Mesoporous Silica Nanotubes Research Articles

Trypsin functionalization and zirconia coating of mesoporous silica nanotubes for matrix-assisted laser desorption/ionization mass spectrometry analysis of phosphoprotein

Trypsin functionalized mesoporous silica nanotubes bioreactor (TEMSN) and zirconia layer coated mesoporous silica nanotubes (ZrO2-MSN) were developed to deal with the long in-solution digestion time of phosphoprotein and detection difficulty of phosphorylated peptides, respectively. Trypsin was immobilized on the mesoporous silica nanotubes via epoxy group and TEMSN were used as a bioreactor for digestion of α-casein within 3min. ZrO2-MSN were performed to enrich phosphopeptides selectively from in-solution digested peptide mixture of β-casein to demonstrate that ZrO2-MSN possessed remarkable selectivity for phosphorylated peptides even at 100/1 molar ratio of BSA/β-casein. The selective ability of ZrO2-MSN was also investigated in comparison to ZrO2 nanoparticles (ZrO2 NP). Moreover, phosphorylated peptides at the femtomole (2.5fmol) level can also be detected with high S/N (signal-to-noise) ratio. Phosphopeptides enriched from TEMSN-bioreactor digested peptide mixture of α-casein was also performed to evaluate the cooperative performance of TEMSN and ZrO2-MSN platform. The experimental results indicated that TEMSN-bioreactor digestion changed the distribution of relative abundance of phosphopeptides and improved the relative intensity of partial phosphopeptides. This analytical strategy has also been applied to the identification of phosphopeptides isolated from non-fat bovine milk and got a comparable results compared with other materials cited from the literature. By matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS), TEMSN and ZrO2-MSN were combined together for the rapid and comprehensive analysis of phosphoprotein.

Preparation of Chiral Mesoporous Silica Nanotubes and Nanoribbons Using a Dual-Templating Approach

Single-handed helical silica nanotubes and nanoribbons have attracted much attention, due to their potential for applications in asymmetric catalysis and enantioseparation. However, their surface areas are usually lower than 200 m2/g. Herein, single-handed coiled silica nanoribbons with mesopores in their walls were prepared by changing the molar ratio of the chiral low-molecular-weight amphiphiles (LMWAs) and the F127 triblock copolymer, using a dual-templating approach. The obtained samples were characterized using field-emission scanning electron microscopy, transmission electron microscopy, N2 sorption measurements, and X-ray diffraction. The BET surface area reached 700 m2/g. The pore diameters did not change significantly at different LMWA/F127 triblock copolymer molar ratios. The formation of the coiled mesoporous silica nanoribbons was studied by taking TEM images at different times during the reaction. The results indicated that the morphology and the mesopores were controlled by the chiral LMWAs...

Mesoporous silica tubular nanocarriers for the delivery of therapeutic molecules

Nanocarriers to load and deliver biomolecules are promising platforms to improve the therapeutic efficacy of the molecules. Here, we report a novel inorganic mesoporous nanotubular carrier made of silicate as an effective delivery system for biomolecules including chemical drugs, proteins and genes. Silicate hollow nanotubes were replicated from carbon nanotubes via a sol–gel process and heat-treatment. In particular, mesopores were generated within the silicate nanotubes to provide a space for the loading of therapeutic molecules. While the surface of the as-prepared mesoporous silica nanotube (mSiNT) was highly negative (−28 mV), an amine-functionalization made the surface highly positive (+32 mV), which provided a switchable platform for selective loading of molecules depending on the surface charge characteristics. As model drugs, sodium-ampicillin, cytochrome C and small interfering RNA (siRNA) were employed to investigate the loading capacity of, and release profile from, the mSiNT. The molecules were loaded onto mSiNTs selectively, taking into account their molecular charge. The mSiNTs were capable of incorporating the therapeutic molecules in a way that was highly dependent on the level of mesoporosity. The loaded ampicillin and cytochrome C were released for a relatively short period (i.e., within 2 days). The siRNA was also easily complexed with the aminated-mSiNTs, and was released for a prolonged period of up to ∼7 days. When the mSiNT–siRNA complex was delivered to HeLa cells, the transfection efficiency was approximately 56%, and the siRNA silencing effect assessed by bcl-2 was also evidenced. Based on this study, the nanotubular form of mesoporous silica is considered as a potential non-viral delivery vehicle for a range of therapeutic molecules.

