Mesoporous Silica Nanomaterials Research Articles

Hard Template Synthesis of Nanomaterials Based on Mesoporous Silica

Diverse hard template synthetic methodologies are being employed for the synthesis of mesostructured metal oxide and carbon nanomaterials, with the application of mesoporous silica as the hard template. We describe the main differences and advantages/disadvantages between the soft and hard templated synthetic routes, provide an overview of the synthesis and characteristics of different templating mesoporous silica nanomaterials and discuss on practical aspects of the hard template synthetic methodology for obtaining various metal-oxide and carbon-based mesostructured nanomaterials. Also, we cover various recent applications of thus constructed mesostructured metal oxide and carbon nanomaterials, such as sensing, energy storage, fuel cells, and catalysis, which demonstrate the highly promising character of the hard template methodology for the synthesis of a new generation of nanomaterials with broad application potential.

Embedded Mesoporous Silica Silver Nanoparticles as potential antibacterial agent againstMultidrug-Resistant Bacteria

Many workers have paid more attention to eco-friendly mesoporous silica silver nanoparticles featuring smaller particle sizes to enhance their remarkable antimicrobial properties. A simple chemical method was developed for synthesize high valence silver nanoparticles immobilized on the mesoporoussilica nanomaterial, which showed strong antibacterial activity. Chemical reduction of silver ion has been regarded in the present work, and a reducing agent , such as hydrazine was used to promote the reduction of the silver ion – precursor. The average particle size of the synthesized mesoporous silica-silver nanoparticles (Ag/NH2-KIT-6(x)) with different concentrations of Ag (3.2 and 7.1%) calculated from Scherrer’s equation for (1 1 1)-plane were 8 and 6.5 nm respectively. The synthesized materials were characterized using X-Ray diffraction (XRD), FTIR spectra, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), which revealed the mesoporous silica nanoparticles. Antibacterial activities of mesoporous silver nanoparticles against Gram- negative Pseudomonas aeruginosa(ATCC 9027) and Gram-positive Staphylococcus aureus(ATCC 43300) were found to be increased with the increasing of Ag concentration in the Ag/NH2-KIT-6(x). The maximum inhibition zone diameter when the concentration 7.1 % was used obtained against P. aeruginosaand S. aureuswith diameters of 32 and 30 mm respectively. The antimicrobial activity of mesoporousAg/NH2-KIT-6(x) was evaluated also using the MIC&MBC tests. The surface structures of both the untreated and the treated bacterial cells were examined by the aid of TEM. The treated bacterial cells were significantly changed, and major damage was observed in the outer cell membrane. In conclusion the use of AgNPs as antibacterialagentwasfoundtobetoxicagainstpathogenicbacteriaandconsidered

Synthesis of cobalt-modified MSN as a model enzyme: Evaluation of the peroxidatic performance

Abstract The cobalt incorporated mesoporous silica nanomaterials (Co-MSN) with different ratios of Si/Co in the framework were synthesized. The as-obtained products were characterized by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF), field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), N2 adsorption/desorption (BET) and UV–Vis spectroscopic techniques. The effect of the various content of Co incorporated into the framework on the catalytic activity was studied. The Co-MSN samples exhibited an excellent catalytic activity toward the reduction of hydrogen peroxide (H2O2) and the oxidation of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) as a chromogenic substrate and followed Michaelis−Menten kinetics. It means that they have intrinsic peroxidase-like activity. The results showed that the Co-MSN catalyst with Si/Co = 75 (as the optimum ratio), has the higher affinity to ABTS and H2O2 and higher catalytic efficiency. These features made this nanocatalyst suitable to apply for the determination of H2O2 and glucose. The linear range for detecting H2O2 was from 22.5 μM to 0.2 mM with a detection limit of 6.7 μM. Coupled with glucose oxidase, the Co-MSN(75) was successfully used for the determination of glucose with the linear range of 11.6 μM−0.1 mM and a detection limit of 3.5 μM.

