SiO2 Capsules Research Articles

Effect of Elasticity of Silica Capsules on Cellular Uptake.

Understanding the impact of the physicochemical properties of nanoparticles (NPs) on cellular uptake is important to design optimal drug-delivery nanocarriers. Therein, the influence of NP elasticity on bio-nano-interactions remains elusive due to the complexity of factors affecting cellular uptake. Herein, we synthesized SiO2 capsules with tunable elasticity using metal-organic frameworks as templates to investigate their interactions with cells. Young's moduli of the resultant water-filled SiO2 capsules with identical size, shape, composition, and surface charge can be controlled from 3.8 MPa to 4.7 GPa via the variation of capsule shell thickness. As a result, increased elasticity of SiO2 capsules results in higher cellular uptake. Stiff SiO2 capsules have almost 9 times as much cellular uptake as the soft ones. In addition, the elasticity of SiO2 capsules influences cellular uptake pathways, where the clathrin-mediated pathway is preferred for stiff capsules while the uptake of the soft capsules is mostly mediated by a caveolae-dependent pathway. This work confirms the important role of NP elasticity in nonspecific cell interactions, which can provide a foundational understanding for engineering drug-delivery nanocarriers.

Silica Capsules Templated from Metal-Organic Frameworks for Enzyme Immobilization and Catalysis.

Inspired by the unique biological microenvironments of eukaryotic cells, hollow capsules are promising to immobilize enzymes due to their advantages for physical protection and improved activity of enzymes. Herein, we report a facile method to fabricate silica (SiO2) capsules using zeolitic imidazole framework-8 nanoparticles (ZIF-8 NPs) as templates for enzyme immobilization and catalysis. Enzyme-encapsulated SiO2 capsules are obtained by encapsulation of enzymes in ZIF-8 NPs and subsequent coating of silica layers, followed by the removal of templates in a mild condition (i.e., ethylenediaminetetraacetic acid (EDTA) solution). The enzyme (i.e., horseradish peroxidase, HRP) activity in SiO2 capsules is improved more than 15 times compared to that of enzyme-loaded ZIF-8 NPs. Enzymes in SiO2 capsules maintain a high relative activity after being subjected to high temperature, enzymolysis, and recycling compared to free enzymes. In addition, multienzymes (e.g., glucose oxidase and HRP) can also be coencapsulated within SiO2 capsules to show a reaction with a high cascade catalytic efficacy. This work provides a versatile strategy for enzyme immobilization and protection with potential applications in biocatalysis.

Development of Silica-Based Biodegradable Submicrometric Carriers and Investigating Their Characteristics as in Vitro Delivery Vehicles.

Nanostructured silica (SiO2)-based materials are attractive carriers for the delivery of bioactive compounds into cells. In this study, we developed hollow submicrometric particles composed of SiO2 capsules that were separately loaded with various bioactive molecules such as dextran, proteins, and nucleic acids. The structural characterization of the reported carriers was conducted using transmission and scanning electron microscopies (TEM/SEM), confocal laser scanning microscopy (CLSM), and dynamic light scattering (DLS). Moreover, the interaction of the developed carriers with cell lines was studied using standard viability, proliferation, and uptake assays. The submicrometric SiO2-based capsules loaded with DNA plasmid encoding green fluorescence proteins (GFP) were used to transfect cell lines. The obtained results were compared with studies made with similar capsules composed of polymers and show that SiO2-based capsules provide better transfection rates on the costs of higher toxicity.

Core–Shell Encapsulation of Salt Hydrates into Mesoporous Silica Shells for Thermochemical Energy Storage

The advent of thermochemical energy storage (TcES), that is, storage of thermal energy by means of reversible chemical reactions, incites finding pathways of stabilization of thermochemical materials for thermal batteries of the future. Currently, hydrates such as LiCl·H2O, CaCl2·6H2O, and SrBr2·6H2O are being actively studied for TcES in buildings due to both high energy storage density (1-2.5 GJ/m3) and high storage duration. In this work, we report the core-shell composites salt in hollow SiO2 spheres with mesopores(salt = LiCl·H2O, CaCl2·6H2O, SrBr2·6H2O) for domestic TcES. The hydrates were encapsulated into submicrometer-sized hollow SiO2 (HS) capsules as confirmed by transmission electron microscopy (TEM) and N2 sorption analyses. High sorption/desorption rates due to mesopores of the shells were shown by thermogravimetric analysis (TGA). The sorption equilibrium for salt@HS was reported, and the applicability of the materials for domestic heat batteries was analyzed. As a result of almost the densest packing of salt@HS, the composites were shown to provide a state-of-the-art energy storage density up to 0.86 GJ/m3 on the bed level for the high-temperature lift of 32-47 °C, showing high energy storage capacity. The stability in at least 50 charging/discharging cycles was confirmed by TGA and TEM.

