Hybrid polymeric systems of mesoporous silica/hydroxyapatite nanoparticles applied as antitumor drug delivery platform

In this study, we report the production of a mesoporous silica/hydroxyapatite-based nanocomposite containing copper (Cu) functionalized with methacrylic acid (MAA), a pH-sensitive polymer. The functionalization of the nanoparticles surface was performed using the microwave method in order to anchor the cross-linking tetraethylene glycol dimethacrylate (TEGDMA), onto the nanoparticles surface followed by MAA polymerization. The materials were characterized by XRD, XRF spectroscopy, scanning and transmission electron microscopy, Fourier transform infrared spectroscopy, thermal analysis, zeta potential, and elemental analysis. Studies of the incorporation and release of the antitumor methotrexate drug were performed in order to evaluate the potential use of these drug carrier systems in cancer therapy. Moreover, the in vitro cytotoxicity of the samples in fibroblast and SAOS-2 cells was investigated, and the activity of the adipose-derived stem cell alkaline phosphatase on nanocomposites was studied by in vitro assays. The results indicate that the Cu-containing nanocomposites can be easily produced and that these compositions have beneficial effects in stem cells, maintaining cell viability, and allowing alkaline phosphatase expression. In conclusion, data from this work show that the nanocomposites obtained have adequate characteristic to be used as drug delivery platform. Furthermore, the biomaterial is a promising structure for treatment of bone tumor.     

Synthesis of hollow mesoporous silica (HMS) nanoparticles as a candidate for sulfasalazine drug loading

Hollow mesoporous silica nanoparticles have emerged as attractive drug delivery carriers. In this work, we report successful synthesis of hollow mesoporous silica nanoparticles (HMSNs) using poly tert-butyl acrylate (PtBA) nanospheres as hard templates and CTAB as structure directing agent for loading sulfasalazine into its porous structure. The samples were synthesized using PtBA; sodium dodecyl sulfate (SDS) - in an aqueous solution of CTAB and tetraethylorthosilicate (TEOS) as the inorganic precursor. Two different methods were utilized to remove organic phases including calcination, and acidic/basic ethanolic solvent extraction approach. For the latter, microstructural studies using SEM and N₂ porosimetery revealed the formation of highly uniform mono-dispersed particles of sphere morphology (~ 130 nm) with the high specific surface area (1501 m²/g) and mean pore size of ~ 2.6 nm. However, rather deformed and aggregated sphere-like particles were obtained for the calcined samples. TEM examinations also confirmed the formation of 20–30 nm thick walls for the prepared HMSNs particles. Further, HMSN samples treated by solvent extraction method were functionalized by 3-aminopropyl triethoxysilane (APTS) compound for drug delivery. DTA/TG analysis showed that the total amount of loaded sulfasalazine drug was 5.1 wt%.     

利用甲基纤维素辅助合成介孔二氧化硅微球

通过调节硅酸四乙酯（TEOS）和嵌段聚合物F127（EO₁₀₆PO₇₀EO₁₀₆）体系的pH值调控TEOS水解的速度,并利用甲基纤维素（MC）在水热条件下形成网格状液晶微滴结构的特点,一步诱导硅胶初级粒子聚沉制备微米级介孔氧化硅微球。研究了溶胶 凝胶的温度、pH值对成球性和孔结构的影响,通过氮吸附（BET）,X射线衍射（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、马尔文激光粒度分析（Malven）等手段分析表征了介孔氧化硅微球的形貌和孔结构,实验结果表明通过向TEOS和F127体系中加入MC,在pH＝1、80℃条件下一步水热晶化可以合成直径在4～6 μm、比表面积为450 m²·g^-1、孔径为4.2 nm的介孔氧化硅微球。     

