Synthesis of large-pore methylene-bridged periodic mesoporous organosilicas and its implications

Bi-functionalized aminoguanidine-PEGylated periodic mesoporous organosilica nanoparticles: a promising nanocarrier for delivery of Cas9-sgRNA ribonucleoproteine

BACKGROUND

There is a great interest in the efficient intracellular delivery of Cas9-sgRNA ribonucleoprotein complex (RNP) and its possible applications for in vivo CRISPR-based gene editing. In this study, a nanoporous mediated gene-editing approach has been successfully performed using a bi-functionalized aminoguanidine-PEGylated periodic mesoporous organosilica (PMO) nanoparticles (RNP@AGu@PEG1500-PMO) as a potent and biocompatible nanocarrier for RNP delivery.

RESULTS

The bi-functionalized MSN-based nanomaterials have been fully characterized using electron microscopy (TEM and SEM), nitrogen adsorption measurements, thermogravimetric analysis (TGA), X-ray powder diffraction (XRD), Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and dynamic light scattering (DLS). The results confirm that AGu@PEG1500-PMO can be applied for gene-editing with an efficiency of about 40% as measured by GFP gene knockdown of HT1080-GFP cells with no notable change in the morphology of the cells.

CONCLUSIONS

Due to the high stability and biocompatibility, simple synthesis, and cost-effectiveness, the developed bi-functionalized PMO-based nano-network introduces a tailored nanocarrier that has remarkable potential as a promising trajectory for biomedical and RNP delivery applications.

Synthesis of cube–rod–tube triblock asymmetric nanostructures for enhanced heterogeneous catalysis

A triblock asymmetric nanostructure is fabricated via a sequential growth process, which can be used as an active nano stir bar with accelerated catalytic performance.

Protecting bactofencin A to enable its antimicrobial activity using mesoporous matrices

There is huge global concern surrounding the emergence of antimicrobial resistant bacteria and this is resulting in an inability to treat infectious diseases. This is due to a lack of new antimicrobials coming to the market and irresponsible use of traditional antibiotics. Bactofencin A, a novel antimicrobial peptide which shows potential as an antibiotic, is susceptible to enzyme degradation. To improve its solution stability and inherent activity, bactofencin A was loaded onto a traditional silica mesoporous matrix, SBA-15, and a periodic mesoporous organosilane, MSE. The loading of bactofencin A was considerably higher onto SBA-15 than MSE due to the hydrophilic nature of SBA-15. While there was no detectable peptide released from SBA-15 into phosphate buffered saline and only 20% of the peptide loaded onto MSE was released, the loaded matrices showed enhanced activity compared to the free peptide during in vitro antimicrobial assays. In addition, the mesoporous matrices were found to protect bactofencin A against enzymatic degradation where results showed that the SBA-15 and MSE with loaded bactofencin A exposed to trypsin inhibited the growth of S. aureus while a large decrease in activity was observed for free bactofencin upon exposure to trypsin. Thus, the activity and stability of bactofencin A can be enhanced using mesoporous matrices and these matrices may enable its potential development as a novel antibiotic. This work also shows that in silico studies looking at surface functional group and size complementarity between the peptide and the protective matrix could enable the systemic selection of a mesoporous matrix for individual bacteriocins with potential antimicrobial therapeutic properties.

Novel Highly Luminescent Amine-Functionalized Bridged Silsesquioxanes

Amine-functionalized bridged silsesquioxanes (BSs) were synthesized from bis[(3-trimethoxysilyl)propyl] amine via a solvent-mediated route. BS-1 and BS-2 were obtained at neutral pH with sub- and stoichiometric amounts of water, respectively, and high tetrahydrofuran content. BS-3 was prepared with hyperstoichiometric water concentration, high tetrahydrofuran content, and hydrochloric acid. BS-4 was synthesized with hyperstoichiometric water concentration, high ethanol content, and sodium hydroxide. BS-1 and BS-2 were produced as transparent films, whereas BS-3 and BS-4 formed white powders. Face-to-face stacking of flat or folded lamellae yielded quasi-hydrophobic platelets with emission quantum yields of 0.05 ± 0.01 (BS-1 and BS-2) or superhydrophilic onion-like nanoparticles with exciting emission quantum yields of 0.38 ± 0.03 (BS-3) and 0.33 ± 0.04 (BS-4), respectively. The latter two values are the largest ever reported for amine-functionalized siloxane-based hybrids lacking aromatic groups. Fast Grotthus proton hopping between = NH2+/ = NH groups (BS-3) and = N⁻/ = NH groups (BS-4), promoted by H⁺ and OH⁻ ions, respectively, and aided by short amine-amine contacts provided by the onion-like morphology, account for this unique optical behavior.

