Silica Loading Research Articles

Robust Ruthenium Catalysts Supported on Mesoporous Cyclodextrin-Templated TiO2-SiO2 Mixed Oxides for the Hydrogenation of Levulinic Acid to γ-Valerolactone.

In this paper, we present a versatile template-directed colloidal self-assembly method for the fabrication in aqueous phase of composition-tuned mesoporous RuO2@TiO2-SiO2 catalysts. Randomly methylated β-cyclodextrin/Pluronic F127 supramolecular assemblies were used as soft templates, TiO2 colloids as building blocks, and tetraethyl orthosilicate as a silica source. Catalysts were characterized at different stages of their synthesis using dynamic light scattering, N2-adsorption analysis, powder X-ray diffraction, temperature programmed reduction, high-resolution transmission electron microscopy, high-angle annular bright-field and dark-field scanning transmission electron microscopy, together with EDS elemental mapping. Results revealed that both the supramolecular template and the silica loading had a strong impact on the pore characteristics and crystalline structure of the mixed oxides, as well as on the morphology of the RuO2 nanocrystals. Their catalytic performance was then evaluated in the aqueous phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) under mild conditions (50 °C, 50 bar H2). Results showed that the cyclodextrin-derived catalyst displayed almost quantitative LA conversion and 99% GVL yield in less than one hour. Moreover, this catalyst could be reused at least five times without loss of activity. This work offers an effective approach to the utilization of cyclodextrins for engineering the surface morphology of Ru nanocrystals and pore characteristics of TiO2-based materials for catalytic applications in hydrogenation reactions.

Explication of hydrophobic silica as effective pore former for membrane fabrication

Membrane development is one of the key aspects to enhance the productivity of a filtration process. This study evaluates a hydrophobic silica as pore former for fabrication of polyvinylidene difluoride (PVDF) membrane for liquid based filtration and compare it with a hydrophilic silica. Membranes incorporated with hydrophobic (M-series) and hydrophilic silica (N-series) with loadings of 1, 2 and 3 wt% in the dope solution were fabricated, characterized and subjected to filtration tests using feeds of pure water, raw wastewater, secondary effluent, microalgae solution and activated sludge. Results show that the hydrophobic silica remained within the membrane matrix (7.24% of elemental Si by EDS), almost three-fold higher than the hydrophilic silica (2.48%). It turned the membrane surface to be more hydrophobic ascribed by increasing water contact angle from 87° from the pristine PVDF membrane up to 97° for the membrane with the highest loading of hydrophobic silica. On the other hand, the addition of hydrophilic decreased the contact angle down to 67° for the membrane with the highest loading. Loading hydrophobic silica enhanced the dope solution viscosities up to 1825–2000 cP, upon dropwise addition of nonsolvent (water), whereas the viscosity remained at 880–950cP for the hydrophilic silica. Addition of hydrophobic silica increased the number of surface pore without significantly altering the pore size of about 0.12 µm. On the other hand, an increase in the pore size (up to 0.33 µm) was observed when hydrophilic silica was added. Despite the smaller pore size, the pure water permeance of the hydrophobic silica loaded membranes (450–984 L/m2hbar) outperformed the hydrophilic silica loaded membranes (420–600 L/m2hbar) due to their higher surface porosities thanks to the higher number of surface pores. The filtration results of multiple feeds showed the advantages of loading more hydrophobic silica in improving the hydraulic performance. The findings demonstrate the efficacy of hydrophobic silica as pore former in PVDF membrane fabrication.

Effect of Fillers on the Recovery of Rubber Foam: From Theory to Applications.

Natural rubber foam (NRF) can be prepared from concentrated natural latex, providing specific characteristics such as density, compression strength, compression set, and so on, suitable for making shape-memory products. However, many customers require NRF products with a low compression set. This study aims to develop and prepare NRF to investigate its recoverability and other related characteristics by the addition of charcoal and silica fillers. The results showed that increasing filler loading increases physical and mechanical properties. The recoverability of NRF improves as silica increases, contrary to charcoal loading, due to the higher specific surface area of silica. Thermodynamic aspects showed that increasing filler loading increases the compression force (F) as well as the proportion of internal energy to the compression force (Fu/F). The entropy (S) also increases with increasing filler loading, which is favorable for thermodynamic systems. The activation enthalpy (∆Ha) of the NRF with silica is higher than the control NRF, which is due to rubber–filler interactions created within the NRF. A thermodynamic concept of crosslinked rubber foam with filler is proposed. From theory to application, in this study, the NRF has better recoverability with silica loading.