Removal of DDT from aqueous solutions using mesoporous silica materials

BACKGROUND: There are few reports about adsorbents for the effective removal of large‐molecule pesticides such as DDT (1,1,1‐trichloro‐2,2′ bis(p‐chlorophenyl)ethane). Some mesoporous silica materials and their modified derivatives might serve as good adsorbents for these large organic molecules because of their large pore diameter and special pore structures. In this work, the adsorption processes of DDT in aqueous solutions were investigated using different mesoporous silica materials, including HMS, MCM‐41, SBA‐15 and MCM‐48. RESULTS: All these materials exhibit efficient DDT removal, and the adsorption is a rapid process with over 50% of DDT removed within approximately 2 h. The efficiency of DDT removal is influenced by the adsorbent characteristics, such as pore volume, pore diameter, connectivity between pore channels and surface OH groups. The influences of water/acetone ratio and initial DDT concentration in solution were also explored. It was found that with enhancing DDT solubility, the addition of acetone in the reaction solution had no evident impact on DDT adsorption efficiency. Increasing the initial concentration of DDT resulted in a decrease of DDT adsorption efficiency. The adsorption kinetics of DDT on mesoporous silica material is shown to be pseudo‐second‐order. After thermal treatment at a relatively low temperature of 450 °C, the adsorbed DDT was completely decomposed and the adsorbents, except MCM‐41, were regenerated well. CONCLUSION: The results demonstrate the potential of a simple and efficient new approach for the removal of OCPs (organochlorine pesticides), especially large OCP molecules from surface water or groundwater. Copyright © 2008 Society of Chemical Industry     

介孔氧化硅负载贵金属催化剂研究进展

有序介孔氧化硅材料具有独特的结构和性质,如高的比表面积、大的孔容、均一的孔径分布、丰富的结构和形貌等,在多相催化领域受到广泛的关注和研究。本文回顾了近年来介孔氧化硅在负载贵金属催化剂方面的研究现状,介绍了直接浸渍法、官能团修饰法、原子层沉积法、一锅合成法等不同的负载方法,归纳比较了各种方法之间的优缺点。同时也指出了介孔有序SiO2材料在催化负载方面存在的一些局限,并对其发展前景做了展望,认为降低介孔氧化硅的成本、提高载体的水热稳定性、开发新结构和性能的介孔氧化硅以及探索新的催化剂负载工艺,将是未来介孔氧化硅在多相催化领域应用研究的重要方向。     

氨改性的介孔二氧化硅的直接合成和CO2吸附

Amine-functionalized mesoporous silica was prepared by using lauric acid and N-stearoyl-l-glutamic acid as structure directing agents via the SN+-I mechanism and applied to CO2 adsorption at room temperature. With γ-aminopropyltriethoxysilane as co-structure directing agent and due to the direct electrostatic interaction with anionic surfactant, most of the amino groups were uniformly distributed at the inner surface of pores and the performance was stable. The amine-functionalized mesoporous silica was characterized by Fourier transform infrared spectrometer, X-ray diffraction, nitrogen physisorption and thermogravimetric analysis. The CO2 adsorption capacity was measured by digital recording balance. At the room temperature and under the atmospheric pres-sure, the adsorption capacity of LAA-AMS-0.2 for CO2 and N2 is 1.40 mmol•g1 and 0.03 mmol•g1, respectively, indicating high separation coefficient of CO2/N2.     

Synthesis of mesoporous silica using a mineral silica source

Mesoporous silica has been applied in catalysis, separations, and drug delivery. It has generally been made using organosilicon precursors such as tetraethyl orthosilicate. For sustainability, it is necessary to find readily accessible mineral sources for making mesoporous silica. In this work, we demonstrate the successful synthesis of mesoporous silica with 10 nm average pore size using the mineral forsterite (Mg₂SiO₄) as a silica source, providing a potentially cheaper and more Earth-friendly route to making technologically important porous silica materials. Pure forsterite was synthesized by a solid-state chemistry route at 1000°C and underwent dissolution–reprecipitation in aqueous hydrochloric acid containing the soft template surfactant, Pluronic P123. Variations of initial reaction pH (−0.2 to 0.6), reaction time (12–24 h), reaction temperature (50 to 90°C), and silica precursor (forsterite and fumed silica) were performed. The mesoporous silica aged at 70°C for 24 h had the highest porosity, with a surface area of 735 m²/g and a pore volume of 1.4 ml/g, comparable to mesoporous silica made using conventional starting materials. This novel geomimetic synthesis route supports the possibility of analogous formation of structured (mesoporous or zeolitic) silica in nature under abiotic or prebiotic conditions.     

