Influence of nickel ions on human multipotent mesenchymal stromal cells (hMSCs)

Nickel‐Titanium‐Shape‐Memory‐Alloys (NiTi‐SMA) are of biomedical interest due to an unusual range of pure elastic deformability (superelasticity) and the shape memory effect which allows this material to return to a predictable previously memorized shape after external changes in temperature. HMSCs (human multipotent mesenchymal stromal cells) are currently the most promising cell type for regenerative medicine and tissue engineering, due to the ability to differentiate into several tissues such as bone, tendon, cartilage or muscle. For tissue engineering newly developed porous NiTi‐SMA materials are evaluated preloaded with hMSCs. For biocompatibility testing the high nickel content (50 %at) of NiTi‐SMA plays a critical role. To analyse the influence of Ni‐ions on hMSCs viability and activation, cells were cultured with or without NiCl₂ for 24h and 7days. Cells were either seeded in media containing NiCl₂ or the NiCl₂ was later added to already adherent cells. Cell metabolism, proliferation and viability were analysed by alamarBlue^TM assay or fluorescence microscopy. Cytokine (IL‐6, 8, 11) release from hMSCs was determined by ELISA . NiCl₂ concentrations below 25 μg/ ml were well tolerated by the cells. A significant decrease in cell proliferation occurred at threshold values of 200 μg/ ml (24 h) and 25 μg/ ml (7 d). There was a significant, dose dependent increase in the release of IL‐8 from hMSCs cultured in the presence of sub toxic NiCl₂ concentrations. The present study demonstrates for the first time that high but non‐toxic concentrations of Ni²⁺ are capable to activate hMSCs. Thus high Ni²⁺ concentrations apart from allergen‐ or particle‐induced inflammation, may lead to tissue inflammation in the vicinity of a NiTi‐SMA implant in vivo and subsequently to implant failure e.g. due to implant loosening.     

Sol-gel preparation and characterisation of mixed metal tin oxide thin films

Mixed metal oxide stannates were prepared by sol-gel methods and coated onto solid titanium substrates as thin films using spin and dip coating methods. Metal oxides such as Sb₂O₅, ZrO₂, CuO, MnO_x and PdO were introduced into a SnO₂ host matrix using sol-gel technology. The mixed metal tin oxide materials prepared via the sol-gel route were extensively characterised in terms of surface characterisation and chemical composition. Thermogravimetric analysis was performed to confirm that at 600 °C (the calcination temperature) no further structural changes due to mass loss occur. UV spectroscopy of the liquid gels allowed the determination of the band gap energy. The surface morphology of the thin film electrodes were characterised by atomic force microscopy and scanning electron microscopy and the effect of the coating method employed i.e. spin or dip coating could be clearly seen in the estimated values of surface roughness. These techniques were also able to confirm the thickness of the films in the nano range. Combined nuclear beam techniques such as Rutherford backscattering spectroscopy and particle induced X-ray emission provided some insight into the chemical composition of the mixed metal tin oxides and confirmed the presence of the dopant element in the SnO₂ host material.     

Gas sensitivity of metal oxide mixed tin oxide films prepared by spray pyrolysis

Various kinds of SnO₂ films, modified with the addition of iron, antimony, copper, titanium, manganese, nickel, cobalt or calcium oxides, were fabricated by using the spray pyrolysis technique and their gas-sensing characteristics were studied. From electrical measurements in air, the relative sensitivity towards inflammable gas of these SnO₂-based film sensors was compared. It was observed that SnO₂-based films of higher electrical resistance had a tendency to have higher sensitivity towards ethanol than the SnO₂-based films of lower resistance. The addition of p-type metal oxides, such as NiO and MnO, to the SnO₂ matrix was found to be effective in increasing the sensitivity towards inflammable gas.     

Scattering and reflective properties of ordered mesoporous silica films

Ordered mesoporous and nonporous silica films were studied by analysis of reflection spectra and hemispherical elastic light scattering (HELS). The real and imaginary parts of the index of the films were estimated from the reflection spectra. The HELS angular distribution of the mesoporous film shows a minimum, which has been interpreted as an interference pattern coming from the beams scattered by the mesopores.     

