A biomimetic mesoporous silica–polymer composite scaffold for bone tissue engineering

A biomimetic organic–inorganic composite system comprising of microspheres fabricated from combination of a biodegradable polymer poly(lactide-co-glycolide) (PLGA) and bioactive mesoporous silica (SBA-15) has been developed through sintering technique for bone regeneration applications. The morphological and structural properties of the SBA-15/PLGA composite scaffold were evaluated using electron microscopy and fourier transform infrared spectroscopy and the results showed spherical morphology and composite nature. The presence of mesopores in the silica was confirmed through nitrogen adsorption–desorption isotherms. The surface area and pore size of mesoporous silica were found to be 792 m² g^?1 and 3.7 nm, respectively. The thermal characteristics of the SBA-15/PLGA composites studied using thermogravimetry analysis shows a weight loss of around 80% with the degradation occurring at 324?°C. The prepared scaffold is also found to support the adhesion and proliferation of osteoblast cells. The expression of specific bone markers is significantly enhanced in the SBA-15/PLGA composite scaffold when compared with the pristine polymeric scaffold indicating the positive effect of mesoporous silica. Hence, these SBA-15/PLGA composite scaffolds can be explored further for bone regeneration applications.     

Effect of Filler Treatment on the Release Properties of Coating on Urea Granules

Polyurethane composite coatings on urea granules were prepared by SBA-15 mesoporous silica (in as-synthesized and calcined forms) as a pseudo-crosslinker without any other chain extenders. The calcination of mesoporous silica leaded to reduction of hydroxyl groups and increase of mesopores. The composite coating containing calcined SBA-15 showed enhanced controlled release properties compared with the other two coatings. At the loading content of 1 wt%, the initial release rate and release duration of urea coated by polyurethane/calcined SBA-15 composite were 0.08% and 83 d, respectively. It is shown that the calcination played an important role in controlling the properties of composite coating.     

聚甲基丙烯酸-介孔氧化硅复合材料的制备及释药研究

采用自由基聚合的方法合成了pH敏感性聚甲基丙烯酸(PMAA)/介孔分子筛SBA-15纳米复合物。用XRD、FTIR、TG、低温N2吸附-脱附、TEM等对复合物进行了表征,并以阿司匹林为模型药物分子,进行了药物释放测试。结果表明,复合材料仍然保持有序六方结构,但比表面积、孔容、孔径有所降低;在pH=7.4的释放介质中,12 h内释放了72%的药物,而在pH=1.0的释放介质中,12 h药物释放量为30%。该纳米复合材料对阿司匹林的释放具有pH敏感性,有望在药物控制释放领域得到应用。     

Structure and catalytic properties of Pd encapsulated in mesoporous silica SBA-15 fabricated by two-solvent strategy

The two-solvent method was employed to prepare Pd encapsulated in mesoporous silica (Pd/SBA-15). A 3.01 wt% Pd loading was achieved without the loss of pore ordering. Highly dispersed and uniform palladium nanoparticles could be detected using transmission electron microscopy confirming also the absence of large particles outside the mesopore silica. The catalytic activities of the Pd/SBA-15 nanocomposites were investigated in Heck coupling reactions with activated and non-activated aryl substrates. The Pd/SBA-15 nanocomposite exhibits excellent catalytic activities and reuse ability in air for the Heck carbon–carbon coupling reactions.     

Effects of mesoporous SBA-15 contents on the properties of polystyrene composites via in-situ emulsion polymerization

Different loading of mesoporous molecular sieve SBA-15 was used to prepare polystyrene (PS)/SBA-15 composite materials via in-situ emulsion polymerization. The influence of SBA-15 silica on the styrene emulsion polymerization was studied regarding to the monomer conversion, particle size and particle size distribution, stability and viscosity of the resulting emulsion. The structure and properties of the composites were investigated by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and gel permeation chromatography (GPC). In addition, the glass transition temperature (T_g), thermal mechanical property and thermal stability of the composite film were measured by differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. The results indicated that the composite emulsion showed high monomer conversion, thick viscosity, low coagulum, uniform particle size and broad size distribution. Molecular weight of the polymer decreased with the increase of mesoporous silica. SBA-15 silica was dispersed evenly in PS matrix at a loading of 5 %. The PS/SBA-15 composite material containing 10 % silica maintained a certain ordered structure. DMA results demonstrated that PS/SBA-15 composite exhibited greater storage modulus and high T_g compared to pure PS. The improved thermal stability and T_g of the composite were also confirmed by the TGA and DSC.     

