Chemiluminescence immunoassay based on dual signal amplification strategy of Au/mesoporous silica and multienzyme functionalized mesoporous silica

A chemiluminescent dual signal amplification strategy for the determination of α-fetoprotein (AFP) was proposed based on a sandwich immunoassay format. Monoclonal antibody of AFP immobilized on the gold nanoparticles doped mesoporous SiO₂ (Au/SiO₂) were prepared and used as a primary antibody. Horseradish peroxidase (HRP) and HRP-labeled secondary antibody (Ab₂) co-immobilized into the mesoporous SiO₂ nanoparticles (HRP-Ab₂/SiO₂) were used as the labeled immunological probe. Due to the high ratio surface areas and pore volumes of the mesoporous SiO₂, not only the amount of AFP monoclonal antibody but also the amount of the modified HRP and Ab₂ in HRP-Ab₂/SiO₂ were largely increased. Thus the chemiluminescent signal was amplified by using the system of luminol and H₂O₂ under the catalysis of HRP. Under the optimal conditions, two linear ranges for AFP were obtained from 0.01 to 0.5 ng mL⁻¹ and 0.5 to 100 ng mL⁻¹ with a detection limit of 0.005 ng mL⁻¹ (3σ). The fabricated signal amplification strategy showed an excellent promise for sensitive detection of AFP and other tumor markers.     

Synthesis of ZnS nanoparticles into the pore of mesoporous silica spheres

The ZnS nanoparticles were exclusively synthesized in the pores of the mesoporous silica (MS) particles which had been coated with two bilayers of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate) (PSS) via the layer-by-layer (LbL) self-assembly technique. Measurements and analysis of XRD and TEM showed that the ZnS nanocrystals were inserted into the pores of the MS spheres. This approach can be used to prepare composite materials involving functional inorganic nanoparticles which have potential application in biological immunoassay and photoelectronic fields.     

A combined top-down and bottom-up approach to fabricate silica films with bimodal porosity

We report a method to fabricate silica films with bimodal porosity based on the surfactant-directed self-assembly process followed by post-treatment with reactive ion etching (RIE). By RIE of a surfactant-templated mesoporous silica film with a 3D hexagonal structure, vertically-etched pores with the size of several tens of nanometers and the depth of ca. 60 nm are generated, while the original caged mesopores (ca. 5 nm in size) are still retained in the unetched parts of the film. Pre-treatment of the mesoporous silica film by wet-etching to expose the pores on the surface, followed by sputter deposition of a Pt layer for partial masking, is crucial for the anisotropic etching of the film. Such a combined top-down and bottom up approach offers an opportunity to fabricate silica films with hierarchical pore architectures.     

Preparation of UV-filter encapsulated mesoporous silica with high sunscreen ability

In this study, a UV-filter encapsulated in a mesoporous silica, MCX-MS, was prepared by the in-situ sol-gel polymerization of tetraethyl orthosilicate (TEOS) with an ionic liquid (IL) as solvent and pore-forming agent and octal methoxycinnamate (MCX) as an additive. MCX-MS was characterized by Fourier transformation infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The result of the thermogravimetric analysis (TGA) showed that the amount of MCX encapsulated in MS was about 65 wt.% of MCX-MS. Comparing with that of the free MCX, the SPF value of the MCX-MS-containing sunscreen cream increased by about 57%, indicating significant enhancement of the UV protection ability of MCX by encapsulation in the mesoporous silica matrix. Furthermore, because the average particle size of MCX-MS emulsion droplets was big enough, damage by penetration through the skin is expected to be prevented.     

Solution plasma for template removal in mesoporous silica: pH and discharge time varying characteristics

The evaluation of the ability of solution plasma process, SPP, depending on the pH of the discharge solution and discharge time for template removal in mesoporous silica was described. In the synthesis of mesoporous silica, ternary surfactant system containing tri-block copolymer EO₂₀PO₆₉EO₂₀ (P123), sodium dodecylbenzene sulfonate (SDBS), and 1,1,2,2,3,3,4,4,4-nonafluoro-1-butyl sulfonate (NFBS) was chemically used for synthesis under acid condition via sol-gel method then SPP was employed for template removal. The ordered 2D hexagonal arrangement was observed by the evidence of high resolution TEM and the diffraction mode of X-ray. The efficiency of SPP depending on the pH of the discharge solution and discharge time was scientifically demonstrated as a function of BET surface area. In the case of pH dependence, it was achieved that the ability of template removal in acid and base solutions was clearly higher than those of such results in neutral solution. In the term of discharge time, moreover, the percentage of template removal comparing in the result of BET surface area increased as the increase in discharge time.     

