Silica Nanostructures Research Articles

Optimization of mirtazapine loaded into mesoporous silica nanostructures via Box-Behnken design: in-vitro characterization and in-vivo assessment

Employment of mesoporous silica nanostructures (MSNs) in the drug delivery field has shown a significant potential for improving the oral delivery of active pharmaceutical products with low solubility in water. Mirtazapine (MRT) is a tetracyclic antidepressant with poor water solubility (BCS Class II), which was recently approved as a potent drug used to treat severe depression. The principle of this research is to optimize the incorporation of Mirtazapine into MSNs to improve its aqueous solubility, loading efficiency, release performance, and subsequent bioavailability. The formulation was optimized by using of Box-Behnken Design, which allows simultaneous estimation of the impact of different types of silica (SBA-15, MCM-41, and Aluminate-MCM-41), a different drug to silica ratios (33.33%, 49.99%, and 66.66%), and different drug loading procedures (Incipient wetness, solvent evaporation, and solvent impregnation) on the MRT loading efficiency, aqueous solubility and dissolution rate. The optimized formula was achieved by loading MRT into SBA-15 at 33.33% drug ratio prepared by the incipient wetness method, which displayed a loading efficiency of 104.05%, water solubility of 0.2 mg/ml, and 100% dissolution rate after 30 min. The pharmacokinetic profile of the optimized formula was obtained by conducting the in-vivo study in rabbits which showed a marked improvement (2.14-fold) in oral bioavailability greater than plain MRT. The physicochemical parameters and morphology of the optimized formula were characterized by; gas adsorption manometry, scanning electron microscopy (SEM), polarized light microscopy (PLM), Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and X-ray powder diffraction (XRPD).

Diatom biosilica in plasmonics: applications in sensing, diagnostics and therapeutics [Invited

Several living organisms are able to synthesize complex nanostructures provided with peculiar physical and chemical properties by means of finely-tuned, genetically controlled biomineralization processes. Frustules, in particular, are micro- and nano-structured silica shells produced by ubiquitous diatom microalgae, whose optical properties have been recently exploited in photonics, solar energy harvesting, and biosensing. Metallization of diatom biosilica, both in the shape of intact frustules or diatomite particles, can trigger plasmonic effects that in turn can find application in high-sensitive detection platforms, allowing to obtain effective nanosensors at low cost and on a large scale. The aim of the present review article is to provide a wide, complete overview on the main metallization techniques applied to diatom biosilica and on the principal applications of diatom-based plasmonic devices mainly but not exclusively in the fields of biochemical sensing, diagnostics and therapeutics.

Lignocellulosic Nanocrystals from Sawmill Waste as Biotemplates for Free-Surfactant Synthesis of Photocatalytically Active Porous Silica.

This work presents a new approach for more effective valorization of sawmill wastes (Beech and Cedar sawdusts), which were used as new sources for the extraction of lignin-containing and lignin-free cellulose II nanocrystals (L-CNCs and CNCs). It was shown that the properties of the extracted nanocrystals depend on the nature of the used sawdust (softwood or hardwood sawdusts). L-CNCs and CNCs derived from Beech fibers were long and thin and also had a higher crystallinity, compared with those obtained from Cedar fibers. Thanks to their interesting characteristics and their high crystallinity, these nanocrystals have been used without changing their surfaces as template cores for nanostructured hollow silica-free-surfactant synthesis for photocatalysis to degrade methylene blue (MB) dye. The synthesis was performed with a simple and efficient sol–gel method using tetraethyl orthosilicate as the silica precursor followed by calcination at 650 °C. The obtained materials were denoted as B/L-CNC/nanoSiO2, B/CNC/nanoSiO2, C/L-CNC/nanoSiO2, and C/CNC/nanoSiO2, when the used L-CNC and CNC cores are from Beech and Cedar, respectively. By comprehensive analysis, it was demonstrated that the nanostructured silica were quite uniform and had a similar morphology as the templates. Also, the pore sizes were closely related to the dimensions of L-CNC and CNC templates, with high specific surface areas. The photocatalytic degradation of MB dye was about 94, 98, 74, and 81% for B/L-CNC/nanoSiO2, B/CNC/nanoSiO2, C/L-CNC/nanoSiO2, and C/CNC/nanoSiO2, respectively. This study provides a simple route to extract L-CNCs and CNCs as organic templates to prepare nanostructured silica. The different silica structures showed excellent photodegradation of MB.

