Mesoporous System Research Articles

Integrated QMMM and Monte Carlo methods for analysis of adsorptive interactions between goethite cluster, carbon nanotubes, and arsenate

AbstractIron‐immobilized nanoporous carbon is a well‐known adsorbent used in treating arsenic‐contaminated waters. In this contribution, we present findings on the adsorptive interactions and dynamics of arsenate–goethite cluster ([FeO(OH)]6) with carbon nanotubes (CNTs) using hybridized quantum mechanics/molecular mechanics (QMMM) calculations. The CNTs adsorption mechanism is of interest since a better understanding of the fundamental interactions between arsenate, goethite, and carbon surfaces would translate to advances in CNT‐based adsorbent production and utilization. Novel applications of general amber force field (GAFF) and isobaric‐isothermal Gibbs ensemble Monte Carlo (NpT‐GEMC) methods are described. By the abovementioned methods, we postulate that the [FeO(OH)]6/CNT‐2.3 (diameter 2.3 nm ‐ mesoporous) system enhances the qualitative (i.e., improved chemisorption) rather than the quantitative adsorptive aspect (i.e., total ions adsorbed) in comparison to the [FeO(OH)]6/CNT‐1.6 (diameter 1.6 nm ‐ microporous) system.

Mesoporous Nanofibers Mediated Targeted Anti-cancer Drug Delivery

ABSTRACTTumor tissue has different acidity compared to normal tissue. Localized drug delivery that release chemotherapeutic medications upon stimulation via pH changes is a promising strategy in cancer therapy for adjuvant therapies after surgical resection to reduce the risk of local recurrence. In this study, a mesoporous nanofibrous system with acidic pH-triggered “caps” has been for the first time developed for localized on-demand drug release to target tumor cells, without biological damage to normal cells while maintaining their structural integrity to support future tissue regeneration. Specifically, polyacrylic acid (PAA) was grafted on electrospun mesoporous silica nanofibers (MSFs) and the obtained PAA-MSFs allowed efficient drug loading at neural pH and on-demand releasing at acidic cancer subcellular compartments, based on pH-dependent electrostatic interactions associated with protonation/deprotonation of PAA. The The hybrid mesoporous nanofibers a low cytotoxicity to normal cells and a high killing efficiency to cancer cells. The system demonstrated a great potential as tumor targeting drug delivery system.

Development of New Bexarotene-loaded Mesoporous Silica Systems for Topical Pharmaceutical Formulations

The present study reports the first time use of MCM-41 mesoporous silica as highly efficient carrier for bexarotene - an antineoplastic agent specific for cutaneous T-cell lymphoma treatment. Bexarotene is highly toxic and poor-water soluble, having low bioavailability in the conventional pharmaceutical forms. Comparative uptake of bexarotene on amino-functionalized silica host at various functionalization degrees is discussed in details taking into account all structural features, of matrix as well as properties of the drug molecules. The obtained results proved a successful bexarotene loading on amino-functionalized MCM-41 silica. The bexarotene molecules are adsorbed on the active centers in non-crystalline state proving the major role of the silica amino-functionalization for the drug solubility and bioavailability enhancing. In vitro dissolution tests showed a prolonged release of bexarotene during 12 h, reaching 50% release of loaded active molecules. The prolonged release has been demonstrated to be a result of the presence of aminopropyl groups on the silica pore walls.

Effect of Porous Structure and Acidity of ZSM-5/SBA-15 Catalyst on 1,3,5-Triisopropylbenzene Cracking Catalytic Activity.

ZSM-5/SBA-15 composite materials with different acidities and mesoporous system formations were successfully synthesized by three-step method. The catalysts were characterized by XRD, HR-TEM, BET, EDX and TPD-NH3 methods. It showed that the Si/Al molar ratio had effect on the formation and property of materials. Among synthesized catalysts with the different Si/Al molar ratios of 30 (HZSC-30), 50 (HZSC-50), 70 (HZSC-70), HZSC-50 catalyst had better mesoporous system formation and acidity. These properties helped this catalyst to have higher catalytic activity in 1,3,5-triisopropylbenzene cracking reaction than other studied catalysts in term of higher benzene product yield. In comparison to HZSM-5 microporous material that had the similar Si/Al molar ratio of 50, it showed that the formation of mesopore system of HZSC-50 catalyst had a major improvement on the cracking catalytic activity.