Hierarchical hematite/TiO2 nanorod arrays coupled with responsive mesoporous silica nanomaterial for highly sensitive photoelectrochemical sensing

The photoelectrochemical (PEC) technique has resulted in substantial progress in chemical sensing applications. However the complicated photoelectrode modification procedures would enable undesired background noise and decreasing sensitivity. Hence, it is important to explore a new approach alternative to inconvenient substrate modification. Herein, inspired by the stimuli-responsive drug delivery systems, an innovative PEC system is developed for efficiently microRNA-21 (miRNA-21) tracing. Hierarchical nanocomposites based on hematite (α-Fe2O3) coated self-ordered titanium dioxide nanorod arrays (TiO2 NRAs) exhibited enhanced response to solar light, promoted charge carrier separation and transfer efficiency was adopted as photoelectrode directly. Functional mesoporous silica nanomaterial (MSN) is prepared as nanocarriers for efficient loading of Cu2+, further capped with miRNA-21 responsive capture RNA probe. Thereafter, the capture RNA probe endows the functional MSN with responsiveness to miRNA-21. With the presence of miRNA-21, this system is thus triggered and a quickly release of capped Cu2+ occurs due to the dissociation of capture RNA probe presented on the MSN surface via base-pair hybridization. The released Cu2+ was then served as electron acceptor reduced to Cu° at the counter electrode to enhance electron-hole pair separation efficiency, leading to a promoted photocurrent response. Consequently, the miRNA-21 can be accurately quantified. Taking advantage of its sensitivity and specificity, this versatile strategy demonstrates a new route for the design PEC sensing approach without any photoelectrode modification procedure, and holds great potential for biosensing and clinical diagnosis.

Silica-based organic-inorganic hybrid nanoparticles and nanoconjugates for improved anticancer drug delivery.

After the introduction of first generation MSNs for drug delivery with some challenges such as large particle sizes, irregular morphologies and aggregations, second generation provided uniform spherical morphologies, tunable pore/particle sizes and compositions. Henceforth, organic-inorganic hybrid mesoporous silica nanosystems have grown rapidly and utilized for active and passive targeting of tumorigenic cells especially conjugated with organic polymers followed by third generation counterparts with improved functionalities for cancer therapy. The aim of this review article is to focus on the advancements in mesoporous silica based organic-inorganic hybrid nanoparticles developed as drug carriers targeting cancer cells. Brief introduction to the state-of-the-art in passive and active targeting methods is presented. Specifically, therapeutic, diagnostic and theranostic applications are discussed with emphases on triggered and ligand conjugated organic-inorganic hybrid mesoporous silica nanomaterials. Although mesoporous silica nanoparticles perform well in preclinical tests, clinical translation progresses slowly as appropriate doses needs to be evaluated for human use along with biocompatibility and efficiency depending on surface modifications.

Mesoporous Silica and Organosilica Nanomaterials as UV-Blocking Agents.

Mesoporous silica nanoparticles (MSN) and periodic mesoporous organosilica nanoparticles containing bridging benzene (PMOBTB) and ethane (PMOBTE) moieties are synthesized, characterized, and evaluated for application in skin protection from UVA/UVB sun irradiation. Furthermore, the influence of surface functionalization with chelating 3-(2-aminoethylamino)propylsilane and Zn2+ ions on the UV-blocking ability of MSN is evaluated, along with the photostability and capability of the synthesized nanomaterials to carry avobenzone, a known UV-absorbing agent. The obtained results reveal promising characteristics of MSN and PMO materials with regard to their potential for sunscreen applications, which could be beneficial in terms of alleviating concerns about health and environmental hazards of sunscreen ingredients.

Overview of Studies Regarding Mesoporous Silica Nanomaterials and Their Biomedical Application.

Synthesis of mesoporous silica nanomaterials occurred in the late 1980s and early 1990s. Since then, we have seen dramatic increase in the number of publication dealing with this nanomaterial. In particular, there have been a large number of publications regarding biomedical application of mesoporous silica nanoparticles including their use in cancer therapy and diagnosis. Various surface modification strategies have been explored to enhance drug loading and to target them to tumor. In addition, the nanoparticles have been armed with controlled release capability. In this review, we point out some crucial issues regarding the material, which will be discussed in more detail in chapters of this volume.

Delivery of [Ru(η6-p-cymene)Cl2{Ph2P(CH2)3SPh-κP}] using unfunctionalized and mercapto functionalized SBA-15 mesoporous silica: Preparation, characterization and in vitro study

