Mesoporous Organosilica Research Articles

Double shelled titanium dioxide@mesoporous organosilica nanotube as an amphiphilic photoactive nanoreactor for efficient photocatalytic oxidation of styrene

In this work, we have proposed a strategy to fabricate double-shell nanotubes as amphiphilic photoactive nanoreactors (HTTBPC) through the ordered hybridization of mesoporous organosilicon (PMO) and titanium dioxide (TiO2) nanotubes. Unlike the previous rough composite, the heterogeneous structure established between cobalt-porphyrin functionalized PMO and conventional TiO2 has a staggered matching band gap, which makes it have excellent light harvesting and high carrier separation ability. This is still unexplored. Interestingly, the prepared photocatalysts exhibited superior activity (99%) and benzaldehyde selectivity (94%) in the oxidation of styrene in water at room temperature, which was 3.8 and 2.8 times higher than that of TiO2 nanotubes and PMO functionalized with cobalt porphyrin, respectively. It was demonstrated that the strong interaction between cobalt porphyrin PMO and TiO2 improved the separation of photogenerated carriers and the amphiphilic properties of mesoporous organosilica boosted the adsorption of substrate molecules in water, contributing to the significantly enhanced photocatalytic activity. This work provides a design of high-performance photocatalysts for alkene oxidation under green conditions.

Surfactant-Assisted Synthesis of Mesoporous Metal Phosphonates to Control Surface Properties Including an Opportunity to Organize a Bulky Biphenyl Linker.

A wide variety of properties by the presence of functional organic groups have so far been investigated by using periodic mesoporous organosilica (PMO)-type materials but not yet discussed with surface properties that are controlled through the success in synthesizing analogous non-silica-based hybrid mesoporous materials and subsequent evaluation and/or comparison of their properties. Here, we demonstrated the advance in synthesizing biphenyl group (-Ph-Ph-, also expressed as -2Ph)-containing mesoporous metal phosphonates with a rational understanding of surface properties. Ordered mesoporous films of aluminum and titanium ones (AOP-2Ph and TiOP-2Ph) were fabricated by spin-coating and their powders were recovered by spray-drying with the confined assembly of spherical mesopores. As in the case of PMO-type materials, the possibility to organize a -Ph-Ph- linker at the molecular scale was found in the powder samples of AOP-2Ph and TiOP-2Ph because thick frameworks would give an opportunity to organize the bulky -Ph-Ph- linker as the small-sized domains even around spherical mesopores. Surface properties of AOP-2Ph and TiOP-2Ph were evaluated by using the data of water (H2O) adsorption isotherms and compared with those containing different organic groups. The unique hydrophilicity starting from the hydration of AlO4 units was drastically reduced by the presence of -Ph-Ph- groups with a disappearance of the capillary condensation by the presence of mesopores. In addition, a partial replacement of TiO6 units with AlO4 and/or its hydrated AlO6 species was proposed for decreasing the strong hydrophobicity of TiOP-2Ph. The contact angle over the spin-coated films was also measured by using a droplet of H2O, indicating that the surface of the films, especially TiOP-2Ph, was extremely hydrophilic. Although surface properties at the molecular scale can be evaluated by using molecular H2O vapor during the measurement of H2O adsorption isotherms, the interaction of the H2O cluster (droplet) with the bulk surface seems to be predominated by inorganic moieties.

CO2 adsorption by ethane periodic mesoporous organosilica at low temperatures and high pressure

In this work, the maximum CO2 adsorption capacity of an ordered mesoporous organosilica with ethylene bridges (PMO-Ethane) was studied. The maximum capture capacity was achieved for the sample at 0 °C and 34 atm (827.8 mg·g-1). This result was better than that obtained by most of the studies on other mesoporous materials found in the literature. Approximately 0.33 g of PMO-Ethane would be sufficient to shrink the concentration of atmospheric CO2 by 1 m3 to preindustrial levels. A study of successive adsorption-desorption cycles has demonstrated the material's potential for use in reversible multicycle CO2 capture processes. The CO2 adsorption curves were fitted using mathematical models: Langmuir, Freundlich, Sips, Toth, DubininRadushkevich and Temkin. Previously, several techniques were used to characterize the material: X-Ray diffraction (XRD), surface area (SBET) and porosity, thermogravimetric and differential thermal analysis (TGA-DTA), particle size, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). These results contribute to the development and use of new materials in GHG capture technologies.

