Enhancing plasma peptide MALDI-TOF-MS profiling by mesoporous silica assisted crystallization

Promising profiling techniques based on new material/solid phase extraction for capturing “molecular signatures” from body fluids are being coupled to MALDI-TOF-MS. Sample preparation significantly influences spectrum quality in this ionization method. Mesoporous silica beads (MSB), by the means of nano-sized porous channels with high surface area, enable harvesting of peptides from plasma and serum excluding large size proteins. We have investigated the morphology of a sample slurry, developed as a new tool for plasma peptides enrichment based on mesoporous materials. Our study highlights a correlation between crystals morphology and enhanced performances in MALDI-TOF-MS analysis. This is the first report which correlates the increase in signal intensity with crystal formation in samples preparations which make use of various kinds of slurries for the analysis of samples clinically relevant like human plasma.     

Preparation of amino-functionalized mesoporous silica thin films with highly ordered large pore structures

Highly ordered amino-functionalized mesoporous silica thin films have been directly synthesized by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of triblock copolymer Pluronic P123 surfactant species under acidic conditions by sol-gel dip-coating. The effect of the sol aging on thin films organization is systematically studied, and the optimal sol aging time is obtained. The amino-functionalized mesoporous silica thin films exhibit a long-range ordering of 2D hexagonal (p6mm) mesostructure with a large pore size of 8.3 nm, a large Brunauer–Emmett–Teller (BET) specific surface area of 680 m² g⁻¹ and a large pore volume of 1.06 cm³ g⁻¹ following surfactant extraction as demonstrated by X-ray diffraction (XRD), Transmission electron microscope (TEM), and physical adsorption techniques. Based on BET surface area and weight loss, the surface coverage of amino-groups for the amino-functionalized mesoporous silica thin films is calculated to be 3.2 amino-groups per nm². Moreover, the functionalized thin films display improved properties for immobilization of cytochrome c in comparison with pure-silica mesoporous thin films.     

Controllable porous fluorinated polyimide thin films for ultralow dielectric constant interlayer dielectric applications

In this paper, silica microspheres were used as template to prepare porous fluorinated polyimide (FPI) thin films from polyamic acid (PAA, precursor of FPI) and silica colloid solution. The strong hydrogen-bonding interaction between silica microspheres and PAA chains have improved the dispersion of silica microspheres in N,N-Dimethylformamide (DMF) solution, resulting in the high weight content of silica template in PAA/silica colloid solution, and thus giving rise to the formation of porous FPI films with maximum porosity of 35%. The interior microstructures of the resultant porous FPI thin films were investigated. It is found that the porous FPI thin films have interconnected “ink-bottle-type” porous structure, and the pore size, porosity could be precisely controlled by the diameter and weight content of silica microspheres, respectively. Although both the tensile strength and young modules declined with the increasing porosity, the high level void of the porous FPI films endowed the FPI ultralow dielectric constant of 1.84 when the porosity increased to 35%. Furthermore, the mechanical and dielectric properties of the porous FPI films were closely related to the microstructures and porosity, indicating the desired properties could be controlled to meet the application in the microelectronics.     

Titanium-containing magnetic mesoporous silica spheres: effective enrichment of peptides and simultaneous separation of nonphosphopeptides and phosphopeptides

Protein phosphorylation is a common posttranslational modification, and involved in many cellular processes. Like endogenous peptides, endogenous phosphopeptides contain many biomarkers of preclinical screening and disease diagnosis. In this work, titanium-containing magnetic mesoporous silica spheres were synthesized and applied for effective enrichment of peptides from both tryptic digests of standard proteins and human serum. Besides, the enriched peptides can be further separated into nonphosphopeptides and phosphopeptides by a simple elution. First, titanium-containing magnetic mesoporous silica spheres were synthesized by a sol-gel method and found to have high surface area, narrow pore size distribution, and useful magnetic responsivity. Then, as the prepared material was used for selective capturing of phosphopeptides, it demonstrated to have higher selectivity than commercial titanium dioxide. Moreover, via combination of size-exclusion mechanism, hydrophobic interaction, and affinity chromatography, titanium-containing magnetic mesoporous silica spheres were successfully applied to simultaneously extract and separate nonphosphopeptides and phosphopeptides from standard protein digestion and human serum.     

