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.     

胺功能化介孔二氧化硅捕集CO2的研究进展

胺功能化介孔二氧化硅因其高选择性、高吸附容量、快速的吸附动力学、良好的再生性能和循环稳定性受到广泛关注,在二氧化碳捕集技术中具有优良的应用前景。本文比较了胺改性的M41S、SBA-n、KIT-n、介孔二氧化硅泡沫、介孔二氧化硅纳米球和六方介孔二氧化硅的吸附性能,总结了MCM-41和SBA-15的结构特点。介绍了胺化合物的负载方式——湿法浸渍、化学接枝和原位聚合的胺负载原理。分析了硅源、载体内部性质、气体选择性和不同添加剂对胺功能化介孔二氧化硅材料吸附二氧化碳能力的影响。最后,点明了吸附剂未来的发展目标,对胺功能化介孔二氧化硅材料的研究方向进行了展望。指出未来可关注介孔二氧化硅微观结构和温度对胺与二氧化碳相互作用的影响,增强胺功能化介孔二氧化硅的稳定性,推进其在实际环境下的应用。     

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&#61485;N+-I&#61485; 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&#8226;g&#61485;1 and 0.03 mmol&#8226;g&#61485;1, respectively, indicating high separation coefficient of CO2/N2.     

Chemical fixation of carbon dioxide to propylene carbonate over amine-functionalized silica catalysts

Amine-functionalized silica catalysts (NH₂/SiO₂, NH(CH₂)₂NH₂/SiO₂ and 1,5,7-triazabicyclo[4,4,0]dec-5-ene/SiO₂ (TBD/SiO₂)), which were characterized by ²⁹Si NMR, elemental analysis, N₂ adsorption–desorption method and indicator dye adsorption, were prepared by ultrasonic technique under mild conditions. Such hybrid solid bases showed high catalytic activity towards CO₂ coupling with epoxide. However, it was found that the reaction conditions had a great influence on the performance. Furthermore, silanols on the surface played an important role in the chemical fixation of CO₂. Based on these, the possible reaction mechanism was proposed for CO₂ coupling with epoxide over such type of catalysts.     

Enhanced CO2 separation performance of mixed matrix membrane by incorporating amine-functionalized silica filler

Mixed matrix membranes (MMMs) owing to the tunable characteristics and functionalization ability can effectively substitute the highly intensive conventional membranes for industrial-scale CO₂ separation. Further, to strengthen the interfacial polymer-filler interaction, an interfacial design strategy incorporating active functional groups in the filler surface can be demonstrated. In this study, as-synthesized silica nanoparticles (SNPs) was surface functionalized by (3-aminopropyl) trimethoxysilane silica modifier (AFSNP). The CO₂ separation of poly (vinyl alcohol)/polyethylene glycol based MMM infused with surface-functionalized SNP (AFSNP) was conducted. The comparative study highlighted in-depth analysis of intrinsic physicochemical properties of as-synthesized membranes and nanoparticles. Detailed characterization such as advanced microscopic analysis, X-ray photoelectron spectroscopy (XPS) analysis and ninhydrin assay validated the successful grafting of amino groups onto the silica surface. The morphological inspection corroborated the consistent dispersion ability of the nanoparticles in the membrane matrix. The effect of the operating conditions on the membrane selectivity and CO₂ permeance were statistically analyzed by ANOVA. The CO₂ permeation result (CO₂ permeance and CO₂/N₂ selectivity) exhibited many fold increment with surface functionalization of SNPs compared to undoped silica MMM. The defect-free, performance-oriented CO₂-selective membrane thus opened up the possibility of this combination as a prospective contender for large-scale carbon capture studies.     

Multicolor core/shell silica nanoparticles for in vivo and ex vivo imaging

Biocompatible highly bright silica nanoparticles were designed, prepared and tested in small living organisms for both in vivo and ex vivo imaging. The results that we report here demonstrate that they are suitable for optical imaging applications as a possible alternative to commercially available fluorescent materials including quantum dots. Moreover, the tunability of their photophysical properties, which was enhanced by the use of different dyes as doping agents, constitutes a very important added value in the field of medical diagnostics.     