A miniaturized analytical system with packed epoxy-functionalized mesoporous organosilica for copper determination using a customized Android-based software.

A smartphone-assisted determination of copper ions is introduced by using adown-scaled microfluidic mixer. The system was coupled with a micro-column packed with a periodic mesoporous organosilica (PMO) material for preconcentration of copper ions. Copper ions were reduced to Cu(I) on-chip to selectively form an orange-colored complex with neocuproine. A novel Android-based software was made to determine the color change of the adsorbent by analyzing red-green-blue (RGB) components of images from the packed PMO material. Four porous framework materials with high porosity and chemical stability were synthesized and compared for the extraction of the Cu-neocuproine complex. The main parameters influencing the complex extraction efficiency were optimized. The analytical performance of the method showed limit of detection and quantification of 0.2 μg L-1 and 0.5 μg L-1, respectively. The accuracy and precision of the method were determined as recovery > 92% and relative standard deviations < 5.2% at medium concentration level (n = 5). Due to accumulation of the retained analyte in a single point and elimination of the stripping step, the RGB-based method showed sensitivity and precision higher than inductively coupled plasma-atomic emission spectrometry (ICP-AES) for determination of copper ions. To investigate the applicability of the method, six different water samples were analyzed. The t-test on the data showed that the method has no significant difference when comparedwith ICP-AES determination.

Dendritic Mesoporous Organosilica Nanoparticles with Photosensitizers for Cell Imaging, siRNA Delivery and Protein Loading.

Dendritic mesoporous organosilica nanoparticles (DMON) are a new class of biodegradable nanoparticles suitable for biomolecule delivery. We studied the photochemical internalization (PCI) and photodynamic therapy (PDT) of DMON to investigate new ways for DMON to escape from the endosomes-lysosomes and deliver biomolecules into the cytoplasm of cells. We added photosensitizers in the framework of DMON and found that DMON were loaded with siRNA or FVIII factor protein. We made four formulations with four different photosensitizers. The photosensitizers allowed us to perform imaging of DMON in cancer cells, but the presence of the tetrasulfide bond in the framework of DMON quenched the formation of singlet oxygen. Fortunately, one formulation allowed us to efficiently deliver proapoptotic siRNA in MCF-7 cancer cells leading to 31% of cancer cell death, without irradiation. As for FVIII protein, it was loaded in two formulations with drug-loading capacities (DLC) up to 25%. In conclusion, DMON are versatile nanoparticles capable of loading siRNA and delivering it into cancer cells, and also loading FVIII protein with good DLC. Due to the presence of tetrasulfide, it was not possible to perform PDT or PCI.

Enabling hydrate-based methane storage under mild operating conditions by periodic mesoporous organosilica nanotubes

Biomethane is a renewable natural gas substitute produced from biogas. Storage of this sustainable energy vector in confined clathrate hydrates, encapsulated in the pores of a host material, is a highly promising avenue to improve storage capacity and energy efficiency. Herein, a new type of periodic mesoporous organosilica (PMO) nanotubes, referred to as hollow ring PMO (HR-PMO), capable of promoting methane clathrate hydrate formation under mild working conditions (273 K, 3.5 MPa) and at high water loading (5.1 g water/g HR-PMO) is reported. Gravimetric uptake measurements reveal a steep single-stepped isotherm and a noticeably high methane storage capacity (0.55 g methane/g HR-PMO; 0.11 g methane/g water at 3.5 MPa). The large working capacity throughout consecutive pressure-induced clathrate hydrate formation-dissociation cycles demonstrates the material’s excellent recyclability (97% preservation of capacity). Supported by ex situ cryo-electron tomography and x-ray diffraction, HR-PMO nanotubes are hypothesized to promote clathrate hydrate nucleation and growth by distribution and confinement of water in the mesopores of their outer wall, along the central channels of the nanotubes and on the external nanotube surface. These findings showcase the potential for application of organosilica materials with hierarchical and interconnected pore systems for pressure-based storage of biomethane in confined clathrate hydrates.