Selective extraction of low molecular weight proteins by mesoporous silica particles with modified internal and external surfaces

A new mesoporous silica material with modified external and internal surfaces (alkyl diol–vinyl-SiO₂) was prepared and applied to selectively extract low molecular weight (LMW) proteins and peptides (less than 11 kDa) from biological samples. X-ray diffraction, N₂ adsorption, transmission electron microscopy, and Fourier transform infrared spectroscopy were used to characterize the alkyl diol–vinyl-SiO₂. This material was used to extract LMW proteins (peptides) from standard proteins, a mixture of peptides, and crude human plasma. We compared the amounts of different proteins adsorbed by alkyl diol–vinyl-SiO₂ and by vinyl-SiO₂ (vinyl group on the internal surface of the mesoporous silica material). The desorption recovery of alkyl diol–vinyl-SiO₂ by different eluents was also investigated by using a standard protein (insulin) as a model LMW protein. The material could efficiently extract LMW proteins and peptides from a mixture of standard proteins and crude human plasma with good extraction efficiency and desorption recovery. Furthermore, the alkyl diol–vinyl-SiO₂ had much better extraction selectivity for LMW proteins and peptides than a commercial C₁₈ solid phase extraction material.     

In situ monitoring of atomic layer deposition in nanoporous thin films using ellipsometric porosimetry

Ellipsometric porosimetry (EP) is a handy technique to characterize the porosity and pore size distribution of porous thin films with pore diameters in the range from below 1 nm up to 50 nm and for the characterization of porous low-k films especially. Atomic layer deposition (ALD) can be used to functionalize porous films and membranes, e.g., for the development of filtration and sensor devices and catalytic surfaces. In this work we report on the implementation of the EP technique onto an ALD reactor. This combination allowed us to employ EP for monitoring the modification of a porous thin film through ALD without removing the sample from the deposition setup. The potential of in situ EP for providing information about the effect of ALD coating on the accessible porosity, the pore radius distribution, the thickness, and mechanical properties of a porous film is demonstrated in the ALD of TiO(2) in a mesoporous silica film.     

Manipulation of molecular transport into mesoporous silica thin films by the infiltration of polyelectrolytes

The design of hybrid mesoporous materials incorporating polymeric assemblies as versatile functional units has become a very fertile research area offering major opportunities for controlling molecular transport through interfaces. However, the creation of such functional materials depends critically on our ability to assemble polymeric units in a predictable manner within mesopores with dimensions comparable to the size of the macromolecular blocks themselves. In this work, we describe for the first time the manipulation of the molecular transport properties of mesoporous silica thin films by the direct infiltration of polyelectrolytes into the inner environment of the 3D porous framework. The hybrid architectures were built up through the infiltration-electrostatic assembly of polyallylamine (PAH) on the mesopore silica walls, and the resulting systems were studied by a combination of experimental techniques including ellipso-porosimetry, cyclic voltammetry and X-ray photoelectron spectroscopy, among others. Our results show that the infiltration-assembly of PAH alters the intrinsic cation-permselective properties of mesoporous silica films, rendering them ion-permeable mesochannels and enabling the unrestricted diffusion of cationic and anionic species through the hybrid interfacial architecture. Contrary to what happens during the electrostatic assembly of PAH on planar silica films (quantitative charge reversal), the surface charge of the mesoporous walls is completely neutralized upon assembling the cationic PAH layer (i.e., no charge reversal occurs). We consider this work to have profound implications not only on the molecular design of multifunctional mesoporous thin films but also on understanding the predominant role of nanoconfinement effects in dictating the functional properties of polymer-inorganic hybrid nanomaterials.     

