Intracellular drug delivery of layered double hydroxide nanoparticles

Intracellular drug delivery of layered double hydroxide (LDH) nanocarriers have been examined in human osteosarcoma Saos-2 cell culture line by both electron and confocal microscopies. For transmission electron microsopic (TEM) study, LDHs and anticancer drug, methotrexate (MTX) loaded LDHs were synthesized and the particle size was controlled. From the scanning electron microscopic (SEM) studies, morphologies of LDH nanoparticle and its MTX intercalated form were proven to be platelike hexagonal with an average size of approximately 150 nm. In order to understand the cellular penetration behavior, both nanoparticles were treated to human osteosarcoma Saos-2 cell culture lines and the cellular uptake pattern with respect to incubation time was observed by TEM and SEM. We observed that the nanoparticles are attached at the cellular membrane at first and then internalized into the cells via endocytosis within 1 h. Then are located in the intracellular vacuole (endosome). In order to examine the intracellular drug delivery mechanism of LDH nanoparticles, fluorescein 5-isothiocyanate (FITC) labeled MTX was intercalated into LDH and treated on Saos-2 cells. Laser scanning confocal microscopic studies revealed that the FITC-MTX molecules were first internalized with LDH nanocarriers via endocytosis, and located in endosome to deliver loaded drug to target cellular organ. It was, therefore, concluded that LDH could play a role as drug delivery nanocarriers.     

Electrochemical behaviors of iron-based layered double hydroxide thin-films

The ordered ultrathin films based on the fabrication of Mg/Fe-LDHs ([Mg₆Fe₂(OH)₁₆CO₃·(H₂O)_4.5]_0.375) nanosheets and hexacyanoferrate(III) anions via the self-assembly procedure were prepared. The electrodes modified by the films demonstrated a couple of well-defined reversible redox peaks attributed to [Fe(CN)₆]^3?/4? and Fe^2+/3+ couples. The effects of cycle number, scan rate and Mg/Fe molar ratio on the CV performance of the thin-film electrodes were observed in K₃[Fe(CN)₆] electrolyte. The [Fe(CN)₆]^3? pillared Mg/Fe-LDHs with Mg/Fe molar ratio of 3 (LDH-(CN)-3) demonstrated an excellent electrochemical behavior with a potential window between ??0.2 and 1.0 V, high specific capacitance and sensitivity, indicating that the high crystallinity, large specific surface area and plentiful [Fe(CN)₆]^3? anions in interlayer spaces were necessary. Especially, the interlayer [Fe(CN)₆]^3? anions significantly affected the electrochemical behavior of the electrode, where the electrode reaction was controlled by the diffusion of [Fe(CN)₆]^3?/4? and Fe^2+/3+ couples. Under current density of 2.5 A g^?1, the optimized LDH-(CN)-3 electrode exhibited high specific capacitance of 250.81 F g^?1 with good cycling stability. This facile synthesis strategy and the good electrochemical properties indicated that the LDH-(CN)-3 was a potential economical alternative material for supercapacitor application.     

MgAlCe水滑石的合成及其表征

采用共沉淀水热法合成了MgAlCe三元复合层状氢氧化物。详细探讨了x(Al)/x(Ce)、水热温度及pH值对合成产物物相的影响。通过XRD、TG/DTG、SEM及TEM对制备的水滑石进行分析。结果表明,当x(M2+)/x(M3+)=1.5,x(Al)/x(Ce)=16∶1,pH值=7.9条件下进行多种离子共沉淀,并经140℃、10h水热处理后,得出的产物结晶度较高,物相纯净,具有典型层状结构,并且其热稳定性较好,层间羟基硝酸根失去温度在300～500℃之间,表明其作为阻燃剂具有很大的潜力。     

Magnetic nanocomposites with drug-intercalated layered double hydroxide shell supported on commercial magnetite and laboratory-made magnesium ferrite core materials

Mg–Al-layered double hydroxide intercalated with a model drug, salicylate, was deposited on laboratory-made magnesium ferrite and commercial magnetite nanoparticles. The obtained core–shell nanocomposites have been characterized by a variety of methods. The combined information from X-ray diffraction patterns, electron diffraction patterns, FTIR spectra, X-ray photoelectron spectra, electron microscopy images, thermogravimetric analysis and microchemical analysis has indicated a similar nature and composition for the two samples. Magnetic measurements have revealed that although the inherent magnetization of magnetite was significantly higher, the nanocomposites displayed nearly similar magnetic properties.     