Comparison of amine-functionalized mesoporous silica particles for ibuprofen delivery

We have prepared three different types of amine-functionalized silica particles: i) mesoporous silica (MESO1); ii) nonporous core-mesoporous shell silica (MESO2); iii) SBA-15 particles. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and nitrogen sorption experiment were used to study the morphology of the synthesized particles. To investigate the drug loading and subsequent release of the particles, ibuprofen was used as a model drug for oral delivery. Loading capacity of the particles in this work was found to be higher than that in the previous studies, and followed the order of MESO1>MESO2>SBA-15 particles. Release experiments showed the similar release rate for MESO1 and MESO2 particles from which only <40% of ibuprofen was released after 5 h. From SBA-15 particles, however, more than 80% of ibuprofen was released in 5 h at pH 4 and 7.4. Ibuprofen release from SBA-15 was slowest at pH 2 (～pH of stomach body) and fastest at pH 7.4 (～pH of proximal intestine). Difference in release rates was ascribed to the different morphology and pore structure of the carrier particles.     

Synthesis and characteristics of Ce modified HY/SBA-15 and its desulfurization performance for simulated oil

A composite zeolite HY/SBA-15 has been synthesized by an overgrowth approach, and then doped with Ce by a liquid phase ion exchange process to form the Ce modified HY/SBA-15 catalyst. The synthesized materials were examined by X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscopy (TEM), BJH analysis and pyridine adsorption Fourier-transform infrared spectroscopy (Py-FTIR). The results showed the existence of two different pores sizes of 1.8 and 6 nm. Thus, the HY/SBA-15 composite includes both microporous and mesoporous structures. Desulfurization activity of the composite materials was evaluated using as simulated oil gas. The results showed that the SO_x adsorption capacity of Ce-HY/SBA-15 was enhanced by 1.97 mg/g compared to HY/SBA-15, which suggested that the Ce plays an important role in the desulfurization of simulated oil over composite zeolite. Furthermore, the Py-FTIR results revealed the relationship between the surface acids and the desulfurization performance. It was found that the weak Lewis acids were important for the improved desulfurization performance, while the Brönsted acids inhibited the desulfurization performance.     

SO3H-functionalized mesoporous carbon/silica composite with a spherical morphology and its excellent catalytic performance for biodiesel production

Mesoporous carbon/silica composites functionalized with –SO₃H groups were prepared via polymerization and carbonization of glucose into mesoporous silica SBA-15 and a followed sulfonation by sulphuric acid. These composites were characterized by powder X-ray diffraction, N₂ adsorption–desorption and transmission electron microscopy, which suggested the preservation of ordered mesoporous structure, as well as a novel spherical morphology. The result of fourier transform infrared spectroscopy indicated the successful modification of –SO₃H groups and the acidity of catalysts was determined by an indirect titration method. The composite with 40 % carbon loading possessing the highest acidity in synthesized catalysts and the ordered mesoporous structure without pore blocking exhibited a remarkable catalytic activity for biodiesel production. Experimental parameters including the carbon loading, molar ratio of reactants, reaction time and reaction temperature were optimized. In addition, a superior recycling property was exhibited after five consecutive cycles.     

Simultaneous control of rod length and pore diameter of SBA-15 for PPL loading

Mesoporous silica materials are attractive materials for immobilizing enzymes because of their well-ordered structures, large surface area are pore volume. Diffusion of large enzyme molecules such as porcine pancreatic lipase (PPL) through the lengthy channels of MPS takes place too slowly. Therefore, the squat of the enzyme at the pore mouth entrance, actually makes the rest of the channel useless. In this study, to overcome this problem, synthesis parameters of SBA-15 were changed, since along with pore diameter increasing, the mesochannel length becomes shorter. The main point to obtain a well-ordered 2D hexagonal pore structure was the pre-hydrolysis of tetraethyl orthosilicate (TEOS) before the addition of 1,3,5-trimethyl benzene as a micelle swelling agent. Due to the strong effect of zirconium in changing the morphology of SBA-15 particles, we modified SBA-15 in the presence of a small amount of ZrOCl₂ in the synthesis solution under acidic conditions. As a result, mesochannel length of SBA-15-Zr was shortened from 600 to <200 nm. The morphology of mesoporous silica was also changed from rod-like to platelet, because of the accelerating effect of Zr(IV) on the self-assembly rate of P123 and TEOS condensation. Characteristic results conducted by low angle XRD, high resolution transmission electron microscopy and nitrogen adsorption, confirmed tuning effect of Zr(IV) in SBA-15. Furthermore, it was shown that the number of pore entrances increases with decreasing the length of SBA-15 mesochannels, leading to obvious improvement of enzyme uptake. PPL has been successfully immobilized in the mesoporous channels of SBA-15-Zr. The total amount of lipase adsorbed on the mesoporous SBA-15-Zr was measured by thermal gravimetric analysis. The largest PPL adsorption capacity was 784 mg/g belonging to the SBA-15-Zr with the length of 150 nm and the mean pore size diameter of 9.22 nm.     