Polymer-coated mesoporous silica nanoparticles for controlled release of the prodrug sulfasalazine

MCM-41 and SBA-15 silicas with particle sizes around 100 nm and 400 nm, respectively, were synthesized. The initial silica materials were modified with amino groups by post-synthesis method. Incipient wetness impregnation was applied for loading of prodrug sulfasalazine. The non-loaded and drug loaded mesoporous silica samples were characterized by XRD, TEM, SEM, N2 physisorption, thermal analysis, and ATR FT-IR spectroscopy. The nanoparticles were post-coated twice by two different layers of polymers (Eudragit RL and Eudragit S), one of them being a pH sensitive one (Eudragit S). The functionalized and polymer coated mesoporous systems are suitable oral drug delivery carriers providing an opportunity to modify the release properties of the loaded drug.

Kinetics Inside, Outside and Through Cucurbiturils

AbstractThis review describes the kinetics at play in Cucurbituril (CB[n])/guest recognition within a very wide time frame, from picoseconds to days. We cover the kinetics of (1) radiative and non‐radiative decays of fluorophores inside and outside CB[n]s, (2) guest motions in the CB[n] cavity, and (3) ingression, egression and threading mechanisms into, out of and through the macrocycles. We then show that the kinetics of guest release or capture can be controlled using CB[n]‐capped mesoporous systems and micelles, or by coupling those processes to the kinetics of ancillary reactions. The last section is devoted to the latest examples of reactions catalyzed and inhibited by CB[n]s.

Facile Synthesis of Chitosan Capped Mesoporous Silica Nanoparticles: A pH Responsive Smart Delivery Platform for Raloxifene Hydrochloride.

An encapsulation of model drug raloxifene hydrochloride (RAL) inside the chitosan decorated pH responsive mesoporous system has a greater potential for accumulating in the tumor cells. The present study involves synthesis of surface modified mesoporous silica nanoparticles (MSN) with the aim of achieving pH sensitive drug delivery system. A silanol skeleton of MSN has been productively modified to amine intermediate which served as a firm platform to adapt chitosan grafted assembly and systematically evaluated. RAL incorporation inside the featured mesopores was performed employing novel immersion solvent evaporation methodology and evaluated further. The pH responsive behavior of formulated nano framework was studied at three different pH of a phosphate buffer saline individually. The in vitro cell viability assay on MCF-7 breast carcinoma cells was performed in time and concentration dependent manner. Finally, the hemolysis assay of designed nanoparticle was accomplished to envisage the hemocompatibility. The outcome of characterization details unveiled a perfect 2D hexagonal spherical structure gifted with higher surface area and optimum pore size for designed nanoparticles. The higher percentage grafting of amine and chitosan residue, i.e., 4.01 and 28.51% respectively along with 31.89 and 33.57% RAL loading efficiency made MSNs more attractive and applicable. Eventually, in vitro release study exhibited higher RAL release in acidic media for extended time periods confirming successful formation of pH responsive nanoparticle having controlled release property. Conclusively potential of designed nanosystem to serve efficient anti-cancer remedy was confirmed by superior behaviour of chitosan grafted MSN towards MCF-7 cells with supreme hemocompatibility.

The Mechanism of Growth of GaN Films by the HVPE Method on SiC Synthesized by the Substitution of Atoms on Porous Si Substrates

The mechanisms of nucleation and growth of GaN films on porous silicon substrates with a buffer layer of silicon carbide grown by new method of substitution of atoms directly in the subsurface layer of the Si substrate were studied. P-type Si(111) plates with a deposited system of periodic mesopores of a diameter of 17 nm and a depth of 1.5 μm were used as the substrates for growth of SiC buffer layer. The buffer AlN layers of a thickness of the order of 500 nm followed by GaN layers of a thickness of the order of 5 μm were deposited by the HVPE method on SiC/Si substrates prepared in different ways. SEM micrographs, Raman and photoluminescence spectra of these samples are given. The influence of the Si substrate preparation method and the conditions of the SiC layer synthesis on the growth mechanisms of both AlN and GaN films has been experimentally revealed. The formation of two types of V-defects during the growth of GaN was observed. A theoretical model for the formation of defects of the first and second types is developed.

Mesoporous silica nanoparticle-based intelligent drug delivery system for bienzyme-responsive tumour targeting and controlled release.