Synthesis and characterization of supported heteropolymolybdate nanoparticles between silicate layers of Bentonite with enhanced catalytic activity for epoxidation of alkenes

A new heterogeneous catalyst (PVMo/Bentonite) consisting of vanadium substituted heteropolymolybdate with Keggin-type structure Na₅[PV₂Mo₁₀O₄₀]·14H₂O (PVMo) supported between silicate layers of bentonite has been synthesized by impregnation method and characterized using X-ray diffraction, Fourier-transformed infrared spectroscopy, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, transmission electron microscopy and elemental analysis. X-ray diffraction and scanning electron microscopy analysis indicated that PVMo was finely dispersed into layers of bentonite as support. The PVMo/Bentonite used as an efficient heterogeneous catalyst for epoxidation of alkenes. Various cyclic and linear alkenes were oxidized into the corresponding epoxides in high yields and selectivity with 30% aqueous H₂O₂. The catalyst was reused several times, without observable loss of activity and selectivity. The obtained results showed that the catalytic activity of the PVMo/Bentonite was higher than that of pure heteropolyanion (PVMo).     

Interfacial nature of Ag nanoparticles supported on TiO2 photocatalysts

Silver nanoparticles supported on anatase TiO₂ nanoparticles have been prepared by deposition–precipitation, and characterized by X-ray photoelectron spectroscopy, including scanning electron microscopy, X-ray diffraction crystallography, Raman, and UV–visible absorption spectroscopy. The Ag 3d peak and the X-ray diffraction patterns show characteristics of purely metallic Ag, with no indication of Ag oxide species. Depth-profiling X-ray photoelectron spectroscopy with Ar⁺ ion beam sputtering show a significant change in Ti 2p, and an asymmetric broadening of Ag 3d to a higher binding energy side. A decrease in major Ti 2p _3/2 at 459.2 eV and a significant increase in lower binding energy peak are due to change in oxidation state of Ti from +4 to +3/+2. A broadening of Ag 3d peak with sputtering time is tentatively assigned to a final state quantum size effect. Upon annealing the deposition–precipitation sample, no significant change in Ag 3d peak is observed, while Ti 2p and O 1s XPS intensities are reduced, plausibly due to change in analyzed surface area for TiO₂. The photocatalytic activity for the photodegradation of methyl orange is dramatically reduced upon high Ag-loading, compared to bare TiO₂. The X-ray photoelectron spectroscopy of Ag on TiO₂ prepared by an electrochemical deposition reveals that Ag is also metallic, with no evidence of an oxide form. Upon annealing the electrodeposited sample, the Ag 3d peak shifts by +0.3 eV, while the Ti 2p and O 1s show no critical change in intensity and peak position.     

Self-assembly and characterization of layered double hydroxide/DNA hybrids

The purpose of this study was to control the fabrication of new labile supramolecular assemblies by formulating associations of DNA molecules with inorganic layered double hydroxides (LDHs). The results show that LDH/DNA hybrids synthesized by a coprecipitation route involving the in situ formation of LDHs around DNA molecules acting as templates were characterized by a lamellar organization, with DNA molecules sandwiched between hydroxide layers, exhibiting a regular spacing of 1.96 nm. Our results indicate that labile complexes resulting from the association of nucleic acids and inorganic materials can be obtained not only by anion exchange but also by a direct self-assembly route.     

New polyethylene nanocomposites prepared by in-situ polymerization method using nickel a-diimine catalyst supported on organo-modified ZnAl layered double hydroxide

New nanocomposites based on polyethylene (PE) and organo-modified ZnAl layered double hydroxide (O-ZnAl-LDH) were prepared by an in-situ polymerization method. The late-transition-metal catalyst, bis(4,4′-methylene-bis-(2,6-diisopropylimino))acenaphthene nickel dibromide complex, was firstly supported on the O-ZnAl-LDH layers and subsequently initiated the polymerization of ethylene. Different from commonly used solution or melt intercalation method, such strategy could induce easily the nanosclae dispersion of the O-ZnAl-LDH layers in the PE matrix, as confirmed by the analyses from X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. From the curves of thermogravimetric analysis (TGA), it was found that the decomposition temperature of the nanocomposite with 12.9 wt% O-ZnAl-LDH could be 60.5 °C higher than that of pure PE when 30% weight loss was selected as a measuring point, showing an improved thermal oxidation stability. From the melt rheological tests, it was found that the resultant PE nanocomposites had obvious increases in the storage modulus and complex viscosity when compared with pure PE, showing an enhanced viscoelastic response.     