Silica foams with ultra-large specific surface area structured by hollow mesoporous silica spheres

Ceramic foams with multi-scale pores and large specific surface area have received extensive attention due to their unique structure and superior properties. Considering that there are still challenges to synthesize porous ceramics with large specific surface area, a novel ceramic foam material with ultra-large specific surface area has been prepared using hollow silica mesoporous spheres (HMSSs) as building block in this work. These building blocks were made weakly hydrophobic in order to produce HMSS particle stabilized foams. The foams exhibit a uniform primary macropore structure, which is composed of a three dimensional HMSS-assembled network, via HMSS-stabilized foams. The influence of sintering temperature on the microstructure and properties of HMSS foams is investigated. The HMSS foams exhibit highest specific surface area of 1733 m²/g, attributed to the radial mesopores in HMSS shell, when sintered at between 500°C and 800°C. This specific surface area is much higher than that of existing ceramic materials. The uniform pore structure and ultra-large specific surface area make it a promising lightweight material in potential application fields, including catalyst, adsorption, fire-resistant thermal insulation, and load and control release system.     

介孔硅SBA-15对水溶液中咪唑基离子液体的吸附性能研究

本文研究了介孔硅SBA-15对水中咪唑基离子液体[Bmim]Cl和[Bmim]OH的吸附行为。合成的SBA-15具有有序的二维六方介孔结构。研究发现升高温度会使SBA-15对离子液体的吸附量降低,吸附过程是放热过程。25℃下将吸附等温数据进行Langmuir和Freundlich方程线性拟合,相比之下Langmuir模型更适合用来描述SBA-15对两种离子液的吸附行为,SBA-15对[Bmim]Cl和[Bmim]OH最大吸附量分别为336.7和467.3mg·g-1。     

Submicron mesoporous carbon spheres by ultrasonic emulsification

In this work submicron mesoporous carbon spheres with the BET surface area of 510–610 m²/g and the mesopore volume of 0.86 cm³/g can be firstly obtained from carbonization of resorcinol-formaldehyde (RF) submicron spheres which are prepared from water-in-oil emulsification with span80 and ultrasonic dispersion followed by freeze drying and pyrolysis. Moreover, surface texture and mesoporous properties can be obviously changed by ultrasonic emulsification. By using ultrasonic emulsification, more number and much smaller size submicron carbon spheres can be observed compared to homogenized and mechanically stirred emulsifications.     

CO2 adsorption using amine-functionalized mesoporous silica prepared via anionic surfactant-mediated synthesis

A series of directly amine-functionalized mesoporous silicas was prepared via an anionic surfactant-mediated synthesis method and applied to CO₂ adsorption at room temperature. The structurally robust amine functionality in the material accompanied by preferential positioning of amine groups normal to the surface of a silica support due to the S⁻N⁺  I⁻ mechanism proved to be beneficial for CO₂ adsorption. Rather than surface area or pore volume, amine content of the mesoporous material was found to be the governing factor to achieve high CO₂ adsorption capacity. Covalently bonded amine species in the mesoporous silica were robust enough to maintain steady adsorption performance during 10 repetitions of the adsorption–desorption cycle.     

介孔硅胶负载次氯酸脱除柴油中的硫化物

采取介孔硅胶负载次氯酸脱除硫含量为150μg·g-1的4,6-二甲基二苯并噻吩模型柴油中的硫化物,考察孔结构和脱硫条件对介孔硅胶负载次氯酸脱除模型柴油硫化物的影响,研究再生条件对脱硫剂再生效果的影响。通过红外光谱和N2等温吸附对硅胶进行表征,N2等温吸附分析结果表明,实验选用的3种硅胶均为介孔硅胶;红外光谱分析结果表明,不同孔结构的介孔硅胶均可以负载次氯酸并将模型柴油中4,6-二甲基二苯并噻吩氧化为砜并吸附在介孔硅胶上。SGA型硅胶脱硫率较低;而在反应温度35℃和剂油质量比0.050条件下,使用次氯酸负载质量分数为90.7%的SGB型硅胶,脱硫率达97.3%,使用次氯酸负载质量分数为79%的SGC型硅胶,脱硫率达99.0%。在反应温度30℃和剂液质量比0.19条件下,分别清洗10次,清洗时间5 min,SGC型硅胶的脱硫率下降幅度很小,而SGB型硅胶的脱硫率明显下降。大孔径有利于介孔硅胶负载次氯酸脱除柴油中的硫化物,而且有利于脱硫剂的再生。     