This paper proposes a novel type of multifunctional envelope-type mesoporous silica nanoparticle (MSN) to achieve cancer cell targeting and drug-controlled release. In this system, MSNs were first modified by active targeting moiety hyaluronic acid (HA) for breast cancer cell targeting and hyaluronidases (Hyal)-induced intracellular drug release. Then gelatin, a proteinaceous biopolymer, was grafted onto the MSNs to form a capping layer via glutaraldehyde-mediated cross-linking. To shield against unspecific uptake of cells and prolong circulation time, the nanoparticles were further decorated with poly(ethylene glycol) polymers (PEG) to obtain MSN@HA-gelatin-PEG (MHGP). Doxorubicin (DOX), as a model drug, was loaded into PEMSN to assess the breast cancer cell targeting and drug release behaviours. In vitro study revealed that PEG chains protect the targeting ligand and shield against normal cells. After reaching the breast cancer cells, MMP-2 overpressed by cells hydrolyses gelatin layer to deshield PEG and switch on the function of HA. As a result, DOX-loaded MHGP was selectively trapped by cancer cells through HA receptor-mediated endocytosis and subsequently release DOX due to Hyal-catalysed degradation of HA. This system presents successful bienzyme-responsive targeting drug delivery in an optimal fashion and provides potential applications for targeted cancer therapy.

Near-infrared light triggered drug release from mesoporous silica nanoparticles.

Stimuli triggered drug delivery systems enable controlled release of drugs at the optimal space and time, thus achieving optimal therapeutic effects. As one of the most important stimuli used in bioapplications, near-infrared (NIR) light possesses unique advantages such as deep tissue penetration with minimum auto-fluorescence & tissue scattering and high biosafety. Mesoporous silica nanoparticles (MSNs) are one of the most studied nanocarriers; apart from having a high surface area and large pore volume for loading of drugs, they can be easily functionalized with inorganic nanomaterials and stimuli responsive polymers or organic switch molecules, creating possibilities for designing complex stimuli triggered drug delivery systems. Considering the high tissue penetration depth of NIR light and the unique mesoporous structure of MSNs, NIR responsive inorganic nanoparticle functionalized MSNs can be further combined with stimuli responsive materials to form smart "nano-devices" for controlled drug delivery toward tumors, and to date much progress has been made. In this article, recent advances in the design of NIR triggered mesoporous silica drug delivery systems are systematically summarized and some outstanding studies are highlighted. We will also discuss the shortcomings, challenges and opportunities in the field.

Crack-free high surface area silica-titania nanocomposite coating as opto-chemical sensor device

This work highlights the versatility of sol-gel-derived nanocomposite silica-titania host matrix along with functionalized organic dyes i.e., bromophenol blue (C19H10Br4O5S), phenol red (C19H14O5S), cresol red (C21H17NaO5S) and phenolphthalein (C20H14O4) encapsulation with surfactant CTAB for pH sensing. The synthesized matrices before and after heat treatment (at 150 °C and 250 °C) are analyzed for chemical and physical uniformity; observed as stable, homogeneous, low surface roughness and with functionalized nano-pore surfaces. Particle size distributions in the range of 2.28 nm, 2.73 nm and 2.54 nm are established. Surface analysis shows that the nanoparticles are uniformly distributed on the surface of the mesoporous channel systems with high surface area 400 m2/g, and highly accessible pore system which has more capability to sense the broad pH range. The films show good optical qualities in the visible region with tunable refractive indices 1.57, 1.52-and 1.56. The response of the prepared sensor even shows stability towards higher pH value 12 and has linear relationship with correlation coefficient R2 ∼0.9341. The sensitivity of the proposed pH sensor is observed to be 0.614 mV/pH.

Nanostructured Zeolites: The Introduction of Intracrystalline Mesoporosity in Basic Faujasite-type Catalysts

A combination of postsynthesis modifications and ion exchange aiming to obtain basic cation-rich hierarchical zeolites X and Y was utilized in this work for the preparation of catalysts for biofuel production from vegetable oils. The secondary mesopore system with a narrow pore size distribution in the 4 nm range was introduced by successive acid and base treatments accompanied by surfactant templating. This was followed by ion exchange with Cs+ and K+ cations to produce strong basic catalysts. The prepared hierarchical zeolites were characterized by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, Fourier transform infrared spectroscopy, and solid-state NMR. The transesterification reaction over the zeolite catalysts was performed in a microwave batch-type reactor, and the effects of the reaction conditions, basic properties, and pore structure of the hierarchical faujasites were studied in detail. The conversion of triglycerides increased with increasing concentration of Cs and K in...