Recovery of diatom bio-silica using chemical, thermal, and plasma treatment

Diatom-based silica nanostructures have drawn attention as high-value nanomaterials. However, removing organic matter from the diatom biomass is a critical step towards biogenic silica recovery. In the present study, chemical treatment: HCl, HNO3, H2O2; high-temperature baking at 550 °C: 60 min, 120 min, 180 min; and oxygen plasma ashing: 30 min, 60 min, 90 min were employed for Denticula sp. cleaning to assess their relative efficiency and provide a quantitative assessment. Baking for 180 min gave the maximum organic matter removal (94.9 ± 0.8%) followed by plasma: 90 min (86.8 ± 1.2%) and HNO3 (84.6 ± 1.3%) exposure. The CHN and FTIR results were in agreement with the trend observed in organics removal. However, in the case of baking and chemical exposure, the structure got damaged with disturbance in pore geometry, as revealed by FESEM and BET analysis. On the contrary, the plasma treatment resulted in un-damaged, negatively charged (−31.6 ± 1.4 mV), high surface area (81.6 ± 2.8 m2 g−1), mesoporous (24.6 ± 1.1 nm) structures, which makes it a right technique to process diatoms. Overall, plasma technology was found to be the most suitable method to recover high quality silica structures.

Application of nanostructured mesoporous silica/ bismuth vanadate composite catalysts for the degradation of methylene blue and brilliant green

Ultrasonication method was used in the incorporation of mesoporous silica (mSiO2) on BiVO4 nanoparticles. The average crystallite size of the BiVO4 nanoparticles was controlled at around 2.4–5.1 nm on mesoporous silica surface. The composites were systematically evaluated as photocatalysts for the degradation of methylene blue (MB) and brilliant green (BG) dyes as a function of mesoporous SiO2 content. A marked compositional dependence of the photocatalytic activity was evidenced for MB and BG degradation under visible light. Compared with the corresponding bare bismuth vanadate nano species, the mSiO2-involved nanocomposites display enhanced photocatalytic activities. The enhancement of photocatalytic activity of BiVO4 nanoparticles with mesoporous silica was attributed to the synergistic effect between mesoporous silica and BiVO4 which improved the separation of photogenerated electrons and holes. Structures and morphologies of the samples were examined by TEM, SEM, XRD, EDS, FT-IR and UV–visible spectroscopy. The effects of operational parameters like dye concentration, mSiO2 content, calcination temperature and reaction time have been analyzed. The results showed that the photocatalytic activity of mSiO2/BiVO4 nanocomposites increases with the modification of BiVO4 by changing the content from 1.0 to 15.0 wt % mesoporous SiO2, the sample of 10.0 wt. % mesoporous SiO2 loaded on BiVO4 showed the higher photocatalytic activity. As the silica in the composites has a very good contact with the BiVO4 nanoparticles it enhances the photo-electron conversion of BiVO4 by reducing the recombination of photo-generated electron–hole pairs based on the band structures of BiVO4. The catalyst is found to be reusable.

Solvent‐dependent gas‐driven fabrication of shape-controlled silica: insights into the active sites and catalytic mechanism of silica-catalyzed Baeyer-Villiger reaction

Silica nanomaterials have attracted widespread attention because of their various advantages. In this work, a solvent-dependent gas-driven mechanism is first demonstrated for manufacturing silica nanostructures with adjustable shell size and morphology under the gas-liquid interface interaction without the templating agent. The condensation rate of tetraethylorthosilicate in water and ethanol is found to play a decisive role in the gas-liquid interface inducing the morphological evolution of silicon nanosheets, hollow structures and nanospheres. The obtained silica show promise in the Baeyer-Villiger (B-V) reaction in the O2/aldehyde system. Detailed experimental results find that the radicals species in silica play a decisive effect in the excellent activity of catalyzing the B-V reaction. Meanwhile, a comparative experiment to further determine that the rate-determining step of the silica catalyzing the B-V reaction is that the catalyst accelerate the process of aldehyde generation peracid. This work provides a solvent-dependent gas-driven strategy to synthesize shape-controlled SiO2 for B-V reaction.

