Bimodal mesoporous silicas functionalized with different level and species of the amino groups for adsorption and controlled release of aspirin

The synthesis of modified bimodal mesoporous materials (BMMs) with a small pore size of around 2.9 nm and a large pore size of about 20 nm has been performed via post-grafting methods. To study the application of functionalized BMMs in drug delivery, loading and releasing profiles using aspirin as model drug were carried out. XRD, SEM, TEM, N2 adsorption, FT-IR, 29Si-NMR, TG and UV-Vis spectroscopy were used to characterize the related samples. The post-grafting modification was performed through the weak chemical interaction or hydrogen bonding in between OH groups of the mesopore surface and 3-aminopropyltriethoxysilane (N-TES) or 3-(2-aminoethylamino) propyItrimethoxysilane (NN-TES). The results showed that N-TES groups with different amount and NN-TES groups were successfully incorporated onto the mesopore surface. Subsequently, the controlled aspirin delivery properties from the resulting modified BMMs were investigated in detail. The aspirin adsorption experiments indicated that the adsorption capacities of modified BMMs were improved with the increasing amount of N-TES groups, while the NN-TES functionalized samples showed higher adsorption capacity than N-TES modified samples with the same ratio of modification. The most reason is that the interaction between the NN-TES groups and aspirin molecules is stronger than that between the N-TES groups and aspirin molecules. The in vitro tests exhibited that aspirin release behaviors mainly depended on the variation of the amount and species of the functional groups in mesoporous carries. According to the Korsmeyer-Peppas model, it is found that the kinetic release constant k reduced with the increase amount of the amino groups on the mesopore surface of modified BMMs, suggesting that the aspirin release rate from the pores of BMMs was influenced directly by organic groups on the surface. The release exponent n of all the situations were above 0.5, indicating the drug release mechanism followed a non-Fickian model that was diffusion based. Therefore, this type of materials described in this paper is of strong potential for the controlled drug release applications.     

Thermal decomposition behavior of amino groups modified bimodal mesoporous silicas as aspirin carrier

Two kinds of amino groups were employed to functionalize bimodal mesoporous silicas and related drug carriers were prepared. The characterization results of XRD, N2 adsorption and desorption, FT-IR and TG all confirmed the structural integrity of the bimodal mesopore architecture after introduction treatment of functional groups and the successful adsorption of aspirin. In order to investigate the interaction among the mesoporous structure, the functional groups grafted onto the mesoporous surface and the existential microenvironment of the drug molecules inside the mesoporous channels, the thermal decomposition behaviors of amino groups modified and aspirin loaded carriers were studied based on the thermogravimetric analysis in details. According to the thermogravimetry and derivative thermogravimetry results, the apparent activation energies E(a) of thermal decomposition for all related samples have been evaluated by Kissinger and Flynn-Wall-Ozawa methods. Meanwhile, their thermal decomposition mechanisms have been suggested by using Coats and Redfern methods. All these featured consequence could provide a deeper understanding for large loading capacity and controlled release of drug-carriers in the pharmaceutical application.     

Pd-porphyrin functionalized ionic liquid-modified mesoporous SBA-15: An efficient and recyclable catalyst for solvent-free Heck reaction

The Pd-porphyrin functionalized ionic liquid could be covalently anchored in the channels of mesoporous SBA-15 through ion-pair electrostatic interaction between imidazolium-cationic and Pd-porphyrin-anionic moieties. Such modified SBA-15 materials were prepared successfully via a post-synthesis (surface sol-gel polymerization) or a one-pot sol-gel procedure, which were characterized by powder X-ray diffraction, UV-visible spectroscopy, Fourier transform infrared spectroscopy, N₂ sorption, elemental analysis, and transmission electron microscopy. The modified SBA-15 materials are efficient and recyclable catalysts for cross-coupling of aryl iodides or activated aryl bromides with ethyl acrylate without activity loss and Pd leaching even after 9 runs.     