SBA-15 (Santa Barbara Amorphous 15) mesoporous silica and its functionalized form (with 3-mercaptopropyltriethoxysilane) SBA-15~SH were used as carriers for [Ru(η6-p-cymene)Cl2{Ph2P(CH2)3SPh-κP}] complex, denoted as [Ru]. Prepared mesoporous silica nanomaterials were characterized by traditional methods. Materials without [Ru] complex did not show any cytotoxic activity against melanoma B16 and B16-F10 cell lines. On the contrary, materials containing [Ru] such as SBA-15|[Ru] and SBA-15~SH|[Ru], exhibited very high activity against tested tumor cell lines, moreover with similar inhibitory potential. According to the loaded amount of the [Ru] in SBA-15|[Ru] and SBA-15~SH|[Ru] the IC50 values are 1–2μM depending on the test used, thus in comparison to [Ru] alone the activity of nanomaterials containing [Ru] are elevated 3–6 times in vitro. However, the mechanism of apoptosis induction differs for these two mesoporous silica. Unlike reference [Ru] compound and SBA-15~SH|[Ru], SBA-15|[Ru] induces high caspase activation. Discrepancy in mechanism of drugs action at intracellular level points towards an influence of functionalization as well as availability of the drug. Moreover, both SBA-15|[Ru] and SBA-15~SH|[Ru] similarly to [Ru] are declining autophagy in B16 cell line.

Biomimetic hierarchical walnut kernel-like and erythrocyte-like mesoporous silica nanomaterials: Controllable synthesis and versatile applications

We developed a facile and controllable strategy to fabricate biomimetic walnut kernel-like mesoporous silica nanomaterial (WMSN) and erythrocyte-like mesoporous silica nanomaterial (EMSN). The former possesses unique multi-shell hollow structure and surface wrinkles while the latter has special multi-stack structure and bowl-shaped depression. These hierarchical materials with distinct structures can be finely tuned by changing the molar ratios of two surfactants, cetyltrimethylammonium bromide and 11-mercaptoundecanoic acid. The mechanism of structural formation through intermolecular interactions was revealed and validated experimentally. The promising potential applications of WMSN and EMSN in adsorption, cellular imaging, drug delivery, and cancer theranostics were further identified.

Synthesis and Structural Characterization of G-SBA-IDA, G-SBA-EDTA and G-SBA-DTPA Modified Mesoporous SBA-15 Silica and Their Application for Removal of Toxic Metal Ions Pollutants

Modified mesoporous SBA-15 silica materials (G-SBA-IDA, G-SBA-EDTA and G-SBA-DTPA) (where IDA, EDTA and DTPA represent iminodiacetic acid, ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid, respectively) were prepared by treatment of grafted monoamine or diamine or triamine mesoporous SBA-15 silica (G-SBA-N, G-SBA-NN , G-SBA-NNN) nanomaterials with ethylchloroacetate, followed by acid hydrolysis of ester groups. These materials were characterized by several techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), small angle X-ray scattering (SAXS), thermal analysis (TGA) and X-ray photoelectron spectroscopy (XPS). TEM and BET analysis revealed that the IDA functionalized amine mesoporous SBA-15 silica materials have maintained their mesostructure after modification of the amine mesoporous silica with ethylchloroacetate. Thermal analysis (TGA-DTA) and FTIR confirmed that ethylchloroacetate groups are covalently bound to the amine groups. The acid forms of IDA functionalized materials showed high potential for extraction and removal of heavy pollutant metal ions (Co2+, Ni2+, Cu2+and Pb2+) from aqueous solutions.

Proline dehydrogenase-entrapped mesoporous magnetic silica nanomaterial for electrochemical biosensing of L-proline in biological fluids.

In this work, physical adsorption was used for immobilization of proline dehydrogenase onto a magnetic mesoporous silica nanomaterial. The immobilization and electrocatalytical activity of proline dehydrogenase entrapped in a magnetic mesoporous silica nanomaterial was studied using cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry. The magnetic mesoporous silica networks having a high surface area (362m2g-1) exhibited excellent properties for entrapment of proline dehydrogenase. The applied approach led to better resistance to temperature and pH inactivation in comparison to the free enzyme. The electrocatalytic current response of proline dehydrogenase entrapped in a magnetic mesoporous silica nanomaterial toward oxidation of L-proline was maintained in the analytical solution temperature up to 70°C. The entrapped proline dehydrogenase was casted onto a polycysteine-modified glassy carbon electrode. The electrode was evaluated as an electrochemical biosensor for electrooxidation and determination of L-proline in phosphate buffer solution. A cyclic voltammetry study indicated that the oxidation process of proline is irreversible and is diffusion controlled. The electrochemical behavior was further exploited as a sensitive detection scheme for L-proline determination by differential-pulse voltammetry. Under optimized conditions, the concentration range and detection limit were 0.01-0.15μM and 0.006μM, respectively. The method was applied to the assay of L-proline in whole blood and normal and malignant cell line lysates (normal cell (L929); gastric cancer cell-CAT 3, colon cancer cell-HCT, colon cancer cell-SW, and breast cancer cell-MCF7).