Nanostructured mesoporous silica materials induce hormesis on chili pepper (Capsicum annuum L.) under greenhouse conditions

Current agricultural practices for vegetable production are unsustainable, and the use of certain nanomaterials has shown significant potential for either plant growth promotion or defense induction in crop species. The aim of the present work was to evaluate the possible effects of two SBA nano-structured silica materials differing in morphology; SBA-15, with porous structure in parallel and with a highly ordered hexagonal array and SBA-16, with spheric nano-cages located in cubic arrays, as plant growth promoters/eustressors on chili pepper (Capsicum annuum L.) during cultivation under greenhouse conditions. The study was carried out at three foliarly applied concentrations (20, 50 and 100 ppm) of either SBA materials to determine effects on seed germination, seedling growth, plant performance and cold tolerance under greenhouse. Phytotoxicity tests were carried out using higher concentrations (100, 1000 and 200 ppm) applied by dipping or spraying onto chili pepper plants. Deionized water controls were included. The results showed that the SBA materials did not affect seed germination; however, SBA-15 at 50 ppm and 100 ppm applied by imbibition significantly increased seedling height (up to 8-fold) and provided enhanced growth performance in comparison with controls under select treatment regimes. Weekly application of SBA-15 at 20 ppm significantly increased stem diameter and cold tolerance; however, SBA-16 showed significant decreases in plant height (20 ppm biweekly applied) and stem diameter (20, 50 and 100 ppm biweekly applied). The results demonstrate that both SBA materials provided hormetic effects in a dose dependent manner on chili pepper production and protection to cold stress. No phytotoxic response was evident. These findings suggested the nanostructured mesoporous silica have potential as a sustainable amendment strategy to increase crop production under stress-inducing cultivation conditions.

Rice Husk-Derived Mesoporous Silica Nanostructure for Supercapacitors Application: a Possible Approach for Recycling Bio-Waste into a Value-Added Product

We synthesized mesoporous SiO2 nanomatrix using rice husks as a precursor through a facile thermal combustion process. XRD, FTIR, EDX, and TEM analyses were used to validate the produced mesoporous SiO2 nanomatrix. Electrochemical measurements were used to determine the specific capacitance of mesoporous SiO2 nanomatrix, and the results showed that the specific capacitances are 216, 204, 182, 163, 152, 142, 135, 133, 124.4, 124 F/g at current densities of 0.5, 1, 2, 4, 6, 8, 10, 12, 14, and 16 A/g. The benefit of impurities, as well as the large surface area and mesoporous structure of rice husk derived SiO2 nanostructures, allow Faradaic redox reactions at the electrode surface and the resulting supercapacitive behavior. This research might lead to a low-cost technique of producing supercapacitor electrodes using rice husk-derived SiO2 as a precursor.

Fabrication and analysis of hydrophobic mesh-metallic surface for moist air condensation

ABSTRACT In the advancement of materials and their processing technologies, the alteration in the morphology of metallic surfaces to enhance the condensation rate of moist air is an emerging area of research for improving the performance of atmospheric water generators. In this work, hydrophobic mesh-metallic surfaces were fabricated via a thermal diffusion process in which a micro-order copper mesh with a diameter of 6 µm thermally diffuses on a steel surface of grade 100. The prepared surface was chemical etched before hexadecyltrimethoxysilane coating via the immersion method to grow silica nanostructure in a hierarchical order. A custom-built goniometer was used for measuring the surface wettability in terms of contact angle. The proposed surface has a 140 ± 5° static contact angle of the water droplet. The coated thermally diffused copper mesh to the steel surface fosters low wettability with respect to water. Eventually, a moist air condensation experiment was carried out in controlled atmospheric conditions on both coated and uncoated surfaces to demonstrate water harvesting from moist air. The hydrophobic mesh-metallic surface has high efficacy for moist air condensation as compared to the uncoated thermally diffused mesh-metallic surface. It makes the proposed hydrophobic coating substrate applicable for water harvesting from moisture.

