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.     

Impact of surface loading on catalytic activity of regular and low micropore SBA-15 in the Knoevenagel condensation

The mesopores of SBA-15 are well-suited for immobilizing catalytic aminosilanes for converting substrates for fine chemicals, but these materials have micropores that could impact the observed reaction rate of immobilized catalysts. Materials are synthesized with conventional methods that produce micropores (Regular Micropore SBA-15; REG) and compared to materials with limited to no micropore volume (NMP SBA-15). These materials are functionalized with aminosilanes for testing in the Knoevenagel condensation. For low amine loadings, NMP materials have a higher observed reaction rate compared to REG materials, achieving twice the conversion in the same time. As the surface density increases, the reaction rate for NMP materials decreases since organosilane functionalization consumes surface silanols that interact cooperatively with the amine. Regardless of surface density, the NMP materials have higher observed reaction rate than the REG materials. These results demonstrate the importance of reducing micropore volume to create highly active catalytic materials.     

B–SBA-15–SO<Subscript>3</Subscript>H: a versatile mesoporous catalyst

Novel approach was developed towards the synthesis of heterogeneous mesoporous B–SBA-15–SO₃H acid catalysts. That is: B–SBA-15 materials were hydrothermally synthesized by using three different boron sources (boric acid, trisiopropylborate and potassium borohydride) and then post-synthetically functionalized with sulfonic acid to test their catalytic activity for the esterification of propionic acid with methanol. Mesoporous and amorphous character of the materials as well as the incorporation of the boron into the framework were verified by XRD, N₂-adsorption/desorption, ICP–OES, SEM and FT-IR techniques. All of the boron incorporated acid catalysts showed better activity than pure SBA-15–SO₃H for methyl propionate synthesis. Combining the advantageous of hydrothermal synthesis and post functionalization, the obtained B–SBA-15–SO₃H catalysts should present versatile catalytic properties in terms of both catalytic activity and reusability. Boron incorporation and post functionalization encourage the structural configuration, since the grafted catalytically active groups may experience similar environments and be isolated from each other.     

Preparation and characterization of octyl and octadecyl-modified mesoporous SBA-15 silica molecular sieves for adsorption of dimethyl phthalate and diethyl phthalate

Octyl (C₈) or octadecyl (C₁₈)-modified mesoporous SBA-15 silica molecular sieves have been prepared by adding SBA-15 silica molecular sieves to octyltrimethoxysilane or octadecyltrimethoxysilane in toluene at 100 °C, and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), nitrogen adsorption–desorption measurements, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). FTIR spectra shows the presence of methylene (–CH₂–) and methyl (–CH₃) bands on the modified SBA-15. Powder XRD data indicate the structure of modified SBA-15 with octyl or octadecyl groups still remains two-dimensional hexagonal mesostructrure. Brunauer–Emmett–Teller (BET) surface area analysis presents that surface area of octyl- and octadeyl-SBA-15 changed from 647 to 449 and 321 m² g⁻¹, respectively, and SEM images show the decreased size of modified SBA-15 particles. TEM images of modified materials with alkyl groups show the structures remain the same as the parent SBA-15 silica. We also have studied the adsorption capacity of the materials to phthalate esters (dimethyl and diethyl phthalate) by dynamic adsorption experiments on high performance liquid chromatography (HPLC). It is found that the modified materials can increase the adsorption of phthalate esters compared to SBA-15 particles, and the adsorption capacity increased with the increased length of alkyl chain on SBA-15. The maximum dynamic adsorption capacity for diethyl phthalate was 3.9 (C₈-SBA-15) or 4.3 (C₁₈-SBA-15) times higher than that of SBA-15 particles, respectively. The results indicate that alkyl SBA-15 particles could be used for enrichment of phthalate esters in water samples before the further analysis.     

Surface functionalization of SBA-15 nanorods for anticancer drug delivery

SBA-15 nanorods with high surface area (1010 m² g⁻¹) were functionalized by post grafting method with three different alkoxysilanes including (3-aminopropyl) triethoxysilane (APTES), 3-[bis(2-hydroxyethyl)amino] propyl triethoxysilane (HAPS) and 3-[2-(2-aminoethylamino) ethylamino] propyl trimethoxysilane (AEPS). The prepared materials were used as nanocarriers for an anticancer drug (gemcitabine). The obtained samples were characterized by SAXS, elemental analysis, TGA, N₂ adsorption/desorption, SEM, TEM, FTIR and UV spectroscopies. The adsorption and release properties of all samples were investigated. It was found that the surface functionalization increases the interaction between the carrier and gemcitabine and results in the loading enhancement of the drug. In addition, the adsorption of gemcitabine on the modified mesoporous matrix depends on the type and the amount of alkoxysilanes groups. The maximum content of the deposited drug in the modified SBA-15 nanorods is close to 22 wt.%. The rate of the drug release from the modified samples containing NH₂ groups on their surfaces is pH dependent.     