Studies on influence of silica filler and rice husk ash on the mechanical properties of vulcanized hybrid rubber composite

The primary aim of this research work is to develop Nitrile butyl rubber (NBR) based hybrid composites, reinforced with cotton fabric and silica-rice husk ash as filler materials. This study aims to investigate the effect of silica and rice husk ash filler loading on the mechanical and swelling properties. The work studied the filler loading by considering two cases: (a) the silica filler addition 10, 20, 30 and 40 phr (b) addition of equal amount of silica and rice husk ash (RHA) 10, 20, 30 and 40phr. The rubber compound with silica or silica + RHA was prepared using a twin-screw extrusion machine and the cotton fabric was coated with a rubber compound. The specimens are vulcanized at temperature 150 °C under pressure 150 kg/cm2 for 20 min duration. The samples were cut and the morphological and mechanical characteristics such as tensile strength, tear strength and hardness are evaluated as per ASTM standards. The results indicate that a more uniform dispersion of silica and RHA make it a good interfacial adhesion among all the phases of the composite. The tensile strength and hardness were increased with increased loading of the fillers but Elongation at break was decreased. The tear strength was increased due to silica filler loading but silica + RHA filler loading increased the tear strength up to 20phr and beyond this level tear strength was decreased.

Cellulose triacetate/LUDOX‐SiO2 nanocomposite for synthesis of pervaporation desalination membranes

AbstractA series of cellulose triacetate/Ludox‐silica nancomposite pervaporation membranes was successfully prepared via solution casting, aiming to improve the performance of cellulose triacetate membranes for desalination. The fabricated nanocomposite membranes were characterized to study the membrane morphology, chemical composition, mechanical properties, and surface hydrophilicity. Furthermore, the desalination performance was investigated as a function of silica (SiO2) loading (ranging from 1 to 4 wt%) and feed concentration at 30 and 60 g/L of sodium chloride (NaCl). Pervaporation experiments showed that incorporating 4 wt% SiO2 into a cellulose triacetate (CTA) membrane increased the water flux by a factor 2.5 compared with pristine CTA (from 2.2 to 6.1 kg m−2 h−1) for a 30 g/L NaCl feed solution at 70°C, while the salt rejection remained above 99%. The CTA/4 wt% SiO2 membrane was found to have only 21% flux reduction when tested with a 60 g/L NaCl feed solution, without changes in membrane selectivity. This suggests that the developed CTA/Ludox‐SiO2 nanocomposite pervaporation membrane is suitable for desalination.

Polycaprolactone-based biodegradable acrylated polyurethanes: Influence of nanosilica amount on functional properties

A series of nontoxic acrylated waterborne polyurethane/silica hybrid composites were synthesized from 1,6-hexamethylene diisocyanate (HDI), polycaprolactone diol (PCL), dimethylolpropionic acid (DMPA), a mixture of 3-aminopropyltriethoxysilane (APTES) and 2-hydroxyethyl methacrylate (HEMA) as chain extender. To control crosslink density the mono-functional HEMA was incorporated into the biodegradable polyurethanes. Different amounts of nanosilica were incorporated into acrylic-based polyurethanes to prepare polyurethane/silica hybrid composites. The structures of the acrylated waterborne polyurethane/silica hybrid composites were characterized by Fourier-transform infrared spectroscopy (FTIR), 1H NMR,13C NMR analysis and scanning electron microscopy (SEM). The effect of the amount of nanosilica on the thermal properties of polyurethane nanocomposite films was investigated by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Wide-angle X-ray scattering (WAXS) was used to investigate the degree of crystallinity of PCL as a soft segment into polyurethane hybrid composites.It is established that all samples containing PCL as a part soft segment with different silica loading are crystallisable polymers. The results from WAXS analysis have shown that the highest degree of crystallinity (37%) is reached in polyurethanes based on 1 wt% content of Aerosil OX50.The highest crystallization enthalpy (ΔHc) value for the sample with 1% nanosilica was 9.77 J/g confirmed by DSC analysis. The decrease of crystallinity of the PCL soft segment in polyurethanes indicates that the restriction of the crystallization of the PCL soft segment depends on the silica content. The incorporation of nanosilica into waterborne polyurethanes increases the thermal stability of the hybrid composite films. It was found that greater thermal and mechanical properties of waterborne polyurethane-silica hybrid composites were obtained due to a condensation process between triethoxysilane groups in the side chains of polyurethane molecules and silanols group on the surface of nanosilica.