Transparent hydrophobic, self-cleaning, anti-icing and anti-dust nano-structured silica based thin film on cover glass solar cell

Silica thin film with anti-reflective, hydrophobic and anti-icing properties was prepared on glass substrate by a sol-gel method. For this purpose, silica sol based on the TEOS and TMMS precursors were prepared. Then, different TCMS concentrations were added to the primary sol solution. Film deposition on glass substrate was performed by a dip coating method. Hydrophobicity, transparency, morphology and chemical analysis of the films were investigated. Icing tests were performed at a constant operating temperature of -12 °C. Also, the self-cleaning behavior of the samples was evaluated by iron oxide powders. The thin film stability under ultraviolet light irradiation was investigated. The results showed that with increasing TCMS, the transmittance of the glass coated substrate increased until 0.2 ml and then decreased. Also, the results of the water contact angle measurements showed that the contact angle increased with increasing the TCMS concentration until 0.33 ml (123°) and then with more increasing the TCMS concentration, it remained constant. Icing tests showed that the start time of the icing and the time required for complete icing on the thin layer of modified silica base with 0.2 mm TCMS is much longer than the uncoated glass. Also, the self-cleaning test showed that the glass coated sample has a self-cleaning behavior. After exposure to the ultraviolet light, the hydrophobicity and transparency of the glass coated sample did not disappear.

Efficacy of porous silica nanostructure as an insecticide against filarial vector Culex pipiens (Diptera: Culicidae)

Efficacy of porous silica nanostructure as an insecticide against filarial vector Culex pipiens (Diptera: Culicidae)

Photonic tools for evaluating the growth of diatom colonies during long-term batch cultivation

Diatoms are unicellular photosynthetic microalgae with a nanostructured silica cell wall – frustule. Diatoms, considered one of the most abundant and ecologically important phytoplankton groups, can also be easily grown in the laboratory and used for different applications. With long-term cultivation, it is essential to monitor their growth properly; therefore, we proposed new, fast and easy-to-use methods based on the absorption and fluorescence of diatom chromophores. The average radiant efficiency of diatom culture Achnanthidium sibiricum obtained using the IVIS SpectrumCT In vivo Imaging system increased up to 45 days of cultivation, after which we observed steady decrease. The highest photoacoustic signal of diatoms mixed with an agarose gel excited by a 532 nm laser was also recorded after 45 days of cultivation. The results obtained are in good agreement with the obtained spectra during the 100-day cultivation period. Thus, photonic methods have proven to be effective for monitoring the growth of diatoms during long-term cultivation, expanding the possibilities of growing and collecting diatoms for various purposes.

Ghost-Template-Faceted Synthesis of Tunable Amorphous Hollow Silica Nanostructures and Their Ordered Mesoscale Assembly.

Despite the enormous applications of and fundamental scientific interest in amorphous hollow-silica nanostructures (h-SiNSs), their synthesis in crystal-like nonspherical polygonal architectures is challenging. Herein, we present a facile one-shot synthetic procedure for various unconventional h-SiNSs with controllable surface curvatures (concave, convex, or angular), symmetries (spherical, polygonal, or Janus), and interior architectures (open or closed walls) by the addition of a metal salt and implementing kinetic handles of silica precursor (silanes/ammonia) concentrations and reverse-micellar volume. During the silica growth, we identified the key role of transiently in situ crystallized metal coordination complexes as a nanopolyhedral "ghost template", which provides facet-selective interactions with amino-silica monomers and guides the differential silica growth that produces different h-SiNSs. Additionally, crystal-like well-defined polygonal h-SiNSs with flat surfaces, assembled as highly ordered close-packed octahedral mesoscale materials (ca. 3 μm) where h-SiNSs with different nanoarchitectures act as building units (ca. 150 nm) to construct customizable cavities and nanospaces, differ from conventionally assembled materials.

