pH-Reversible Cationic RNase A Conjugates for Enhanced Cellular Delivery and Tumor Cell Killing

Intracellularly-acting therapeutic proteins are considered promising alternatives for the treatment of various diseases. Major limitations of their application are low efficiency of intracellular delivery and possible reduction of protein activity during derivatization. Herein, we report pH-sensitive covalent modification of proteins with a histidine-rich cationic oligomer (689) for efficient intracellular transduction and traceless release of functional proteins. Enhanced Green fluorescent protein (EGFP), as model for the visualization of protein transduction, and RNase A, as therapeutic protein with antitumoral effect, were modified with the pH-sensitive bifunctional AzMMMan linker and varying amounts of cationic oligomer. The modification degree showed impact on the internalization and cellular distribution of EGFP as well as the biological effect of RNase A conjugates, which mediated considerable toxicity against cancer cells at optimal ratio. The presented conjugates demonstrate their qualification to achieve efficient intracellular delivery and controlled release without protein inactivation and potential prospective applications in protein-based therapies

Ultrathin Dendritic Pt₃Cu Triangular Pyramid Caps with Enhanced Electrocatalytic Activity

Here we report on the synthesis of novel dendritic Pt₃Cu triangular pyramid caps via a solvothermal coreduction method. These caps had three-dimensional caved structures with ultrathin branches, as evidenced by high-resolution transmission electron microscopy (HRTEM) and HAADF-STEM characterization. Tuning the reduction kinetics of two metal precursors by an iodide ion was believed to be the key for the formation of an alloyed nanostructure. Electro-oxidation of methanol and formic acid showed dramatically improved electrocatalytic activities and poison-tolerance for these nanoalloys as compared to commercial Pt/C catalysts, which was attributed to their unique open porous structure with interconnected network, ultrahigh surface areas, as well as synergetic effect of the two metallic components

A Selective Blocking Method To Control the Overgrowth of Pt on Au Nanorods

A method for the preparation of smooth deposits of Pt on Au nanorods is described, involving sequential deposition steps with selective blocking of surface sites that reduces Pt-on-Pt deposition. The Au–Pt nanorods prepared by this method have higher long-term stability than those prepared by standard Pt deposition. Electrochemical data show that the resulting structure has more extended regions of Pt surface and enhanced activity toward the carbon monoxide oxidation and oxygen reduction reactions

Strain Engineering to Enhance the Electrooxidation Performance of Atomic-Layer Pt on Intermetallic Pt₃Ga

Strain engineering has been a powerful strategy to finely tune the catalytic properties of materials. We report a tensile-strained two-to-three atomic-layer Pt on intermetallic Pt₃Ga (AL-Pt/Pt₃Ga) as an active electrocatalyst for the methanol oxidation reaction (MOR). Atomic-resolution high-angle annular dark-field scanning transmission electron microscopy characterization showed that the AL-Pt possessed a 3.2% tensile strain along the [001] direction while having a negligible strain along the [100]/[010] direction. For MOR, this tensile-strained AL-Pt electrocatalyst showed obviously higher specific activity (7.195 mA cm^–2) and mass activity (1.094 mA/μg_Pt) than those of its unstrained counterpart and commercial Pt/C catalysts. Density functional theory calculations demonstrated that the tensile-strained surface was more energetically favorable for MOR than the unstrained one, and the stronger binding of OH* on stretched AL-Pt enabled the easier removal of CO*

Bimetallic Ru–Co Clusters Derived from a Confined Alloying Process within Zeolite–Imidazolate Frameworks for Efficient NH₃ Decomposition and Synthesis