Preparation of PDLLA based nanocomposites with modified silica by in situ polymerization: Study of molecular, morphological, and mechanical properties

In order to prepare poly-D,L-lactide/silica nanocomposites and to improve the interfacial adhesion between these two materials, silanization of silica was realized adopting two different organosilanes, i.e. 3-glycidyloxytrimethoxysilane or 3-aminopropyltrimethoxysilane. Then, resulting modified silica with epoxy or amino terminal functions served as initiating sites for D,L-lactide in situ polymerization allowing the production of poly-D,L-lactide/silica nanocomposites.Silica dispersion and mechanical properties of these hybrids were compared to composites prepared with hydrophilic or hydrophobic commercial silica by in situ polymerization. These latter composites disclosed heterogeneities with microscale agglomerates and a drop in mechanical properties for 5 wt% of silica loading. In contrast, composites made from poly-D,L-lactide chains chemically grafted on silica carrying initiation sites disclosed nanoscale dispersion of nanofiller in the PDLLA matrix. In particular, with only 1 wt% of these modified silicas, thanks to the nanoscale dispersion of the inorganic nanofiller, an improvement of 24 % for Young modulus and 51 % for ultimate tensile strength was achieved.

Investigation of nanoparticle-polymer interaction in bio-based nanosilica-filled PLA/NR nanocomposites: molecular dynamics simulation.

Molecular dynamics (MD) simulation, by employing the COMPASS force field, was utilized to investigate structural and thermal characteristics as well as interfacial interactions between components of nanocomposite consisting of poly(lactic acid) (PLA)/natural rubber (NR)/nanosilica, abbreviated as PSxN, where 1 ≤ x ≤ 7 and it represents the parts of SiO2 nanoparticles added to the PLA/NR (PN) blend. Analysis of the obtained results including density (ρ), fractional free volume (FFV), glass transition temperature (Tg), interaction energy (Einteraction), and radial distribution function (RDF) of these nanocomposites was performed. Comparing Einteraction of nanocomposites with that of the PN blend showed that the interactions between the chains of the two polymers are highly dependent on the added amounts of silica nanoparticles, so that by adding silica to the PN blend to obtain PS1N and PS3N nanocomposites, the amount of Einteraction was reduced to a smaller positive value, which indicates the tendency of the nanocomposite's components to interact with each other. By further addition of silica nanoparticles to have PS5N and PS7N nanocomposites and then by analysis of the RDF results, it was found that the nanoparticles were not well dispersed in these two nanocomposites and they were accumulated in the NR rubbery phase. Therefore, the percolation threshold for silica loading on the PN blend is at most 3 parts (x = 3). These results as well as the other obtained simulation results were compared with the available experimental data, and the agreement observed between them approved the simulation procedure and validated the obtained results.

Applications of Mesoporous Silica-Encapsulated Gold Nanorods Loaded Doxorubicin in Chemo-photothermal Therapy.

We investigate the chemo-photothermal effects of gold nanorods (GNRs) coated using mesoporous silica (mSiO2) loading doxorubicin (DOX). When the mesoporous silica layer is embedded by doxorubicin drugs, a significant change in absorption spectra enables to quantify the drug loading. We carried out photothermal experiments on saline and livers of mice having GNRs@mSiO2 and GNRs@mSiO2-DOX. We also injected the gold nanostructures into many tumor-implanted mice and used laser illumination on some of them. By measuring the weight and size of tumors, the distinct efficiency of photothermal therapy and chemotherapy on treatment is determined. We experimentally confirm the accumulation of gold nanostructures in the liver.