Synthesis of Hf/SBA-15 Lewis acid catalyst for converting glycerol to value-added chemicals

Hf/SBA-15 catalyst containing highly ordered two-dimensional hexagonal mesoporous silica with a large surface area is prepared in a facile one-step sol–gel method with hafnia content ranging from 2.5 to 10%. The synthesized catalyst is characterized by X-ray diffraction analysis, N₂ adsorption–desorption isotherm, scanning electron microscope and transmission electron microscope. The oxidation state and Lewis acidic properties of 10% Hf/SBA-15 are investigated by diffuse reflectance UV–Vis technique, X-ray photoelectron spectroscopy and pyridine-adsorbed FT-IR analysis. The catalytic activity of Hf/SBA-15 is employed in the acetalization of glycerol with acetophenone and benzaldehyde, order of activity of the catalyst is 10 > 5 > 2.5% Hf/SBA-15. The 10% Hf/SBA-15 is given 43 and 21% selectivity of six-membered (1,3-dioxane) and five-membered (1,3-dioxolane) acetals. Hence, this catalyst is further exploited in the acetalization of glycerol with substituted acetophenone and benzaldehyde. The catalyst could be recycled for five times without a significant decrease in activity.     

New mesoporous carbon materials synthesized by a templating procedure

The new porous carbon materials were obtained by templating procedure using mesoporous silica (SBA-15) as template. The ordered mesoporous silica materials were synthesized by using Pluronic P123 (non-ionic triblock copolymer, EO₂₀PO₇₀O₂₀). SBA-15/cryogel carbon composites were obtained by sol–gel polycondenzation of resorcinol and formaldehyde in the presence of different amount of SBA-15. The polycondenzation was followed by freeze drying and subsequent pyrolysis. One set of SBA-15/sucrose carbon composites was prepared by using sucrose as carbon source. The silica template was eliminated by dissolving in hydrofluoric acid (HF) to recover the carbon material. The obtained carbon replicas were characterized by nitrogen adsorption–desorption measurements, X-ray diffraction and scanning electron microscopy (SEM). It was revealed that the samples have high specific surface (533–771 m² g^?1), developed meso- and micro-porosity and amorphous structure. Porous structure of carbon replicas was found to be a function of the carbon source, properties of SBA-15 and silica/carbon ratio. Room temperature adsorption of nitrogen and adsorption of phenol from aqueous solutions were investigated.     

A novel room temperature synthesis of mesoporous SBA-15 from silatrane

Well-ordered and stable two dimensional mesoporous silica, SBA-15, was synthesized at room temperature (RT) from a silatrane precursor and a non-ionic triblock copolymer (EO₂₀PO₇₀EO₂₀) as the structure-directing agent. Using a combination of small angle X-ray scattering, electron microscopy, and nitrogen gas absorption–desorption isotherms, the RT product was found to be equivalent to SBA-15 prepared using more elaborative microwave-assisted hydrothermal methods. Both synthesis routes yielded large surface areas (486–613 m²/g), pore diameters (45–67 Å) and channel volumes (0.6–0.8 cm³/g). All materials condensed as sinuous bundles of silica tubes in a morphology that approximates p6mm symmetry, but where long range order was absent. In addition, portions of the products consisted of fine crystalline mosaics or were aperiodic. The simplicity of the room temperature synthesis route may create an inexpensive and energy-saving process for the large scale production of thermally stable SBA-15 as a catalyst support.     