Surface PEGylation of Mesoporous Silica Nanorods (MSNR): Effect on loading, release, and delivery of mitoxantrone in hypoxic cancer cells

Mesoporous silica nanomaterials show great potential to deliver chemotherapeutics for cancer treatment. The key challenges in the development of injectable mesoporous silica formulations are colloidal instability, hemolysis and inefficient drug loading and release. In this study, we evaluated the effect of PEGylation of mesoporous silica nanorods (MSNR) on hemolysis, colloidal stability, mitoxantrone (MTX) loading, in vitro MTX release, and cellular MTX delivery under hypoxic conditions. We found that PEGylation prevented dose-dependent hemolysis in the concentrations studied (0–10 mg/ml) and improved colloidal stability of MSNR. A negative effect of PEGylation on MTX loading was observed but PEGylated MSNR (PMSNR) demonstrated increased MTX release compared to non-PEGylated particles. Under hypoxic conditions, a decrease in the IC50 of MTX and MTX-loaded MSNR was observed when compared to normoxic conditions. These results showed that MSNR could deliver the chemotherapeutic agent, MTX to tumor cells and induce effective cell killing. However, the effect of PEGylation needs to be carefully studied due to the observed adverse effect on drug loading.

A Voltage-Responsive Free-Blockage Controlled-Release System Based on Hydrophobicity Switching.

Controlled-release systems based on mesoporous silica nanomaterials (MSNs) have drawn great attention owing to their potential biomedical applications. Various switches have been designed to control the release of cargoes through the construction of physical blocking units on the surface of MSNs. However, such physical blockages are limited by poor sealing ability and low biocompatibility, and most of them lack closure ability. Herein, a voltage-responsive controlled-release system was constructed by functionalizing the nanopore of MSNs with ferrocene. The system realized free-blockage controlled release and achieved pulsatile release. The nanopores of the ferrocene-functionalized MSNs were hydrophobic enough to prevent invasion of the solution. Once a suitable voltage was applied, the nanopores became hydrophilic, which was followed by invasion of the solution and the release of the cargos. Moreover, pulsatile release was realized, which avoided unexpected release after the stimulus disappeared. Thus, we believe that our studies provide new insight into highly effective blockage for MSNs. Furthermore, the voltage-responsive release system is expected to find use in electrical stimulation combination therapy and bioelectricity-responsive release.

Progress in Nanotheranostics Based on Mesoporous Silica Nanomaterial Platforms.

Theranostics based on nanoparticles (NPs) is a promising paradigm in nanomedicine. Mesoporous silica nanoparticle (MSN)-based systems offer unique characteristics to enable multimodal imaging or simultaneous diagnosis and therapy. They include large surface area and volume, tunable pore size, functionalizable surface, and acceptable biological safety. Hybridization with other NPs and chemical modification can further potentiate the multifunctionality of MSN-based systems toward translation. Here, we update the recent progress on MSN-based systems for theranostic purposes. We discuss various synthetic approaches used to construct the theranostic platforms either via intrinsic chemistry or extrinsic combination. These include defect generation in the silica structure, encapsulation of diagnostic NPs within silica, their assembly on the silica surface, and direct conjugation of dye chemicals. Collectively, in vitro and in vivo results demonstrate that multimodal imaging capacities can be integrated with the therapeutic functions of these MSN systems for therapy. With further improvement in bioimaging sensitivity and targeting specificity, the multifunctional MSN-based theranostic systems will find many clinical applications in the near future.

Application of graphene and mesoporous silica nanomaterials on the orthopaedic implants: recent advances

Graphene and mesoporous silica nanomaterials have attracted much interest for applications in orthopaedic implants. This review focuses on more recent advances in orthopaedic implants based on Graphene and mesoporous silica nanomaterials during 2013 to May 2016. The purpose of this article was to give a general description of studies of nanostructured graphene/mesoporous silica for orthopaedic implants. In this review, we highlight how graphene/mesoporous silica family nanomaterials are being exploited for orthopaedic implants. Firstly, the main requirements for orthopaedic implants were discussed. Also, the effects of structural properties of graphene/mesoporous silica-based nanomaterials on the development of new orthopaedic implants were discussed. Finally, the present review intends to provide the reader an overview of the current state of the graphene/mesoporous silica-based biomaterials in orthopaedic implants, its limitations and hopes as well as the future research trends for this exciting field of science.