Pyrogenic synthetic amorphous silica (NM-203): Genotoxicity in rats following sub-chronic oral exposure

The genotoxicity of nano-structured synthetic amorphous silica (SAS), a common food additive, was investigated in vivo in rats. A 90-day oral toxicity study was performed according to OECD test guideline 408 and the genotoxicity of pyrogenic SAS nanomaterial NM-203 was assessed in several organs, using complementary tests. Adult Sprague-Dawley rats of both sexes were treated orally for 90 days with 0, 2, 5, 10, 20, or 50 mg SAS/kg bw per day. Dose levels were selected to approximate expected human dietary exposures to SAS. DNA strand breaks were evaluated by the comet assay in blood, bone marrow, liver, and spleen according to OECD test guideline 489; mutations induced in bone marrow precursors of erythrocytes were assessed by the Pig-a assay and chromosome/ genome damage by the micronucleus assay in blood (OECD test guideline 474) and colon. No treatment-related increases of gene (Pig-a) or chromosome/genome (micronucleus) mutations were detected in the blood. The percentage of micronucleated cells was not increased in the colon of treated rats. Among the organs analyzed by the comet assay, the spleen was the only target showing a weak but biologically relevant genotoxic effect.

Sorption of Nanomaterials to Sandstone Rock.

We investigated the interaction of silica nanostructured particles and sandstone rock using various experimental approaches, such as fluid compatibility, batch sorption and single-phase core-floods. Diol and polyethylenglycol (PEG) surface-modified nanostructured silica materials were tested using two brines differing in ionic strength and with the addition of sodium carbonate (Na2CO3). Berea and Keuper outcrop materials (core plug and crushed samples) were used. Core-flood effluents were analysed to define changes in concentration and a rock’s retention compared to a tracer. Field Flow Fractionation (FFF) and Dynamic Light Scattering (DLS) were performed to investigate changes in the effluent’s size distribution. Adsorption was evaluated using UV–visible spectroscopy and scanning electron microscopy (SEM). The highest adsorption was observed in brine with high ionic strength, whereas the use of alkali reduced the adsorption. The crushed material from Berea rock showed slightly higher adsorption compared to Keuper rock, whereas temperature had a minor effect on adsorption behaviour. In core-flood experiments, no effects on permeability have been observed. The used particles showed a delayed breakthrough compared to the tracer, and bigger particles passed the rock core faster. Nanoparticle recovery was significantly lower for PEG-modified nanomaterials in Berea compared to diol-modified nanomaterials, suggesting high adsorption. SEM images indicate that adsorption spots are defined via surface roughness rather than mineral type. Despite an excess of nanomaterials in the porous medium, monolayer adsorption was the prevailing type observed.

Affinity-Based Enrichment of Extracellular Vesicles with Lipid Nanoprobes.

Extracellular vesicles (EVs) are lipid-bilayer-enclosed vesicles with sub-micrometer size that are released by various cells. EVs contain a tissue-specific signature wherein a variety of proteins and nucleic acids are selectively packaged. Growing evidence has shown important biological roles and clinical relevance of EVs in diseases. For EV-related studies to thrive, rapid efficient isolation of pure EVs is a prerequisite. However, lengthy procedure, low yield, low throughput, and high contaminants stemmed from existing isolation approaches hamper both basic research and large-scale clinical implementation. We have shown that lipid nanoprobes (LNP) enable spontaneous labeling and rapid isolation of EVs by coupling with magnetic enrichment. Recently, we further developed a one-step EV isolation platform that utilizes EV size-matched silica nanostructures and surface-conjugated LNPs with an integrated microfluidic mixer. EVs, derived from up to 2-ml clinical plasma, can be processed with this point-of-care device using optimized flow rate. Subsequently, contents of isolated EVs can be extracted on-chip and eluted from the device for downstream molecular analyses. The LNP-functionalized microfluidic device combined with state-of-the-art analysis platforms could have great potential in promoting EV-centered research and clinical use in the future.