Electrochemically assisted self-assembly of mesoporous silica thin films

Supported mesostructured thin films are of major importance for applications in optical, electrochemical and sensing devices. However, good performance is restricted to mesostructured phases ensuring good accessibility from the film surface, which would be straightforward with cylindrical pores oriented normal to the underlying support, but this remains challenging. Here, we demonstrate that electrochemistry is likely to induce self-assembly of surfactant-templated (organo)silica thin films on various conducting supports, homogeneously over wide areas. The method involves the application of a suitable cathodic potential to an electrode immersed in a surfactant-containing hydrolysed sol solution to generate the hydroxyl ions that are necessary to catalyse polycondensation of the precursors and self-assembly of hexagonally packed one-dimensional channels that grow perpendicularly to the electrode surface. The method is compatible with controlled and localized deposition on heterogeneous supports, opening the way to electrochemically driven nanolithography for designing complex patterns of widely accessible mesostructured materials.     

Effects of sol aging on mesoporous silica thin films organization

Cetyltrimethylammonium bromide (CTAB) templated mesoporous silica thin films were deposited on glass slides by evaporation-induced self-assembly (EISA) process using a dip-coating method. The effects of sol aging on the mesophase structure of the thin films organization were investigated. Identification of the structures was accomplished by coupling X-ray diffraction (XRD) and transmission electron microscope (TEM) investigations, and corresponding sol was characterized by ²⁹Si solution state nuclear magnetic resonance (²⁹Si NMR) and UV-Vis spectrophotometer for studying the mesophase structure evolution. Results indicate that sol aging has great effects on the mesophase structure of the films organization, which includes degree of order and phase transformation of mesoporous silica thin films. To obtain a better understanding of the effects of sol aging on the mesophase structure, the theories of apparent mass fractal dimension and charge density matching were introduced to explain the self-assembly process.     

有序介孔氧化硅孔道氧化锰团簇组装研究

以有序介孔氧化硅MCM-41为主体材料,通过浸渍法及后续热处理工艺,在孔道中组装氧化锰的团簇粒子,并对其进行结构表征。通过XRD、HR—TEM、XPS及N2吸附表明氧化锰的团簇粒子已经成功组装到MCM-41有序孔道中。通过对不同孔径有序介孔材料的氧化锰团簇粒子的组装,表明随着孔道中组装量的增加,350nm附近光致发光强度增强,吸收边发生红移,同时1000nm附近吸收带宽化。     

Ultra low-dielectric-constant methylated mesoporous silica films with high hydrophobicity and stability

Vapor phase treatment with tetraethyl orthosilicate (TEOS) is used to improve the performance of methylated mesoporous silica films spin-coated on silicon wafers. Subsequent calcination leads to formation of ultra low dielectric-constant (k) films with high hydrophobicity and structural stability. The k value of the films is about 1.75, and remains as low as 1.82 in an 80%-relative-humidity environment over seven days. Mechanical strength (elastic modulus and hardness) is high enough to withstand the stresses that occur during the chemical mechanical polishing and wire bonding process (E = 10.9 GPa). Effects of the methyl group and TEOS vapor treatment on the structural stability and hydrophobicity are systematically studied.     

Charge-gated transport of proteins in nanostructured optical films of mesoporous silica

The admission into and diffusion through nanoscale pores by molecules is a fundamental process of great importance to biology and separations science. Systems (e.g., chromatography, electrophoresis) designed to harness such processes tend to remove the separation process from the detection event, both spatially and temporally. Here, we describe the preparation and characterization of thin optical Fabry-Pe?rot films of mesoporous silica (pSiO(2)) that can detect protein infiltration by optical interferometry, which probes the separation process in real time and in the same ultrasmall physical volume (5 nL). Admission of a protein into the pores is controlled by the diameter (～50 nm) and the surface charge of the pores, and both the rate and the degree of protein infiltration are a function of solution pH. Test proteins bovine serum albumin (BSA, 66 kDa), bovine hemoglobin (BHb, 65 kDa), and equine myoglobin (EMb, 18 kDa) are admitted to or excluded from the nanophase pores of this material based on their size and charge. The rate of protein transport within the pores of the pSiO(2) film is slowed by 3 orders of magnitude relative to the free-solution diffusion values, and it is maximized when pH = pI.     