Roles of particle size, shape and surface chemistry of mesoporous silica nanomaterials on biological systems

The successful application of mesoporous silica nanomaterials (MSNs) in biomedical fields requires careful consideration of their spatial dimensions, biofunctionality, specific cellular uptake efficiency, biocompatibility and targeting delivery efficacy. A deep understanding of the interactions between MSNs and biological systems is thus of significant importance. To this end, over the past few decades, studies aimed at synthesis of MSNs with controlled size, shape and surface chemistry properties and exploring the roles of these properties on in vitro and in vivo biological performance have been conducted. These studies provide new and foundational information for engineering the next generation of mesoporous silica-based nanoscale devices. This review highlights the current progress on the controlled synthesis of size, shape and surface chemistry tuneable MSNs, emphasises the roles of size, shape and surface chemistry on biological systems with a special focus on the direct comparison studies, and discusses the emerging design paradigm for building mesoporous silica-based particulate systems.

Shape matters when engineering mesoporous silica-based nanomedicines.

Mesoporous silica nanomaterials have been successfully employed in the development of novel carriers for drug delivery. Numerous studies have been reported on engineering mesoporous silica-based carriers for drug loading, release, cellular uptake, and biocompatibility. A number of design parameters that govern the in vitro and in vivo performance of the carriers, including particle diameter, surface chemistry, and pore size, have been tuned to optimize nanomedicine efficacy. However, particle shape, which may generate a high impact on nanomedicine performance, has still not been thoroughly investigated. This is probably due to the limited availability of strategies and techniques to produce non-spherical mesoporous silica nanomaterials. Recent breakthroughs in controlling the particle shape of mesoporous silica nanomaterials have confirmed the important roles of shape on nanomedicine development. This review article introduces various fabrication methods for non-spherical mesoporous silica nanomaterials, including rod, ellipsoid, film, platelet/sheet, and cube, and the roles of particle shape in nanomedicine applications.

Sol-Gel Silica Matrix as Reservoir for Controlled Release of Paracetamol: Characterization and Kinetic Analysis

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are usually suitable candidates for the development of drug delivery devices. Sol-gel chemistry represents an easy method to obtain porous silica nanoparticles. Mesoporous silica nanomaterials have been widely used for drug delivery purposes. In this work we synthesized silica based materials using two molar alkoxide:water ratios 1:4 and 1:8, incorporating paracetamol to develop a nano-sized matrix for controlled release purposes. The samples exhibited different values for surface area, porosity, particle size and distinct punctual defects. Infrared and UV-visible spectroscopic studies were carried out to demonstrate the effect of water concentration and the adequate incorporation of paracetamol molecules. Nitrogen adsorption characterization was realized and the estimated BET surface values were from 532 to 825 m2/g. Kinetic analysis of drug release profiles was performed using the hyperbola model. Transmission electron micrographs showed that all the materials formed aggregates of small particles with size between 10 - 60 nm. Mesoporous SiO2 materials were proved to be a suitable system for controlled release of paracetamol.

Sulfides Synthesis: Nanocatalysts in C–S Cross-Coupling Reactions

The C–S cross-coupling reaction of aryl halides with thiols or sulfur sources is a key and valuable synthetic transformation in chemistry and medicine as well as in biology, and the development of novel efficient synthetic protocols for the synthesis of the corresponding products (sulfides) is highly desired. Among a wide range of catalysts used in C–S coupling reactions, metallic nanocatalysts have attracted notable interest. Herein, we summarize recent breakthroughs in the arena of metal nanocatalysts employed in C–S cross-coupling reactions with the goal of stimulating further progress in this field. This review is divided into three main sections according to the nature of the metal nanocatalysts discussed. The first section focuses on naked or purely metallic catalysts in nano-size, such as Cu, Pd, Ni, and In. The second section focuses on the role of Fe3O4 magnetic nanoparticles and mesoporous silica nanomaterials, such as MCM-41 and SBA-15, as catalyst supports. Finally, the third section focuses on the catalytic activities of copper ferrite nanoparticles in C–S cross-coupling reactions. Additionally, the recovery and reusability of the nanocatalyst, which are very important from commercial and economical points of view, are comprehensively discussed in this review.

Shape control of mesoporous silica nanomaterials templated with dual cationic surfactants and their antibacterial activities.

Mesoporous silica nanomaterials of different shapes (film, platelet, sphere, rod) were synthesized simply by tuning the mole ratio of dual cationic surfactant templates, cetyltrimethylammonium bromide (CTAB) and tetrabutylammonium iodine (TBAI). The film showed the most potent antibacterial activity against mycobacteria.