Functionalized Mesoporous Silica Research Articles

Functional Mesoporous Silica Nanomaterials for Catalysis and Environmental Applications

Abstract Silica materials are used in a wide range of applications such as catalysis, photocatalysis, CO2 capture, and environmental remediation. These nanomaterials (NMs) have been extensively investigated since the advent of Stöber silica. However, the absence of pores and small surface area of Stöber silica limits its applications. Later, the discovery of MCM-41 type mesoporous silica using surfactants as structural directing agents became revolutionary in the field of silica NMs. This review focuses on the methods used for synthesizing mesoporous silica nanomaterials (NMs), especially mesoporous nanoparticles (NPs), and their applications in various fields including catalysis (i.e., support for nanoparticle catalysts) and environmental remediation (CO to CO2 conversion, volatile organic compound (VOC) removal, and CO2 capture). The current issues/challenges in realizing the practical applications of these conventional materials are also highlighted. This review also compares the characteristics and applications of MCM-41, SBA-15, and KCC-1 to demonstrate the effect of the morphology and pore architecture of silica on the properties of silica-based NMs. The scope for future developments in the synthesis and applications of silica materials with different pore sizes and morphologies is discussed.

Functional mesoporous silica with controlled pore size for selective adsorption of free fatty acid and chlorophyll

Abstract Mesoporous silica functionalized with (3-aminopropyl)trimethoxysilane was used as a selective adsorbent for free fatty acids (FFAs) and chlorophyll in olive oil. A series of mesoporous silica with 2, 5 and 10 nm pore diameters was modified with 3-aminopropyltrimethoxysilane via a post-synthetic reaction. The structural characteristics were confirmed by powder X-ray diffraction, electron microscopy and nitrogen-sorption analyses, and the adsorption capacity, selectivity, composition and thermal stability of olive oil were investigated. The adsorption of FFAs and chlorophyll depended on the surface functionalization and pore size, respectively. We discovered that aminopropyl-functionalized silica with a 5 nm pore size selectively adsorbed FFAs and chlorophyll without adsorbing other ingredients and changing the fatty acid composition ratio. The adsorption results obtained using regenerated silica also showed that this material can be used several times without severe performance degradation.

Effective Delivery of the CRISPR/Cas9 System Enabled by Functionalized Mesoporous Silica Nanoparticles for GFP‐Tagged Paxillin Knock‐In

AbstractIn this study, direct and effective intracellular delivery of CRISPR/Cas9 plasmids for homology‐directed repair is achieved by functionalized mesoporous silica nanoparticles (MSNs). The functionalized MSNs (Cy5.5‐MSNs‐NLS) are synthesized by in situ labeling of a fluorescent dye (Cy5.5) and surface conjugation of nuclear localization sequence (NLS, PKKKRKV), showing a high loading efficiency (50%) toward the plasmids (PXN cutdown plasmid: GFP‐Cas9‐paxillin_gRNA and repair plasmid: AICSDP‐1: PXN‐EGFP). Subsequently, a polymeric coating of the poly(dimethyldiallylammonium chloride) (PDDA) is electrostatically deposited onto the plasmid‐loaded Cy5.5‐MSNs‐NLS by microfluidic nanoprecipitation. The coating layer offers effective protection against the denaturation of plasmids by EcoRV restriction enzymes, and is shown to prevent premature release. Moreover, owing to the positive charge and pH‐responsive disaggregation of PDDA, enhanced cellular internalization (16 h) and endosomal escape (4 h) of the nanocarrier are observed. After escape of nanocarrier system into the cytoplasm, the NLS on the surface of MSNs facilitates nuclear transport of the CRISPR/Cas9 plasmids, achieving successful GFP‐tag knock‐in of the PXN genomic sequence in U2OS cells. This intracellular delivery system thus offers an attractive method to overcome physiological barriers for CRISPR/Cas9 delivery, showing considerable promise for paxillin‐associated focal adhesion and signaling regulator investigation.