Invasion of a Widespread, Non‐Native Grass Causes Downstream Reductions in Bioavailable Silica

AbstractThis study shows that riverine riparian (shoreline) zones — and plant management decisions made therein — can measurably influence the availability of silica delivered to lower reaches of rivers, estuaries, and some coastal oceans. The aims were to determine how much silica is sequestered by riparian vegetation in a river, and what processes govern that effect. We used the invasion and rapid spread of the non‐native grass Phragmites australis (common reed) in the Platte River (central United States) to quantify the biochemical and physical mechanisms by which silica is removed from the river flow and stored in sediments. Specifically, we measured bioavailable silica in sediment, native and non‐native vegetation biomass, and river water over a period of four years. The robust biomass production and high silica content of Phragmites led to biochemical production of amorphous silica particles (ASi) that was 1.5× higher than native willow and 2× higher than native Phragmites. And, the denser growth habit of non‐native Phragmites contributed to more rapid physical sequestration of ASi than with other vegetation. Altogether, the rapid vegetation change due to this invasion caused sequestered silica to increase 1.5× in this reach, which is ~7% of the Platte’s annual silica load. Subsequent Phragmites eradication efforts, wherein the plants were sprayed with herbicide and left physically intact, allowed rapid silica remobilization but it was highly variable.

Super typhoon induced high silica export from Arakawa River, Japan.

Dissolved silicate (DSi) and particulate silica (PSi) concentrations were measured at Arakawa River and at sewage treatment plants (STP) during October 2018 to October 2019. These included flooding observations after super Typhoon Hagibis. At ordinary water levels, the STP effluents were found to be the largest source of DSi in the river. Although DSi concentrations during the flooding events (165μmolL-1) decreased by about 25% compared to that of ordinary water level (221μmolL-1), PSi was more than sixteen times higher value (301μmolL-1) compared to that of ordinary water level (18μmolL-1). Loading amounts of DSi and PSi (± 1 standard error) were 1.5 × 108 (± 0.1 × 108) and 0.15 × 108 (± 0.02 × 108) mol year-1, respectively, excluding the data of Typhoon Hagibis. Loading amounts during flooding events of DSi and PSi were 1.2 × 108 (± 0.1 × 108) and 2.4 × 108 (± 0.4 × 108) mol 15days-1, respectively. Although the silica loading at ordinary water level was mainly derived from DSi, the silica loading during flooding events was extremely large due to both high level of DSi and PSi; moreover, it was higher than the annual loading amount.

Silica-supported carboxylated cellulose nanofibers for effective lysozyme adsorption: Effect of macropore size

Engineering hierarchical macro/mesoporous structures that offer an abundance of accessible binding sites are highly desirable in protein adsorption processes. However, numerous significant challenges remain. Herein, cellulose nanofiber (CNF)-loaded macroporous silica (CNF-MPS) particles were successfully synthesized with a high degree of accessible binding sites by tuning the macropore size of the silica particles and loading a highly carboxylated CNF via smart and rational design. The as-prepared CNF-MPS particles exhibited a high negative charge (~−59 mV) and excellent protein adsorption ability (>1000 mg/g) in <5 min. Furthermore, tuning the macropore size influenced the CNF deposition either to the external surface or penetrating within the pores. As a result, the optimum macropore successfully enhances the adsorption capability to >1500 mg/g as a result of improved interconnectivity between the channels. Here exposed macropores of >100 nm allows ingress of protein to the interior structure that houses an abundance of binding sites comprising the dispersed CNF. Additionally, the adsorption kinetics, thermodynamics, and isothermal parameters were studied to analyze the mechanism of lysozyme adsorption. The adsorption process is confirmed to occur spontaneously at any temperature with a pseudo-second-order model describing the kinetic model, and CNF deposition affecting the heterogeneity of the binding sites.

Preparation and characterization of a novel green silica/PVA membrane for water desalination by pervaporation

In this study, silica was extracted from rice husk (RH) waste to develop a novel green silica/PVA hybrid membrane for improving the desalination performance by pervaporation. A thermal method with citric acid leaching was applied for the extraction of green silica under different conditions, and the best high-cost purity silica obtained was incorporated into the PVA membrane with loadings of 0%, 10% and 20%. The effect of the green silica content on the membrane characteristics, desalination performance, and pervaporation temperature was investigated. The purest silica (>97 wt%) was obtained for a 5% acid leaching solution, which was used as the filler in the PVA membrane, and at a combustion temperature of 700 °C. The green silica/PVA membrane exhibited a higher roughness and hydrophilicity and a lower crystallinity compared with pure PVA, indicating an enhancement in the permeation flux. The flux of hybrid membranes reached the maximum value of 12.3 kg m−2h−1 at 60 °C for 10% silica loading with a 3.5 wt% NaCl feed concentration. Salt rejection remained higher than 99.9% for all membranes, and the apparent activation energy showed no significant difference between experiments. The results showed that the pervaporation performance was successfully improved by incorporating the RH silica into the PVA membrane.