Nano-architectural silica thin films with two-dimensionally connected cagelike pores synthesized from vapor phase

Novel mesostructured silica thin films were prepared on a Si substrate by a vapor-phase synthesis. Vapor of tetraethoxysilane (TEOS) was infiltrated into a surfactant film consisting of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer. Nanophase transition from a lamellar structure to a two-dimensional cage structure of a silica-surfactant nanocomposite was found under vapor infiltration. The rearrangement into the cage structure implies high mobility of the silica-surfactant composites in solid phase. The silica thin films have two-dimensionally connected cagelike mesopores and are isotropic parallel to the film surface. The structure of pores of the films is advantageous for next-generation low-k films. The mesoporous structure has a large lattice parameter d of approximately 102 A, silica layer thickness of approximately 58 A, pillar diameter in the middle of approximately 60 A, pore size of approximately 72 A, BET surface area of approximately 729 m(2)/g, and pore volume of approximately 1.19 cm(3)/g. The films synthesized by the vapor infiltration show a lower concentration of residual Si-OH groups compared to the films prepared by a conventional sol-gel method. The films show high thermal stability up to 900 degrees C and high hydrothermal stability. This method is a simpler process than conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous films.     

陶瓷泡沫空气过滤器涂覆中孔TiO2薄膜用于室内空气净化中高效光催化降解NO

由于人们80%的时间呆在室内,室内空气的质量直接影响人类健康,因此近年来室内空气质量越来越受到人们的关注.室内污染物包括CO氮氧化物(NOx)和挥发性有机化合物(VOCs),它们给人体健康带来众多负面影响.更为重要的是,考虑到节能,现代建筑的空气密闭性大都较高,但这种减少吸入新鲜空气的设计直接导致室内各种污染物的累积.有些家用电器,如燃气灶和热水器,在使用的时候会涉及到煤、油和天然气的燃烧,特别是通风较差的情况下会成为室内主要的污染源.常规的治理技术,包括吸附和过滤,其成本相对较高,也不适用于低浓度污染物的治理.尤其是更换不及时的过滤器在排风系统中可能会成为VOCs的一个来源.因此,很有必要开发一种新型的技术以降低室内污染物的浓度和保持一个清洁的室内空气环境,从而保障人们的身体健康.光催化是去除室内空气污染物的有效方法.例如, TiO2、钛酸铋和钛酸锶等具有强氧化能力和稳定的光催化活性,因而是高效的光催化剂.一般而言,通常报道的TiO2光催化剂是高度分散的、或悬浮于液体介质中的细小颗粒或粉末.然而,粉末状的TiO2光催化剂不适宜于室内空气净化,因为它变得可吸入而对人体健康造成不利的影响.因此,人们尝试将TiO2颗粒作为薄膜固定在不同的刚性载体上,如玻璃、不锈钢和铝合金板.对基体进行涂覆可显著影响光催化时反应物的表面吸附行为.一般而言,光催化薄膜通常涂覆在平面上,如蜂窝空气过滤器.三维(3D)多孔的陶瓷泡沫对气体通过具有非常好的流体性质,因此本文以它作为涂覆的基体.这种陶瓷泡沫具有3D多孔结构,多种孔密度、比表面积和化学性质.3D多孔陶瓷泡沫空气过滤器的床层空隙率较高,因此使用时压降较低,且不像蜂窝空气过滤器,它具有复杂多变的孔结构,可增强流体的扰动和混合.另外,3D多孔陶瓷泡沫空气过滤器的开发多孔和网状的结构使得在催化体系具有非常好的气体动力学性质,催化剂表面和气体反应物有充分的接触.多孔材料在液相或气相催化反应中具有独特的优势,因此,陶瓷泡沫、多孔的氧化铝、多孔硅胶.分子筛和活性炭经常被用作催化剂载体.在固体基体上TiO2膜的形成可能使得TiO2光催化剂的有效比表面积降低,从而导致其光催化活性下降.然而,由于具有中孔结构的TiO2薄膜的比表面积大,其用于催化反应的活性位也更多,因此使用时仍然具有较高的活性.前期研究表明,涂覆在平面玻璃、不锈钢和氧化铝基体上的中孔TiO2薄膜用于环境净化时表现出增强的光催化效率.另外,室内环境中NO和NO2的浓度一般分别为几百个ppb之内和100 ppb以下.可见, NO是主要的室内空气污染物,对人体健康危害较大.基于此,本文首次采用反胶束法将中孔锐钛矿TiO2薄膜均匀一地涂覆在3D多孔高比表面积的泡沫过滤器上,采用X射线衍射、扫描电镜、X射线光电子能谱、N2吸附-脱附、紫外-可见光光谱和原子力显微镜对所制样品进行了表征,并将样品用于紫外光下催化降解NO,以揭示所制的中孔TiO2涂层具有高的比表面积和高的光催化活性,从而克服使用TiO2粉末所带来的不足.结果表明,由于中孔TiO2薄膜涂层具有较大的有效比表面积,其表面存在很多吸附活性位,用于吸附在反应过程中形成的水蒸汽、气相反应物和产物,因而具有更高的光催化活性,因此在陶瓷泡沫空气净化系统中可以高效地光催化NO降解：在所考察的不同孔密度的陶瓷泡沫过滤器涂覆的TiO2上400 ppb的NO单程转化率均在92.5%以上,高于涂覆在平面陶瓷砖上的TiO2.该陶瓷过滤器的3D多孔特性可增强流体的扰动和混合,使得气相反应物与光催化剂表面有着充分的接触;其大的孔密度也导致高的光催化速率.另外,本文所制样品在所有反应过程中均保持较高且稳定的NO降解速率,这表明其在NO降解反应中没有失活.     