Double Epitaxy as a Paradigm for Templated Growth of Highly Ordered Three-Dimensional Mesophase Crystals

Molecular templating and self-assembly are fundamental mechanisms for controlling the morphology of biominerals, while in synthetic two-dimensional layered materials similar levels of control over materials structure can be achieved through the epitaxial relationship with the substrate. In this study these two concepts are combined to provide an approach for the nucleation and growth of three-dimensional ordered mesophases on solid surfaces. A combined experimental and theoretical study revealed how atomic ordering of the substrate controls the structure of surfactant template and the orientation and morphology of the epitaxially grown inorganic material. This dual epitaxial relationship between the substrate, surfactant template, and inorganic mesophase gives rise to a highly ordered porous mesophase with a well-defined cubic lattice of pores. The level of control over the material's three-dimensional architecture achieved in this one-step synthesis is reminiscent of that in biomineralization.

Hybrid periodic mesoporous organosilica designed to improve the properties of immobilized enzymes

Hybrid organosilica supports synthesized with pore size adjusted to enzyme dimensions provide high stability in organic solvent systems and prevent leaching.

Periodic Mesoporous Organosilicas: from simple to complex bridges; a comprehensive overview of functions, morphologies and applications

Periodic Mesoporous Organosilicas (PMOs) were developed in 1999 and are basically ordered templated mesoporous organosilicas, prepared by the combination of a surfactant as template and a silsesquioxane as the organosilica precursor. They were one of the first examples of the so-called "hybrid" organic/inorganic materials. In the years that followed, an amazing variety of functional groups, morphologies and applications has been developed. Some of these high-end applications, like low-k buffer layers in microelectronics, chiral catalysts, chromatographic supports, selective adsorbents and light-harvesting devices, have clearly shown their potential. In this review, we will give a comprehensive overview of all these different functionalities and applications that have been created for Periodic Mesoporous Organosilicas.

Preparation and characterization of 5-sulphosalicylic acid doped tetraethoxysilane composite ion-exchange material by sol-gel method

In this manuscript, we report the preparation and characterization of sulphosalicylic doped tetraethoxysilane (SATEOS), composite material by sol-gel method as a new ion exchanger for the removal of Ni(II) from aqueous solution. The fine granular material was prepared by acid catalyzed condensation polymerization through sol-gel mechanism in the presence of cationic surfactant. The material has an ion exchange capacity of 0.64 mequiv./g(dry) for sodium ions, 0.60 mequiv./g(dry) for potassium ions, 1.84 mequiv./g(dry) for magnesium ions, 1.08 mequiv./g(dry) for calcium ions and 1.36 mequiv./g(dry) for strontium ions. Its X-ray diffraction studies suggest that it is crystalline in nature. The material has been characterized by SEM, IR, TGA and DTG so as to identify the various functional groups and ion exchange sites present in this material. Quantum chemical computations at DFT/B3LYP/6-311G (d,p) level on model systems were performed to substantiate the structural conclusions based ion instrumental techniques. Investigations into the elution behaviour, ion exchange reversibility and distribution capacities of this material towards certain environmentally hazardous metal ions are also performed. The material shows good chemical stability towards acidic conditions and exhibits fast elution of exchangeable H(+) ions under neutral conditions. This material shows remarkable selectivity for Ni(II) and on the basis of its Kd value (4×10(2) in 0.01M HClO4) some binary separations of Ni(II) from other metal ions are performed.

Face-centered-cubic large-pore periodic mesoporous organosilicas with unsaturated and aromatic bridging groups

Large-pore ethenylene-bridged (-CH═CH-) and phenylene-bridged (-C(6)H(4)-) periodic mesoporous organosilicas (PMOs) with face-centered-cubic structure (Fm3m symmetry) of spherical mesopores were synthesized at 7 °C at low acid concentration (0.1 M HCl) using Pluronic F127 triblock copolymer surfactant in the presence of aromatic swelling agents (1,3,5-trimethylbenzene, xylenes-isomer mixture, and toluene). In particular, this work reports an unprecedented block-copolymer-templated well-ordered ethenylene-bridged PMO with cubic structure of spherical mesopores and an unprecedented block-copolymer-templated face-centered cubic phenylene-bridged PMO, which also has an exceptionally large unit-cell size and pore diameter. The unit-cell parameters of 30 and 25 nm and the mesopore diameters of 14 and 11 nm (nominal BJH-KJS pore diameters of 12-13 and 9 nm) were obtained for ethenylene-bridged and phenylene-bridged PMOs, respectively. Under the considered reaction conditions, the unit-cell parameters and pore diameters were found to be similar when the three different methyl-substituted benzene swelling agents were employed, although the degree of structural ordering appeared to improve for phenylene-bridged PMOs in the sequence of decreased number of methyl groups on the benzene ring.