Encapsulation of organic UV ray absorbents into layered double hydroxide for photochemical properties

Organic–inorganic nanohybrids, 3,4-dihydroxycinnamic acid/layered double hydroxide (CA/LDH), 4-hydroxy-3,5-dimethoxycinnamic acid/layered double hydroxide (SA/LDH), and 3-amino-5-triflouromethylbenzoic acid/layered double hydroxide (FBA/LDH) have been synthesized by co-precipitation reaction of organic ultraviolet (UV) ray absorbents such as 3,4-dihydroxycinnamic acid, 4-hydroxy-3,5-dimethoxycinnamic acid, 3-amino-5-triflouromethylbenzoic and Zn₂Al layered double hydroxide (LDH). Detailed structural and absorption properties of the nanohybrids were studied by using X-ray diffraction (XRD), FT-IR and UV-Vis transmittance spectra which revealed that organic UV absorbents have been intercalated into the interlayer spaces of LDH and all nanohybrids showed excellent UV ray absorption. All the nanohybrids showed a lower catalytic activity as compared to the net organic UV ray absorbents by applying air oxidation to castor oil.     

Reconstitution effect of Mg/Ni/Al layered double hydroxide

Layered double hydroxide (LDH) having a different cation (Mg, Ni, Al) composition was successfully synthesized by the low supersaturation method. The sample was thermally decomposed and reconstituted in water and nitrate media at different temperatures. X-ray powder diffraction and X-ray fluorescence were used to investigate the differences between the obtained layered materials and those after the reconstitution process. To the best of our knowledge, there are only few studies where the influence of the third metal cation on the reconstitution process was analyzed.     

Intercalation of collagen and soybean peptides into Zn-Al layered double hydroxide

In order to develop a new type biocompatible organic/inorganic nanohybrid material, an intercalation of collagen peptides (CP) and soybean peptide (SP) into Zn-Al layered double hydroxide (LDH) by the coprecipitation reaction has been investigated. The peptide/LDH has been characterized by chemical analysis, powder X-ray diffraction (XRD), Raman spectroscopy, thermal gravimetric analysis (TG) and transmission electron microscopy (TEM). According to the XRD patterns and Raman spectra, the solid products were found to contain peptide and to show broad diffraction peaks with LDH structures. The CP/LDH and SP/LDH possess the expanding LDH structure, d(00l) = 2-3 nm, confirming that both peptides were intercalated into the LDH interlayer space with low organized stacking arrangement.     

Layer-by-layer self-assembly of polyimide precursor/layered double hydroxide ultrathin films

The layer-by-layer (LBL) self-assembly has been extensively used as a simple and effective method for the preparation of polyelectrolyte multilayer films. In this work, we utilized this unique method to prepare polyimide precursor/layered double hydroxide (LDH) ultrathin films. Well-crystallized Co-Al-CO₃ LDH and subsequent anion exchanged Co-Al-NO₃ LDH were prepared and characterized by scanning electron microscopy and X-ray diffraction (XRD). By vigorous shaking of the as-prepared Co-Al-NO₃ LDH, positively charged and exfoliated LDH nanosheets were obtained. Atomic force microscopy and XRD investigations indicated the delamination of LDH nanosheets. The precursor of polyimide, poly(amic acid) tertiary amine salt (PAS) was prepared by the polycondensation of dianhydride and diamine, and subsequent amine salt formation. By using the LBL method, heterogeneous ultrathin films of PAS and LDH were prepared. The formation of the ordered nanostructured assemblies was confirmed by the progressive enhancement of UV absorbance and the XRD results.     

Removal of bacteria and viruses from waters using layered double hydroxide nanocomposites

We have identified synthetic layered double hydroxides (LDH) nanocomposites as an effective group of material for removing bacteria and viruses from water. In this study, LDH nanocomposites were synthesized and tested for removing biological contaminants. LDH was used to remove MS2 and øX174 (indicator viruses), and Escherichia coli (an indicator bacterium) from synthetic groundwater and to remove mixed communities of heterotrophic bacteria from raw river water. Our results indicate that LDH composed of magnesium–aluminium or zinc–aluminium has a viral and bacterial adsorption efficiency ≥99% at viral concentrations between 5.9 × 10⁶ and 9.1 × 10⁶ plaque forming units (pfu)/L and bacterial concentrations between 1.6 × 10¹⁰ and 2.6 × 10¹⁰ colony forming units (cfu)/L when exposed to LDH in a slurry suspension system. Adsorption densities of viruses and bacteria to LDH in suspension ranged from 1.4 10¹⁰ to 2.1 10¹⁰ pfu/kg LDH and 3.2 × 10¹³–5.2 × 10¹³ cfu/kg LDH, respectively. We also tested the efficiency of LDH in removing heterotrophic bacteria from raw river water. While removal efficiencies were still high (87–99%), the adsorption capacities of the two kinds of LDH were 4–5 orders of magnitude lower than when exposed to synthetic groundwater, depending on if the LDH was in suspension or a packed column, respectively.     