Surface protein-retractive and redox-degradable mesoporous organosilica nanoparticles for enhanced cancer therapy

Targeted delivery along with controlled drug release is considered crucial in development of a drug delivery system (DDS) for efficient cancer treatment. In this paper, we present a strategy to obtain such a DDS by utilizing disulfide-incorporated mesoporous organosilica nanoparticles (MONs), which were engineered to minimize the surface interactions with proteins for better targeting and therapeutic performance. That is, after MONs were loaded with a chemodrug doxorubicin (DOX) through the inner pores, their outer surface was treated for conjugation to the glutathione-S-transferase (GST)-fused cell-specific affibody (Afb) (GST-Afb). These particles exhibited prompt responsivity to the SS bond-dissociating glutathione (GSH), which resulted in considerable degradation of the initial particle morphology and DOX release. As the protein adsorption to the MON surface appeared largely reduced, their targeting ability with GSH-stimulated therapeutic activities was demonstrated in vitro by employing two kinds of the GST-Afb protein, which target human cancer cells with the surface membrane receptor, HER2 or EGFR. Compared with unmodified control particles, the presented results show that our system can significantly enhance cancer-therapeutic outcomes of the loaded drug, offering a promising way of designing a more efficacious DDS.

Pd Nanoparticles Supported on N-Incorporated Hybrid Organosilica as an Active and Selective Low-Temperature Phenol Hydrogenation Catalyst

A heterogeneous Pd-NPMO hybrid-silica catalyst is synthesized and its application for aqueous phase selective hydrogenation of phenol to cyclohexanone at near ambient temperature (40 °C) and under atmospheric hydrogen pressure is demonstrated. The homogeneously distributed Pd nanoparticles on N-bridged hybrid mesoporous organosilica showed remarkable activity and selectivity for cyclohexanone compared to the unmodified Pd-SBA-15 catalyst. Control experiments strongly claim the role of nitrogen domains in the organic framework of hybrid silica support in stabilizing small Pd nanoparticles and possibly modifying the Pd sites responsible for catalysis to activate the substrate molecules in water. The hybrid silica catalyst was stable and reused several times without any significant drop-in activity, proving the heterogeneity of the bifunctional Pd catalyst. Based on the density functional theory study and experimental interventions, a possible reaction mechanism for the low-temperature phenol hydrogenation explaining the role of organic domains in the hybrid-silica framework is proposed.

Mesoporous Organosilica-Based Hydrogen Sulfide Nanogenerator for Enhanced Tumor Chemotherapy

Conventional chemotherapy is bothered by systematic toxicity and confined therapeutic effects. Gas therapy has emerged as a potent tumor treatment, and hydrogen sulfide (H2S), a traditional gasotransmitter, has been found to show a tumor inhibition effect. Therefore, we established a mesoporous organosilica-based H2S nanogenerator (MON-TPGS-DOX). Tetrasulfide bond-incorporated mesoporous organosilica nanoparticles were modified with d-α-tocopheryl polyethylene glycol succinate (TPGS), namely, MON-TPGS, and then loaded with doxorubicin (DOX) to obtain the nanogenerator. Tetrasulfide bonds in the nanogenerator could be triggered by glutathione (GSH) to release H2S, further resulting in the degradation of nanogenerator and DOX release. GSH consumption and H2S release led to oxidative stress in 4T1 cells, activation of apoptotic signaling cascades, and enhanced cell-killing effect. Furthermore, the nanogenerator effectively suppressed tumor growth in a tumor-bearing mice model with good biosafety, providing a promising approach for H2S-enhanced tumor chemotherapy.