Biodegradability of mesoporous silica nanoparticles

Biodegradability significantly impacts the bioapplication of mesoporous silica nanoparticles (MSN). In recent years, immense efforts have been made to understand and tailor the biodegradability of MSN. In this mini review, we overview the recent reports on the biodegradation of MSN, with a focus on the correlation between biodegradation and physicochemical properties including specific surface area, morphology, pore size, particle diameter and condensation degree of silicon-oxygen network. In addition, strategies for improving the biodegradability of MSN such as metal ions and organic species doping are also introduced.     

Polycarbonate reinforced with silica nanoparticles

Nanocomposites of polycarbonate (PC) reinforced with nanosized silica particles were prepared by a melt mixing technique in an internal mixer. Two kinds of commercial hydrophilic fumed silicas differing in their specific surface area were added in amounts up to 5% by volume, and their reinforcing action was compared to that of organically modified silica, loaded in the same amounts. Particle–matrix interactions were investigated by means of rheological and dynamic-mechanical thermal analysis, demonstrating the important role played by the organic modification in the interactions with the polymer matrix, and showing an optimal nanoparticle loading around 2 vol%. The scratch resistance of the nanocomposites obtained from hydrophilic silicas was investigated, and a remarkable enhancement in the indenter’s penetration resistance was observed for all the compositions with respect to pristine PC. The same behaviour was observed for the Shore D hardness and for the impact resistance of the nanocomposites that also significantly improved with the maximum load shifting from a minimum value of 521 N for pristine PC up to values grater than 1330 N for the nanocomposites, demonstrating the activation of effective mechanisms of energy dissipation due to the presence of the nanofillers.     

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.     

纳米二氧化硅的制备与表征

本文以正硅酸四乙酯(TEOS)为前驱物,通过溶胶-凝胶法制备了SiO_2纳米粉体。并用FT- IR、SDTA、XRD、TEM表征了所制备的SiO_2纳米粉体的结构和形貌。结果表明SiO_2纳米粒子呈球状,粒径在50～100nm范围内,分布均匀,呈无定形态。     

Super-hydrophilic coatings based on silica nanoparticles

This work focuses on the use of silica nanoparticles for producing durable, transparent, and super-hydrophilic coatings on painted surfaces. Two methods were studied in detail: bottom-up approach using layer-by-layer (LbL) assemblies of hydroxylated SiO₂ nanoparticles, and top-down approach based on hybrid polymer/silica nanoparticles coatings. Of the two approaches studied, only the hybrid polymer/SiO₂ nanocomposite coatings containing 50–90%wt. SiO₂ exhibited durable super-hydrophilic surface properties less than 5° water contact and sliding angles. In the latter case, a unique micrometer-sized cracking pattern was developed. The LbL-assembled SiO₂ coatings showed a gradual degradation over time from the initial super-hydrophilic properties, indicated by the increase of the contact angles from less than 5^o to greater than 30^o after accelerated aging. To investigate the effect of environmental exposure on developing hydrophilicity, a variety of analytical methods were employed such as: atomic force microscopy, scanning electron microscopy, optical microscopy, and Fourier transform infrared. Experimental results and associated modeling indicated that the combination of micro- and nano-surface roughness and the surface chemical composition were the dominant factors affecting the durability of the hydrophilic attributes of the coatings containing silica nanoparticles.     