Synthesis and growth mechanism of various SiO 2 nanostructures from straight to helical morphologies

Abstract Taking into account the high demands and applications of amorphous SiO2 in various nanostructured forms, here we have synthesized various nanostructures of SiO2 including nanosprings, straight nanofibers, nanotubes and nanobelts. A simple catalytic chemical vapor deposition (CCVD) technique is developed where Si, SiO2 and graphene capsules are utilized as starting materials. The structural and chemical analysis of the as-prepared nanostructures confirms the amorphous nature of SiO2 and shows the minor existence of SiC, which acts as a growth directing agent for various shapes of SiO2. The electron microscopic observations delineate the morphologies of the as-prepared nanostructures with different shapes i.e. nano-fibers, tubes, springs and belts. It is observed that straight SiO2 fibers having diameter of ∼440 nm are thicker than the fibers (∼220 nm) constructing the nanosprings while the overall helical diameter falls in the range of 530–690 nm. The in-depth structural and morphological studies reveal that the growth mechanism of SiO2 nanostructures is in the vapor-liquid-solid (VLS) growth mode. The unique microstructures with special morphologies straight, helical and hollow shapes make them potential candidate for several functional applications such as nanoelectron-magnetic devices, mechanical sensor system and flexible energy storage devices.

Synthesis of nanosheet-based MnO2 hollow capsules and their application in lithium batteries

ABSTRACTIn this work, nanosheet-based MnO2 hollow capsules have been fabricated by a hydrothermal process using the pre-fabricated hollow SiO2 capsules as sacrificial templates. When the obtained nanosheet-based MnO2 hierarchical hollow capsules are tested as the electrode material of Li-ion batteries, they show a large discharge capacity of 1182.9 mAhg−1 for the initial cycle and 198.4 mAhg−1 after 500 cycles.

Synthesis of polystyrene core/SiO2 shell composite particles and fabrication of SiO2 capsules out of them

Systemic studies on the dependence of the morphology of polystyrene core/SiO2 shell composite particles on the conditions of their fabrication have been performed. Spherical polystyrene particles synthesized in the presence of a cationic initiator of polymerization were used as cores. SiO2 shells were formed by modified Stober’s method. Exposure of the synthesized composite particles to high temperatures has been shown to cause destruction of their polystyrene core, thereby allowing the formation of mesoporous SiO2 capsules with a mean pore diameter of ~3 nm and specific surface area of ~270 m2/g. Model experiments on loading the SiO2 capsules with amoxicillin have been carried out. Spectrophotometry in the UV and visible spectral regions has been used to estimate the kinetics of amoxicillin release from the SiO2 capsules.

Multiple Emulsion Templating of Hybrid Ag/SiO2 Capsules for Antibacterial Applications

Silver nanoparticles (NPs) encapsulated in amorphous silica shells are synthesized and evaluated for their antibacterial action using the Gram‐negative Escherichia coli bacterium. These inorganic capsules are synthesized using a new approach that comprises the use of oil‐in‐water‐in‐oil (O/W/O) multiple emulsions to fabricate SiO2 capsules incorporating organically capped Ag NPs. This strategy is explored as a mean to promote the bioadhesion of the microorganisms to the silica rough surfaces while still keeping the system with a high surface area for the active metal. The results have shown that the hybrid capsules enable a slow release of cationic silver from the interior of the silica microsphere to the external medium probably through the pore channels in the shell. The antibacterial activity against E. coli is mainly determined by the Ag+ ion release rate, suggesting that these particulates can be employed as a robust system for prolonged used as an antimicrobial material.

Encapsulation of essential oils in SiO2 microcapsules and release behaviour of volatile compounds

Natural substances derived from plants such as essential oils (EOs) are used in a variety of applications such as in the release of fragrances or active substances in cosmetics, in food industries to protect sensitive ingredients against oxidative processes and as antimicrobial agents. However, the labile and volatile nature of EOs reduces their activity during application or storage. Here, the microencapsulation of EOs in silica capsules was investigated as a mean to control the fast release of their volatile constituents. The preparation of silica capsules with oil cores was obtained by employing a sol-gel method to oil-in-water-in-oil (O/W/O) multiple emulsions. The volatile release from the SiO2 capsules was investigated by comprehensive two-dimensional gas chromatography with time of flight mass spectrometry detection (GC × GC–ToFMS). This research demonstrates that the SiO2 capsules have selectively encapsulated the different volatile species and the corresponding release profiles depend on the chemical properties of each component.