The synergistic effect of fluorosilicone and silica towards the compatibilization of silicone rubber and fluoroelastomer based high performance blend

Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from ⁓3 μm to ⁓200 nm) of the fluorocarbon phase by the synergistic effect of silica and fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature.

Pure and mixed gas permeation study of silica incorporated polyurethane‐urea membrane modified by MOCA chain extender

AbstractPolyurethane‐urea (PUU) nanocomposite membranes have been prepared using various loadings of silica (SiO2) nanoparticles. A Novel PU was fabricated by a two‐step bulk polymerization technique based on polycaprolactone (PCL), hexamethylene diisocyanate (HDI), and diamine chain extender, 4,4‐methylenebis(2‐chloroaniline) (MOCA). The FTIR spectra indicated that the extent of phase separation reduces with increasing SiO2 content. The presence of crystal regions in the soft and hard segments was confirmed by DSC and XRD analyses. The obtained results illustrated a decrement in the gases' permeation in the presence of SiO2 particles. By increasing the filler content up to 15 wt% and pressure of 8 bar, the gas permeation value of the CO2, O2, and N2 decreased 36%, 54%, and 59%, respectively. However, the permselectivity of the CO2/N2 and O2/N2 increased considerably, 55% and 13% respectively. On the contrary, by raising the temperature, a dramatic augmentation in the permeability of all gases with a simultaneous reduction in the selectivity values of both gas pairs was revealed. Increasing the pressure led to a decrease in the permeability values of all membranes for O2 and N2, whereas the permeability for CO2 increased with the pressure. Nevertheless, the selectivity values for the pair of gases increased (at a pressure of 10 bar, 1.66 and 1.17 times the neat PU for CO2/N2 and O2/N2, respectively). Furthermore, the permeability of the CO2, O2, and N2 for the mixed gases was smaller than for pure ones at the same gas upstream pressure. Nonetheless, like the pure gas, the selectivity of both pair gases increased.

Effects of Tetraethyl Orthosilicate on Improving Adhesion Between Polyurethane Sponge/Hydrophobic Silica Gel Composite Materials for Oily Wastewater Treatment

The environmental disposal of oily wastewater is a challenge to household and food industries. Cost-effective oil absorbent materials for oily wastewater treatment have been developed by various methods, one of which, the modification with hydrophobic particles. However, the oil absorbents still suffer high cost and low reusability because of the insufficient adhesion between supported material and the hydrophobic particles. Herein, a low cost and simple method to fabricate oil absorbents were reported by immersing commercial polyurethane (PU) sponge in hydrophobic silica gel. The adhesion between hydrophobic silica gel to the 3D surface of PU was assisted with the use of tetraethyl orthosilicate (TEOS) as a silane coupling agent. Only 0.5% TEOS was required for up to 73% improvement of adhered calculated from % silica loading. The use of TEOS showed adhesion enhancement between the surface of PU and the silica which in turn improve reusability. Reusability test mimics the real situation of squeezing the PU/silica sponge to demonstrate good mechanical properties and flexibility. Furthermore, the PU/silica sponge displayed good and rapid absorption capacity. Results from Water Contact Angle (WCA), Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectroscopy (FT-IR) were also used to confirm successful modification of PU with hydrophobic silica gel.

Production of High Flux Poly(Ether Sulfone) Membrane Using Silica Additive Extracted from Natural Resource.