Diatomite silica nanoparticles for drug delivery

Diatomite is a natural fossil material of sedimentary origin, constituted by fragments of diatom siliceous skeletons. In this preliminary work, the properties of diatomite nanoparticles as potential system for the delivery of drugs in cancer cells were exploited. A purification procedure, based on thermal treatments in strong acid solutions, was used to remove inorganic and organic impurities from diatomite and to make them a safe material for medical applications. The micrometric diatomite powder was reduced in nanoparticles by mechanical crushing, sonication, and filtering. Morphological analysis performed by dynamic light scattering and transmission electron microscopy reveals a particles size included between 100 and 300 nm. Diatomite nanoparticles were functionalized by 3-aminopropyltriethoxysilane and labeled by tetramethylrhodamine isothiocyanate. Different concentrations of chemically modified nanoparticles were incubated with cancer cells and confocal microscopy was performed. Imaging analysis showed an efficient cellular uptake and homogeneous distribution of nanoparticles in cytoplasm and nucleus, thus suggesting their potentiality as nanocarriers for drug delivery.

PACS

87.85.J81.05.Rm; 61.46. + w     

聚多巴胺修饰纳米SiO2颗粒

纳米SiO₂颗粒粒径小、比表面积大,广泛用做填料、涂料、催化剂等。由于纳米SiO₂颗粒表面能高、亲水性强、易团聚、在聚合物基体中的分散性差,需要对其表面修饰改性。多巴胺（DA）分子具有类似贻贝分泌的黏附蛋白的结构单元儿茶酚和活性基团氨基,在碱性条件下,通过氧化自聚可在多种材料表面沉积,形成富含活性基团的聚多巴胺（PDA）包覆层,可进行二次修饰,是近期发展的一种新型表面修饰方法。本文针对纳米SiO₂颗粒表面的PDA功能化修饰,分析了该修饰方法的工艺特点及优势,阐述了SiO₂@PDA纳米颗粒及SiO₂/PDA共聚复合颗粒的制备路线及应用,总结了SiO₂@PDA颗粒表面二次功能化修饰的研究进展。分析表明,SiO₂@PDA表面易于接枝功能化聚合物分子,并可负载功能纳米颗粒,有利于拓展SiO₂纳米颗粒的多功能应用。关于多巴胺与SiO₂纳米颗粒的表面反应机制、沉积动力学、聚合机理等仍需进一步研究。     

Incorporation of Pd nanoparticles in mesostructured silica

Monodisperse Pd nanoparticles were prepared by controlled reduction in organic phase and subsequent transfer to aqueous phase. A systematic study was carried out to finely tune nanoparticle size and optimize particle size distribution. The use of 4-dimethylaminopyridine as a transfer agent allowed for the easy and quantitative extraction of the Pd to the aqueous phase. The quaternary amine-functionalized metal nanoparticles were then used as metallic micelle replicas to grow silica around them. This novel and facile metal incorporation method provided an excellent dispersion and homogeneity of Pd nanoparticles on silica supports. In addition, cationic surfactants, such as cetyltrimethylammonium bromide, can be used to produce mesoporosity in these nanoparticles-containing silicas. As an alternative, the metal nanoparticles were functionalized with alkoxysilanes by covalent binding using mercaptopropyltriethoxysilane and then co-polymerized with tetraethoxysilane via basic-catalyzed hydrolysis in the presence of cationic surfactants.     

Direct electrochemistry of catalase at amine-functionalized graphene/gold nanoparticles composite film for hydrogen peroxide sensor

Direct electrochemistry and electrocatalysis of catalase (Cat) was studied based on a nano-composite film consisting of amine functionalized graphene and gold nanoparticles (AuNPs) modified glassy carbon electrode. Graphene was synthesized chemically by Hummers and Offeman method and then was functionalized with amino groups via chemical modification of carboxyl groups introduced on the graphene surface. The nano-composite film showed an obvious promotion of the direct electron transfer between Cat and the underlying electrode, which attributed to the synergistic effect of graphene-NH₂ and AuNPs. The resultant bioelectrode retained its biocatalytic activity and offered fast and sensitive H₂O₂ quantification. Under the optimized experimental conditions, hydrogen peroxide was detected in the concentration range from 0.3 to 600 μM with a detection limit of 50 nM at S/N = 3. The biosensor exhibited some advantages, such as short time respond (2 s), high sensitivity (13.4 μA/mM) and good reproducibility (RSD = 5.8%).     