A new nano lead-doped mesoporous carbon composite as negative electrode additives for ultralong-cyclability lead-carbon batteries

We propose and realize a new nano lead-doped mesoporous carbon composite as the negative electrode additives, which realize the abundant nano-lead electrodeposition into carbon pores and the remarkable suppression of irreversible sulfation, to effectively prolong the cycle life of lead-carbon batteries. We show that through NaOH activation and followed air oxidation, porous carbon could obtain more mesopore volume and appropriate acidic groups, which are two critical parameters for effective nano-lead electrodeposition on the internal surface of them. We for the first time demonstrate that these mesopore system could be loaded much more deposits in them, and confine the size of lead deposits to be in nano scale by their local effect, ensuring a much more remarkable suppression of hydrogen evolution and better reversibility of Pb/PbSO4. In addition, we show that these nano-lead electrodeposits could stably contribute remarkable pseudocapacitance. All these merits contribute to the ultralong cyclability achieved by lead-carbon batteries, which will translate into promising inexpensive systems that could revolutionize the large-scale energy storage fields.

Role of Drug Adsorption onto the Silica Surface in Drug Release from Mesoporous Silica Systems.

Factors contributing to incomplete drug release from a number of mesoporous silica formulations are not well understood. This study aims to address this gap in knowledge by exploring the role of drug adsorption onto silica substrates during the drug release process in dissolution media. Adsorption isotherms were generated to understand drug adsorption behavior onto the silica surface. Two silica materials were selected (SBA-15 (mesoporous) and Aerosil 200 (nonporous)) to investigate the influence of porous architecture on the adsorption/dissolution processes. The ability of the dissolution medium to wet the silica surface, particularly the porous network, was investigated by the addition of a surfactant to the dissolution medium. The results demonstrated that a larger amount of drug was bound/m2 to the nonporous surface than to the mesoporous material. Adsorption isotherms proved useful in understanding drug adsorption/release behavior for the nonporous silica formulation. However, the quantity of drug remaining on the mesoporous silica surface after dissolution was significantly higher than the amount predicted using adsorption isotherm data. These results suggest that a fraction of loaded drug molecules were tightly bound to the silica surface or attached to sites which are inaccessible for the dissolution media. The presence of surfactant, sodium dodecyl sulfate, in the media enhanced drug release from the silica surface. This behavior can be attributed to both the improved wetting characteristics of the media and adsorption of the surfactant to the silica surface. The findings of this study reinforce the significance of the role that silica porous architecture plays in the dissolution process and indicates that accessible surface area is an important parameter to consider for mesoporous systems in relation to drug release.

Mesoporous systems for poorly soluble drugs – recent trends

When poor aqueous solubility of active pharmaceutical ingredients is encountered during a drug formulation process, the toolbox typically utilized contains pharmaceutical salts, co-crystals, solid dispersions, cyclodextrins, lipids, liposomes and nanocrystals etc. Especially in the pharmaceutical industry, the option which confers the greatest benefit with the lowest risk is usually chosen. Several factors affect the final decision, but new technologies should also be considered especially if they can address several issues at the same time. Mesoporous inorganic systems are emerging technologies which can be utilized for improving the dissolution of poorly soluble drugs. The number of the scientific papers in this field is steadily increasing and the focus of the studies is moving away from in vitro to in vivo experiments with the first human trial already completed. Meanwhile, several start-up companies focusing on mesoporous carriers have been established. Therefore, it is conceivable that the first commercial products will find their way to pharmacies during the next 5–10 years.The present review surveys recent progress in research on mesoporous materials as carriers of poorly soluble drugs. We will concentrate on the research published since our previous review published in 2012 [10.1016/j.ijpharm.2012.09.008] up to the present day.

PH-Sensitive mesoporous silica nanoparticles for chemo-photodynamic combination therapy

In order to optimize the chemotherapeutic efficacy of doxorubicin (DOX) and improve the photodynamic therapeutic effectiveness of rose bengal (RB), a mesoporous silica nanoparticle system was designed as the carrier of RB and DOX for chemo-photodynamic combination therapy. A pH-sensitive strategy has been exploited to enhance the delivery efficiency. Our results suggested that the production of singlet oxygen was independent of the release of RB while strongly influenced by the external DOX layer. This method showed several benefits, including accelerating cellular uptake of the payloads and enabling chemo-photodynamic combination therapy for synergistic cancer treatment. Our study provides a new way for co-delivery of chemotherapy agents and photosensitizers.