Nanoporous silica films containing aluminum and titanium

By utilizing surfactant aggregates as supramolecular templates, mesoporous and mesostructured silicas with highly ordered structures became available. The resulting mesoporous silicas are promising candidates to host various photo- and electro-active species along with catalytically active species, due to their large and controllable pore sizes, highly ordered pore arrangements with low dimensional geometries, and reactive surfaces. We have developed the rapid solvent evaporation method, which is a modified sol-gel process, for synthesizing the mesostructured silica-surfactant films as well as the mesoporous silica films. Supported thin films, self-standing films and bubbles of mesoporous silicas have been synthesized by the rapid solvent evaporation method. The microstructures of the films have also been successfully controlled by changing the synthetic conditions. Taking advantage of the ease of synthetic operation and the transparency and homogeneity of the resulting materials, we have been interested in the introduction of functional units into the mesostructured materials. This paper reports the synthesis of transparent films of titanium- and aluminum-containing nanoporous silicas to modify the surface properties (such as adsorptive and catalytic) of nanoporous silicas. The incorporation of Al led to the formation of cation exchange or acidic sites on the mesopore surface, as revealed by the cationic dye adsorption experiments. The photocatalytic reactions of the Ti-containing nanoporous silica films were also examined.     

新型SiO2/SiO2核壳型固定相的制备与评价

采用层层自组装的方法,以微米多孔硅胶小球为核,将硅胶纳米粒子多层包覆,制备了核壳型SiO2/SiO2硅胶小球.透射电子显微镜表明这种硅胶小球具有明显的核壳结构,氮气吸附实验证明该硅胶小球是典型的介孔材料,具有良好的介孔结构和窄的孔径分布.将其作为基质制备碳十八键合核壳型SiO2/SiO2色谱固定相,该固定相的碳含量与未...     

Probing the impact of advanced melting and advanced adsorption phenomena on the accuracy of pore size distributions from cryoporometry and adsorption using NMR relaxometry and diffusometry

The penetration of compressed CO(2) in hydrocarbon and fluorocarbon regions of concentrated surfactant mesophases are interpreted from differences in the CO(2)-processed pore expansion of mesoporous silica thin films templated by three surfactants containing varying degrees of hydrocarbon and fluorocarbon functionality. Ordered silica thin films are synthesized for the first time using the 16-carbon (C(16)) partly fluorinated surfactant, 11,11,12,12,13,13,14,14,15,15,16,16,16-tridecafluorocetyl pyridinium bromide (HFCPB), as a templating agent. Silica films templated with surfactants containing a 8-carbon (C(8)) fluorocarbon tail (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl pyridinium chloride (HFOPC)) and a 16-carbon (C(16)) hydrocarbon tail (cetyl pyridinium bromide (CPB)) and HFCPB (C(16)) are processed in compressed CO(2) (69-172 bar, 25 °C and 45 °C) during synthesis. CO(2) processing results in significant pore expansion for films templated with both fluorinated surfactants, while pore expansion is negligible for the hydrocarbon templated material suggesting that preferential CO(2) penetration occurs in the 'CO(2)-philic' fluorocarbon segments of the surfactant template. The effect of substrate surface energy on the final uniformity of the dip-coated films is studied by varying the substrate from unmodified glass to a fluorocarbon-capped substrate. The ability to create dip-coated thin films on low surface energy substrates through favorable interaction of surfactant template tail with the substrate surface functional groups is demonstrated.     