This paper reports the application of silica derived from natural biomasses of rice husk and bagasse ashes as membrane modifying agents. The modification was conducted on poly(ether sulfone) (PES) membrane by blending the silica into the dope solution. The modification was aimed to improve the structure and hydraulic performance of the resulting PES membrane. The effects of silica addition to the membrane system were evaluated through the analysis of change in chemical structure using ATR-FTIR, surface morphological change using AFM, and surface hydrophilicity using water contact angle measurement. SEM and AFM images show the silica loading significantly affects the membranes morphologies. Silica loading also promotes hydrophilic property as shown by the decrease in water contact angles from 82° to 52–60° due to the presence of polar groups in some residual silica in the membrane matrix. Silica blending also leads to the formation of membranes with higher permeability of up to three folds but lower humic acid rejection (78–62%). The findings indicate the role of silica to enhance the membrane pore size. The ability of membrane to reject humic acid (of 0.8 nm minimum diameter) indicating that the resulting membranes were in between tight ultrafiltration and nanofiltration type. Nonetheless, applying too-high silica concentration decreased the humic acid rejection most likely due to over enlargement of the membrane pore size.

Hybrid membranes based on polybenzimidazoles and silica with imidazoline-functionalized surface, candidates for fuel cells applications

Hybrid membranes were prepared by incorporating silica with propyl-imidazoline groups in polybenzimidazoles (phthalide-containing PBI or PBI based on 2,6- or 2,5-pyridinedicarboxylic acids). The influence effects of the silica precursor hydrolysis conditions on the conductivity of the hybrid membranes are studied. Ionic conductivity, water uptake, phosphoric acid doping, and gas permeability of the obtained materials were found to depend on the preparation method and the silica loading. The materials with 10 wt% of functionalized silica present the highest conductivity. A decrease of hydrogen permeability is observed for low silica loadings.

Study of near-infrared light-induced excitation of upconversion nanoparticles as a vector for non-viral DNA delivery.

Clinical requirements have necessitated the development of biomedical nanomaterials that can be implanted into tissues or bodies. Physiological regulation can be achieved in these nanomaterials through external light. The combination of nanomaterials with infrared optics can be termed optogenetics. The low autofluorescence of upconversion nanoparticles (UCNPs) has several applications in the biological field. For optogenetics applications, UCNPs with high fluorescence performance and photostability can solve the penetration depth problem. NaYF4:Yb,Tm nanocrystals with controllable sizes, shapes, and compositions were synthesized using a rapid coprecipitation method in organic solvent. UCNPs using single crystal nanoparticles provide higher chemical stability than those using amorphous phase. However, because UCNPs are usually capped with hydrophobic ligands, it is particularly important to prepare biocompatible UCNPs with specific molecular recognition capabilities. Surface modification and subsequent functionalization are essential for the application of inorganic nanomaterials in the biological environment and are arousing increasing research interest. Due to the high biocompatibility and high loading of materials, mesoporous silica and amine groups were selected as the best candidates. Expression of plasmid DNA in vivo and transfection efficiency were determined by fluorescence microscopy and flow cytometry. The MTT assay was used to evaluate the particle biocompatibility; the results showed that UCNP@mSiO2 has great biocompatibility. Additionally, at neutral pH, the cell surface is negatively charged. Therefore, the surface is functionalized with amino groups and can be electrostatically bound to DNA. Finally, UCNP@mSiO2-NH2 as a vector was applied in live cells by loading DNA; according to the results, DNA-UCNPs were successfully transfected in the primary cells, and NaYF4:Yb,Tm@mSiO2-NH2-DNA were observed to have good transfection efficiency by flow cytometry. It is expected that this work will provide a different method from the traditional adenovirus method and improve the immune response and side effects caused by adenovirus.

Synthesis and Characterization of Mesoporous Silica Carrier Releasing Valsartan

The aim of the present study is to synthesize a mesoporous silica MCM-48 and loading it with the poorly soluble drug valsartan. The MCM-48 was characterized by Brauner-Emmett-Teller surface area analyzer, scanning electron microscope, powder X-ray diffraction, thermal gravimetric analysis and Fourier transform infra-red (FTIR). The exact loading capacity was found to be 40.12%. in vitro dissolution studies at physiological conditions demonstrated controlled release of 57.2% valsartan over 240 min. The controlled dissolution was attributed to the incomplete amorphization of crystalline valsartan by MCM-48 as evidenced by PXRD studies. The interactions between the mesoporous silica surface and drug molecules were evidenced by FTIR studies and the diffusion of therapeutic agent molecules through the silica pores. The results of the present study confirmed that the controlled adsorption and liberation of valsartan demonstrated a long-term release, which is important for its antihypertensive activity. Moreover, the structural properties of mesoporous silica assured the feasibility of designing reliable drug delivery systems by appropriate choice of the carrier