Efficient in vitro delivery of paclitaxel by a nanocellulose-coated dendritic mesoporous organosilica nanoparticle for enhanced chemodynamic cancer therapy

Dendritic mesoporous organosilica nanoparticles (DMONs) with larger pore volumes, accessible interior regions, and open-pore channels have shown great potential in drug delivery for cancer treatment. However, the mesoporous structure of DMONs often leads to drug leakage, which ultimately results in premature drug release. Herein, cellulose nanocrystal (CNC) and polydopamine (PDA) coated DMONs were prepared to develop biocompatible and pH-responsive nanocarriers for effective paclitaxel (PTX) delivery (PTX@DMONs-PDA/CNC). CNC encapsulation was employed to prevent drug leakage while ensuring efficient drug release from nanocarriers at the tumor site. PDA was embedded as an external coating, a biocompatible molecule that enhances cellular uptake by increasing cell adhesion, as well as achieving the stimuli-response release of drugs. The nanocarriers exhibit excellent cellular uptake and acid-response release properties, the accumulated drug release reached up to 80.59% in 85 h at pH 5.5. Furthermore, the apoptosis effect of PTX@DMONs-PDA/CNC presents 14-fold higher than the control group. The CNC-coated drug delivery system provides a promising solution for the efficient and controlled release of drugs in chemodynamic cancer therapy.

Inside Front Cover: Mesoporous silica/organosilica nanoparticles for cancer immunotherapy (EXP2 3/2023)

Mesoporous silica-based nanoparticles, including silica, organosilica and metal doped silica and organosilica nanoparticles, have widespread applications in biomedical applications. This review summarizes the applications of mesoporous silica-based nanoparticles in the field of cancer immunotherapy. Strategies to regulate the tumour microenvironment for immune activation are presented by highlighting the structural and compositional attributes of the silica-based nanoparticles.

Gas therapy potentiates aggregation-induced emission luminogen-based photoimmunotherapy of poorly immunogenic tumors through cGAS-STING pathway activation

The immunologically “cold” microenvironment of triple negative breast cancer results in resistance to current immunotherapy. Here, we reveal the immunoadjuvant property of gas therapy with cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway activation to augment aggregation-induced emission (AIE)-active luminogen (AIEgen)-based photoimmunotherapy. A virus-mimicking hollow mesoporous tetrasulfide-doped organosilica is developed for co-encapsulation of AIEgen and manganese carbonyl to fabricate gas nanoadjuvant. As tetra-sulfide bonds are responsive to intratumoral glutathione, the gas nanoadjuvant achieves tumor-specific drug release, promotes photodynamic therapy, and produces hydrogen sulfide (H2S). Upon near-infrared laser irradiation, the AIEgen-mediated phototherapy triggers the burst of carbon monoxide (CO)/Mn2+. Both H2S and CO can destroy mitochondrial integrity to induce leakage of mitochondrial DNA into the cytoplasm, serving as gas immunoadjuvants to activate cGAS-STING pathway. Meanwhile, Mn2+ can sensitize cGAS to augment STING-mediated type I interferon production. Consequently, the gas nanoadjuvant potentiates photoimmunotherapy of poorly immunogenic breast tumors in female mice.

Synthesis of double-shelled periodic mesoporous organosilica nanospheres/MIL-88A-Fe composite and its elevated performance for Pb2+ removal in water

Herein, we report the synthesis of double-shelled periodic mesoporous organosilica nanospheres/MIL-88A-Fe (DSS/MIL-88A-Fe) composite through a hydrothermal method. To survey the structural and compositional features of the synthesized composite, a variety of spectroscopic and microscopic techniques, including FT-IR, XRD, BET, TEM, FE-SEM, EDX, and EDX-mapping, have been employed. A noteworthy point in this synthesis procedure is the integration of MOF with PMO to increase the adsorbent performance, such as higher specific surface area and more active sites. This combination leads to achieving a structure with an average size of 280 nm and 1.1 μm long attributed to DSS and MOF, respectively, microporous structure and relatively large specific surface area (312.87 m2/g). The as-prepared composite could be used as an effective adsorbent with a high adsorption capacity (250 mg/g) and quick adsorption time (30 min) for the removal of Pb2+ from water. Importantly, DSS/MIL-88A-Fe composite revealed acceptable recycling and stability, since the performance in Pb2+ removal from water remained above 70% even after 4 consecutive cycles.