Palladium supported on functionalized mesoporous silica as an efficient catalyst for Heck reaction

Pd nanoparticles supported in functionalized mesoporous silica were prepared. Mesoporous silica support was modified with [3-(2-aminoethyl aminopropyl)] trimethoxysilane. Palladium ions were grafted onto the functionalized mesoporous silica and reduced with hydrazine hydrate to obtain the Pd nanoparticles supported on functionalized mesoporous silica. The Pd loading in the nanocomposite of Pd supported on the functionalized mesoporous silica is 4.30 wt%. CO chemisorption analysis on the nanocomposite shows a Pd dispersion as high as 35% and a Pd surface area of 156 m²/g. The surface area, pore size, and pore volume decrease slightly with the incorporation of the Pd nanoparticles into the functionalized mesoporous silica. Pd supported on the functionalized mesoporous silica with controlled molar ratio of amino groups to palladium exhibits an excellent catalytic activity and low Pd leaching for the Heck carbon-carbon coupling reaction. The catalyst can be reused for at least six recycles in air with only a minor loss of activity.     

Polyethyleneimine-functionalized large pore ordered silica materials for poorly water-soluble drug delivery

Four ordered mesoporous silica supports with different pore structure characteristics were investigated for their drug loading and release abilities with regard to their structural variabilities as well as implications of surface modification. The (model) drug molecule in question was the poorly water-soluble glucocorticoid Prednisolone, composed of a steroid skeleton with functional groups in the form of carbonyls and hydroxyls. Under non-aqueous conditions, such as those applied for drug loading, these functional groups are expected to interact with the surface silanols of the silica supports, but this interaction could possibly also be enhanced by introducing amino groups to the silica surfaces. Thus, all four supports were further functionalized by surface hyperbranching of polyethyleneimine), PEI, which was successfully incorporated to all supports in high amounts (>30 wt%). However, the accessibility of the pore system after organic modification was dependent on the pore sizes and structures, highlighting the importance of using large-pore mesophases with adequate structures when aiming for applications involving (bulky) guest molecules. Additionally, after incorporation of large amounts of guest molecules (40 wt%), full water accessibility was retained in that the loaded cargo could be rapidly released from the carrier matrixes, which is a crucial requirement when formulating poorly soluble substances. Results displayed that the release of Prednisolone from the silica supports occurred faster than the dissolution of the pure drug. All silica materials released more than 85 % of the adsorbed drug in 5 h, independently of the support material. Thus, the confinement of Prednisolone inside the mesopores seems to be the main reason for the faster kinetic release rate. These constraints imply that Prednisolone becomes more mobile inside the pores, and therefore more soluble in release medium. These results confirm the potential of silica supports as drug delivery carriers for drugs with limited water solubility such as steroids.     

Redox/pH dual stimuli‐responsive ZnO QDs‐gated mesoporous silica nanoparticles as carriers in cancer therapy

New drug delivery system (ZnO@CMS) of the redox and pH dual‐stimuli responsive based on colloidal mesoporous silica nanoparticles (CMS) has been designed, in which zinc oxide quantum dots (ZnO QDs) as a capping agent was conjugated on the surface of nanoparticles by amide bonds. The release behaviour of doxorubicin (DOX) as the model drug from ZnO@CMS (ZnO@CMS‐DOX) indicated the redox and pH dual‐stimuli responsive properties due to the acidic dissolution of ZnO QDs and cleavage of the disulphide bonds. The haemolysis and bovine serum albumin adsorption assays showed that the modification of ZnO QDs on the mesoporous silica nanoparticles modified by mercapto groups (CMS‐SH)(ZnO@CMS) had better biocompatibility compared to CMS‐SH. The cell viability and cellular uptake tests revealed that the ZnO@CMS might achieve the antitumour effect on cancer cells due to the cytotoxicity of ZnO QDs. Therefore, ZnO@CMS might be potential nanocarriers of the drug delivery system in cancer therapy. The in vivo evaluation of ZnO@CMS would be carried out in future work.Inspec keywords: biochemistry, nanomedicine, cellular biophysics, pH, toxicology, tumours, semiconductor quantum dots, proteins, colloids, II‐VI semiconductors, mesoporous materials, silicon compounds, oxidation, cancer, drug delivery systems, zinc compounds, adsorption, molecular biophysics, nanomagnetics, drugs, biomedical materials, nanofabrication, nanoparticles, nanoporous materialsOther keywords: cancer therapy, drug delivery system, amide bonds, haemolysis, bovine serum albumin adsorption assays, mercapto groups, cancer cells, cytotoxicity, antitumour effect, redox/pH dual stimuli‐responsive zinc oxide quantum dots‐gated colloidal mesoporous silica nanoparticles, ZnO, SiO₂      

Organic modified mesoporous MCM-41 through solvothermal process as drug delivery system

MCM-41 materials modified by organic aminopropyl groups have been successfully prepared through solvothermal process and have been used as drug-controlled delivery system of aspirin. The results show that the releasing properties of this delivery system are affected by the amount of aminopropyl groups on the pore wall and the ordered structure of mesoporous materials. These materials were characterized by XRD, TG, FT-IR, TEM, UV and N₂ adsorption.     