Recent Advances in Functionalized Mesoporous Silica Frameworks for Efficient Desulfurization of Fuels.

Considerable health and climate benefits arising from the use of low-sulfur fuels has propelled the research on desulfurization of fossil fuels. Ideal fuels are urgently needed and are expected to be ultra-low in sulfur (10–15 ppm), with no greater than 50 ppm sulfur content. Although several sulfur removal techniques are available in refineries and petrochemical units, their high operational costs, complex operational needs, low efficiencies, and higher environmental risks render them unviable and challenging to implement. In recent years, mesoporous silica-based materials have emerged as promising desulfurizing agents, owing to their high porosity, high surface area, and easier functionalization compared to conventional materials. In this review, we report on recent progress in the synthesis and chemistry of new functionalized mesoporous silica materials aiming to lower the sulfur content of fuels. Additionally, we discuss the role of special active sites in these sorbent materials and investigate the formulations capable of encapsulating and trapping the sulfur-based molecules, which are challenging to remove due to their complexity, for example the species present in JP-8 jet fuels.

Poly(ester amide)-Bioactive Glass Hybrid Biomaterials for Bone Regeneration and Biomolecule Delivery.

Designing bioactive materials for repairing or regenerating bone defects is an active area of research and discovery. Despite advances made in sol-gel-derived hybrid biomaterials design, three challenges remain: (i) the choice of biodegradable polymers that can form a homogeneous solution in the presence of water is very limited, (ii) low-temperature (below 50 °C) incorporation of calcium into the inorganic matrix while having molecular-level mixing has proven to be a difficult task, and (iii) incorporation of drug-loaded mesoporous nanoparticles into polymer-bioactive glass hybrid scaffolds has not been achieved. In this study, we developed bioactive biomaterials for bone repair/regeneration from an α-amino acid-derived biodegradable poly(ester amide) (PEA) and a tertiary bioglass (SiO2-CaO-P2O5), where calcium was incorporated into the glass network at ambient temperature. Furthermore, drug-loaded functional mesoporous silica nanoparticles prepared by surfactant templating were successfully incorporated into PEA-bioglass porous scaffolds. The resulting homogenous single-phase materials showed deposition of hydroxyapatite on their surfaces, supported mesenchymal stem cell attachment and proliferation, and showed a sustained and slow release of a model compound. Taken together, these biomaterials have the potential to be used as a bifunctional platform for bone regeneration via ion release and biomolecule delivery.

Glutathione and pH serial responsive functional mesoporous silica nanoparticles for drug delivery

In this work, a novel glutathione and pH serial dual-responsive drug delivery system has been developed, which was constructed with chitosan (CS), carbon dots (CDs) and hyaluronic acid (HA) modified the mesoporous silica nanoparticles (MSNs). The system showed excellent drug loading efficiency, controlled release and targeted delivery. In addition, the platform (MSN-CS@HA-CDs) exhibited fluorescence imaging property. The prepared drug delivery system appeared to be a promising cancer treatment platform.

Intracellular Nanomaterial Delivery via Spiral Hydroporation.

In recent nanobiotechnology developments, a wide variety of functional nanomaterials and engineered biomolecules have been created, and these have numerous applications in cell biology. For these nanomaterials to fulfill their promises completely, they must be able to reach their biological targets at the subcellular level and with a high level of specificity. Traditionally, either nanocarrier- or membrane disruption-based method has been used to deliver nanomaterials inside cells; however, these methods are suboptimal due to their toxicity, inconsistent delivery, and low throughput, and they are also labor intensive and time-consuming, highlighting the need for development of a next-generation, intracellular delivery system. This study reports on the development of an intracellular nanomaterial delivery platform, based on unexpected cell-deformation phenomena via spiral vortex and vortex breakdown exerted in the cross- and T-junctions at moderate Reynolds numbers. These vortex-induced cell deformation and sequential restoration processes open cell membranes transiently, allowing effective and robust intracellular delivery of nanomaterials in a single step without the aid of carriers or external apparatus. By using the platform described here (termed spiral hydroporator), we demonstrate the delivery of different nanomaterials, including gold nanoparticles (200 nm diameter), functional mesoporous silica nanoparticles (150 nm diameter), dextran (hydrodynamic diameters between 2-55 nm), and mRNA, into different cell types. We demonstrate here that the system is highly efficient (up to 96.5%) with high throughput (up to 1 × 106 cells/min) and rapid delivery (∼1 min) while maintaining high levels of cell viability (up to 94%).