Rational synthesis of pH-responsive mesoporous organosilica nanoparticles functionalized with 2-aminothiophenol for controlled release of curcumin

Rational synthesis of pH-responsive mesoporous organosilica nanoparticles functionalized with 2-aminothiophenol for controlled release of curcumin

Preparation of phenyl-bridged hybrid organic-inorganic mesoporous vesicles with high thermal stability and hierarchical buildups

Hollow periodic mesoporous organosilicas have promising applications due to their excellent properties but have difficulty withstanding harsh working conditions, and current synthesis techniques typically require strong acids or strong base substances. In this study, we report an environmentally friendly synthesis technique of phenyl-bridged hybrid organic-inorganic mesoporous vesicles (Ph-HPMOs) with high thermal stability and hydrothermal stability using 1,4-bis(triethoxysilyl)benzene (BTEB) as an organosilica precursor in alkaline phosphate buffer solution. The Ph-HPMOs were robust with a diameter of 100–200 nm and a shell thickness up to 50 nm. In addition, the Ph-HPMOs had a unique hierarchical pore size distribution of macropores, cavities, mesopores and micropores with a high surface area of 560–930 m2/g and a large pore volume of 0.6–1.3 cm3/g. Also, the effect of different variables on the structural morphologies of the products were investigated. The optimized conditions for the Ph-HPMOs were 1 SDS:1.5 CTAB: 13.575 BTEB: 4.525 TEOS: 316.26 EtOH: 5119.92H2O (molar ratio). Additionally, aluminum ions (Al3+) were doped into Ph-HPMOs, and the catalytic properties were investigated in a fixed bed reactor, highlighting their high practical value as catalysts or adsorbents.

Pt(IV)-ion imprinted ordered mesoporous organosilica for platinum preconcentration prior to electrothermal atomic absorption spectrometry determination in geological samples

Pt(IV) ion-imprinted thiocyanato-functionalized SBA-15 material (Pt(IV)S1) was proposed for preconcentration of Pt(IV) ions from digested geological samples before its electrothermal atomic absorption spectrometry (ETAAS) determination. The ion-imprinted material exhibited very good adsorption affinity towards Pt(IV) ions. Under the optimal pH (pH = 3) the maximum static adsorption capacity for Pt(IV) was equal to 175 mg g−1. The use of Pt(IV)S1 as an adsorbent allowed for the quantitative adsorption of Pt(IV) ions from solutions with concentrations up to 25 mg L−1. The creation of ion imprinted adsorption centres resulted in an increase of the adsorption rate and selectivity towards Pt(IV) compared to the similar non-ion imprinted material. The analytical procedure was based on the adsorption of Pt(IV) ions and dissolution of the Pt-loaded sorbent in a small volume of hydrofluoric acid before its dilution with 5% hydrochloric acid and introduction into an electrothermal atomizer. The enrichment factor of the proposed procedure was 38, while the limit of quantification was 0.079 mg kg−1.

Mesoporous silica/organosilica nanoparticles for cancer immunotherapy.

Cancer is one of the fatal diseases in the history of humankind. In this regard, cancer immunotherapeutic strategies have revolutionized the traditional mode of cancer treatment. Silica based nano-platforms have been extensively applied in nanomedicine including cancer immunotherapy. Mesoporous silica nanoparticles (MSN) and mesoporous organosilica nanoparticles (MON) are attractive candidates due to the ease in controlling the structural parameters as needed for the targeted immunotherapeutic applications. Especially, the MON provide an additional advantage of controlling the composition and modulating the biological functions to actively synergize with other immunotherapeutic strategies. In this review, the applications of MSN, MON, and metal-doped MSN/MON in the field of cancer immunotherapy and tumor microenvironment regulation are comprehensively summarized by highlighting the structural and compositional attributes of the silica-based nanoplatforms.