Synthesis of l-theanine using enzyme/mesoporous silica conjugates under high pH conditions

We present a new enzymatic process for synthesis of l-theanine using glutaminase combined with immobilization technique on a mesoporous silica (MPS). The MPS was firstly attempted to modify with zirconia in order to enhance the durability against the reaction under high pH conditions. The glutaminase on the MPS successfully catalyzed the reaction for the synthesis of l-theanine. The glutaminase/MPS conjugate was subsequently recovered and employed for the reaction again. The conjugate showed the corresponding activity to the first synthesis. This indicates that the conjugate functions as a catalyst for synthesis of l-theanine, having the operational stability sufficient for reuse.     

Ag nanoparticle incorporation in mesoporous silica synthesized by solution plasma and their catalysis for oleic acid hydrogenation

The incorporation of Ag nanoparticles on mesoporous silica as the supporting material and their catalysis for oleic acid hydrogenation were described in this study. The template removal and Ag nanoparticle incorporation were concurrently taken place in the novel glow discharge in a solution, namely solution plasma process under controlled conditions. With only 15 min of discharge time, Ag nanoparticles were incorporated on the mesoporous silica matrix confirmed by the evidences of XRD and TEM and the template inside mesopores was mostly removed confirmed by FTIR spectra. The hydrogenation catalysis of oleic acid was preliminarily tested using UV-VIS spectroscopy after oxidation using permanganate ions (MnO₄⁻). It was found that the conversion was observed to be 12.83% in the butanol system and reached to 90.56% in ethanol.     

Synthesis and properties of dense bulks for mesoporous silica SBA-15 by a modified hydrothermal method

Dense SBA-15 bulks with mesoporous structure as well as powdered SBA-15 were successfully synthesized by the modified hydrothermal method. These SBA-15 bulks have the higher density of 1.16 to 1.19 g/cm³, compared to green density of 0.68 g/cm³ for the pellet from SBA-15 powder. Obtained SBA-15 bulks possessed extremely high BET surface area of 467 m²/g and mesopore of 4.0 nm in diameter The possibility of densification for SBA-15 bulks using this method was confirmed.     

A mesoporous silica functionalized by a covalently bound pyridine derivative for selective optical sensing of thymidine

Fluorescent receptor 1 immobilized mesoporous silica (FMS) possessing the diaminopyridine moiety as a fluorescent receptor was fabricated by sol-gel reaction. The binding ability of FMS with nuclobases was evaluated by fluorophotometry. Interestingly, among nucleobases, addition of thymidine to a suspension of FMS in water resulted in the largest decrease in fluorescence intensity of diaminopyridine in FMS. These results indicate that FMS recognizes selectively thymidine in nucleobase.     

A facile method for the production of high-surface-area mesoporous silica gels from geothermal sludge

Mesoporous silica gels were successfully produced from geothermal sludge by alkali extraction followed by acidification. The silica in the geothermal sludge was dissolved by NaOH solution to produce a sodium silicate solution, which was then reacted with HCl or tartaric acid to produce silica gels. The effects of silica concentration and pH on the silica gel properties were investigated. In addition, an improved method was proposed by incorporating two-step aging. The first aging step, which was conducted at pH 10, was used to induce Ostwald ripening to increase the size of the primary particles, and the second step was used to strengthen the gel network. Decreasing the silica concentration by diluting the as-prepared sodium silicate solution tended to increase the surface area and pore volume of the prepared silica gels. The silica gels produced by tartaric acid possessed higher surface area and pore volume than those by HCl. The surface area and pore volume reached approximately 450 m² g⁻¹ and 0.8 cm³ g⁻¹, respectively. When the gelation pH was decreased to 6, the surface area exceeded 600 m² g⁻¹. The first aging process increased the size and uniformity of the primary particles, which in turn increased the surface area of the particles. The pore diameter for all cases was greater than 5 nm, indicating that the silica gels were mesoporous.     