The Synthesis and Application of Functionalized Mesoporous Silica SBA-15 as Heterogeneous Catalyst in Organic Synthesis

The Synthesis and Application of Functionalized Mesoporous Silica SBA-15 as Heterogeneous Catalyst in Organic Synthesis

Mesoporous silica based recyclable probe for colorimetric detection and separation of ppb level Hg2+ from aqueous medium

Functional mesoporous silica probes, MCM-TFM and SBA-TFM, have been synthesized with varying pore sizes and having S-donor sites judiciously selected to bind soft metal centers. The soft S-donor centers are contributed by the thiol functional groups that are introduced into the silica matrices by functionalization with tris(4-formylphenyl)amine followed by 2-aminothiophenol. The materials rapidly and selectively detect Hg2+ colorimetrically and the change in color profile can be perceived through bare eyes. The probes can decontaminate the pollutant heavy metal from aqueous medium at ppb level and the materials are recyclable and reusable for several separation cycles.

Functional mesoporous silica nanoparticles for delivering nimesulide with chiral recognition performance

Abstract It is predictable that carriers presented with chiral structure can display different drug delivery effect, which is of great interest and novelty in material science and pharmacy. Herein, we synthesized functional mesoporous silica nanoparticles (F-MSNs) with molecular level chiral function property. The obtained levorotatory MSNs and dextrorotatory MSNs were named as FL-MSNs and FD-MSNs, respectively. To explore their special features in delivering drug molecules, drug delivery systems based on FL-MSNs and FD-MSNs were established by using nimesulide (NMS) as model drug. Characterization techniques, including Fourier Transform infrared spectrometer (FTIR), circular dichroism (CD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption/desorption measurement, were applied. The results showed that after loading NMS into FL-MSNs and FD-MSNs, most crystalline NMS converted to amorphous phase confirmed by differential scanning calorimeter (DSC) and X-ray power diffraction (XRD) analysis. Besides, FL-MSNs and FD-MSNs showed responses in corresponding chiral medium and FD-MSNs turned out to be the superior carrier. The superior chiral response performance of FD-MSNs was also confirmed using molecular simulation and wettability study. Finally, in vivo pharmacokinetics and anti-inflammatory pharmacodynamics studies indicated that both FL-MSNs and FD-MSNs could improve the oral bioavailability of NMS (698.45% and 887.03% respectively), and FD-MSNs delivered more NMS after making response to the in vivo environment and thereafter presented stronger anti-inflammatory pharmacodynamics performance.

Folic Acid-Polyethyleneimine Functionalized Mesoporous Silica Nanoparticles as a Controlled Release Nanocarrier.

