Latest ArticlesMelanoma is one of the most malignant skin tumors, whose high invasion is generally associated with BRAF gene mutation. Although new chemotherapeutic drugs, such as vemurafenib, have been developed to inhibit the growth of melanoma, these drugs are usually administered intravenously or orally, resulting in toxic side effects on major tissues and organs. Tetrahedral framework nucleic acids (tFNAs) are a novel type of DNA nanostructures with excellent biocompatibility and versatility which have been proven to penetrate through skin barrier with ease. In this study, we prepared tFNAs with vemurafenib and connected DNA aptamer AS1411 at the apex of tFNAs (AS1411-tFNAs/vemurafenib). On one hand, AS1411-tFNAs/vemurafenib could kill melanoma cells by blocking the mutated BRAF gene in vitro. Compared with free vemurafenib, AS1411-tFNAs/vemurafenib had no obvious toxicity to normal cells. On the other hand, AS1411-tFNAs could transfer vemurafenib to cross through the skin barrier and permeate into tumor tissues. In vivo, transdermal delivery of AS1411-tFNAs/vemurafenib could inhibit the growth of human A375 melanoma, whose inhibiting effect was stronger than intravenous administration of vemurafenib. These results demonstrated the application prospects of tFNAs combined with chemotherapeutic drugs in skin tumors.
Using gas-liquid segmented micromixers to prepare nanoparticles that have a homogeneous particle size, controllable shape, and monodispersity advantages. Although nanoparticle aggregation within a microfluid has been shown to be affected by the shear effect, the shear effect triggering conditions in gas-liquid two-phase flow is unclear and the aggregation behavior of nanoparticles under the shear effect is difficult to predict, resulting in uncontrollable physical and chemical properties of nanoparticle aggregates. In this study, a numerical simulation of nanoparticle aggregation in gas-liquid two-phase flow under the shear effect is performed using the CFD-DEM method. Then, the effects of total flow rate, gas-liquid two-phase flow ratio, and particle volume fraction on particle aggregation were analyzed to achieve control of particle aggregation shape and size. Meanwhile, the triggering mechanism of the shear effect and the mechanism of the shear effect on the aggregation of nanoparticles were clarified. The results show that increasing the total flow rate or decreasing the gas-liquid two-phase flow rate ratio can induce the shear effect, which reduces the particle aggregation size and makes the morphology tend to be spherical. Moreover, increasing the particle volume fraction, and total flow rate or decreasing the gas-liquid two-phase flow rate ratio also increases the number of particle collisions and induce interparticle adhesion. Hence, particle adhesion and the shear effect compete with each other and together affect particle aggregation.
Unspecific peroxygenases (UPOs, EC 1.11.2.1) is a kind of thioheme enzyme capable of catalyzing various oxidations of inert C–H bonds using H2O2 as an oxygen donor without cofactors. However, the enhancement of the H2O2 tolerance of UPOs is always challenging. In this study, the A161C mutant of rDcaUPO, which originates from Daldinia caldariorum, was found to be highly H2O2-resistant. Compared with the wild type, the mutant rDcaUPO-A161C showed a 10-h prolonged half-life and a 64% improved enzyme activity when incubated in 10 mmol/L H2O2. The crystal structure analysis at 1.47 Å showed that rDcaUPO-A161C exhibited 10 α-helixes (cyan) and a series of ordered rings, forming a single asymmetric spherical structure. The two conserved domains near heme formed an active site with the catalytic PCP and EHD regions (Glu86, His87, Asp88 residues). The H2O2 tolerance of rDcaUPO-A161C was preliminarily explored by comparing its structure with the wild type. Notably, rDcaUPO-A161C showed significantly higher catalytic efficiency than the wild type for the production of hydroxyl fatty acids. This study is anticipated to provide an insight into the structure-function relationship and expand potential applications of UPOs.
Waste polyolefin plastics, accounting for 50% of all plastic waste, represent a tremendously unexploited carbon source. Efficiently upcycling polyolefin waste into value-added carbon materials for waste water treatment avoiding using noble metals is challenging but economically and environmentally sustainable. In this work, MAX-Ti3AlC2 supported Fe selectively catalyzes polyolefin into few-layered graphene in 5 min under microwave treatment. Graphene and MAX supported Fe (Fe@MLC) can completely (99.9%) degrade chloramphenicol (CAP) within 60 min, retain robust after 10 cycles and work efficiently at a wide pH range (3.87–13.03), avoiding the usage of noble metal. Moreover, the electrochemical active surface area (ECSA) of Fe@MLC is 2.7 times higher than that of commercial Pt/C. This work provides a cheap and efficient catalyst that promotes deconstruction of plastic wastes and indirectly degrades antibiotics thereby realizes the treatment of waste water with waste plastic.
Light-driven nitrogen fixation to produce ammonia is a green and economical technology of nitrogen reduction but is still quite challenging, especially in an air atmosphere without any sacrificial reagents. Herein, we demonstrate efficient photocatalytic nitrogen fixation using water and air directly by loading lanthanide–transition metal (4f–3d) cluster NdCo3 on two-dimensional P-doped graphitic carbon nitrides (PCN) material surface. Benefiting from the increase in the number of nitrogen vacancies (NVs) and highly matched band gap structure and excellent hole trapping ability of clusters, the NdCo3/PCN photocatalyst exhibits efficient nitrogen reduction activity with 371 (in air) and 825 µmol h−1 g−1 (in pure nitrogen) without any sacrificial reagents. The introduction of potassium sulfate inhibits hydrogen production and promotes nitrogen reduction activation. This work suggests that anchoring precisely structured clusters on 2D materials may enhance photocatalytic nitrogen reduction under normal temperature and pressure.
