Hollow Mesoporous Silica Microspheres Research Articles

A mixed-function-grafted magnetic mesoporous hollow silica microsphere immobilized lipase strategy for ultrafast transesterification in a solvent-free system

A novel magnetic mesoporous hollow silica microspheres immobilized lipase is described for ultrafast transesterification of phytosterol with fatty acids and triglycerides in a solvent-free system.

Adsorption of Hg2+ by thiol functionalized hollow mesoporous silica microspheres with magnetic cores

Thiol functionalized hollow mesoporous silica spheres with magnetic cores were synthesized and found to be highly selective adsorbents of Hg2+.

Sequential enrichment with titania-coated magnetic mesoporous hollow silica microspheres and zirconium arsenate-modified magnetic nanoparticles for the study of phosphoproteome of HL60 cells

As one of the most important types of post-translational modifications, reversible phosphorylation of proteins plays crucial roles in a large number of biological processes. However, owing to the relatively low abundance and dynamic nature of phosphorylation and the presence of the unphosphorylated peptides in large excess, phosphopeptide enrichment is indispensable in large-scale phosphoproteomic analysis. Metal oxides including titanium dioxide have become prominent affinity materials to enrich phosphopeptides prior to their analysis using liquid chromatography-mass spectrometry (LC-MS). In the current study, we established a novel strategy, which encompassed strong cation exchange chromatography, sequential enrichment of phosphopeptides using titania-coated magnetic mesoporous hollow silica microspheres (TiO2/MHMSS) and zirconium arsenate-modified magnetic nanoparticles (ZrAs–Fe3O4@SiO2), and LC-MS/MS analysis, for the proteome-wide identification of phosphosites of proteins in HL60 cells. In total, we were able to identify 11,579 unique phosphorylation sites in 3432 unique proteins. Additionally, our results suggested that TiO2/MHMSS and ZrAs–Fe3O4@SiO2 are complementary in phosphopeptide enrichment, where the two types of materials displayed preferential binding of peptides carrying multiple and single phosphorylation sites, respectively.

Evaluation of serum phosphopeptides as potential cancer biomarkers by mass spectrometric absolute quantification

Mass spectrometric quantification of phosphopeptides is a challenge due to the ion suppression effect of highly abundant non-phosphorylated peptides in complex samples such as serum. Several strategies for relative quantification of serum phosphopeptides based on MS have been developed, but the power of relative quantities was limited when making direct comparisons between two groups of samples or acting as a clinical examination index. Herein, we describe an MS absolute quantification strategy combined with Titania Coated Magnetic Hollow Mesoporous Silica Microspheres (TiO2/MHMSM) enrichment and stable isotopic acetyl labeling for phosphopeptides in human serum. Four endogenous serum phosphopeptides generated by degradation of fibrinogen were identified by LC–ESI–MS/MS following TiO2/MHMSM enrichment. The ESI–MS signal intensity ratios of the four phosphopeptide standards labeled with N-acetoxy-H3-succinimide (H3-NAS) and N-acetoxy-D3-succinimide (D3-NAS), following TiO2/MHMSM capture are linearly correlated with the molar ratios of the “light” to “heavy” phosphopeptides over the range of 0.1–4 with an r2 of up to 0.998 and a slope of close to 1. The recovery of the four phosphopeptides spiked at low, medium and high levels in human sera were 98.4–111.9% with RSDs ranging 2.0–10.1%. The absolute quantification of the phosphopeptides in serum samples of 20 healthy persons and 20 gastric cancer patients by the developed method demonstrated that 3 out of the 4 phosphopeptides showed remarkable variation in serum level between healthy and cancer groups, and the phosphopeptide DpSGEGDFLAEGGGVR is significantly down-regulated in the serum of patients, being a potential biomarker for gastric cancer diagnosis.