Mechanism of cellular uptake of genotoxic silica nanoparticles

ABSTRACT: Mechanisms for cellular uptake of nanoparticles have important implications for nanoparticulate drug delivery and toxicity. We have explored the mechanism of uptake of amorphous silica nanoparticles of 14 nm diameter, which agglomerate in culture medium to hydrodynamic diameters around 500 nm. In HT29, HaCat and A549 cells, cytotoxicity was observed at nanoparticle concentrations 1 mug/ml, but DNA damage was evident at 0.1 mug/ml and above. Transmission electron microscopy (TEM) combined with energy-dispersive X-ray spectroscopy confirmed entry of the silica particles into A549 cells exposed to 10 mug/ml of nanoparticles. The particles were observed in the cytoplasm but not within membrane bound vesicles or in the nucleus. TEM of cells exposed to nanoparticles at 4 C for 30 minutes showed particles enter cells when activity is low, suggesting a passive mode of entry. Plasma lipid membrane models identified physical interactions between the membrane and the silica NPs. Quartz crystal microbalance experiments on tethered bilayer lipid membrane systems show that the nanoparticles strongly bind to lipid membranes, forming an adherent monolayer on the membrane. Leakage assays on large unilamellar vesicles (400 nm diameter) indicate that binding of the silica NPs transiently disrupts the vesicles which rapidly self-seal. We suggest that an adhesive interaction between silica nanoparticles and lipid membranes could cause passive cellular uptake of the particles.     

Effective catalytic hydrodechlorination of 4-chlorophenol over a Rh immobilized on amine-functionalized magnetite nanoparticles in aqueous phase

Amine-functionalized magnetite nanoparticles synthesized from a facile one-pot template-free method were applied as carriers for depositing Rh nanoparticles using RhCl₃ as the precursor. The as-prepared nanocomposites were applied for the hydrodechlorination of 4-chlorophenol at room temperature and atmospheric pressure. A complete conversion of 4-CP was obtained with the generation of phenol, cyclohexanone as the main products. The excellent catalytic activity, stability and recyclability of the catalyst were probably contributed to the functionalities of amine groups for stabilizing the Rh nanoparticles and the magnetic effect of Fe₃O₄ support during consecutive recycling of the catalyst.     

Highly bright and photostable cyanine dye-doped silica nanoparticles for optical imaging: Photophysical characterization and cell tests

Spherical silica nanoparticles containing fluorescent trimethine indocyanine dyes (λ_abs = 547 nm, λ_em = 570 nm) were prepared using a water-in-oil microemulsion method. The nanoparticles were of 50 nm diameter and were almost monodispersed in aqueous solution at pH 5.5. Entrapment of dye molecules in the silica matrix stabilised photoemission over several hours of continuous irradiation. The photoemission intensity of the indocyanine was increased 13-fold over that recorded in solution. As each nanoparticle contained 110 dye molecules, the photoemission brightness of each particle was enhanced by three orders of magnitude. The fluorescent nanoparticles have been tested as imaging tools in in vitro tests. As an example of non-macrophagic cells, a highly differentiated neuronal cell line (GT1-7) was used and the results showed that the prepared nanoparticles can be incorporated into these cells with no apparent toxicity for up to three days.     

Transparent PMMA/silica nanocomposites containing silica nanoparticles coating under supercritical conditions

This work reports the preparation of PMMA/silica nanocomposites with high optical transparency and enhanced mechanical properties using a melt compounding method. The surface of SiO₂ particles was modified with a γ-methacryloxypropyltrimethoxy silane coupling agent in a supercritical carbon dioxide-ethanol mixture and by conventional procedure. Dispersion of silica nanoparticles in ethanol at low temperatures plays an important role in deagglomeration and dispersion of nanosilica, which leads to the optimal particle-matrix bonding in composites. The optimal mechanical and optical properties were found for composites loaded with 5 wt% silica nanoparticles treated under supercritical coating method.