Aptamer-modified DNA tetrahedra-gated metal–organic framework nanoparticle carriers for enhanced chemotherapy or photodynamic therapy

UiO-66 metal–organic framework nanoparticles (NMOFs) gated by aptamer-functionalized DNA tetrahedra provide superior biomarker-responsive hybrid nano-carriers for biomedical applications. Hybrid nano-carriers consisting of ATP-aptamer or VEGF-aptamer functionalized tetrahedra-gated NMOFs are loaded with the chemotherapeutic drug, doxorubicin (DOX). In the presence of ATP or VEGF, both abundant in cancer cells, the tetrahedra-gated NMOFs are unlocked to release the drug. Enhanced and selective permeation of the DOX-loaded ATP/VEGF-responsive tetrahedra-gated NMOFs into MDA-MB-231 breast cancer cells as compared to the reference ATP/VEGF-responsive duplex-gated NMOFs or non-malignant MCF-10A epithelial breast cells is observed. This results in enhanced and selective cytotoxicity of the tetrahedra-gated DOX-loaded NMOFs toward the malignant cells. Additional nano-carriers, consisting of photosensitizer Zn(ii) protoporphyrin IX (Zn(ii)-PPIX)-loaded VEGF-responsive tetrahedra-gated NMOFs, are introduced. The VEGF-triggered unlocking of the NMOFs yields separated G-quadruplex-VEGF aptamer complexes conjugated to the tetrahedra, resulting in the release of loaded Zn(ii)-PPIX. Association of the released Zn(ii)-PPIX to the G-quadruplex structures generates highly fluorescent supramolecular Zn(ii)-PPIX/G-quadruplex VEGF aptamer-tetrahedra structures. The efficient and selective generation of the highly fluorescent Zn(ii)-PPIX/G-quadruplex VEGF aptamer-tetrahedra nanostructures in malignant cells allows the light-induced photosensitized generation of reactive oxygen species (ROS), leading to high-efficacy PDT treatment of the malignant cells.

UiO-66 metal–organic framework nanoparticles (NMOFs) gated by aptamer-functionalized DNA tetrahedra provide superior biomarker-responsive hybrid nano-carriers for biomedical applications.     

Kinetics of graft copolymerization of methyl methacrylate onto polychloroprene with tricaprylylmethylammonium chloride as a phase‐transfer catalyst

The phase‐transfer catalyzed graft copolymerization of methyl methacrylate onto polychloroprene was carried out using tricaprylylmethylammonium chloride as a phase‐transfer catalyst in a two‐phase system of an aqueous Na₂S₂O₈ solution and toluene at 55 °C under a nitrogen atmosphere. The initial rate of graft copolymerization was expressed as the combined terms of quaternary onium cation and peroxydisulfate anion in the aqueous phase rather than the fed concentrations of catalyst and Na₂S₂O₈. The observed initial rate of graft copolymerization was used to analyze the graft copolymerization mechanism with a cycle phase‐transfer initiation step in the heterogeneous liquid–liquid system. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3543–3549, 2000     

Bis­[(2,2‐di­methyl‐1,3‐propane­diamine‐κ2N,N′)(piperidine‐2‐car­boxylato‐κ2N,O)­platinum(II)] sulfate

The title compound, [Pt(C₆H₁₀NO₂)(C₅H₁₄N₂)]₂(SO₄), crystallizes with two cations in the asymmetric unit. The two complex cations, which have a square‐planar Pt^II coordination, are chemically identical but differ slightly in the conformations of their amine groups. A neutral complex, viz. (2,2‐di­methyl‐1,3‐propane­di­amine‐κ²N,N′)bis(2‐piperidine­carb­oxyl­ato‐κN)platinum(II), is shown to form in solution and to change rapidly into the title compound.     

Pore formation in in situ processed MgB2 superconductors

MgB₂ bulks were prepared by an in situ process which utilizes the reaction between boron and magnesium powder. The reaction time was fixed at 0.5 h and the temperature was changed from 600 °C to 1000 °C. The density decrease due to pore formation and mass (mainly magnesium) loss during the formation reaction of MgB₂ was observed in all samples. In addition to the pore formation, a pellet expansion which can be explained by the outgrowth of MgB₂ grains was also observed. Two different mechanisms were adopted to explain the pore formation; Kirkendall pores formed at a temperature below the melting point (m.p.) of magnesium by a difference in the diffusivity between magnesium and boron, and the pores formed at a temperature above the m.p. by melting of magnesium and a capillary movement. The density, T_c and J_c results suggest that the current carrying capacity can be improved by a careful control of the process parameters regarding a pore evolution.     

Domination number in graphs with minimum degree two

A set D of vertices of a graph G = （V, E） is called a dominating set if every vertex of V not in D is adjacent to a vertex of D. In 1996, Reed proved that every graph of order n with minimum degree at least 3 has a dominating set of cardinality at most 3n/8. In this paper we generalize Reed＇s result. We show that every graph G of order n with minimum degree at least 2 has a dominating set of cardinality at most （3n ＋IV21）/8, where V2 denotes the set of vertices of degree 2 in G. As an application of the above result, we show that for k ≥ 1, the k-restricted domination number rk （G, γ） ≤ （3n＋5k）/8 for all graphs of order n with minimum degree at least 3.     

Anti-biofouling properties of comblike block copolymers with amphiphilic side chains

Surfaces of novel block copolymers with amphiphilic side chains were studied for their ability to influence the adhesion of marine organisms. The surface-active polymer, obtained by grafting fluorinated molecules with hydrophobic and hydrophilic blocks to a block copolymer precursor, showed interesting bioadhesion properties. Two different algal species, one of which adhered strongly to hydrophobic surfaces, and the other, to hydrophilic surfaces, showed notably weak adhesion to the amphiphilic surfaces. Both organisms are known to secrete adhesive macromolecules, with apparently different wetting characteristics, to attach to underwater surfaces. The ability of the amphiphilic surface to undergo an environment-dependent transformation in surface chemistry when in contact with the extracellular polymeric substances is a possible reason for its antifouling nature. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) was used, in a new approach based on angle-resolved X-ray photoelectron spectroscopy (XPS), to determine the variation in chemical composition within the top few nanometers of the surface and also to study the surface segregation of the amphiphilic block. A mathematical model to extract depth-profile information from the normalized NEXAFS partial electron yield is developed.     

Physical and electrical properties of band-engineered SiO2/(TiO2) x (SiO2)1−x stacks for nonvolatile memory applications

In our study, the physical properties of (TiO₂) _x (SiO₂)_1?x , including band-gap, band-offset, and thermal stability and the electrical properties of band-engineered SiO₂/(TiO₂) _x (SiO₂)_1?x tunnel barrier stacks, including the tunneling current and charge-trapping characteristics for applications to nonvolatile memory devices were investigated. It was observed that the band-gap and band-offset of (TiO₂) _x (SiO₂)_1?x can be controlled by adjustment in the composition of the (TiO₂) _x (SiO₂)_1?x films. Ti-silicate film with TiO₂:SiO₂ cycle ratio of 1:5 was maintained in an amorphous phase, even after annealing at 950 °C. The tunneling current of the band-engineered SiO₂/(TiO₂) _x (SiO₂)_1?x stacked tunnel barrier was larger than that of a single SiO₂ barrier under a higher external bias, while the tunneling current of a SiO₂/(TiO₂) _x (SiO₂)_1?x stacked tunnel barrier under a lower external bias was smaller. Charge-trapping tests showed that the voltage shift for SiO₂/(TiO₂) _x (SiO₂)_1?x is slightly larger than that for single SiO₂.