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite with sulfonic acid for acid-catalyzed reactions

Chemical functionalization of chitosan biopolymer and chitosan-magnetite nanocomposite was performed with sulfonic acid functional groups to achieve new solid acid materials. The sulfonic acid functional groups were created through the ring opening nucleophilic reaction of amine groups of chitosan with 1,4-butane sultone. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopies (XPS) verified the successful sulfonic acid functionalization of chitosan. The obtained sulfonic acid functionalized chitosan-magnetite nanocomposite showed superparamagnetic properties according to the vibrating sample magnetometry analysis and exhibited magnetic separation feature from dispersed mixtures. Nitrogen adsorption-desorption analysis indicated the increase in surface area after formation of chitosan-magnetite nanocomposite and functionalization with sulfonic acid. Both of the prepared solid acids exhibited high catalytic activities in the acid-catalyzed acetic acid esterification with n-butanol and benzaldehyde acetalization with ethylene glycol as model reactions. Furthermore, they can be reused several times without considerable loss of their activities.     

Synthesis and Characterization of Silica–Polymer Nanocomposites Functionalized with Piperazine for the Synthesis of β-Nitro Alcohols

Abstract  

In order to compare the activity and selectivity for the synthesis of β-nitro alcohols, piperazine was functionalized directly and after surface modification into the ordered mesoporous SBA-15 framework. The materials were characterized by powder X-ray diffraction, N₂-adsorption–desorption isotherm, FT-IR, SS-NMR and scanning electron microscopy. The catalyst synthesized via surface modification under solvent free conditions showed very high activity and selectivity of β-nitro alcohols compared to the one synthesized by direct functionalization of SBA-15. Finally the possible reaction pathways were explained mechanistically.     

In-vitro drug release kinetics studies of mesoporous SBA-15-azathioprine composite

The mesoporous silica (or SBA-15) was loaded with azathioprine drug. Azathioprine drug was incorporated into mesoporous silica by post impregnation method to reduce its toxic effects by controlling the drug release property. The synthesized pure SBA-15 and SBA-15-azathioprine composite were characterized by UV–visible spectrophotometry, thermo-gravimetric analysis, small and large angle powder X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption–desorption analysis. The successful inclusion of azathioprine drug in host material SBA-15 was confirmed by the reduced surface area (114 m²/g) and pore diameter (6.5 nm) of the organic–inorganic composite material. The drug entrapment efficiency of 90.67 % and loading efficiency of 72.67 % was achieved. The azathioprine drug release process from the mesoporous silica to simulated gastric, intestinal and body fluid were examined and the controlled release effect of the azathioprine drug in all fluids were studied. The Korsmeyer–Peppas model fits well the drug release data with the non-Fickian diffusion model and zero order kinetics for produced mesoporous silica. The controlled drug release enhanced the bioavailability and reduces its repeated administration. Hence, the composite drug can reduce the toxicity and side effects of the azathioprine.     

粒径对磺酸官能化介孔材料性能的影响

以聚乙氧基-聚丙氧基-聚乙氧基三嵌段共聚物(P123)为模板剂、正硅酸乙酯(TEOS)为硅源,保持P123和TEOS的浓度比,改变P123和TEOS在合成体系中的浓度,水热法合成了系列具有不同粒径的介孔分子筛SBA-15.采用后合成法,将3-巯基丙摹三甲氧基硅烷(MPTMS)嫁接到具有不同粒径的介孔分子筛SBA-15表面上,经氧化后得到含有强酸性的磺酸基因的固体酸样品SBA-15-SO_3H.采用SEM、XRD、FT-IR、TG-DTA、N_2吸附以及酯化反应考察了粒径对所制备的SBA-15-SO_3H的物化性能和催化性能的影响.结果表明,SBA-15的粒径大小对MPTMS在其上的嫁接量没有很人影响,但对后续氧化过程有较大的影响,SBA-15粒径的减小有利于巯基被氧化为磺酸基,导致磺酸的负载量随着粒径的减少而增大.SBA-15-SO_3H在乙酸和乙醇的酯化反应中表现出不同的催化性能,催化性能的差异是粒径大小、酸量及磺酸基和巯基相互作用的综合结果.     