Hierarchical mesoporous silica microspheres as unique hard-template for preparation of hierarchical mesoporous TiO2 microspheres with trimodal mesoporosities via nanocasting

This work for the first time reported that hierarchical meso-mesoporous SBA-15 silica microspheres (HMM-SiO₂-MSs) can serve as a unique and suitable hard-template for the nanocasting preparation of mesoporous TiO₂ with both hierarchical mesostructures and well-preserved microsphere particle morphology. A two-step impregnation (TSI) method was developed and customized and its effectiveness was studied in comparison with the single-step impregnation method. Trimodal mesoporosities and their origin are newly recognized and analyzed. The materials were examined by various techniques, including the FE-SEM, N₂ sorption, TEM and XRD. Under optimized conditions, the hierarchical mesostructures and spherical particle morphology of HMM-SiO₂-MSs can be replicated for HMM-TiO₂-MSs. The high surface area and pore volume of HMM-TiO₂-MSs reach 194 m² g^-1 and 0.68 cm³ g^-1, respectively, with the latter more than twice those templated by conventional SBA-15s. Besides HMM-TiO₂-MSs, such HMM-SiO₂-MSs as hard-template might be extended to the preparation of other materials with hierarchical mesostructures.     

Facile synthesis of sulfo-functionalized mesoporous silica with strong acidity by temperature-controlled calcination

The facile synthesis of sulfo-functionalized mesoporous silica (MCM-41) by a one-step process of surfactant removal and thiol oxidation technique through a temperature-controlled calcination of a precursor is presented. Thiol containing mesoporous silica is synthesized as a precursor by hydrolysis and co-condensation of tetramethoxysilane (TMOS) and mercaptopropyl trimethoxysilane (MPTMS). The samples thus prepared are shown to preserve the ordered two-dimensional hexagonal structure and pore characteristics of MCM-41, while functionalizing the material with sulfo groups which was oxidized from thiol groups providing strong acidity. The acidity of the material is demonstrated by high ammonia uptakes and low differential adsorption energy of ammonia.     

Dual responsive block copolymer coated hollow mesoporous silica nanoparticles for glucose-mediated transcutaneous drug delivery

A self-regulated anti-diabetic drug release device mimicking pancreatic cells is highly desirable for the therapy of diabetes. Herein, a glucose-mediated dual-responsive drug delivery system, which combines pH- and H₂O₂-responsive block copolymer grafted hollow mesoporous silica nanoparticles (HMSNs) with microneedle (MN) array patch, has been developed to achieve self-regulated administration. The poly[4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate]-b-poly[2-(dimethylamino)ethyl methacrylate] (PPBEM-b-PDM) polymer serves as gate keeper to prevent drug release from the cavity of HMSNs at normoglycemic level. In contrast, the drug release rate is significantly enhanced upon H₂O₂ and pH stimuli due to the chemical change of H₂O₂ sensitive PPBEM block and acid responsive PDM block. Therefore, incorporation of anti-diabetic drug and glucose oxidase (GOx, which can oxidize glucose to gluconic acid and in-situ produce H₂O₂) into stimulus polymer coated HMSNs results in a glucose-mediated MN device after depositing the drug-loaded nanoparticles into MN array patch. Both in vitro and in vivo results show this MN device presents a glucose mediated self-regulated drug release characteristic, which possesses a rapid drug release at hyperglycemic level but retarded drug release at normoglycemic level. The result indicates that the fabricated smart drug delivery system is a good candidate for the therapy of diabetes.     