Immobilization of lipase on aminopropyl-grafted mesoporous silica nanotubes for the resolution of (R, S)-1-phenylethanol

Mesoporous silica nanotubes and aminopropyl-grafted mesoporous silica nanotubes were prepared as supports to immobilize lipase from Candida sp. 99-125(ClLip) by physical adsorption. The immobilization conditions were investigated. Moreover, immobilized lipases on both kinds of supports were employed to catalyze olive oil hydrolization and resolution of 1-phenylethanol by esterification. The results showed that the hydrolization activity of the lipase immobilized on aminopropyl-grafted mesoporous silica nanotubes was almost twice of that on mesoporous silica nanotubes. In addition, the resolution of 1-phenylethanol catalyzed by the former catalyst also increased 22%. Circular dichroism spectra revealed a reduction of α-helix and an increase of β-sheet when lipase was adsorbed on aminopropyl-grafted mesoporous silica nanotubes, which suggested that parts of α-helix were extended and reformed to be β-sheet.

Hierarchical Mesoporous Silica Nanotubes Derived from Natural Cellulose Substance

Bioinspired synthesis of hierarchical mesoporous silica nanotubes by using natural cellulose substance (filter paper) and cetyltrimethylammonium bromide (CTAB) micelles as dual templates was achieved. CTAB micelles were adsorbed onto the surfaces of ultrathin titania film precoated cellulose nanofibers, followed by hydrolysis and condensation of tetraethyl orthosilicate around these micelles to form silica. After calcination and sulfuric acid treatment to remove the organic templates and the thin titania film, bulk white sheets composed of natural hierarchical silica nanotubes with mesopores in the walls were obtained, to which silver nanoparticles were further induced to give a silica-nanotube/metal-nanoparticle hybrid.

Synthesis of Mesoporous Silica Nanotube Bundles

Mesoporous silica nanotube bundles with short channels were synthesized through a surfactant-templated process with the addition of dodecane. Transmission electron microscope (TEM) and high resolution scanning electron microscope (HRSEM) studies show that the channels of the silica nanotubes are parallel gathered in nano-size bundles. Each particle of these nano-size bundles contains less than 10 silica nanotubes. The length of the silica nanotube channel is about 200 nm while the pore size of the channels is about 11 nm. Dodecane solubilized in the hydrophobic cores of P123 micelles leads to large pore size and the unique bundle structure of the silica nanotubes.

Formation and characterization of mesostructured silica nanotubes

The multi-walled mesoporous silica nanotubes are prepared using cetyltrimethylammonium bromize (CTAB) as the surfactant micellar template and tetraethylorthosilicate (TEOS) as the silica precursor via a one-step wet chemical approach. The synthesized tubes are found to be double/triple walled and of amorphous nature. Their diameter and the length are about 100 nm to 1 μm and about 0.1–20 μm, respectively. The specific surface area approaches 1,488 m2/g. Based on the transmission electron microscopy analysis, it is inferred that the formation of the double/triple walled silica nanotubes is associated with the lamellar curling mechanism. A striking photoluminescence effect is detected in the mesostructured silica nanotubes. These nanotubes are expected to be a promising material for various applications such as gas storage, catalyst, or catalyst supports.

Templated-assisted one-dimensional silica nanotubes: synthesis and applications

Silica (SiO2) is one of the most frequently used inorganic materials. This review covers the research progress in the synthesis of one-dimensional silica nanotubes as well as the newest aspects of silica nanotubes in applications where their structural attributes are exploited. The synthetic methods for well-defined silica nanotubes and a variety of specific silica nanotubes including hollow silica nanotubes, mesoporous silica nanotubes, chiral or helical silica nanotubes are summarized. One-dimensional tubular silica nanomaterials display structures that differ from those of other kinds of nanostructured silica materials and provide unique features such as very uniform diameter, open at both ends. In addition, sol–gel process and silane chemistry offer the reliable and robust surface modification or functionalization of silica nanotubes. Attractively, end functionalization of silica nanotubes may be able to control drug release, resulting in their wide applications in controlled drug and gene delivery; also their distinctive inner and outer surfaces can be differentially functionalized making silica nanotubes ideal multifunctional nanostructure candidates for biomedical applications in various areas such as biosensing, bioseparation and biocatalysis.

Mesoporous silica nanotubes coated with multilayered polyelectrolytes for pH-controlled drug release

Two kinds of inorganic/organic hybrid composites based on mesoporous silica nanotubes (MSNTs) and pH-responsive polyelectrolytes have been developed as pH-controlled drug delivery systems via the layer by layer self-assembly technique. One system was based on alternatively loading poly(allylamine hydrochloride) and sodium poly(styrene sulfonate) onto as-prepared MSNTs to load and release the positively charged drug doxorubicin. The other system was synthesized by alternately coating sodium alginate and chitosan onto amine-functionalized MSNTs, which were used as vehicles for the loading and release of the negatively charged model drug sodium fluorescein. Controlled release of the drug molecules from these delivery systems was achieved by changing the pH value of the release medium. The results of in vitro cell cytotoxicity assays indicated that the cell killing efficacy of the loaded doxorubicin against human fibrosarcoma (HT-1080) and human breast adenocarcinoma (MCF-7) cells was pH dependent. Thus, these hybrid composites could be potentially applicable as pH-controlled drug delivery systems.