Synthesis of urea-pyridyl ligand functionalized mesoporous silica hybrid material for hydrophobic and hydrophilic drug delivery application

In this work, we propose the synthesis of urea-pyridyl (UPy) ligand functionalized mesoporous silica hybrid material as novel and effective drug delivery system for loading/release of both hydrophobic and hydrophilic drugs. For the synthesis of UPy ligand functionalized mesoporous silica hybrid material, the combination of sol–gel co-condensation technique and post silica surface modification method were adapted. The prepared UPy ligand functionalized mesoporous silica hybrid (UPy-MSH) material was characterized by X-ray diffraction, Fourier-transform infrared, N₂ adsorption–desorption analysis. The material morphology and mesopore channels were observed by scanning and transmission electron microscopic analyses. The content of modified organic ligand functionalities present in the UPy-MSH material surface was determined by thermogravimetric analysis. The hydrophilic anticancer drug, 5-Fluorouracil and the hydrophobic anti-inflammatory drug, Ibuprofen was used as a model drugs to determine the loading and pH-responsive release efficiency of the synthesized UPy-MSH material under different pH (pH 7.4 and 5.0) conditions, respectively. In addition, the biocompatibility of the UPy-MSH material was evaluated on MDA-MB-231 cells. The experimental results depicted that the synthesized UPy-MSH material is biocompatible and has high drug loading capacity, selective and controlled release of specific drug with respect to the pH condition.     

Synthesis and characterization of the SBA-15/carbon cryogel nanocomposites

The ordered mesoporous silica SBA-15 materials were synthesized using Pluronic P123 (non-ionic triblock copolymer, EO₂₀PO₇₀O₂₀), under acidic conditions. SBA-15/carbon cryogel composites were obtained by sol–gel polycondensation of resorcinol and formaldehyde followed by freeze drying, and subsequent pyrolysis, in the presence of different amounts of SBA-15. For comparison purpose, SBA-15/carbon composite was also prepared using sucrose as carbon source. These materials were characterized by room temperature nitrogen adsorption–desorption measurement, X-ray diffraction, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. It was revealed that the samples have amorphous structure, high specific surface area (350–520 m² g^?1) and developed meso- as well as microporosity. The porosity of structure depends on the carbon source and Si/C ratio which can be easily controlled by varying concentration of starting solution.     

Direct synthesis of nano titania on highly-ordered mesoporous SBA-15 framework for enhancing adsorption and photocatalytic activity

This paper reports the synthesis of TiO₂-containing mesoporous catalysts for effectively enhancing the adsorption and photocatalytic activity. The factors that affect the photocatalytic activity of catalyst composites, including types of silica support, TiO₂ content, calcination temperature, and catalyst mass, were examined in this study. The samples were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and surface area analysis. The experimental results showed that incorporating TiO₂ nanoparticles into silica gel or SBA-15 frameworks could enhance the photodegradation rate more effectively than pure TiO₂. The TiO₂/SBA-15 sample displayed much higher adsorption and photocatalytic activity levels than did TiO₂/silica-gel. The pore volume and pore size of TiO₂/SBA-15 were as high as 1.317 cm³/g and 7.51 nm, respectively, which exceeded those of TiO₂/silica-gel (0.437 cm³/g and 3.68 nm, respectively). The rate constants of photocatalysis were determined. The photodegradation rate of the catalyst increased with decreasing TiO₂ content and increasing calcination temperature. The proposed method of preparing mesoporous photocatalysts is simple and suitable for mass production.     

Progesterone inclusion into cyclodextrin-functionalized mesoporous silica

SBA-15 type mesoporous silica has been modified to produce a covalent bond with β-cyclodextrin by two different synthetic approaches to obtain an hybrid system able to work as a drug delivery system for progesterone. In the first approach, SBA-15 silica was first let to react with 3-glycidyloxypropyltrimethoxysilane to produce an epoxide ring functional group on mesoporous silica. The latter was then reacted under basic conditions with mono-6-deoxy-6-mercapto-β-cyclodextrin (β-CDCH₂SH), prepared in its turn in two steps from β-cyclodextrin (β-CD) through monotosylation to give β-CDCH₂OTs followed by thiolation with thiourea. In the second approach, a silica suitably functionalized with a terminal thiol group (obtained by the reaction of SBA-15 silica with 3-mercaptopropyltrimethoxysilane) was reacted with β-CDCH₂OTs. The obtained materials were characterized by X-Ray powder diffraction, nitrogen adsorption, ¹³C Cross Polarization Magic Angle Spin Nuclear Magnetic Resonance (¹³C CP/MAS NMR). Progesterone was loaded on the materials producing complete filling of mesopores and cyclodextrin cavities. Its release was studied at different pH values. Only one of the two progesterone-loaded delivery device is able to retain the drug in the system during the first period at acid pH (2 h) and release it after pH increase.     