介孔材料CO2吸附性能的研究进展

介孔材料以其适中的孔径、大的比表面积、较高的热稳定性和水热稳定性,在吸附、催化、分离等方面有着广阔的应用前景。综述了近年来介孔材料在CO2吸附领域的研究进展,重点介绍了介孔材料及改性介孔材料吸收CO2的方法;并指出以新材料特别是介孔材料为主体进行碳捕集是今后的主要研究方向。     

Mesoporous carbon-containing MoS2 materials formed from the in situ decomposition of tetraalkylammonium thiomolybdates

Molybdenum disulfide with unique mesoporous structure was synthesized from tetraalkylammonium thiometallate precursors in situ decomposed in a batch reactor in the presence of dibenzothiophene (DBT). The precursors used in this study were tetraalkylammonium thiomolybdates with alkyl groups ranging from propyl to octyl. Molybdenum disulfide thus prepared presents high surface area (from 255 up to 329 m²/g), high content of carbon (C/Mo=2.7-4.0) and type IV nitrogen adsorption-desorption isotherms when decomposed from tetrahexyl-, tetraheptyl- or tetraoctylammonium thiomolybdates. The as-formed materials are poorly crystallized with a very weak intensity of the (0 0 2) peak of the 2HMoS₂ structure. Such diffraction patterns are characteristic of exfoliated samples. Characterization by TEM shows a disordered layered structure with no long range order for the MoS₂ catalysts. Therefore, the nature of the alkyl group in the precursor affects both the surface area and the pore size distribution of the final MoS₂ catalysts with a progressive morphological modification up to a mesoporous organization.     

Surface modification of nano-TiO2 with trimellitylimido-amino acid-based diacids for preventing aggregation of nanoparticles

Nanoparticles (NPs) are an essential material for science and technology, for instance in materials, medicals, and cosmetics. Controlling the dispersion of NPs is necessary to manage the properties of the final products. For this reason the surface modification of NPs is done by many techniques. In this work Nano-TiO₂ were modified using methanol as solvent and diacids based on natural amino acids as modifier at room temperature and using ultrasonic irradiation. Diacids were grafted onto the surface of TiO₂ NPs to improve the dispersion of the particles. The obtained modified TiO₂ were characterized by Fourier transform IR spectroscopy (FT-IR), X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. These analyses proved this modification process at room temperature was possible. TEM and FE-SEM showed that fairly good dispersed TiO₂ NPs were obtained after surface modification. Since TiO₂ and diacids which were used in this work are biologically active, the modified powder would be environmentally friendly.     

Synthesis of mesoporous Co/Ce-SBA-15 materials and their catalytic performance in the catalytic oxidation of benzene

Cerium-containing SBA-15 mesoporous materials, with different Ce/Si molar ratios, were synthesized by a direct hydrothermal synthesis method and further modified by impregnation with 10, 15 and 20 wt.% Co. Characterizations by powder X-ray diffraction (XRD), N₂ sorption, inductively coupled plasma (ICP) and UV-vis spectroscopy were carried out. The small-angle XRD and N₂ sorption characterizations showed that these Co supported materials have less-ordered mesoporous structures with partial blockage of pores, and their specific surface area, pore volume and pore size were relatively lower than those of unsupported cerium-containing SBA-15. Spinel Co₃O₄ constituted the predominant cobalt phase in the prepared catalysts, and CeO₂ was also detected. All the Co supported catalysts exhibited high catalytic activity in the oxidation of benzene.     

Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO₂). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N₂ adsorption–desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV–vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO₂ tubes than in mesoporous silica matrix.     