In an effort to develop a biocompatible, cancer-targetable, controllable carrier for use in smart delivery systems, including drug delivery, this study designed a novel polymer-mesoporous silica nanoparticle hybrid material functionalized with dicarboxylic acid-modified MCM-41 (DA-MCM41) and branched polyethylenimine (PEI). First, mesoporous silica nanoparticles (MSNs) were coated with a folic acid (FA)-PEI layer; MCM-41 was prepared by a sol-gel process and diacidfunctionalized MCM-41 was prepared by post-modification. Subsequently, DA-MCM-41 was coated with FA grafted PEI via an electrostatic interaction. The cellular uptake of DA-MCM-41 and the FAPEI layered MSNs by MCF-7 cells was evaluated using dansyl labeled methylene blue (MB). The FA-PEI-functionalized MSNs exhibited higher cellular uptake to MCF-7 cells than DA-MCM-41. This novel nanocarrier was internalized into the targeted tumor cells site-specifically by FA-mediated internalization and the pH-responsive release of guest molecules (here, methylene blue) was realized by an electrostatic interaction between FA-PEI and DA-MCM-41. Overall, FA-PEI-functionalized MSNs may have potential applications in the targeted and controlled delivery of guest molecules for cancer therapy.

Encapsulation and Controlled Release of Resveratrol Within Functionalized Mesoporous Silica Nanoparticles for Prostate Cancer Therapy.

Resveratrol (RES) is a naturally existing polyphenol which exhibits anti-oxidant, anti-inflammatory, and anti-cancer properties. In recent years, RES has attracted attention for its synergistic effect with other anti-cancer drugs for the treatment of drug resistant cancers. However, RES faces the issues of poor pharmacokinetics, stability and low solubility which limits its clinical application. In present study, RES has been loaded onto uniformly sized (~60 nm) mesoporous silica nanoparticles (MSNs) to improve its in vitro anti-proliferative activity and sensitization of Docatexal in hypoxia induced drug resistance in prostate cancer. RES was efficiently encapsulated within phosphonate (negatively charged) and amine (positively charged) modified MSNs. The effect of surface functionalization was studied on the loading, in vitro release, anti-proliferative and cytotoxic potential of RES using prostate cancer cell line. At pH 7.4 both free and NH2-MSNs loaded RES showed burst release which was plateaued with almost 90% of drug released in first 12 h. On the other hand, PO3-MSNs showed significantly slower release kinetics with only 50% drug release in first 12 h at pH 7.4. At pH 5.5, however, both the PO3-MSNs and NH2-MSNs showed significant control over release (around 40% less release compared with free RES in 24 h). Phosphonate modified MSNs significantly enhanced the anti-proliferative potential of RES with an IC50 of 7.15 μM as compared to 14.86 μM of free RES whereas amine modified MSNs didn't affect proliferation with an IC50 value higher than free RES (20.45 μM). Furthermore, RES loaded onto PO3-MSNs showed robust and dose dependent sensitization of Docatexal in hypoxic cell environment which was comparable to pure RES solution. This study provides an example of applicability of MSNs loaded with polyphenols such as RES as next generation anticancer formulations for treating drug resistant cancers such as prostate cancer.

Economic and Efficient phosphonic functional groups mesoporous silica for uranium selective adsorption from aqueous solutions

A novel mesoporous silica with enhanced phosphonic functional groups (PFGs) and without any silane agents was provided by Sol-Gel technique for selective adsorption of U(VI) from aqueous solutions (AqS). The absorbent was synthesized based on the achieving the four best performance characteristics including availability, economically, adsorption efficiency, and selectivity which are undoubtedly defined the usefulness of the adsorbents. The sorption results exhibited the highest uranium adsorption capacity, qe, of 820.7 mg/g at pH ≈ 8 which indicated the adsorbent is the best alternative for uranium adsorption from the nearly neutral solutions such as seawater. The recovery percentages by the adsorbent in the aqueous environments involving other elements such as Mg, Cd, Hg, As, Ca, Na, Ni and the salty environment with high concentration of Cl− ions are indicated that the adsorbent presents the acceptable selectivity for uranium adsorption from the AqS such as industrial wastewater. Several activities and factors including removing the silane agents, using sodium metasilicate as an available and low-cost source of silica, and using the Sol-gel method as an unexpansive synthesis technique caused to reduce the synthesis costs from 222.787 EUR/kg for the template method to 60.078 EUR/kg for Sol-gel method which confirm the synthesis of a cost-effective adsorbent.