Synthesis and structural evolution of hollow flower-type mesoporous silica microspheres

Hollow flower-type mesoporous silica microspheres (designated as HFMSs) with tunable smaller pores and lager pores in the shell have been successfully synthesized via a structural difference-based selective etching treatment of solid silica core/mesoporous silica shell (sSiO2@mSiO2) microspheres. The structure of sSiO2@mSiO2 microspheres could evolve to rattle-type, hollow structure, flower-type structure, and peanut-type structure from core/shell structure just by varying the etching agent from Na2CO3 solution to ammonia solution and adjusting the concentration of etching agent, respectively. Transmission electron microscopy, scanning electron microscopy, and nitrogen adsorption–desorption analysis are applied to characterize the synthesized samples. The mechanism of such a structural evolution is explained in this work.

Preparation of novel magnetic hollow mesoporous silica microspheres and their efficient adsorption

Magnetic hollow mesoporous silica microspheres (MHMSs) were successfully prepared by employing yolk-shell magnetic silica spheres as the template together with the coating of tetraethoxysilane (TEOS)/hexadecyl trimethoxysilane (C16TMS) hybrid. The microstructure and properties of MHMSs were studied by TEM, SEM, XRD, BET, and VSM characterizations. The average diameter of MHMSs was about 300nm and the mesoporous shell thickness was totally around 70nm. The 11nm magnetite nanoparticles were homogeneously embedded in the mesoporous silica shell. Meanwhile, the adsorption and separation process of Rhodamine B were carried out to demonstrate that the material could be used for the adsorbent.

“Ship‐in‐a‐Bottle” Growth of Noble Metal Nanostructures

AbstractNoble metal nanostructures are grown inside hollow mesoporous silica microspheres using “ship‐in‐a‐bottle” growth. Small Au seeds are first introduced into the interior of the hollow microspheres. Au nanorods with synthetically tunable longitudinal plasmon wavelengths and Au nanospheres are obtained through seed‐mediated growth within the microspheres. The encapsulated Au nanocrystals are further coated with Pd or Pt shells. The microsphere‐encapsulated bimetallic core/shell nanostructures can function as catalysts. They exhibit high catalytic performance and their stability is superior to that of the corresponding unencapsulated core/shell nanostructures in the catalytic oxidation of o‐phenylenediamine with hydrogen peroxide. Therefore, these hollow microsphere‐encapsulated metal nanostructures are promising as recoverable and efficient catalysts for various liquid‐phase catalytic reactions.

Hollow mesoporous silica microspheres as sensitive labels for immunoassay of prostate-specific antigen

A novel electrochemical immunosensor for sensitive detection of cancer biomarker prostate-specific antigen (PSA) has been reported based on nanoporous gold (NPG) and hollow mesoporous silica microspheres (HSMs). The immunoassay was conducted by following the typical procedure for sandwich-type immunoreaction. Nanoporous gold (NPG) foils were immobilized onto a glassy carbon electrode (GCE) for primary anti-PSA (Ab(1)) anchoring. Making use of the unique properties of NPG, antibodies could be self-assembled onto the support-free NPG via amine-Au affinity with a high loading amount and reserve high immunological activity. HSMs were used as a secondary anti-PSA antibody (Ab(2)) label. For the preparation of the label, mediator thionine (TH) was first conjugated onto amino-functionalized HSMs (NH(2)-HSMs) via crosslinking with glutaraldehyde, and then the amino group of TH was used to immobilize horseradish peroxidase (HRP) and Ab(2). Due to the large specific surface area of NH(2)-HSMs, the loading of antibodies as well as mediator and enzyme onto HSMs was substantially increased, which increased the sensitivity of the immunosensor. The immunosensor exhibited a high sensitivity and showed a linear response within the range of 0.01-10 ng mL(-1) PSA, low detection limit (6.00 pg mL(-1)), good reproducibility and stability. Significantly, the new method may be quite promising, with potential broad applications for clinical immunoassays.

Fabrication and characterization of aluminum silicate fiber–reinforced hollow mesoporous silica microspheres composites

Aluminum silicate fiber (ASF)/hollow mesoporous silica microspheres (HMSM) composites were fabricated by a vacuum filtration technique, followed by pressureless sintering at 1100 °C. Properties namely: bulk density, microstructure, mechanical strength and thermal conductivity were investigated with the ASF content. Results showed that bulk density of the resultant composites increased from 0.17 to 0.26 g/cm 3 with the increase of ASF content, and the ASF was intimately bonded to the HMSM matrix. When the ASF content was 15 wt.%, the composites exhibited the highest compressive strength (5.07 MPa) and flexural strength (3.32 MPa), then the mechanical strength decreased on further addition (20 wt.%). The thermal conductivity of composites ranged from 0.048 to 0.081 W/(m K) at room temperature, which makes aluminum silicate fiber/hollow mesoporous silica microspheres composites a promising choice for thermal insulation.