Tetraethylorthosilicate as molecular precursor to the formation of amorphous silica networks. A DFT-SCRF study of the base catalyzed hydrolysis

Quantum chemical calculations using density functional theory have been carried out to investigate two chemical pathways for the last step of the hydrolysis of tetraethylorthosilicate (TEOS) in basic catalyzed environment. The two models that are introduced in this study depend on the number of water molecules involved at the base catalyzed hydrolysis. Solution equilibrium geometries of the molecules involved in the transition states, reactants and product complexes of the two chemical pathways were fully optimized at B3LYP level of theory with the standard 6-31+G(d) basis set, modeling solvent effects using a polarizable continuum solvation model (PCM). Both models predict relative low activation energies. However, the model with two water molecules seems to be more adequate to describe the basic hydrolysis. A natural bond orbital (NBO) analysis seems to show that the proton transfer from water to ethoxy group would occur through a large hyperconjugative interaction, LP(O) → σ*(O-H), which is related to the nonbonding oxygen lone pair orbital from ethoxy group with the vicinal σ*(O-H) anti bonding orbital O-H of a water molecule.

Synthesis of ultralarge-pore FDU-12 silica with face-centered cubic structure

Ultralarge-pore FDU-12 (ULP-FDU-12) silicas with face-centered cubic structures (Fm3m symmetry) of spherical mesopores were synthesized at low initial temperature (∼14 °C) using commercially available PEO-PPO-PEO triblock copolymer Pluronic F127 as a micellar template and xylene as a micelle expander. Xylene was selected on the basis of its predicted higher swelling ability for the Pluronic surfactant micelles in comparison to 1,3,5-trimethylbenzene that was used previously to obtain large-pore FDU-12. The optimization of the synthesis conditions afforded as-synthesized ULP-FDU-12 materials with unit-cell parameters up to 56 nm, which is comparable to the highest reported values for Fm3m structures templated by custom-made surfactants. Calcined silicas were obtained with unit-cell parameters up to 53 nm and pore diameters up to ∼36 nm (for N(2) adsorption at 77 K, the capillary condensation relative pressure was up to 0.938). The preferred silica source was tetraethylorthosilicate, but tetramethylorthosilicate was also found suitable. The pore diameter was dependent on the unit-cell size of the as-synthesized material, but was further tuned by adjusting the time and temperature of the treatment in the HCl solution. If the synthesis was performed at low temperature only, highly ordered closed-pore silicas were obtained at calcination temperatures as low as 450 °C. On the other hand, the hydrothermal treatments, including the acid treatment at 130 °C, afforded silicas with large pore entrance sizes. The present synthesis constitutes a major advancement in the synthesis of ordered silicas with very large open and closed spherical mesopores.

Ultrafast sonochemical synthesis of methane and ethane bridged periodic mesoporous organosilicas

Periodic mesoporous organosilicas (PMOs) with methane and ethane bridging groups were synthesized by the condensation of bis(triethoxysilyl)methane and bis(triethoxysilyl)ethane, respectively, in an ultrafast sonochemical method with a short reaction time of 30 min using a cationic template (1-hexadecyl)trimethylammonium bromide (HTABr). Subsequently, the template HTABr was extracted by another 30 min of sonication in an acetone/HCl mixture. The whole experimental process for the synthesis and extraction of the PMOs took about 1 h, which is much shorter than any other reported methods. Both the PMOs have very high surface areas of 1200-1390 m(2) g(-1) with a narrow pore size distribution of approximately 3 nm. This sonochemical method further extended for the synthesis of large pore (pore size of approximately 5 nm) methane and ethane bridged PMOs using a triblock copolymer Pluronic P123 as template. The methane and ethane bridged PMO materials thus obtained were characterized by small-angle X-ray scattering, transmission electron microscopy, nitrogen sorption, and solid-state NMR techniques.

Structural and morphological transformations of mesostructured titanium phosphate through hydrothermal treatment

The phase transformation of mesostructured titanium phosphate (TiPO) from hexagonal to lamellar structure was observed in a simply hydrothermal treatment, accompanied by drastically morphological changes in the micrometer-sized particles. XRD pattern revealed that different mesostructures were obtained by simply varying hydrothermal temperature or treatment duration. SEM and TEM observations showed the morphological evolution from individual particles to interconnected nanoplatelets. A significant blue shift in UV-vis spectra was observed for lamellar mesostructured material, which may be associated with the different coordinated Ti-sites in the hexagonal and lamellar mesostructures. FT-IR spectra and detailed (31)P MAS NMR studies indicated that additional POH groups were presented in the lamellar structure, which might play a key role in the structural and morphological transformations of mesostructures.