Functional Mesoporous Silica Nanocomposites: Biomedical applications and Biosafety.

The rise and development of nanotechnology has enabled the creation of a wide number of systems with new and advantageous features to treat cancer. However, in many cases, the lone application of these new nanotherapeutics has proven not to be enough to achieve acceptable therapeutic efficacies. Hence, to avoid these limitations, the scientific community has embarked on the development of single formulations capable of combining functionalities. Among all possible components, silica—either solid or mesoporous—has become of importance as connecting and coating material for these new-generation therapeutic nanodevices. In the present review, the most recent examples of fully inorganic silica-based functional composites are visited, paying particular attention to those with potential biomedical applicability. Additionally, some highlights will be given with respect to their possible biosafety issues based on their chemical composition.

Cyclodextrin Functionalized Mesoporous Silica for Environmental Remediation of Methylene Blue Dye.

Functionalization of mesoporous silica KIT-6 with β-cyclodextrin (β-CD) was successfully realized via post-grafting method as a new adsorbent for environmental remediation of methylene blue (MB) dye from aqueous solutions. The mesostructure properties were characterized by transmission electron microscope (TEM), low-angel X-ray diffraction (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA) and N₂ sorption isotherm. The remarkable adsorption of MB into β-CD-KIT-6 adsorbent was studied using UV-visible spectroscopy. The β-CD-KIT-6 exhibited higher adsorption capacity compared with unmodified-KIT-6. The adsorption behavior of MB into the β-CD-KIT-6 and unmodified-KIT-6 was carefully investigated using different kinetic and isotherm models. The adsorption process followed a pseudo-second order kinetic model and well-fitted to Langmuir isotherm. The thermodynamic parameters were evaluated and the adsorption of MB was found to be an exothermic and spontaneous process. The adsorption of MB into the β-CD-KIT-6 was highly dependent on the solution pH.

Synthesis, Characterization of Metal-Schiff Base Functionalized Mesoporous Silica for Pesticide Adsorption

Synthesis, Characterization of Metal-Schiff Base Functionalized Mesoporous Silica for Pesticide Adsorption

Synthesis, Characterization of Metal-Schiff Base Functionalized Mesoporous Silica for Pesticide Adsorption

The mesoporous silica modified by salicylaldimine was prepared through a co-condensation method. Through the bridge effect from metal ion (copper ion, zinc ion, manganese ion), the model drug-avermectin was supported on the metal-Schiff base functionalized mesoporous silica (M-MCM-41) to form a highly efficient adsorbents for pesticidedelivery and removal. The experimental results showed that the sequence in adsorption capacity (AC) for avermectin (AVM) of various mesoporous silica in different adsorption time was Zn-MCM-41 > Cu-MCM-41 > Mn-MCM-41 > MCM-41 > SA-MCM-41. The AC of Zn-MCM-41 was 151 mg/g, while the MCM-41 was 78 mg/g which increased nearly 100 % after modification due to its strongest coordination ability. The FT-IR and XPS results confirmed the existence of coordination bond between SA-MCM-41 and metal ions as well as the coordination bond between M-MCM-41 and avermectin. The kinetic data and the equilibrium isotherms are modeled by three kinetic models, the pseudo-first-order, the pseudo-second-order and intraparticle diffusion, and two isotherm models, Langmuir and Freundlich, respectively. The kinetic mechanism of the adoption changed from physical adsorption to the intraparticle diffusion due to the stronger interaction between avermectin and the mesoporous silica through coordination. Adsorption isotherm of the samples were well-represented by Freundlich model which indicated that the adsorption was reversible.

Versatile Nanocarrier Based on Functionalized Mesoporous Silica Nanoparticles to Codeliver Osteogenic Gene and Drug for Enhanced Osteodifferentiation.