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。     

AuPd bimetal immobilized on amine-functionalized SBA-15 for hydrogen generation from formic acid: The effect of the ratio of toluene to DMF

The volume ratio of toluene to N,N-dimethylformamide (DMF) was adjusted during the amine functionalization of SBA-15 to change the amine content of SBA-15. XPS, FTIR, and TGA analyses indicated that under the experimental synthetic conditions the number of amine groups varies with the ratio of toluene/DMF, and the highest content of amine could be obtained with a volume ratio of toluene/DMF = 3:2. The hydrogen production experiment of formic acid decomposition showed that the hydrogen production efficiency over the Au-Pd-SBA-15-NH₂ catalysts increased with the increase in the surface amine content of the Au-Pd-SBA-15-NH₂. The optimal Au-Pd-SBA-15-NH₂-TD (toluene/DMF = 3:2) catalyst proved to have the smallest Au-Pd bimetal nanoparticle size and exhibited a turnover frequency (TOF) = 631 hours⁻¹ and an activation energy (Ea) = 20.8 kJ · mol⁻¹ at 25°C. The catalytic performance of hydrogen generation from the formic acid was improved due to the synergistic effect between the amine-functionalized SBA-15 and the Au-Pd bimetal (metal-support interactions).     

Efficient cyclohexyl acrylate production by direct addition of acrylic acid and cyclohexene over SBA-15-SO3H

A set of propysulfonic acid modified mesostructured silica materials (SBA-15-SO₃H) were prepared by a convenient one-pot co-condensation method. Samples were characterized by XRD, FT-IR, Py-FTIR, N₂ adsorption–desorption, elemental analysis and acid–base titration. The catalysts exhibited excellent activities and selectivities for addition esterification of acrylic acid and cyclohexene. The highest catalytic activity (82.8 %) and selectivity (92.6 %) were obtained over SBA-15-SO₃H (15 %). The efficient catalytic performance of SBA-15-SO₃H (15 %) was attributed to the high surface area, proper mesopore texture and presence of sulfonic acid groups in its structure. SBA-15-SO₃H catalyst was easily separated and recycled with high stability.     

Effects of SBA-15 and its content on MMA solution polymerization and PMMA composites

An ordered mesoporous material, such as SBA-15 was considered as a promising reinforcement agent for polymeric materials due to its large surface area and uniform pore structure. In this paper, poly(methyl methacrylate) (PMMA)/SBA-15 composites were prepared by in situ free-radical solution polymerization of MMA in the presence of SBA-15. The effects of SBA-15 content on solution polymerization and the properties of the final polymer composite were investigated. The PMMA molecular weight and its distribution in PMMA/SBA-15 composites were determined by gel permeation chromatography. Fourier-transform infrared spectra, X-ray diffraction, thermal gravimetric analysis (TGA), differential scanning calorimeter and dynamic mechanical analysis were used to characterize the structure and properties of the composites. The morphology of the composites was observed by scanning electric microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the monomer conversion dropped off, but the polymer average molecular weight increased upon the introduction of SBA-15 into solution polymerization process. When compared with pure PMMA, the storage modulus of the composites was improved and the highest improvement was acquired at 1 wt% of SBA-15, based on the monomer feed content. The glass transition temperatures of the composites were increased slightly. TGA results confirmed that the thermal stability of the composite was not influenced much and a higher degree of terminal vinyl groups was formed in the product of polymerization. SEM and TEM images indicated that SBA-15 particles were incorporated into the polymer matrix.     

Preparation of Mesoporous Catalyst Supported on Silica with Finely Dispersed Ni Particles

A novel nickel catalyst supported on SBA-15 type mesoporous silica was synthesized by the grafting of N-(trimethoxysilylpropyl)ethylene diamine triacetic acid salt (EDTA) onto the surface of SBA-15 and followed by adsorption of nickel ions and calcinations (Ni-E-SBA). The catalysts prepared were characterized using XRD, TEM, TED, SAXS and N₂ adsorption/desorption measurements. While nickel particles loaded on catalysts prepared by the wet impregnation method were found to be aggregated on the outer wall of the supports, nickel particles were finely dispersed on the surface of the mesopores in the Ni-E-SBA catalyst. The catalytic performances of the prepared catalysts were evaluated using the hydrodechlorination (HDC) of 1,1,2-trichloroethane (TCEa) as a model reaction. Results showed that the Ni-E-SBA catalyst had the highest activities of the catalysts examined under the given conditions.     