Control the Diameters of Mesoporous Silica Nanotubes by Varying Stirring Time

A chiral cationic gelator derived from L-alanine was synthesized. Sol-gel transcriptions were carried out to control mesoporous silica nanostructures using the organic self-assemblies of this gelator as templates. It was found that the morphologies of the obtained mesoporous silicas were sensitive to stirring time. With increasing the stirring time, the morphologies of mesoporous silicas changed from nanotubes constructed by double twisted nanoribbons to those constructed by single-strip coiled nanoribbons. The diameters of the nanotubes increased from 80 to 400 nm. This result indicated that the formation of the nanotubes following a dynamic templating process. For a better understanding the pore architectures, the TEM images of the mesoporous silicas were simulated using the 3D studio MAX software.

Fluorescent mesoporous silica nanotubes incorporating CdS quantum dots for controlled release of ibuprofen

Mesoporous silica nanotubes (MSNTs) and amine-functionalized MSNTs (NH 2-MSNTs) have been successfully synthesized via a sol–gel route using needle-like CaCO 3 nanoparticles as inorganic templates and post-modification with 3-aminopropyltriethoxysilane. Subsequently, the preformed nanotubes were functionalized with blue fluorescent CdS quantum dots, as demonstrated by transmission electron microscopy and confocal laser scanning microscopy. The morphology and microstructure of the produced materials were characterized by scanning electron microscopy and N 2 adsorption–desorption measurements. A comparative study of the capacity of several kinds of nanotube materials to store ibuprofen indicated that the drug-loading amount in CdS-NH 2-MSNTs (CdS-incorporated NH 2-MSNTs) could reach up to 740 mg/g silica, similar to that in as-prepared MSNTs (762 mg/g silica) and NH 2-MSNTs (775 mg/g silica). Drug release studies in simulated body fluid revealed that the loaded ibuprofen released from amine-functionalized systems at a significantly lower release rate as compared to that from amine-free systems, and the incorporation of CdS quantum dots had nearly no effect on the ibuprofen release process. Further study on the ibuprofen release from CdS-NH 2-MSNTs in other media, i.e. borate buffer saline, pure water and normal saline, indicated that CdS-NH 2-MSNTs are pH- and ion-sensitive drug carriers, which should facilitate controlled drug delivery and disease therapy.

Organization of helical mesoporous silica nanotubes

Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of a gelator as template previously. The TEM images were simulated using Autodesk 3D studio MAX 9.0 here. These hierarchical nanotubes were organized into μm-size balls by increasing the concentration of gelator and controlling stirring speed. Bimodal pore structure was identified by a N2 adsorption method.

Synthesis and Characterization of Silica Nanotubes with Radially Oriented Mesopores

AbstractHierarchical silica nanotubes with radially oriented mesoporous channels perpendicular to the central axis of the tube were synthesized by using self‐assembled chiral anionic surfactant, co‐structure directing agent (CSDA) and silica precursor. The average inner diameter and the wall thickness were ∼94, ∼62, and ∼62 nm and to ∼27, ∼33, and ∼45 nm, respectively, by manipulating the synthesis gel composition, while the diameter of the wall mesopores was kept constant at ∼4 nm. These materials with such a unique structure were produced only with chiral surfactant and achiral or racemic surfactant did not give rise to mesoporous silica nanotubes. The existence of helicity in the lipid bilayer template was confirmed by means of circular dichroism spectroscopy. The mesoporous penetrating from outside to inside of silica nanotubes are thought to originate from the initial formation of self‐assembled lipid tubes with helical bilayers, which in turn re‐assemble to form the mesopores in the wall of the nanotubes upon addition of co‐structure directing agent and silica source.

A Novel Route for Synthesizing Silica Nanotubes with Chiral Mesoporous Wall Structures

Right- and left-handed excess chiral mesoporous silica nanotubes with a helical channel in the wall have been formed by the self-assembly of an achiral surfactant sodium dodecyl sulfate (SDS) in the presence of (R)-(+)- and (S)-(−)- 2-amino-3-phenyl-1-propanol ((R)-(+)- and (S)-(−)-APP) chiral molecules. Transmission electron microscopy combined with computer simulations confirmed the presence of ordered chiral channels winding around the central axis of the tubes of ∼100 nm inner diameter. Furthermore, it has been found that these have been produced through a specific crystallization route that hollows out the chiral mesoporous silica rod, which is different from the tube synthesis pathways reported previously. The enantiomeric excess ee of chiral mesoporous silica has been increased from 0 to a maximum value of 32% with increasing (R)-(+)-APP/SDS molar ratios from 0 to 0.8.