Preparation and characterization of multifunctional magnetic mesoporous calcium silicate materials

Abstract

We have prepared multifunctional magnetic mesoporous Fe–CaSiO₃ materials using triblock copolymer (P123) as a structure-directing agent. The effects of Fe substitution on the mesoporous structure, in vitro bioactivity, magnetic heating ability and drug delivery property of mesoporous CaSiO₃ materials were investigated. Mesoporous Fe–CaSiO₃ materials had similar mesoporous channels (5–6 nm) with different Fe substitution. When 5 and 10% Fe were substituted for Ca in mesoporous CaSiO₃ materials, mesoporous Fe–CaSiO₃ materials still showed good apatite-formation ability and had no cytotoxic effect on osteoblast-like MC3T3-E1 cells evaluated by the elution cell culture assay. On the other hand, mesoporous Fe–CaSiO₃ materials could generate heat to raise the temperature of the surrounding environment in an alternating magnetic field due to their superparamagnetic property. When we use gentamicin (GS) as a model drug, mesoporous Fe–CaSiO₃ materials release GS in a sustained manner. Therefore, magnetic mesoporous Fe–CaSiO₃ materials would be a promising multifunctional platform with bone regeneration, local drug delivery and magnetic hyperthermia.     

功能化SBA-15介孔材料的制备及其吸附性能研究

硅基介孔材料因其特有的特性,被用于去除废水中重金属离子的吸附剂.为了提高对目标污染物的吸附容量, 本文采用一步法和两步法制备了氨基或巯基功能化SBA-15介孔材料,利用傅里叶红外光谱仪、场发射扫描电镜、X射线衍射仪和氮气吸附脱附表征测试了材料的化学组成、微观形貌和物相结构.测试结果显示经功能化处理后的样品成功地接枝氨基或巯基功能基团.研究发现,经功能化处理后,材料的骨架结构及介孔孔道均未被破坏,但有序性下降且出现少许团聚,物性参数也有一定程度下降,功能化材料对Zn²⁺、Pb²⁺、Cr³⁺和Cu²⁺的吸附率均有大幅度提高.经氨基或巯基功能化后,SBA-15介孔材料对水体中重金属离子的吸附率有很大提高,但一步法制备的功能化硅基介孔材料因模板剂去除不彻底而影响了对重金属离子的吸附效率,两步法制备的功能化硅基介孔材料对重金属离子的吸附效果更好,说明本文的功能化硅基介孔材料工艺是可行有效的,但两步法合成的功能化介孔材料具有更好的吸附效果.     

Encapsulation of Coumarin 151 into the mesopores of modified rodlike SBA-15

Dye Coumarin 151 was postgrafted into the rodlike SBA-15 mesoporous materials, which were synthesized by a direct hydrothermal synthesis method and further modified by an organic silane with a terminal amino group. Characterization by powder X-ray diffraction, N₂ adsorption-desorption, transmission electron microscopy, photoluminescence and scanning electron microscopy were carried out. Small-angle X-ray diffraction and N₂ adsorption-desorption characterizations showed that these dye containing materials remained as ordered mesostructures and the pore size was from 6 nm for blank sample to 3.6 nm for postgrafting sample. PL characterization of composite samples exhibited optical properties with different dye concentrations. The characterization showed the existence of Coumarin 151 in the channels of SBA-15 and the composite materials with novel optical properties enabled possible applications in optical sensing and electron acceptors.     

On the preparation and application of novel PVDF–POSS systems

Novel systems based on poly(vinylidene fluoride) (PVDF) and polyhedral oligomeric silsesquioxane (POSS) have been prepared by grafting amino-containing POSS (POSS–NH₂) onto the surface of modified PVDF (PVDFm). Namely, the approach consists of a preliminary modification of PVDF by a chemical treatment with an alkaline solution, in order to obtain unsaturations, and a subsequent surface reaction of PVDFm with POSS molecules characterized by an amino group as reactive side. The level of polymer unsaturation, measured by Raman spectroscopy, turned out to be finely tuned by varying the dehydrofluorination reaction time. The surface grafting of POSS has been studied by SEM-EDS analysis, Raman and XPS spectroscopy. Indeed, while the level of modification of PVDFm has been found to decrease as a consequence of the reaction with POSS, thus indicating a likely saturation of double bonds by silsequioxane molecules, the Si concentration turned out to increase with increasing the concentration of the polymer surface unsaturation. The feasibility of the application of POSS grafting onto the surface of membranes, based on PVDFm, has also been verified.     