To achieve enhanced stimulatory effects on the osteogenic differentiation of stem cells, the combination of dual factors with synergistic bioactivity has been regarded as the most effective and powerful strategy. In this study, polylysine-modified polyethylenimine (PEI-PLL) copolymers with various molecular weight PEI blocks were first synthesized and evaluated focusing on their cytotoxicity and gene transfection efficiency, and the results demonstrated that the synthesized copolymer PEI-PLL-25k (synthesized using 25 kDa PEI) exhibited lower cytotoxicity and higher in vitro transfection efficiency than commercial PEI-25k (Mw = 25 kDa). In order to effectively load and deliver plasmid DNA and osteogenic drug dexamethasone (DEX), PEI-PLL-25k copolymer and arginine-glycine-aspartate (RGD) peptide were successively anchored onto the surface of mesoporous silica nanoparticles (MSNs) to construct the dual-factor delivery system, which allows the surface adsorption of DNA and DEX loading in the mesopores of MSNs. The modification of PEI-PLL-25k copolymer and RGD on nanoparticles was successfully characterized by various techniques. The functionalized MSNs with RGD conjugation on the surface showed good cytocompatibility as evidenced by in vitro cell viability assays and cytoskeleton observation. The dual-factor delivery system could quickly release plasmid DNA (pDNA), while releasing DEX in a sustained manner. When cultured with the vector bearing bone morphogenetic protein-2 (BMP-2) pDNA, the transfected bone mesenchymal stem cells (BMSCs) were capable of expressing BMP-2 protein. With the simultaneous delivery of DEX and the BMP-2 gene, this dual-factor delivery system could significantly enhance the level of osteogenic differentiation of BMSCs, as demonstrated by in vitro results of alkaline phosphatase (ALP) activity, expression of osteo-related genes, and calcium deposition. Therefore, the versatile functionalized MSNs nanocarrier for codelivery of osteogenic gene and drug may be considered as a promising dual-delivery system to synergistically enhance the osteogenic outcomes of stem cells.

Polyethylene Oxide Functionalized Mesoporous Silica Nanoparticles for pH- Responsive Quercetin Release

Abstract Mesoporous silica nanoparticles (MSN) known as one of the best material of nanotechnology for drug delivery application with their unique properties that suit a therapeutic field. However, the major challenge for nanotechnology is premature release before reached to target cell. Thus, by incorporation of polyethylene oxide (PEO) in MSN loaded with quercetin (QT), the release profile properties can be controlled by meeting to specify pH value of cancer cell, in form of MSN/QT/PEO membrane. The samples have been characterized using FTIR, XRD, TEM, and FESEM-EDX while the adsorption of QT was carried out for 10 hours contact time which results in 80%. Based on the characterization, MSN specified a relatively higher number of pores with larger diameters while MSN/QT/PEO membrane produced the new functional group between MSN/QT with the PEO which indicate to the stronger bonded and pH-responsive at lower pH value. The image of the structure clearly differentiates the composition ratio of MSN/QT/PEO membrane in ratio of 1:0.02:4 respectively and the fabrication using a drying method for 3 days in ambient condition. The release profile had been analyzed in pH 7 and pH 4 at 37°C, and the result shows that MSN/QT released maximum rate of QT within 4 hours for pH 7 while there was negligible release of QT (less than 1%) for MSN/QT/PEO membrane meanwhile at pH 4, MSN profile release burst within early third hours in 50% while the sustained and slowly released was shown by MSN/QT/PEO membrane up to 20 hours. From this study, efficient encapsulation of drug molecules can be suggested as an alternative to the drug delivery application

A Novel Amino and Carboxyl Functionalized Mesoporous Silica as an Efficient Adsorbent for Nickel(II)

In this study, the as-prepared spherical mesoporous silica was modified by amino and cyano groups via grafting, and the amino and carboxyl functionalized adsorption materials (MSS@NH2@COOH) were ob...