Synthesis of a Novel Rigid Artificial Superoxide Dismutase Based on Modified Hollow Mesoporous Silica Microspheres

Hollow silica microspheres (HSMs) that mimics superoxide dismutase (SOD) activity has been developed by using the HSMs modified with the novel metallosalen complex through the esterification between the carboxy and silanol. A novel metallosalen complex, named Fe-(bis(salicylaldehyde)-3,4-diaminobenzoic acid), with superoxide scavenging activity was prepared. We found that the novel complex has a higher superoxide scavenging activity than traditional complex, named Fe-(bis(salicylaldehyde)ethylenediamine), without the carboxy, the catalytic process was studied and explained. The property and SOD activity of the above metallosalen-modified HSMs were investigated. These novel rigid metallosalen-modified HSMs possess excellent SOD activity and it can be easily immobilized to fabricate biomimetic sensor or other catalytic unit/receptor, it solves many practical problems such as easy recovery and repeat utilization. In addition, the metallosalen can be replaced by other active centers to mimetic novel kind of enzymes.

Yolk−Shell Catalyst of Single Au Nanoparticle Encapsulated within Hollow Mesoporous Silica Microspheres

Synthesis and catalysis of yolk−shell microspheres containing a single Au nanoparticle core and a mesoporous shell of hollow mesoporous silica microspheres (HMSM) are reported. This synthesis employs polystyrene-co-poly(4-vinylpyridine) microspheres as both template to fabricate the HMSM shell through sol−gel process and scaffold to immobilize the Au nanoparticle. Since the single Au nanoparticle core is supernatant within the inert HMSM shell, the yolk−shell catalyst has minimum support effect and is a promising model to explore the origin of Au catalysis. Catalyzed reduction of 4-nitrophenol with NaBH4 demonstrates size-dependent induction or activation and size-dependent activity of the Au nanoparticle core of the yolk−shell catalyst.

Plasmon-Modulated Light Scattering from Gold Nanocrystal-Decorated Hollow Mesoporous Silica Microspheres

Localized surface plasmon resonances of noble metal nanocrystals are powerful in enhancing a variety of linear and nonlinear optical signals and photorelated processes. Here we demonstrate the plasmonic enhancement of the light scattering from hollow mesoporous silica microspheres by attaching a dense layer of gold nanocrystals onto the outer surface of the microspheres. The attachment of gold nanocrystals induces both the shift and intensity increase in the resonant scattering peaks of the microspheres. The spectral region of the resonant scattering enhancement can be controlled by using gold nanocrystals with different plasmon resonance wavelengths. The spectral region of the enhancement is independent of the microsphere diameter. The scattering enhancement factor ranges from 20 to 130, depending on the plasmonic properties and surface coverage of the attached gold nanocrystals. The systematic evolution of the scattering spectra of the individual microspheres is also revealed by chemically etching away the attached gold nanocrystals gradually.

Synthesis of hollow mesoporous silica microspheres through surface sol–gel process on polystyrene -co-poly(4-vinylpyridine) core–shell microspheres

Synthesis of hollow mesoporous silica microspheres (HMSM) through directed surface sol–gel process of tetraethylorthosilicate (TEOS) on the template of core–shell microspheres of polystyrene -co-poly(4-vinylpyridine) (PS -co-P4VP) in the presence of the CTAB surfactant in neutral aqueous solution at room temperature is discussed. Ascribed to the inherently pendent catalyst of the Lewis alkaline P4VP segment on the template surface of the PS -co-P4VP core–shell microspheres, the sol–gel process of TEOS is directed exclusively onto the template, and thus well-defined HMSM are fabricated. The thickness of the mesoporous silica shell of HMSM can be tuned by changing the weight ratio of the template of the PS -co-P4VP core–shell microspheres to the coating material of TEOS. Following this method of directed surface sol–gel process, well-defined HMSM with shell thickness ranging from 13 to 39 nm are synthesized. Transmission electron microscopy (TEM), thermogravimetric analysis (TGA), powder X-ray diffraction (XRD) and nitrogen adsorption–desorption analysis are applied to characterize the synthesized HMSM.