Reflectance of surfactant-templated mesoporous silica thin films: Simulations versus experiments

In this study, cubic and hexagonal mesoporous amorphous silica thin films were synthesized using evaporation-induced self-assembly process followed by calcination leaving highly ordered spherical or cylindrical pores in a silica matrix. The films featured pores with diameter between 4 and 11 nm, lattice parameter from 7.8 to 24 nm, and porosity between 22% and 45%. All films were dehydrated prior to reflectance measurements except for one film which was fully hydrated. The present study compares the spectral reflectance measured experimentally between 400 and 900 nm with that computed numerically by solving three-dimensional Maxwell's equations in mesoporous silica thin films with the same morphology as those synthesized. The matrix was assumed to have the same optical properties as bulk fused silica. The pore optical properties were either those of air or liquid water whether the film was dehydrated or hydrated, respectively. Excellent agreement was found between experimental and numerical reflectance for both cubic and hexagonal mesoporous silica films. This study experimentally validates our simulation tool and offers the prospect of ab-initio design of nanocomposite materials with arbitrary optical properties without using effective medium approximation or mixing rules.     

First direct synthesis of highly ordered bifunctionalized mesoporous silica thin films

Optically transparent and highly ordered mesoporous organosilica thin films functionalized with two different organic groups in various proportions were synthesized by templated-directed cocondensation of tetraethylorthosilicate (TEOS) and a mixture of two distinct and functional organotriethoxysilanes [NC(CH2)3Si(OEt)3 and O=P(OEt)2(CH2)3Si(OEt)3]. The mesostructured films obtained by evaporation induced self-assembly (EISA) approach were deposited on glass or silicon substrates by dip-coating. They were characterized by Grazing Incidence Small Angle X-ray Scattering (GISAXS) and X-ray reflectivity. We showed that whatever the proportion in organic groups, only 2D hexagonal phase having p6m symmetry was observed for all the materials indicating a good compatibility between the organic groups. The bi-functionalization of the internal pores surface by the organotriethoxysilanes groups was clearly evidenced by using micro-Raman spectroscopy.     

On the etching of silica and mesoporous silica films determined by X-ray reflectivity and atomic force microscopy

X-ray reflectometry and atomic force microscopy were used to characterize the etching effect of 0.1 mol dm^− 3 NaOH solution on mesoporous silica films < 100 nm thick produced by the evaporation induced self assembly route using a nonionic triblock co-polymer as the template. The effect of this treatment on films that had been partly condensed at 80 °C or fired at 400 °C in air are compared to non-porous films produced using conventional sol-gel technique. The evolution of film structure was monitored by atomic force microscopy and X-ray reflectometry. Thicknesses obtained from these measurements were used as an order parameter to determine the etch rate. For the mesoporous films, distinct stages corresponding to (a) film compression; (b) removal of the weakly organised caplayer; (c) progressive removal of bilayers of pores/silicated layres; and finally film collapse were revealed.     

Development of human mesenchymal stem cells on DC sputtered titanium nitride thin films

The biocompatible properties of titanium nitride (TiN) have opened a new field of applications for this material. In the present work, TiN coatings with thicknesses around 1 m have been prepared by DC magnetron sputtering. The aim has been to evaluate the adherence, growth and proliferation of human pluripotent mesenchymal stem cells (hMSCs) on the surface of TiN films with contrasted structural, electrical, and mechanical properties. For this purpose, the films were characterized by X-ray diffraction, scanning electron microscopy, sheet resistance measurements, and nanoindentation. Biological tests show that hMSCs adhere and proliferate onto TiN surfaces. The combination of the mechanical, electrical, and biological responses suggest that TiN coatings present appropriate properties to induce the in vitro stimulated differentiation of hMSCs. This possibility gives an added value to TiN based biomaterial coatings.     