Hybrid surfactant-templated mesoporous silica formed in ethanol and its application for heavy metal removal

With cetyltrimethylammonium (CTAB) and tetramethylammonium hydroxide (TMAOH) as hybrid surfactant templates, a mesoporous adsorbent (adsorbent C) was synthesized in ethanol via the integration of "One-step" procedure and "Evaporation-Induced Self-Assembly" procedure. During the synthesis, TMAOH served as the subsidiary structure-directing agent. Adsorbent C exhibited higher pore diameter (centered at 6.1 nm), BET surface area (421.9 m(2)/g) and pore volume (0.556 cm(3)/g) than the other two adsorbents only using P123 (adsorbent A) or CTAB (adsorbent B) as the surfactant. The adsorbents were also characterized by XRD and FTIR spectroscopy. The adsorption of copper, zinc, lead, iron, silver and manganese ions on adsorbent C was investigated by contrast tests with adsorbent A and B. The experimental data showed that adsorbent C possessed better adsorption properties than the counterparts. The order of adsorption capacity for six metal ions was Mn(2+)相似文献   

Effects of sol aging on mesoporous silica thin films organization

Cetyltrimethylammonium bromide (CTAB) templated mesoporous silica thin films were deposited on glass slides by evaporation-induced self-assembly (EISA) process using a dip-coating method. The effects of sol aging on the mesophase structure of the thin films organization were investigated. Identification of the structures was accomplished by coupling X-ray diffraction (XRD) and transmission electron microscope (TEM) investigations, and corresponding sol was characterized by ²⁹Si solution state nuclear magnetic resonance (²⁹Si NMR) and UV-Vis spectrophotometer for studying the mesophase structure evolution. Results indicate that sol aging has great effects on the mesophase structure of the films organization, which includes degree of order and phase transformation of mesoporous silica thin films. To obtain a better understanding of the effects of sol aging on the mesophase structure, the theories of apparent mass fractal dimension and charge density matching were introduced to explain the self-assembly process.     

Aqueous heavy metals removal by adsorption on amine-functionalized mesoporous silica

Amino functional mesoporous silica SBA-15 materials have been prepared to develop efficient adsorbents of heavy metals in wastewater. Functionalization with amino groups has been carried out by using two independent methods, grafting and co-condensation. Three organic moieties have been selected to incorporate the active amino sites: aminopropyl (H(2)N-(CH(2))(3)-), [2-aminoethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(3)-) and [(2-aminoethylamino)-ethylamino]-propyl (H(2)N-(CH(2))(2)-NH-(CH(2))(2)-NH-(CH(2))(3)-). Materials have been characterized by XRD, nitrogen sorption measurements and chemical analysis. We have found that all materials preserve the mesoscopic order and exhibit suitable textural properties and nitrogen contents to act as potential adsorbents. Metal removal from aqueous solution has been examined for Cu(II), Ni(II), Pb(II), Cd(II), and Zn(II); adsorption performances of materials prepared by the two functionalization methods have been compared. In addition, copper adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for some selected materials. Aqueous Cu(II) adsorption rates show that the overall process is fast and the time evolution can be successfully reproduced with a pseudo-second-order kinetic model. Whole copper adsorption isotherms have been obtained at 25 degrees C. Significant maximum adsorption capacities have been found with excellent behavior at low concentration.     

Effective heavy metal removal from aqueous systems by thiol functionalized magnetic mesoporous silica

A thiol-functionalized magnetic mesoporous silica material (called SH-mSi@Fe₃O₄), synthesized by a modified Stöber method, has been investigated as a convenient and effective adsorbent for heavy metal ions. Structural characterization by powder X-ray diffraction, N₂ adsorption-desorption isotherm, Fourier transform infrared spectroscopy and elemental analyses confirms the mesoporous structure and the organic moiety content of this adsorbent. The high saturation magnetization (38.4 emu/g) make it easier and faster to be separated from water under a moderate magnetic field. Adsorption kinetics was elucidated by pseudo-second-order kinetic equation and exhibited 3-stage intraparticle diffusion mode. Adsorption isotherms of Hg and Pb fitted well with Langmuir model, exhibiting high adsorption capacity of 260 and 91.5 mg of metal/g of adsorbent, respectively. The distribution coefficients of the tested metal ions between SH-mSi@Fe₃O₄ and different natural water sources (groundwater, lake water, tap water and river water) were above the level of 10⁵ mL/g. The material was very stable in different water matrices, even in strong acid and alkaline solutions. Metal-loaded SH-mSi@Fe₃O₄ was able to regenerate in acid solution under ultrasonication. This novel SH-mSi@Fe₃O₄ is suitable for repeated use in heavy metal removal from different water matrices.     