Facile and scalable synthesis of a novel rigid artificial superoxide dismutase based on modified hollow mesoporous silica microspheres

A novel metallosalen complex, named Mn-(bis(salicylaldehyde)-3,4-Diaminobenzoic acid), with superoxide scavenging activity was prepared from manganese(III) acetate dehydrate and bis(salicylaldehyde)-3,4-Diaminobenzoic acid in ethanol. We found that the novel complex has a higher superoxide scavenging activity than traditional complex, named n-(bis(salicylaldehyde)ethylenediamine), without the carboxy, the catalytic process was studied and explained. Hollow silica microspheres (HSMs) that mimics superoxide dismutase activity has been developed by using the HSMs modified with the novel metallosalen complex through the esterification between the carboxy and silanol. The property and superoxide dismutase activity of the metallosalen-modified HSMs were investigated. These novel rigid metallosalen-modified HSMs possess excellent superoxide dismutase activity and it can be easily immobilized to fabricate biomimetic sensor or other catalytic unit/receptor, it solves many practical problems such as easy recovery and repeat utilization. An application test of this novel rigid artificial SOD was performed by fabricating a novel biomimetic sensor to determine superoxide based on mesoporous hollow silica microspheres receptor and rhodanine chemiluminescence detector. In addition, the metallosalen can be replaced by other active centers to mimic novel kind of enzymes and immobilized in/on other devices to establish novel biomimetic sensors.

A novel enzyme biosensor for glucose based on rhodanine derivative chemiluminescence system and mesoporous hollow silica microspheres receptor

In this work, hollow silica microspheres (HSMs), which have hollow interiors and nanoporous shells, were used in the immobilization of enzyme to establish a novel chemiluminescence biosensor. The immobilization behavior of enzyme in HSMs with different pore sizes has been studied. The results revealed that the pore size and the surface area of HSMs play important roles in their immobilization performance. Compared with traditional methods, this immobilization method not only provides tunable and consistent pore system and restricted microspaces for enzyme immobilization, but also exhibits a larger immobilization capacity and a higher adsorption rate. A rhodanine derivative-KMnO 4-HCl-H 2O 2 was used to replace traditional chemiluminescence system (luminol-horseradish peroxidase-H 2O 2) to reach the purpose of high sensitivity, simple operation and pH expansion for chemiluminescence biosensor. The linear range of this novel method is 7.72 × 10 −6 to 2.54 × 10 −2 mol L −1 ( r = 0.9994). The detection limit is 8.0 × 10 −7 mol L −1. The Michaelis–Menten constant of glucose oxidase was 0.3 mmol L −1. With glucose oxidase as a test enzyme, the proposed method gave an accurate and satisfactory result once applied to the determination of glucose in four different human serum samples.

Titania coated magnetic mesoporous hollow silica microspheres: fabrication and application to selective enrichment of phosphopeptides

Titania coated magnetic hollow mesoporous silica spheres with high surface area were created, which can be used in efficient and rapid capture of phosphopeptides from peptide mixtures.

An inexpensive route to prepare mesoporous hollow silica microspheres using W/O ethanol/edible soybean oil macroemulsion as the template

Mesoporous hollow silica microspheres were prepared by using W/O emulsion consisting of ethanol droplets as a template in edible soybean oil. Ethanol droplets containing ammonia solution were generated by employing ultrasonication in pure soybean oil. The droplets were colloidally stabilized by means of a cationic surfactant, cetyltrimethylammonium bromide (CTAB). Later on, another proportion of soybean oil dissolving tetraethyl orthosilicate (TEOS) was added to the W/O emulsion. The sol–gel reaction of TEOS was achieved only at the interface of the emulsion droplets, resulting in hollow silica microspheres. After washing the resultant with acetone, mesoporous hollow silica microspheres were simply obtained. Throughout this liquid template-based process, mesoporous hollow silica microspheres can be inexpensively synthesized without employing solid templates.