Saponin-loaded SBA-15: release properties and cytotoxicity to Panc-I cancer cells

In this study, first time a nanoformulation, saponin-loaded SBA-15 has been developed for an improved and continuous release. The SBA-15 nanopowder was synthesized by a hydrothermal process. Saponin was introduced into the mesoporous channels of SBA-15 and its concentration in SBA-15 was measured by UV–visible spectrophotometry. The pristine SBA-15 and saponin-loaded SBA-15 were characterized by small-angle XRD, FESEM, HRTEM, TGA, FTIR. N₂ adsorption–desorption isotherms were used to measure the specific surface area and pore channel structure parameters of pristine and loaded SBA-15. Saponin release was studied in phosphate buffered saline (pH 7.4), which revealed that the release rate could be effectively controlled. The controlled drug release is highly desired for cancer treatment. The cytotoxicity of pristine and loaded SBA-15 was analyzed on Panc-I cancer cells. Both the pristine SBA-15 and saponin-loaded SBA-15 nanoparticles showed specific toxicity on the cancer cells. The preliminary results showed that saponin-loaded SBA-15 could be an effective therapeutic agent for Panc-I cancer cells.     

Effect of different lanthanum source and preparation method on the lanthanum-doped mesoporous SBA-15 synthesis

Lanthanum-substituted mesoporous SBA-15 molecular sieve has been prepared by direct synthesis and post-synthesis procedures using lanthanum nitrate or lanthanum chloride as lanthanum source. Characterizations by atomic absorption, X-ray diffraction, nitrogen adsorption, UV–Vis spectra analysis, FT–IR spectroscopy and scanning electron microscopy have been carried out to evaluate the efficiency of the incorporation of lanthanum by these procedures. Results showed that Lanthanum was well incorporated into the hexagonal framework of SBA-15 molecular sieves by these two procedures. These LaSBA-15 mesoporous molecular sieves retain the hexagonal order and physical properties of siliceous SBA-15 material. Compared to lanthanum chloride, the lanthanum nitrate is a suitable lanthanum source, which can match the hydrolysis rate of silicon precursor and composite materials possess larger specific surface area, uniform mesopore size distribution.     

Morphological control of mesoporous silica SBA-15 synthesized at low temperature without additives

Fiber-like or rod-like mesoporous SBA-15 silicas with different lengths and diameter of macrostructures and pore diameter could be synthesized by the self-assembly of silica-surfactant (commonly used Pluronic P123 (EO₂₀-PO₇₀EO₂₀) as a structure-directing agent) through careful control of the synthetic temperature and stirring time without any additives. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms are used to characterize these mesoporous silica materials. Compared with those reports on conventional SBA-15, our work is focused on one-step synthesis and the morphological control of ordered mesoporous silica synthesized at low temperature under low concentration of P123 (0.67 wt%) without the addition of inorganic salts, where pre-hydrolyzed silica species may favor the self-assembly of silica-polymer hybrid micelles. Moreover, the pore diameter of fiber-like SBA-15 synthesized at 40 °C is slightly smaller than that of conventional SBA-15, revealing that the average micellar radius of P123 micelles in this low concentration of P123 solution was almost same as that for the conventional synthesis of SBA-15.     

Effect of SBA-15 on the energy absorption characteristics of epoxy resin for blast mitigation applications

The energy absorption characteristics of silica-filled epoxy composites, for potential application as a blast mitigating retrofitting polymer coating has been explored. Mesoporous silica (SBA-15) with controlled pore size of 5.4 nm was synthesized by the hydrolysis of tetraethyl orthosilicate in the presence of amphiphilic copolymer (PEO-PPO-PEO) which was characterized by nitrogen physisorption studies at 77 K. The porous siliceous rods were homogeneously dispersed in the epoxy resin by ultrasonication (0.5–7 wt%) and subsequently cured using triethylene tetra-amine hardener to prepare silica reinforced composites. Structural, thermal and mechanical properties of the composites were evaluated under dynamic as well as quasi-static conditions which revealed that introduction of SBA-15 at low loadings (1 wt%) led to an increase in the toughness of the base resin but macroporous silica led to deterioration in the properties. The results clearly revealed that the mesoporous nature of silica plays a major role towards improving the dispersion of the filler which in turn resulted in improved properties. Neat epoxy samples fractured in a brittle fashion, but in the presence of SBA-15, the sample exhibited ductile failure, which was explained on the basis of a crack pinning mechanism. High strain rate studies (~10³ s^?1) of selected compositions were performed on a Split Hopkinson pressure bar and the effect of addition of mesoporous silica on the energy absorption characteristics were established. Finite element analysis was used to predict the behavior of concrete slabs on exposure to dynamic loadings resulting from TNT explosions, both in the presence and absence of the epoxy layer, which revealed the role of the retrofit as a fragment arrestor.