层状双金属氢氧化物的原位改性及其吸附性能

为了改善层状双金属氢氧化物(LDHs)材料对水体中碘离子的吸附性能,通过共沉淀法制备铜基LDH材料,利用煅烧及煅烧后还原分别制得层状双金属氧化物(CLDH)和Cu-Cu_2O-CLDH材料,并探究这3种LDHs材料对水体中I-的吸附性能。扫描电镜观察到Cu-Cu_2O-CLDH的表面上长出了小颗粒,X射线衍射结果证明这些小颗粒为Cu及Cu_2O,比表面积测试结果表明Cu-Cu_2O-CLDH的比表面积达到了316. 76 m~2/g,远远大于LDH及CLDH材料。吸附实验结果显示:LDH和CLDH对I-的饱和吸附容量分别为23. 8、84. 8 mg/g,而改性后的CuCu_2O-CLDH对I-的饱和吸附容量提升到了134. 5 mg/g。根据I-的吸附实验结果及吸附后的样品表征,发现Cu、Cu_2O能够与I-反应生成Cu I,加上与CLDH的协同作用,使得材料对I-的吸附效率进一步提高。     

Synthesis of well-dispersed Ag nanoparticles on eggshell membrane for catalytic reduction of 4-nitrophenol

A novel functional bio-nanocomposite was prepared by deposition of Ag nanoparticles onto the surface of natural eggshell membrane fibers. Practically, the functional groups exposed on the fiber surface can provide locations to anchor Ag ions when immersed into metal precursor solution. The synthesized small-sized Ag nanoparticles with uniform distribution is well decorated on the surface of interwoven fibers of eggshell membrane. The effectiveness of the as-prepared AgNPs/ESM composites as a solid phase heterogeneous catalyst has been evaluated, for the first time, on the well-known 4-nitrophenol reduction to 4-aminophenol in the presence of excess borohydride. Moreover, the kinetics of the reduction reaction was investigated at different temperatures to determine the activation energy. This work provides an important example in the introduction of natural membranes for the fabrication of functional hybrid nanocomposites which could be very useful in varying fields.     

Oxidizing synthesis of Ni–Mn layered double hydroxide with good crystallinity

Ni²⁺–Mn³⁺ layered double hydroxide (LDHs) with good crystallinity and uniform morphology has been hydrothermally synthesized at 180 °C for 2 days using urea as hydrolysis agent and ammonium peroxodisulfate as oxidant. The obtained Ni²⁺–Mn³⁺ LDHs material has been characterized by XRD, SEM, XPS, FT-IR, and TG–DTA. Ammonium peroxodisulfate as oxidant plays an important role for the formation of Ni²⁺–Mn³⁺ CO₃²⁻ LDHs material, and Mn²⁺ ions are oxidized into Mn³⁺ ones during the precipitation of Mn²⁺ ions, giving rise to layered hydroxide with the hydrotalcite structure. Ni²⁺–Mn³⁺ LDHs material with Ni/Mn molar ratio of 4 has a layered structure with a basal spacing of 0.739 nm. The morphology, size, and uniformity of the as-prepared materials connect with the hydrothermal treatment temperatures, and uniform and regular flowerlike spheres with a mean lateral size of 3.5 μm are observed for Ni²⁺–Mn³⁺ LDHs material with good crystallinity and uniform morphology.     

Effects of morphology and cesium promotion over silver nanoparticles catalysts in the styrene epoxidation

Silver nanowires have been obtained by polyol reduction of silver nitrate in presence of polyvinyl-pyrrolidone (PVP). The as-synthesized silver nanowires were deposited on α- Al₂O₃. For comparison silver catalysts were also prepared by wetness impregnation obtaining irregularly shaped silver particles. Epoxidation of styrene to styrene oxide (SO) by molecular oxygen was studied using the silver catalysts. The main products were styrene oxide (SO) and phenylacetaldehyde (Phe). The promotion effect of the Cs on the silver nanowires catalysts was investigated. The Cs loading was in the range of 0–1 wt.% (refereed to silver). Furthermore, the effect of O₂:C₈H₈ molar ratio on the catalytic epoxidation was also investigated. Silver nanowires catalysts showed superior catalytic activity compared to those prepared by impregnation method. Besides, higher O₂:C₈H₈ ratios improved the selectivity to SO. The catalytic activity showed a maximum performance for silver nanowires promoted with 0.25 wt.% of Cs, achieving 94.6% of conversion and total selectivity to desired oxidation products (styrene oxide and phenylacetaldehyde). Moreover, the cesium promotion also contributed to the increase in the selectivity to styrene oxide. Temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS) were employed to detect the presence of different species of oxygen in the catalysts indicating that subsurface oxygen was beneficial for the epoxidation. The samples were also structurally characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible absorption spectra and selected area electron diffraction pattern (SAED).