Developing accurate and sensitive DNA methyltransferase (MTase) analysis methods is essential for early clinical diagnosis and development of antimicrobial drug targets. In this work, by coupling WO3−x dots-encapsulated metal-organic frameworks (MOFs) as co-reactants and terminal deoxynucleotidyl transferase (TdT)-mediated template-free branched polymerization, a dual signal-amplified electrochemiluminescent (ECL) biosensor was constructed to detect DNA adenine methylation (Dam) MTase. The employment of WO3−x dots-encapsulated MOFs (i.e., NH2-UIO66@WO3−x) was not only beneficial for biomolecule conjugation because of the abundant amino groups but also led to a 7-fold enhanced ECL response due to the increased loading of WO3−x. Moreover, TdT-mediated template-free branched polymerization promoted the capture of ECL emitters on the electrode surface, achieving 20-fold enhanced signal amplification. The presented ECL biosensor demonstrated a low detection limit of 2.4 × 10−4 U/mL, and displayed high reliability for the detection of Dam MTase in both spiked human serum and E. coli cell samples, and for the screening of potential inhibitors. This study opens a new avenue for designing a dual signal amplification-based ECL bioassay for Dam MTase and screening inhibitors in the fields of clinical diagnosis and drug development.
Electrochemical nitrogen reduction reaction (ENRR) provides a promising strategy to achieve sustainable synthesis of ammonia. However, despite great efforts devoted to this research field, the problems such as low energy efficiency and weak selectivity still impede its practical implementation. Most of the research to date has been concentrated on creating sophisticated electrocatalysts, and adequate knowledge of electrolytes is still lacking. Herein, the recent progress in electrolytes for ENRR, including alkaline, neutral, acidic, water-in-salt, organic, ionic liquid, and mixed water-organic electrolytes, is thoroughly reviewed to obtain an in-depth understanding of their effects on electrocatalytic performance. Recently developed representative electrocatalysts in various types of electrolytes are also introduced, and future research priorities of different electrolytes are proposed to develop new and efficient ENRR systems.
One of the largest subfamilies within the famous Daphniphyllum alkaloid family is made up of the yuzurimine-type (or macrodaphniphyllamine-type) alkaloids. Their complex aza-polycyclic caged structures, several contiguous stereogenic centers, and vicinal all-carbon quaternary centers make these alkaloids formidable challenge for synthetic chemists. Recently, synthesis of these alkaloids has received extensive attention from our community. Herein, we wish to report the total synthesis of C14–epi-deoxycalyciphylline H, a putative member of yuzurimine-type alkaloid subfamily. Key transformations employed in our approach include an intramolecular Prins reaction and a Pd-catalyzed enyne cycloisomerization. In addition, synthesis of a daphnezomine L-type alkaloid, paxdaphnidine A, was also studied.
Supported Pd based catalysts are considered as the efficient candidates for low-carbon alkane oxidation for their outstanding capability to break C-H bond. Whereas, the irreversible deactivation of Pd based catalysts was still frequently observed. Herein, we reinforced the extruded Pd nanoparticles with quantitive Pt to assemble the evenly distributed PdPt nanoalloy onto ferrite perovskite (PdPt-LCF) matrix with strengthened robustness of metal/oxide support interface. We further co-achieved the enhanced performance, anti-overoxidation as well as resistance of vapor-poisoning in durability measurement. The operando X-ray photoelectron spectroscopy (O-XPS) combined with various morphology characterizations confirms that the accumulation of surface deep-oxidation species of Pd4+ is the culprit for fast activity loss in exsolved Pd system, especially at high temperature of 400 ℃. Conversely, it could be completely suppressed by in-situ alloying Pd with equal amount of Pt, which helps maintain the metastable Pd2+/Pd shell and metallic solid-solution core structure. The density function theory (DFT) calculations further buttress that the dissociation of CH was facilitated on alloy/perovskite interface which is, on the contrary, resistant toward O–H bond cleavage, as compared to Pd/perovskite. Our work suggests that the modification of exsolved metal/oxide catalytic interface could further enrich the toolkit of heterogeneous catalyst design.
Inverse vulcanized polymers (IVPs) that generated from elemental sulfur and smaller amounts of alkenes have found broad promising applications such as cathode materials for Li-S batteries, dynamic and repairable materials, optics applications, and metal sorption. However, their exploration in organic synthesis is still unprecedented. Here we first report the application of inverse vulcanized polymers in catalysis for organic transformations. A biomass-derived inverse vulcanized polymer (IVP-EAE) is found to be capable of catalyzing cross-coupling reactions in a transition-metal-free fashion under visible light. This method allows the direct CH functionalization of pyrroles and N-arylacrylamides with (hetero)aryl halides, respectively, leading to the formation of two sets of structurally important scaffolds including pyrrole-containing biaryls and 3,3′-disubstituted oxindoles with high selectivity. We anticipate this study will not only unveil the new potential of IVPs, but also offer a distinct type of catalysts for organic transformations.
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