3D cubic mesoporous silica microsphere as a carrier for poorly soluble drug carvedilol

The present work was proposed not only to exploit the potential of 3D cage-like mesoporous silica SBA-16 with a well-defined spherical morphology as a carrier for poorly soluble drugs, but also to compare the drug loading and release properties of 3D cubic SBA-16 with that of classic 2D hexagonal MCM-41. SBA-16 microsphere with highly ordered mesostructures was synthesized by a facile method using block co-polymer F127 as template, cetyltrimethylammonium bromide (CTAB) as co-template and tetraethyl orthosilicate (TEOS) as silica source. Carvedilol (CAR), an antihypertensive agent, was used as a model drug and loaded into mesoporous silica via solvent deposition method at drug-silica ratio of 1:3. In vitro dissolution was performed in both simulated intestinal fluid (SIF, pH 6.8) and simulated gastric fluid (SGF, pH 1.2). Of particular interest was that in SIF both MCM-41 and SBA-16 samples exhibited promoted dissolution profile for CAR as compared to its corresponding crystalline form which exhibited poor dissolution behavior. This dissolution-enhancing effect might be due to the non-crystalline state and increased surface area of confined CAR as well as the hydrophilic nature of silica. In comparison with MCM-41, SBA-16 displayed a more rapid release profile in both SIF and SGF, which may be ascribed to the 3D interconnected pore networks and the highly accessible surface areas. The suitability of the utilization of SBA-16 microsphere as carriers will open new avenues for the formulation of poorly soluble drugs.     

CO2/N2开关型脒基表面活性剂软模板制备介孔二氧化硅

模板法是制备介孔SiO₂的常用方法之一,而模板法通常需要脱除模板后才能得到介孔结构。以传统表面活性剂为模板合成介孔二氧化硅,除模板方法还有高温焙烧、溶剂萃取等,但这些方法均存在一定的缺点,如导致结构坍塌、消耗大量溶剂等。本文采用开关型表面活性剂N'-十二烷基-N,N-二甲基乙基脒碳酸氢盐为模板剂,以正硅酸四乙酯(TEOS)为硅源在碱性条件下合成SiO₂。与常规除模板法不同,本实验在反应结束后加热并通入N₂使表面活性剂分解失去表面活性,用水和丙酮洗涤后得到了形貌规整、孔道有序、具有较高比表面积和孔容的介孔SiO₂。同时还研究了有机盐乙二胺四乙酸二钠(Na₂EDTA)对介孔有序度、所得介孔材料比表面积、孔容孔径和模板残留量的影响。     

Influence of the structure characteristics of ordered mesoporous silica materials on their properties as supports for Ni-modified hydrogenation catalysts

The structure characteristics of Ni-modified (7 wt% Ni) mesoporous materials with cubic (Ia3d and Fm3m space groups) structure have been compared to that of the hexagonal MCM-41 material with uni- dimentional channel arrangement by X-ray diffraction and N₂ adsorption–desorption measurements. Thermal gravimetric analysis and toluene hydrogenation have been used for characterization of the reducibility of the supported Ni phase and its catalytic activity in this test reaction, respectively. The results from N₂ physisorption suggest that substantially higher pore blockage with Ni occurs when it is deposited on the 1D channel structure of MCM-41 compared to the cage-like pores of Fm3m and the interconnected pores of Ia3d material. It is proposed that the pore architecture determines the distribution of the oxide metal phase and its reducibility and strongly influences the hydrogenation activity of the catalysts.     

Ordered mesoporous magnesium silicate with uniform nanochannels as a drug delivery system: The effect of calcination temperature on drug delivery rate

Magnesium silicate nanostructured biomaterials with good bioactivity, biocompatibility, and mechanical properties are promising for applications in various biomedical fields. Herein, ordered mesoporous magnesium silicate (OMMS) was prepared by sol-gel method and the effect of calcination temperature to evaluate its application as ibuprofen (IBU) drug delivery system was investigated. The synthesized powders were calcined at 350, 550, 750 °C and characterized by X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR), N₂ adsorption–desorption, and transmission electron microscopy (TEM). All samples demonstrated mesoporous characteristics with high specific surface area ranging from 386 to 504 m²/g. It was found that the sample calcined at 350 °C showed the slowest drug release rate among all samples, which is due to smaller pore size and the existence of larger amounts of intrawall microporosity. Cytotoxicity of MG63 osteoblast cell line was investigated by MTT assay, indicating no toxicity for IBU- loaded sample calcined at 550 °C with a concentration less than 10 mg/ml. This study has revealed that altering the calcination temperature may change the drug delivery behavior of OMMS by influencing textural properties and suggests OMMS as a promising local drug delivery system in bone tissue engineering applications.