Rattle-type hierarchical particles containing multilevel cores (Ag@AgCl@SiO2 and Au/Ag@AgCl@SiO2) as versatile catalysts

A protocol for the synthesis of rattle-type core@shell particles containing Ag@AgCl or Au/Ag@AgCl core structures was developed, and the use of these particles as catalysts for the decomposition of toxic materials was demonstrated. A monometallic Ag or bimetallic Au/Ag core was incorporated into the interior of SiO2 capsules via controlled heat treatment of metal nanoparticle/SiO2-coated polymer particles, resulting in the formation of rattle-type core@shell structures. By appropriate treatments, it was possible to transform the Ag or Au/Ag core into multilevel cores (Ag@AgCl or Au/Ag@AgCl) within the SiO2 capsules (Ag@AgCl@SiO2 or Au/Ag@AgCl@SiO2). This method for the synthesis of rattle-type core@shell particles is useful for further introducing AgCl fused with plasmonic materials into the capsule structures. The rattle-type core@shell structures were used as photocatalysts for the decomposition of organic pollutants such as methyl orange. Furthermore, these nanocatalysts containing semiconductors such as AgCl were also applied toward the reduction of nitrophenol (NPh) to aminophenol (APh). The Ag@AgCl@SiO2 or Au/Ag@AgCl@SiO2 catalysts showed excellent catalytic properties in the decomposition of toxic substances in terms of their activity and reusability.

SiO2 capsulized Cu active nanoparticles: synthesis and activity study

Cu active nanoparticles (Cu ANPs) were synthesized in weakly acidic solution to preserve their catalytic activity. SiO2 capsules were designed to insulate Cu ANPs from oxidation. The weak interaction between SiO2 capsules and Cu ANPs ensured that the designed nanoparticles had good anti-oxidation property and potentially high activity. The increased anti-oxidation property with thicker SiO2 capsules (Cus3 > Cus2 > Cus1) and the order of reactivity to oxygen (Cus1 = Cus2 > Cus3) showed that Cu ANPs with SiO2 capsules (Cus2) of appropriate thickness would be the best for application. By using the samples to construct non-enzymatic sensors, the detected activity toward electro-catalytic oxidation of glucose confirmed this conclusion. Dehiscence of SiO2 capsules recovered the activity of the Cu ANPs in the catalytic ammonium perchlorate (AP) decomposition process. With the addition of 1.5% of Cu ANPs, the high temperature decomposition of AP decreased by 184.2 °C.

X射线相衬成像法在线表征冷冻靶技术

A brief review of X-ray phase contrast imaging theory for spherical objects is given. Using Tracepro, simulated X-ray phase-contrast images of SiO2/DD cryogenic capsules are produced. The ability of phase contrast enhanced X-ray imaging for characterization of cryogenic fuel layers inside ablator shells has been proven with the simulation result. X-ray phase contrast imaging equipment has been established for characterization of cryogenic targets, with which imaging experiments for low density divinyl benzene foam shells and SiO2/DD cryogenic capsules have been carried out, and phase contrast images of cryogenic DD fuel layers in SiO2 capsules are obtained, with a resolution up to 1.5 m. Ablator and cryogenic fuel layers can be simultaneously characterized by X-ray phase contrast imaging.

Entrapment of trans, trans-farnesol in amorphous silica capsules and its release behaviour: On the route of futur applications

Farnesol, a compound widely found in several plant-related matrices, including agro-food by-products, is an important bioactive agent that can be exploited in cosmetics and pharmaceutics but the direct bioapplication of this compound is limited by its volatility. Here the entrapment of farnesol in silica capsules was investigated to control the release of this bioactive compound in the vapor phase and in ethanol solutions. The preparation of silica capsules with oil cores was obtained by employing a sol-gel method using O/W/O multiple emulsions. Two distinct chemical vehicles for farnesol have been investigated: retinol (A) and oleic acid (B). The release of farnesol from the prepared SiO2 capsules was investigated. It is demonstrated that these capsules are efficient for the long controlled release of farnesol and that the respective profiles depend on the chemical parameters employed in the synthesis of the capsules. It is well known that terpene compounds (e.g. trans,trans-farnesol) are praised for their beneficial effects to human health, namely as anti-oxidant agents. The release profiles reported here are compatible with the needs of an anti-oxidant effect in fast stress oxidative situations or in cases of a preventive action for longer periods of time.

Release behavior of trans,trans-farnesol entrapped in amorphous silica capsules

Farnesol, a compound widely found in several agro-food by-products, is an important bioactive agent that can be exploited in cosmetics and pharmaceutics but the direct bioapplication of this compound is limited by its volatility. Here the entrapment of farnesol in silica capsules was investigated to control the release of this bioactive compound in the vapor phase and in ethanol solutions. The preparation of silica capsules with oil cores was obtained by employing a sol–gel method using O/W/O multiple emulsions. Two distinct chemical vehicles for farnesol have been investigated, retinol and oleic acid, that afterwards have been emulsified as internal oil phases. The volatile release of farnesol from the as-prepared SiO2 capsules was investigated by headspace solid phase microextraction (HS-SPME) followed by gas chromatographic analysis (GC), and the release to ethanol was carried out by direct injection of the ethanolic fraction into the GC system. It is demonstrated that these capsules are efficient for the long controlled release of farnesol and that the respective profiles depend on the chemical parameters employed in the synthesis of the capsules.