石墨烯基有序介孔金属氧化物复合材料的制备及研究进展

综述了以石墨烯作为载体,利用有序介孔金属氧化物特殊的3D结构,以及两者共存产生的协同效应,开发系列新型石墨烯基有序介孔金属氧化物复合材料的最新研究进展。介绍了本课题组在有序介孔金属氧化物的可控合成、与石墨烯的有效复合以及复合材料的光电性能等方面的探索性研究。着重对石墨烯基有序介孔金属氧化物复合材料的制备方法、形成机理及其在催化、电化学、传感和能量储存等领域的最新应用进行概述,并展望了其未来的发展趋势。     

原子层淀积制备金属氧化物薄膜研究进展

原子层淀积(ALD)技术作为一种先进的薄膜制备方法近年来越来越得到重视,它能精确地控制薄膜的厚度和组分,实现原子层级的生长,生长的薄膜具有很好的均匀性和保形性,因而在微电子和光电子等领域有广泛的应用前景。本文综述了ALD技术的基本原理,及其在金属氧化物薄膜制备上的研究进展。     

Control of wall thickness in the formation of ordered mesoporous silica films

Ordered mesoporous silica thin films using block copolymer have drawn an attention for low-k application due to its ordered pore structure. From the respect of dielectric and mechanical properties of the film, there is trade-off between pore size and wall thickness. In this work, factors for increase of wall thickness were investigated. It was found that body-centered cubic structure was maintained irrespective of the concentration of catalytic acid. The catalytic acid thickens the framework wall because counterion reduces the repulsion force between silicic acids. The highly ordered mesoporous silica films were obtained although high concentration of acid was added to the silica sol. However, wormlike micelle exists more with high HCl concentration due to fast gellation rate. And excess water, which has the role similar to the humid atmosphere, also increases the thickness of silica wall. However, large amount of excess water at the micelle interface disrupts organic-inorganic electrostatic interaction. As a conclusion, optimization of HCl concentration in the silica sol and control of humidity during spin coating can simultaneously increase the framework thickness while maintaining the pore periodicity.     

Facile synthesis and large third-order optical nonlinearity of Manganese-loaded mesoporous silica thin films

An in-situ reduction method is adopted to incorporate MnO₂ nanoparticles into mesochannels of silica thin films by using KMnO₄ as the oxidizing agent and manganese precursor. As the reduction time in KMnO₄ solution increases, the ordered mesostructure collapses, and the loaded MnO₂ nanoparticles become bigger in size, resulting in a narrower band gap. Z scan measurement demonstrates a large third-order nonlinear susceptibility of the composite films under the picosecond Nd:YAG laser excitation. A sign reversion of the third-order nonlinear refractive index coefficient in the sample with longer reduction time is also observed, which can be attributed to the variation in the band gap energy.     

Synthesis and sensitivity properties of Pd-doped tin oxide nanoparticles dispersed in mesoporous silica

Pd-doped tin oxide nanoparticles dispersed in mesoporous silica were prepared by a thermal-decomposing method and characterized by isothermal nitrogen adsorption measurement, X-ray diffraction (XRD) and transmission electron microscopy (TEM). Tin oxide nanoparticles grow up slowly owing to confinement of the pores of the mesoporous silica. Due to the unique microstructure of the mesoporous silica, the obtained nanocomposite consists of a three-dimensional web of interconnected crystallites of tin oxide and exhibits electronic conductivity when enough tin oxide is assembled in the silica pores. The obtained nanocomposite has also a large specific surface area, and the tin oxide nanoparticles have a free surface in contact with the ambient air. Therefore, the samples exhibit a high sensitivity to CO gas, and have potential application.     

Ordered mesoporous silicon through magnesium reduction of polymer templated silica thin films

This paper describes the process of making ordered mesoporous silicon (Si) thin films. The process begins with mesoporous silica (SiO 2) thin films that are produced via evaporation induced self-assembly (EISA) using sol-gel silica precursors with a diblock copolymer template. This results in a film with a cubic lattice of 15 nm diameter pores and 10 nm thick walls. The silicon is produced through reduction of the silica thin films in a magnesium (Mg) vapor at 675 degrees C. Magnesium reduction preserves the ordered pore-solid architecture but replaces the dense silica walls with 10-17 nm silicon crystallites. The resulting porous silicon films are characterized by a combination of low and high angle X-ray diffraction, combined with direct SEM imaging. The result is a straightforward route to the production of ordered nanoporous silicon.