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.     

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。     

A simple method to synthesize layered double hydroxide nanoscrolls

Layered double hydroxide (LDH) is a promising drug carrier, ion exchanger, absorbent, and catalyst or even catalyst support due to its inimitable sandwich structure. If the LDH could be synthesized into the nanoscrolls, it will be promising ion channels for the biomolecule transfer, ion exchange, or catalysis. In this report, a simple technique has been developed to prepare layered double hydroxide nanoscrolls on a large scale. The composition of LDH nanoscrolls can be conveniently adjusted through experiment conditions. We proved the “rolling mechanism” to explain the formation of LDH nanoscrolls. Moreover, we unambiguously proposed the driving force for “rolling mechanism”, which is the change of the forces between the brucite-like sheets and the interanions and between the cations and cations in the brucite-like sheets.     

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.     

Sepiocite, sepiolite-like nanoclay derived from hydrotalcite-like layered double hydroxide

Sepiocite, a synthetic sepiolite-like nanoclay, was derived from hydrotalcite-like Mg2Al(CO3)0.5-layered double hydroxide (LDH) under phase transformation at 270 +/- 3 degrees C. The crystal structure of sepiocite is conceptually very similar to that of sepiolite derived from montmorillonite clay because sepiocite is formed through the alternation of the blocks and tunnels along the crystallographic c-axis, with a partial dehydroxylation of the octahedral Mg-(OH)-Al configuration into tetrahedral ones. Three important findings regarding sepiocite were arrived at: (i) its high specific surface area of 128.25 m2/g with an average particle size of 200 nm, which is approimately equal to 3.5 times larger than the specific surface area of the pristine LDH (34.21 m2/g); (ii) its non-swelling property; and (iii) its strongly reduced anion-exchange capacity.     

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.     

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.     

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。     

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.     

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.     

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.     

The role of oleate-functionalized layered double hydroxide in the melt compounding of polypropylene nanocomposites

In this research, the oleate-functionalized magnesium and aluminum layered double hydroxide (LDH; Mg:Al = 3:1) o-LDH was applied as nanofiller in the melt blending of polypropylene (PP) nanocomposites, in order to understand its role in this process. o-LDH was prepared using the memory effect of the calcined carbonated LDH. Blending of PP and low o-LDH filler contents of 0.45 and 0.90 wt.% afforded the nanocomposites PP0.45 and PP0.90, respectively, which were characterized by transmission electron microscopy, X-ray diffraction, small angle X-ray scattering, thermo-gravimetric analysis, differential scanning calorimetry and dynamic mechanical analysis. The oleate LDH surface functionalization enhanced the system compatibility as a relative regular dispersion of o-LDH tactoids was observed within the matrix, together with partial PP intercalation. This o-LDH incorporation increased the PP relative crystallinity, induced crystalline orientation and decreased the glass transition temperature. Furthermore, the nanocomposites showed improved initial resistance to decomposition and stiffness. These results showed that the o-LDH acted as both nucleating agent and plasticizer, and that the presented approach can be used for the development of PP nanocomposites with distinguished properties.     

Preparation and characterization of melt processed poly(l-lactide)/layered double hydroxide nonocomposites

This work reports the fabrication and physical properties of biodegradable poly(l-lactide) (PLLA) composites containing a fraction of unmodified layered double hydroxides (LDH–NO₃) and γ-polyglutamate-modified layered double hydroxides (γ-LDH) by melt blending process. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) experimental results showed that the original LDH–NO₃ with the certain amount of aggregates was unevenly dispersed throughout the PLLA matrix. Conversely, γ-LDH allows the formation of an intercalated nanocomposite. Although the water vapor permeability of the PLLA/LDH systems was decreased with increasing the loading of LDH, the barrier property of PLLA reinforced with γ-LDH is superior to that of PLLA-L composites. The effects of both LDHs on mechanical and thermal properties of PLLA were also investigated.     

Enhanced catalytic performances of Ag nanoparticles supported on layered double hydroxide for styrene epoxidation

Catalysts or support to catalysts based on layered double hydroxides (LDHs) have been widely investigated in the last few years. Supported Au nanoparticles (NPs), prepared typically by a homogeneous deposition–precipitation technique, have been utilized as catalysts with high activity and selectivity for styrene epoxidation. We herein present a preparation of chemically reduced and cost-saving Ag NPs on the LDH support used as catalyst for styrene epoxidation. A proper reaction condition is optimized, for example, a loading of 2.67 wt% Ag, a conversion temperature of 82 °C, and a conversion time of 8 h. The Ag/LDH catalyst exhibits enhanced reaction selectivity and product yield in comparison with the Au/LDH reported previously. Our results may initiate a facile framework appropriate for noble metallic NPs supported on layered inorganic crystal compounds.     

Synthesis and thermo-optical stability of o-methyl red-intercalated Ni–Fe layered double hydroxide material

In the present letter, an anionic azo dye, o-methyl red (2-(4-(dimethyl-amino) phenylazo) benzoic acid, MR), was incorporated successfully into the interlayer domain of Ni–Fe layered double hydroxide (LDH) by coprecipitation route. X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR) and simultaneous thermogravimetric and differential thermal analysis (TG-DTA) revealed the presence of supramolecular host–guest interaction between the host matrix and interlayer anionic dye guest with an expanded interlayer distance. The UV–visible diffuse reflectance (UV–VIS/DR) spectra showed that the dye-intercalated LDH had higher photostability than the pristine dye. Moreover, there was no significant change for the interlayer MR anions in the UV–VIS/DR spectra of the dye-intercalated sample after heating up to 200 °C, indicating that the thermostability of dye is markedly enhanced by the intercalation into the gallery domain of NiFe-LDH.