Ultra-small MoS_2 nanodots-incorporated mesoporous silica nanospheres for pH-sensitive drug delivery and CT imaging

Functionalization of mesoporous silica spheres with well-dispersed and ultra-small nanodots to exert their synergistic effects for biomedical applications has been considered to be an urgent challenge.Herein,homogeneously incorporation of ultra-small and monodispersed MoS₂ nanodots in the mesoporous silica nanospheres(MSN)was achieved by a facile one-step solvothermal reaction.The as-synthesized UsMSND@MSN possessed uniform size(~115 nm)and favorable biocompatibility inherited from MSN.The dispersed UsMSND within MSN could act as anchoring sites for aromatic anti-cancer drug DOX loading,and consequently achieved pH-responsive release based on the specialπ-π/electrostatic interactions with the DOX molecules.More importantly,the well-dispersed UsMSND in MSN could function as the non-toxic contrast agent for the sensitive in vivo CT imaging in various tumors including breast cancer and glioma with different sections.This work promises a good strategy for dispersed incorporation of UsMSND into MSN as an excellent pH-responsive platform for simultaneous cancer imaging and therapy.     

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates

A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol-gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N₂ adsorption-desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m²/g, large pore volume with more than 0.8 cm³/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.     

Synthesis of mesoporous silica grafted with 3-glycidoxypropyltrimethoxy-silane

Hexagonal mesoporous silicas chemically modified with 3-glycidoxypropyltrimethoxy-silane functional groups were synthesized through the post-synthesis of surfactant free mesoporous silica (OSU-6-W). The solid state ²⁹Si NMR, titration method and elemental analysis of the modified samples showed that the average number of pendant groups in these hybrids were around 2.17 and 3.49 group/nm², respectively. The surface area analysis showed that these materials have pore diameters of 40.7 and 33.2 Å and surface areas of 966 and 720 m²/g, respectively. Infrared spectroscopy, solid state NMR for ¹³C and ²⁹Si nuclei and X-ray diffraction patterns are in agreement with the success of the proposed synthetic procedures, as confirmed for the formation of the mesoporous hybrids. They have shown good performance towards metal-ion adsorption.     

Synthesis and characterization of mesoporous silica thin films as a catalyst support on a titanium substrate

Mesoporous silica films with a thickness of 500-900 nm were synthesized on a titanium substrate by the evaporation-induced self-assembly method (with 900-1200 rpm for 90 s) using cetyltrimethylammonium bromide (CTAB) as structure-directing agent and tetraethyl orthosilicate as the silica source. Prior to coating deposition, the titanium substrate was oxidized to increase the surface roughness up to 500 nm and to produce a thin titania layer. Just before the synthesis, the titania layer was made super hydrophilic by an UV treatment for 2 h to provide a better adhesion of the silica film to the substrate. Films with hexagonal and cubic mesostructures with a uniform pore size of 2.8 nm and a surface area of 1080 m²/g were obtained and characterized by different methods. An alternative approach for surfactant removal by gradual heating up to 250 °C in vacuum was applied. Complete removal of CTAB from the as-synthesized silica films was confirmed by infrared spectroscopy.     

Facilitating drug release in mesoporous silica coated upconversion nanoparticles by photoacid assistance upon near-infrared irradiation

Near-infrared (NIR) light-triggered pH-manipulation has been realized by utilizing upconversion nanoparticle assisted ring-closing reactions of the conventional photoacid merocyanine (MC). This pH manipulation behavior was then used to regulate the switch of an acid-labile cap for facilitating drug release on the basis of mesoporous silica coated upconversion nanoparticles, in which the drug release rate and amount and the cell killing ability have been greatly improved upon NIR light irradiation due to the locally high concentration of H⁺ within pore channels that is generated by upconversion assisted MC. This proof of concept may provide a way to utilize NIR light to regulate pH change for new drug delivery system designs and applications in biomedical field.     

On-chip encapsulation of lipase using mesoporous silica: A new route to enzyme microreactors

A polydimethylsiloxane/glass microfluidic reactor containing lipase-mesoporous silica (FSM-22) conjugates has been successfully constructed without chemical cross-linking between enzyme and support. A direct visualization of conjugates of lipase and FSM-22 immobilized in the microreactor by optical microscopy revealed that the enzymes were uniformly dispersed throughout the particles of the FSM-22, because of the successful immobilization of the enzyme. Moreover, the lipase-FSM-22 conjugates contained in the microreactor indicated higher enzymatic activity in hydrolysis of triglyceride, as compared with a batch experiment. These results demonstrate that the microreactor using mesoporous silica performs not only the reagent-less enzyme immobilization but also the high reactivity of the enzyme.