Supercritical carbon dioxide processing of fluorinated surfactant templated mesoporous silica thin films

The effect of processing mesoporous silica thin films with supercritical CO2 immediately after casting is investigated, with a goal of using the penetration of CO2 molecules in the tails of fluorinated surfactant templates to tailor the final pore size. Well-ordered films with two-dimensional hexagonal close-packed pore structure are synthesized using a cationic fluorinated surfactant, 1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)pyridinium chloride, as a templating agent. Hexagonal mesopore structures are obtained for both unprocessed films and after processing the cast films in CO2 at constant pressure (69-172 bar) and temperature (25-45 degrees C) for 72 h, followed by traditional heat treatment steps. X-ray diffraction and transmission electron microscopy analysis reveal significant increases in pore size for all CO2-treated thin films (final pore diameter up to 4.22 +/- 0.14 nm) relative to the unprocessed sample (final pore diameter of 2.21 +/- 0.20 nm) before surfactant extraction. Similar pore sizes are obtained with liquid and supercritical fluid treatments over the range of conditions tested. These results demonstrate that combining the tunable solvent strength of compressed and supercritical CO2 with the "CO2-philic" nature of fluorinated tails allows one to use CO2 processing to control the pore size in ordered mesoporous silica films.     

Mesoporous silica reinforced by silica nanoparticles to enhance mechanical performance

Silica nanoparticle/mesoporous silica composite films were prepared by direct mixing with mechanical stirring and thermal imidization. The structural morphology was elucidated by scanning electron microscopy and the surface of the film was imaged by atomic force microscopy. The functional groups and desorption process of the films were elucidated by Fourier transform infrared spectroscopy and thermal desorption spectroscopy. The mechanical properties were investigated using a nanoindenter system. The gel matrix and the filler are very compatible because they have similar molecular content. The composite films had a higher mechanical strength than pure porous silica film. Their strength is related to the silica nanoparticle content. The interfacial compatibility, dispersion effect, and interfacial strength also affect the mechanical strength of composite films.     

Investigation of the properties of organically modified ordered mesoporous silica films

Organically modified, ordered mesoporous silica films, which can provide hydrophobicity and low polarizability to the framework, were prepared using Brij-76 block copolymer as a template. Due to a fast condensation reaction of the silica precursor, mesostructured silica films were not properly synthesized. To circumvent this problem, a synthesis procedure was modified to provide an enhancement of pore periodicity through the incorporation of methyl ligands on the framework. The micropore volume was reduced, and the pore size was enlarged, as the concentration of the methyl ligands on the framework was increased. A mesophase transition from a two-dimensional hexagonal structure to a body-centered cubic (BCC) structure was observed according to the concentration of incorporated methyl ligands. The mechanical properties of the fabricated films were investigated according to the pore ordering and film density. The mechanical properties of the films with random pore geometry show a positive correlation between film density and elastic modulus. Meanwhile, the mechanical behavior of organically modified mesoporous silica films with periodic pore distribution represents a negative correlation within a certain density range, which is advantageous to the low-k materials. Especially, film with a low micropore volume fraction and BCC pore ordering is more applicable to a low-k material due to low dielectric constant and high mechanical strength.     

Mesoporous silica thin films as a spatially extended probe of interfacial electric fields for amplified signal transduction in surface plasmon resonance spectroscopy

A new simpler concept about the signal amplification of surface plasmon resonance (SPR) that is based on the utilization of mesoporous silica thin films is demonstrated. As compared to monolayer based coatings, mesoporous silica thin films of approximately 200 nm extend the interaction arena away from the metal, thus permitting the integration of the change in optical contrast at different distances from the sensor surface.     