Electrochemical behavior of two and one electron redox systems adsorbed on to micro- and mesoporous silicate materials: Influence of the channels and the cationic environment of the host materials

Electrochemical behavior of two electron redox system, phenosafranine (PS⁺) adsorbed on to micro- and mesoporous materials is investigated by cyclic voltammetry and differential pulse voltammetry using modified micro- and mesoporous host electrodes. Two redox peaks were observed when phenosafranine is adsorbed on the surface of microporous materials zeolite-Y and ZSM-5. However, only a single redox peak was observed in the modified electrode with phenosafranine encapsulated into the mesoporous material MCM-41 and when adsorbed on the external surface of silica. The observed redox peaks for the modified electrodes with zeolite-Y and ZSM-5 host are suggested to be primarily due to consecutive two electron processes. The peak separation ΔE and peak potential of phenosafranine adsorbed on zeolite-Y and ZSM-5 were found to be influenced by the pH of the electrolyte solution. The variation of the peak current in the cyclic voltammogram and differential pulse voltammetry with scan rate shows that electrodic processes are controlled by the nature of the surface of the host material. The heterogeneous electron transfer rate constants for phenosafranine adsorbed on to micro- and mesoporous materials were calculated using the Laviron model. Higher rate constant observed for the dye encapsulated into the MCM-41 indicates that the one-dimensional channel of the mesoporous material provides a more facile micro-environment for phenosafranine for the electron transfer reaction as compared to the microporous silicate materials. The stability of the modified electrode surface was investigated by multisweep cyclic voltammetry.     

Catalytic properties and deactivation behavior of modified H-ZSM-5 in the conversion of methanol-to-aromatics

A comparative study on the effects of SiO₂ modification and mesoporous structures on catalytic performances over ZSM-5 zeolites in MTA conversion both theoretically and experimentally was done. Experimental results showed that hierarchical pores increased the production of aromatics. However, DFT calculation proved that energy barriers for producing aromatics over mesoporous ZSM-5 were larger than that of parent ZSM-5 due to decreasing acid strength after alkali treatment which significantly influenced rate-determining step. Furthermore, diffusion behaviors of toluene were studied by Molecular Dynamics. Larger pores led to the improvement of diffusion behaviors over hierarchical ZSM-5 owing to the decrease of collision frequency between molecules. Therefore, the formation of aromatics was mainly determined by diffusion limitation over hierarchical ZSM-5. The lowest BTX selectivity was obtained over SiO₂ deposited mesoporous ZSM-5 due to decreasing acid strength and blockage of pore mouth. Additionally, the deactivation of ZSM-5 serial catalysts in MTA was attributed the formation of insoluble coke. Moreover, the introduction of mesopores and silylation on external surface alleviated the deactivation of catalysts.     

Catalytic activity of Co/MCM-41 and Co/SBA-15 materials in toluene oxidation

Cobalt-containing MCM-41 and SBA-15 mesoporous materials were prepared by the pH-adjusting of the impregnation solution. The modified materials were investigated by X-ray diffraction, N₂ physisorption, temperature-programmed reduction, DR UV–Vis diffuse reflectance, and FT-IR spectroscopy of adsorbed pyridine. The pH of the impregnation solution influences the surface charge of the mesoporous support and therefore determines the strength of interaction between the cobalt precursor and the mesoporous support. The formation of different cobalt oxide species in different ratios, depending on the pH of the impregnation solution, was established for both materials. The modified Co/MCM-41 and Co/SBA-15 materials were active in toluene oxidation. Their catalytic activity is predetermined by the nature, the reducibility, and the dispersion of the obtained cobalt oxide species.     

Preparation of hydrophilic mesoporous carbon and its application in dye adsorption

A hydrophilic mesoporous carbon (H-MS) has been prepared by a rapid redox reaction between mesoporous carbon (CMK-3) and an acidic potassium permanganate (KMnO₄) solution at room temperature. The obtained material has a hydrophilic surface by the modification of oxygen-containing groups, and meanwhile retains the ordered mesoporous structure. No obvious difference of pore size between H-MS and CMK-3, and the slight decrease of surface area and pore volume is due to the modification of oxygen-containing groups on the carbon surface. An improved property for adsorbing dyes in aqueous solution was observed in H-MC, and the adsorption amount at equilibrium is ~ 3 times higher than that of CMK-3.