Herein, a series of carbocatalysts containing Ru-based clusters have been prepared by the assistance of zeolite–imidazolate frameworks (ZIFs). The introduction of Ru is based on the adsorption of well-defined Ru₃(CO)₁₂ within the cavity of ZIFs following decomposition at 900 °C. Moreover, without breaking the skeleton and porosity of ZIFs, the as-generated Ru species would bond with the Co nodes in situ to form bimetallic Ru–Co clusters if the Co-bearing metal–organic frameworks were utilized as the host. Within the confined space of ZIFs, the assembly of Ru and Co could be rationally designed, and their structures could be sophisticatedly controlled at the atomic scale. Among these Ru-based compositions, the Ru–Co clusters@N–C exhibited remarkable catalytic activity for the NH₃ decomposition to H₂ and NH₃ synthesis versus Ru–Co NPs@N–C, Ru clusters@N–C, and Ru NPs@N–C. This study may open up a new routine to synthesize metallic clusters or other subnano structures by the confinement of ZIFs

Ordered Porous Pd Octahedra Covered with Monolayer Ru Atoms

Monolayer Ru atoms covered highly ordered porous Pd octahedra have been synthesized via the underpotential deposition and thermodynamic control. Shape evolution from concave nanocube to octahedron with six hollow cavities was observed. Using aberration-corrected high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, we provide quantitative evidence to prove that only a monolayer of Ru atoms was deposited on the surface of porous Pd octahedra. The as-prepared monolayer Ru atoms covered Pd nanostructures exhibited excellent catalytic property in terms of semihydrogenation of alkynes

Isolated Single-Atom Pd Sites in Intermetallic Nanostructures: High Catalytic Selectivity for Semihydrogenation of Alkynes

Improving the catalytic selectivity of Pd catalysts is of key importance for various industrial processes and remains a challenge so far. Given the unique properties of single-atom catalysts, isolating contiguous Pd atoms into a single-Pd site with another metal to form intermetallic structures is an effective way to endow Pd with high catalytic selectivity and to stabilize the single site with the intermetallic structures. Based on density functional theory modeling, we demonstrate that the (110) surface of <i>Pm</i>3̅<i>m</i> PdIn with single-atom Pd sites shows high selectivity for semihydrogenation of acetylene, whereas the (111) surface of <i>P</i>4/<i>mmm</i> Pd₃In with Pd trimer sites shows low selectivity. This idea has been further validated by experimental results that intermetallic PdIn nanocrystals mainly exposing the (110) surface exhibit much higher selectivity for acetylene hydrogenation than Pd₃In nanocrystals mainly exposing the (111) surface (92% vs 21% ethylene selectivity at 90 °C). This work provides insight for rational design of bimetallic metal catalysts with specific catalytic properties

Atomically Dispersed Ru on Ultrathin Pd Nanoribbons

We report a one-pot synthesis of atomically dispersed Ru on ultrathin Pd nanoribbons. By using synchrotron radiation photoemission spectroscopy (SRPES) and extended X-ray absorption fine structure (EXAFS) measurements in combination with aberration corrected high-resolution transmission electron microscopy (HRTEM), we show that atomically dispersed Ru with content up to 5.9% was on the surface of the ultrathin nanoribbon. Furthermore, the ultrathin Pd/Ru nanoribbons could remarkably prohibit the hydrogenolysis in chemoselective hydrogenation of CC bonds, leading to an excellent catalytic selectivity compared with commercial Pd/C and Ru/C

Uncoordinated Amine Groups of Metal–Organic Frameworks to Anchor Single Ru Sites as Chemoselective Catalysts toward the Hydrogenation of Quinoline

Here we report a precise control of isolated single ruthenium site supported on nitrogen-doped porous carbon (Ru SAs/N–C) through a coordination-assisted strategy. This synthesis is based on the utilization of strong coordination between Ru³⁺ and the free amine groups (−NH₂) at the skeleton of a metal–organic framework, which plays a critical role to access the atomically isolated dispersion of Ru sites. Without the assistance of the amino groups, the Ru precursor is prone to aggregation during the pyrolysis process, resulting in the formation of Ru clusters. The atomic dispersion of Ru on N-doped carbon can be verified by the spherical aberration correction electron microscopy and X-ray absorption fine structure measurements. Most importantly, this single Ru sites with single-mind N coordination can serve as a semihomogeneous catalyst to catalyze effectively chemoselective hydrogenation of functionalized quinolones