Synthesis of NiMo Catalysts Supported on Gallium-Containing Mesoporous Y Zeolites with Different Gallium Contents and Their High Activities in the Hydrodesulfurization of 4,6-Dimethyldibenzothiophene

Mesoporous MY-xGa zeolites exhibiting both crystallized pore walls and narrowly dispersed mesopores with different Ga content were successfully synthesized. The synthesized samples were characterized by XRD, N2 adsorption desorption isotherms, SEM, TEM, XPS, FTIR, 29Si MAS NMR, 71Ga MAS NMR, and Py-FTIR methods. The results show that the synthesized samples exhibit unique open channel like mesopore systems and outstanding crystallite natures; no nonframework Ga species were observed over the MY-xGa series samples, and their acidic properties can be modulated by varying the Ga/Al ratio in the initial synthesis gel. The corresponding NiMo/HMY-xGa catalysts were prepared via the incipient wetness coimpregnation method; the morphologies of the sulfide catalysts were characterized by HRTEM, and the covalent states of the active metals were characterized by XPS. The catalytic activities of the investigated catalysts for the 4,6-DMDBT HDS reaction were assessed, and the collected products were analyzed by GC and...

Improved performance of hierarchical porous Mo/H-IM-5 catalyst in methane non-oxidative aromatization

Two novel hierarchical porous IM-5-S and IM-5-M materials were synthesized using mesoporous silica SBA-15 and MCM-48 as the silica sources, and for comparison conventional IM-5-C zeolite was also synthesized with the same synthesis composition. IM-5-S and IM-5-M samples exhibited larger crystal sizes and different textural properties than the conventional IM-5-C zeolite. Moreover, Mo-modified catalysts, Mo-IM-5-S, Mo-IM-5-M, and Mo-IM-5-C, were prepared for the non-oxidative aromatization of methane. The physical properties and acidities of the samples were characterized by XRD, SEM, TEM, BET, and NH3-TPD. Compared with Mo-IM-5-C, the Mo-IM-5-S and Mo-IM-5-M catalysts showed higher yields of aromatics and better stabilities. The preferable catalytic behaviors of Mo-modified mesoporous IM-5 catalysts may be attributed to the generation of secondary mesoporous systems within the zeolite crystals, which may influence the location and state of the active Mo species, simultaneously lead to easier access to the active sites for reactants and be favorable for the diffusion of products formed in the microporous channels during the methane aromatization reaction.

ATP mediated rolling circle amplification and opening DNA-gate for drug delivery to cell

Here, we have developed a facile fluorometric system for the detection of adenosine triphosphate (ATP) by a rolling circle amplification (RCA) based on proximity ligation mediated amplification, and simultaneously achieved the release of the anticancer drug doxorubicin (DOX) through the mesoporous silicon system. Once the ATP molecule is present, the linker DNA will be released from the graphene oxide (GO) surface and hybridized to the template DNA of the GO surface joining with ligation enzyme. RCA reaction is followed by the addition of the phi29 DNA polymerase. The product of RCA reaction contains a base fragment complementary to the signal DNA, allowing the fluorescent oligonucleotide probe to be released from the GO surface and fluorescence is recovered. The strong fluorescence signal realized the sensitive detection of ATP. Gate DNA were modified to the surface of the mesoporous silica (MSN) by electrostatic attraction to encapsulate DOX. After the above-mentioned RCA process, its result that long DNA chain containing a base fragment complementary to gate DNA, would be hybridized to the gate DNA strand on the surface of MSN, which opened the MSN hole and released the drug DOX into cell for HeLa cell therapy. And the specificity to folate receptor overexpressed on cell surface was satisfactory which would be beneficial for cancer therapy.

Viscosity and Conductivity Tunable Diode-like Behavior for Meso- and Micropores.

Rectifying pores, which transport ions mainly in one direction blocking the ionic flow in the other, were shown to be important in the preparation of chemical sensors, components of ionic circuits, and mimics of biological channels. Ionic rectification has been shown with various engineered systems, but pores with similar opening diameters often rectify to a various uncontrolled extent. In this Letter we present a system of single meso-pores, whose current-voltage curves and rectification can be tuned with great precision via viscosity and conductivity gradients of solutions placed on both sides of the membrane. The mechanism of rectification is based on electroosmotically induced flow, which fills the entire volume of the pore with a single solution from either side of the membrane. The highly predictable rectifying system can find various applications, including measuring viscosity of unknown media and tuning electrokinetic passage of particles.