Investigation of the effect of Berkovich and Cube Corner indentations on the mechanical behavior of fused silica using molecular dynamics and finite element simulation

In this study, elastic modulus and hardness of fused silica were evaluated and then simulated by molecular dynamics (MD) and finite element analysis (FEA). The reduced modulus, hardness of the surfaces, and elastic modulus caused by the process along the depth of the indentation on the surfaces are evaluated by the nanoindentation method on the fused silica. The obtained results indicate that applying different indenters such as Berkovich and Cube-Corner reduces the amount and size of surface microcracks. The load-displacement of various indenters such as Berkovich and Cube-Corner with similar load at about 50 mN for the Berkovich shows a 400 nm displacement and a 1600 nm for the Cube-Corner indenter. In this study, the MD was used to describe the mechanical behavior of fused silica structures with atomic nanostructure as simulated at T0 = 300 K and P0 = 1 bar as the initial condition. The mechanical constants such as hardness (with Berkovich tip), elastic modulus (with Berkovich tip), and fracture toughness (with Cube Corner tip) of fused silica nanostructure can be calculated from this MD simulation in which the hardness of the atomic matrix is obtained at 8.84 GPa.

Synthesis and Processing of Nanomaterials Mediated by Living Organisms

AbstractNanomaterials offer exciting properties and functionalities. However, their production and processing frequently involve complex methods, cumbersome equipment, harsh conditions, and hazardous media. The capability of organisms to accomplish this using mild conditions offers a sustainable, biocompatible, and environmentally friendly alternative. Different nanomaterials such as metal nanoparticles, quantum dots, silica nanostructures, and nanocellulose are being synthesized increasingly through living entities. In addition, the bionanofabrication potential enables also the in situ processing of nanomaterials inside biomatrices with unprecedented outcomes. In this Minireview we present a critical state‐of‐the‐art vision of current nanofabrication approaches mediated by living entities (ranging from unicellular to higher organisms), in order to expand this knowledge and scrutinize future prospects. An efficient interfacial interaction at the nanoscale by green means is within reach through this approach.

Synthesis and Processing of Nanomaterials Mediated by Living Organisms.

Nanomaterials offer exciting properties and functionalities. However, their production and processing frequently involve complex methods, cumbersome equipment, harsh conditions, and hazardous media. The capability of organisms to accomplish this using mild conditions offers a sustainable, biocompatible, and environmentally friendly alternative. Different nanomaterials such as metal nanoparticles, quantum dots, silica nanostructures, and nanocellulose are being synthesized increasingly through living entities. In addition, the bionanofabrication potential enables also the in situ processing of nanomaterials inside biomatrices with unprecedented outcomes. In this Minireview we present a critical state‐of‐the‐art vision of current nanofabrication approaches mediated by living entities (ranging from unicellular to higher organisms), in order to expand this knowledge and scrutinize future prospects. An efficient interfacial interaction at the nanoscale by green means is within reach through this approach.

Sustainable utilization of rice husk waste for preparation of ordered nanostructured mesoporous silica and mesoporous carbon: Characterization and adsorption performance

Rice husk has a high heating value, making it an attractive source of renewable energy. Rice husk ash (RHA) forms after the combustion of rice husk to heat energy. The recovery and reuse of RHA is a sustainable strategy in a circular economy. In this research, RHA was used as the raw material for the preparation of mesoporous silica, Santa Barbara Amorphous (SBA-15). Ordered mesoporous carbon, carbons mesostructured from Korea–3 (CMK-3), was synthesized utilizing SBA-15 as a template by injecting it with sucrose. According to transmission electron microscopy (TEM) images, both SBA-15 and CMK-3 consisted of high order and hexagonal arrays of mesopores. SBA-15 and CMK-3 contained large pore volumes of 1.260 and 1.185 cm3/g, high surface areas of 820 and 1005 m2/g, and uniform pore sizes of 6.41 and 3.44 nm, respectively. The amino-groups were successfully grafted on the SBA-15 surface. The amino-modified SBA-15 and CMK-3 revealed excellent adsorption of tannic acid. The effects of adsorption conditions, namely the solution temperature, adsorbent dosage, solution pH, and initial tannic acid concentration, were examined. Amino-modified SBA-15 and CMK-3 exhibited maximum adsorption capacities of 278.9 and 488.9 mg/g, respectively. Thermodynamic parameters were also investigated. The results indicated that the tannic acid adsorption was an exothermic process. Kinetic behaviors and adsorption equilibrium optimally matched the pseudo-second-order model and Langmuir isotherm. Overall, recovered RHA was useful in the preparation of mesoporous adsorbents for removing chemicals containing tannic acid from liquid waste.