Improved selection of LMW over HMW proteins from human plasma by mesoporous silica particles with external modification

Selective extraction of low molecular weight (LMW) proteins and peptides from complex biological samples plays an important role in the discovery of useful biomarkers and signaling molecules. Various methods, such as solid-phase extraction (SPE), ultrafiltration, and size-exclusion chromatography have been developed for such extraction purpose. In this study, we present, to our knowledge, the first demonstration of alkyl-diol@SiO₂ mesoporous material MCM-41 (alkyl-diol group on the external surface of mesoporous material) for selective extraction of LMW proteins and peptides from complex biological samples. The adsorption kinetics of LMW proteins, the influence of pH on adsorption and the desorption recovery by different elution solvents were investigated by using standard proteins as model samples. It was demonstrated that the modification of alkyl-diol group on the external surface could efficiently decrease the adsorption of HMW protein and increase the desorption recovery of LMW protein. Furthermore, the mesoporous materials were applied to selectively extract LMW proteins and peptides (<10 kDa) from crude human plasma. And the modified MCM-41 material had much better extraction selectivity and efficiency for LMW proteins and peptides than unmodified one.     

Analysis of the human urine endogenous peptides by nanoparticle extraction and mass spectrometry identification

Peptides in urine are excreted by kidney from the blood and tissues, which are composed of a large amount of hormones, cytokines, regulatory factors and the metabolized fragments of proteins. The peptide distribution in urine will reflect the physiological and pathophysiological processes in body. In past, limited information was reported about the composition of the peptides in urine. One possible reason is that the peptides in urine are fairly low abundant and there are high concentrations of salts and organic metabolites in the urine. In this report, we extracted the peptides from human urine by highly ordered mesoporous silica particles with the pore size of 2 nm, which will exclude the high molecular weight proteins over 12 kDa. The extracted peptides were then separated into fractions according to their molecular weight by size exclusion chromatography. Each of the fractions was further analyzed by MALDI-TOF MS and μRPLC–MS/MS. Totally, 193 peptides were identified by two-dimensional SEC/μRPLC–MS/MS analysis. By analyzing the progenitor protein of the peptides; we found that two-thirds of the proteins differed from the reported urine proteome database, and the high abundant proteins in urine proteome were less detected in the urine peptidome. The developed extraction and separation methods were efficient for the profiling of the endogenous peptides in human urine. The peptidome in human urine was complementary to the human urinary proteome and may provide an emerging field for biomarker discovery.     

Immobilization and electrochemistry of cytochrome c on amino-functionalized mesoporous silica thin films

The immobilization and electrochemistry of cytochrome c (cyt c) on amino-functionalized mesoporous silica thin films are described. The functionalized silica films with an Im3m cubic phase structure were deposited on conducting ITO substrate by co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) in the presence of Pluronic F127 under acidic conditions. The high specific surface area, large pore size and functional inner surface of mesoporous silica thin films result in a high cyt c loading, and the cyt c immobilization on this silicate framework is stable. After adsorption of cyt c, the ordered cubic structure of mesoporous silica and the redox activity of immobilized cyt c are retained as demonstrated by X-ray diffraction (XRD), Transmission electron microscope (TEM) and cyclic voltammetry. The redox behavior of the cyt c/silica film-modified ITO electrode is a surface-controlled quasi-reversible process for the experimental conditions used in this work and the electron transfer rate constant is calculated is 1.33 s⁻¹. The ITO electrode modified by cyt c/silica film possesses a high stability; even cyt c retains its redox activity following immobilization for several months. Furthermore, the electrocatalytic activities of the modified ITO electrode to hydrogen peroxide and ascorbic acid have been studied. Since these behaviors are quite pronounced, the modified electrode can be used for detection of hydrogen peroxide and ascorbic acid.     

有序介孔氧化硅薄膜制备及其组装化学

本文综述了近年来利用有机模板法合成有序介孔二氧化硅薄膜的研究进展，重点阐述了两相界面外延生长和蒸发诱导自组装两种制备方法及其合成机理。此外，讨论了有序介孔二氧化硅薄膜的组装化学，包括金属元素掺杂，纳米粒子在介孔薄膜中的组装，以及有机物/二氧化硅纳米复合薄膜的制备，并对介孔二氧化硅薄膜未来的发展趋势做了展望。