Synthesis and characterization of Co-containing SBA-15 catalysts

Two Co-SBA-15 catalysts were synthesized and characterized by thermogravimetry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, porosity, UV–visible diffuse reflectance and temperature programmed reduction with H₂. The first catalyst was prepared synthesizing SBA-15 and then adding Co ions by impregnation (Co_imprSBA-15). The second catalyst was prepared using a more complex procedure of immobilization of cobalt ions in the presence of pyridine and H₂O₂ on –COOH groups anchored to the SBA-15 structure [Co-SBA-15(COOH)]. These COOH groups were created starting from cyano groups introduced during the synthesis of the periodic mesoporous materials as 4-triethoxysilylbutyronitrile. Characterization of the samples indicates that in both cases the typical 2D periodical hexagonal structure of SBA-15 was obtained, but with less ordered packing in the second case. The cobalt is highly dispersed in the SBA-15 (up to 9% w/w) and is present mainly as Co²⁺ ions in highly distorted tetrahedral or square pyramidal coordination. Some coordinatively unsaturated Co(II) Lewis acid centers are present in Co_imprSBA-15, while in Co-SBA-15(COOH) coordination of pyridine to cobalt tentatively may induce the formation of Co³⁺ ions, although in both catalysts the dominant species are Co²⁺ ions in a very close environment.     

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.     

In situ Formation of Palladium Nanoparticles Inside the Pore Channels of Ordered Mesoporous Silica

Palladium-containing SBA-15 (SBA-15-Pd) was synthesized via an in situ approach. In this procedure, molecular assembly template was employed as a hydrophobic carrier to provide the compatible environment for the hydrophobic compounds. The hydrophobic solvent (CHCl₃) was used as a transport medium to inject the Pd precursor (Pd(acetylacetonate)₂) directly into the inner core of the surfactant micelles. A 1.46 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 SBA-15-Pd nanocomposites were investigated in Heck coupling reactions with activated and non-activated aryl substrates. The SBA-15-Pd nanocomposites exhibit excellent catalytic activities and reuse ability in air for the Heck carbon–carbon coupling reactions.     

改性介孔分子筛对布洛芬的吸附与控制释放

采用合成后改性将氨基嫁接进介孔MCM41和SBA-15孔道内,对功能化的2种分子筛进行药物吸附与控制释放的研究。利用红外光谱仪(IR)、智能重量分析仪(IGA)等表征手段对吸附剂的物理结构和化学组成进行表征。对药物布洛芬(IBU)的吸附量进行比较,结果表明,氨基改性的MCM41(MCM41-NH2)对布洛芬的吸附性能大...     

Applications of Amine-functionalized Mesoporous Silica in Fine Chemical Synthesis

SBA-15 silica containing homogeneously distributed amine-functional groups and of fiber or platelet morphology was prepared through a modified co-condensation method using P123 copolymer as template under acidic condition. Synthetic factors which led to well-ordered mesoporous materials with high loadings of various amine groups were discussed. The resultant mesoporous materials were efficient base catalysts in Knoevenagel and Claisen–Schmidt addition reactions. The activities over SBA-15 materials with different amino-functional groups are compared. Moreover, the advantage of ordered large mesopores of SBA-15 in catalyzing liquid phase reactions was demonstrated, and the reaction rate could be further increased when SBA-15 was with platelet morphology and short mesochannels.     

组装法制备巯基改性磁性SBA-15

采用热分解法制备了单分散、平均粒径约15nm的锰铁氧体磁性纳米粒子。通过正硅酸乙酯与磁性纳米粒子表面油酸盐的配体交换将磁性纳米粒子锚定在SBA-15表面。并且将负载过程与巯基改性过程耦合制备了巯基改性的磁性SBA-15。考察了合成SBA-15过程中干燥方式对其结构和性质的影响,研究了负载磁性纳米粒子和巯基改性顺序对巯基改性磁性SBA-15的结构和性能的影响。结果表明,喷雾干燥法合成的SBA-15介孔孔壁较薄,但具有更大的比表面积、孔体积和平均孔径。以其为载体时磁性纳米粒子负载量更大,所得磁性SBA-15的饱和磁强度更高。当将巯基改性和负载磁性纳米粒子分为前后两步时,巯基改性SBA-15的表面疏水环境有利于吸附疏水磁性纳米粒子,所得磁性SBA-15负载磁性纳米粒子量更大,饱和磁强度更高。磁性纳米粒子粒径大于SBA-15孔径,其主要负载于SBA-15外表面,有利于得到介孔孔道通畅的磁性SBA-15。巯基改性的磁性SBA-15的孔体积介于0.56~0.6cm³/g,比表面积介于353~432m²/g,饱和磁强度最高达到0.91emu/g,可作为一种大容量的吸附材料用于吸附分离、药物缓释等领域。