Synthesis of Porous Silica Nanotubes using Rosette Nanotubes as Templates

ABSTRACTRosette nanotubes (RNTs) were used as structure-directing agents for the synthesis of microporous and/or mesoporous silica nanotubes. The silica nanomaterials were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and CO2 and nitrogen physisorptions. The results show that the mode of the obtained porous systems as well as the surface areas and volume of micro- and/or mesopores depend on the nature of the pendant attached to the rosette nanotubes surface.

Structure Elucidation of the Highly Active Titanosilicate Catalyst Ti‐YNU‐1

Three novel zeolites (M-IEZ-MWW, IEZ-FER and IEZ-CDO) have been successfully synthesised from the corresponding precursors. Structure characterisation of those materials was conducted by TEM. Our studies show that the structure of the new zeolites keeps identical layer to the corresponding known 3D zeolite, except for the distinct expansion of the layer spacing. Combining with results from XRD, N2 adsorption, IR and NMR, the expansion can be explained by the pillaring of T sites between the layers. Meanwhile, the intergrowth of 3D MWW and IEZ-MWW was observed in the Al-IEZ-MWW and Si-IEZ-MWW crystals, IEZ-CDO structure was found in the IEZ-FER crystals, and the intergrowth of CDO and new polymorph was observed in the CDS-1 crystal. Moreover, two new zeolites IM-5 and SSZ-57 were also studied by TEM. We found that the space group of IM-5 is non-centrosymmetrical, and in SSZ-57 the new structure with slightly larger c parameter was observed compared to MEL. Chiral mesoporous silica nanotube and chiral mesoporous carbon nanotube were aslo investigated by TEM. We found that the former was synthesised by hollowing out process and it possesses chiral mesopores in the wall, the latter was synthesised by templating and seeding method. Electron tomography was first applied to study the handedness of the chiral mesoporous nanotube. Furthermore, TEM studies verified that bifunctional mesoporous silica has a Fm-3m structure, and mesoporous carbon FDU-16 has a Im-3m structure.

Synthesis of nano-sized mesoporous silicas with metal incorporation

The metal oxide-incorporated or -grafted mesoporous silica nanoparticles and nanotubes have been prepared efficiently via a two-step synthetic process, which includes a pre-hydrolysis of the TEOS and metal alkoxides or salts in acidic solution (pH < 1.0), and fast co-condensation of silica, metal oxides and surfactant in alkaline ammonia solution (pH 8.0–9.0). Because the presence of the cationic surfactant and a proper pH range could make the silica condensation fast enough to match a relatively quick metal-oxide condensation, various metal oxides (e.g. Al-, Ti-, V-, Zr-, Fe-oxides) can be homogeneously incorporated into the silica framework or grafted on the silica surface. The XRD, reflectance UV–vis and FT-IR spectrometry and solid state NMR have been performed to further identify the successful incorporation and grafting of metal oxides. The metal oxides-incorporated mesoporous silica nanotubes or nanoparticles with high surface area, large mesoporosity and textural porosity can be considered as a capable catalyst of high connectivity and accessibility. The Al-incorporated mesoporous silica nanoparticles show higher catalytic activity toward the cumene-cracking reaction than the typical mesoporous aluminosilicate.

Formation of Mesoporous Silica Nanotubes

[29] M. A. van Dijk, R. van den Berg, Macromolecules 1995, 28, 6773.[30] From the morphology of the polymer blend thin film, it was alreadypointed out that there is no clear affinity for one of the two hydropho-bic phases to preferentially wet the hydrophilic silicon substrate.[31] V. Z.-H.Chan,E. L. Thomas, R. G. H.Lammertink, M. A. Hempenius,G. J. Vancso, H. Wang,R. J. Composto, unpublished.[32] Auger electron spectroscopy (AES) data obtained for oxygen etchedPFS homopolymer are consistent with the XPS results. Depth profiling(argon ion sputtering) indicated an approximately 10 nm thin layerrich of iron, silicon, and oxide at the surface of the oxygen etchedpolymer film.[33] A. B. Fischer, J. B. Kinney, R. H. Staley, M. S. Wrighton, J. Am.Chem. Soc. 1979, 101, 6501.

Nanocomposites Prepared by Threading Polymer Chains through Zeolites, Mesoporous Silica, or Silica Nanotubes

The purpose of this brief review is to describe some recent, preliminary attempts to prepare nanocomposites in which polymer chains thread through the cavities or channels of several types of inorganic materials, specifically zeolites, a mesoporous hexagonal form of silica, and silica nanotubes. One goal is to determine the effects of the constraining geometry on the properties of the chains, in particular, their glass transition temperatures. Another is the hope that this molecular threading will provide such intimate interactions between the polymer chains and their inorganic environment that novel reinforcement effects will be obtained.