Nanoparticles in Ordered Mesoporous Carbons: Toward Highly Active and Stable Heterogeneous Catalysts

A coordination-assisted synthetic approach is reported here for the synthesis of highly active and stable gold nanoparticle catalysts in ordered mesoporous carbon materials using triblock copolymer F127 as a structure-directing agent, thiol-containing silane as a coordination agent, HAuCl₄ as a gold source, and phenolic resin as a carbon source. Upon carbonization, the gold precursor becomes reduced to form monodispersed Au nanoparticles of ca. 9.0 nm, which are entrapped or confined by the “rigid” mesoporous carbonaceous framework. Nanoparticle aggregation is inhibited even at a high temperature of 600 °C. After removal of the silica component, the materials possess the ordered mesostructure, high surface area (∼1800 m²/g), large pore volume (∼1.19 cm³/g), and uniform bimodal mesopore size (<2.0 and 4.0 nm). The monodispersed gold nanoparticles are highly exposed because of the interpenetrated bimodal pores in the carbon framework, which exhibit excellent catalytic performance. A completely selective conversion of benzyl alcohol in water to benzoic acid can be achieved at 90 °C and 1 MPa oxygen. Benzyl alcohol can also be quantitatively converted to benzoic acid at 60 °C even under an atmospheric pressure, showing great advantages in green chemistry. The catalysts are stable, poison resistant, and reusable with little activity loss due to metal leaching. The silane coupling agent played several functions in this approach: (1) coordinating with gold species by the thiol group to benefit formation of monodispersed Au nanoparticles; (2) reacting with phenolic resins by silanol groups to form relatively “rigid” composite framework; (3) pore-forming agent to generate secondary pores in carbon pore walls, which lead to higher surface area, larger pore volumes, and higher accessibility to to the gold nanoparticles. Complete removal of the silica component proves to have little effect on the catalytic performance of entrapped Au nanoparticles

DNA Framework-Engineered Assembly of Cyanine Dyes for Structural Identification of Nucleic Acids

DNA nanostructures serve as precise templates for organizing organic dyes, enabling the creation of programmable artificial photonic systems with efficient light-harvesting and energy transfer capabilities. However, regulating the organization of organic dyes on DNA frameworks remains a great challenge. In this study, we investigated the factors influencing the self-assembly behavior of cyanine dye K21 on DNA frameworks. We observed that K21 exhibited diverse assembly modes, including monomers, H-aggregates, J-aggregates, and excimers, when combined with DNA frameworks. By manipulating conditions such as the ion concentration, dye concentration, and structure of DNA frameworks, we successfully achieved precise control over the assembly modes of K21. Leveraging K21’s microenvironment-sensitive fluorescence properties on DNA nanostructures, we successfully discriminated between the chirality and topology structures of physiologically relevant G-quadruplexes. This study provides valuable insights into the factors influencing the dynamic assembly behavior of organic dyes on DNA framework nanostructures, offering new perspectives for constructing functional supramolecular aggregates and identifying DNA secondary structures