Etched hollow periodic mesoporous organosilica with enlarged pore size for high-performance solid phase microextraction of polybrominated biphenyls

Hollow mesoporous silica has attracted increasing attention due to its outstanding characteristics such as low density, large void, mesoporous channel, and large specific surface area. Herein, a kind of etched hollow periodic mesoporous organosilica (EHPMOS) with enlarged mesopore size was successfully synthesized for high-performance solid phase microextraction (SPME). The etched silica material was prepared as a SPME fiber with uniform morphology, and the enrichment capacities for polybrominated biphenyls (PBBs) were systematically studied. In particular, the EHPMOS showed significant enrichment factors (158–9516) for PBBs. In addition, based on the home-made SPME fiber and gas chromatography-mass spectrometry (GC–MS), an ultra-sensitive analytical method was developed, with low limits of detection (0.11–0.32 ng·L-1), a wide linear range (1–1000 ng·L-1), and satisfactory reproducibility. And accurate quantifications of ultra-trace PBBs in environmental water sample were achieved.

Proton pump inhibitor-enhanced nanocatalytic ferroptosis induction for stimuli-responsive dual-modal molecular imaging guided cancer radiosensitization.

Although radiotherapeutic efficiency has been revealed to be positively correlated with ferroptosis, the neutral/alkaline cytoplasm pH value of tumor cells remains an intrinsic challenge for efficient Fenton/Fenton-like reaction-based ferroptosis induction. Herein, PEGylated hollow mesoporous organosilica nanotheranostics (HMON)-GOx@MnO2 nanoparticles (HGMP NPs) were designed as a ferroptosis inducer, which could specifically release Mn2+ in tumor cells to activate the Fenton-like reaction for ferroptosis induction. Proton pump inhibitors (PPIs) were synchronously administered for cytoplasm pH level regulation by inhibiting V-H+-ATPases activity, enhancing Fenton-like reaction-based ferroptosis induction. Moreover, reactive oxygen species production was facilitated via the glucose oxidase triggered cascade catalytic reaction by utilizing intracellular β-D-glucose for H2O2 self-supply and generation of additional cytoplasm H+. The PPI enhanced ferroptosis inducing nanosystem effectively inhibited tumor growth both in vitro and in vivo for tumor-specific ferroptosis induction and radiotherapy sensitization, suggesting that PPI administration could be an efficient adjuvant to reinforce Fenton/Fenton-like reaction-based ferroptosis induction for radiosensitization. STATEMENT OF SIGNIFICANCE: The cytoplasm pH value of tumor cells is typically neutral to alkaline, which is higher than that of the Fenton/Fenton-like reaction desired acidic environments, hindering its efficiency. In this study, PEGylated hollow mesoporous organosilica nanotheranostics (HMON)-GOx@MnO2 nanoparticles were synthesized as a ferroptosis inducer, which could specifically release Mn2+ via depleting glutathione and then activate the Fenton-like reaction in the tumor microenvironment. The glucose oxidase was applied for H2O2 self-supply and addition of cytoplasm H+ to further boost the Fenton-like reaction. We found that proton pump inhibitors (PPIs) increased intracellular acidification by inhibiting the activity of V-H+-ATPases to enhance the Fenton reaction-based ferroptosis induction, suggesting PPIs administration could be a feasible strategy to reinforce ferroptosis induction for radiosensitization.

Periodic Mesoporous Organosilica Nanomaterials with Unconventional Structures and Properties.

Periodic mesoporous organosilicas (PMOs) are high surface area organic-inorganic hybrid nanomaterials that have found broad applications in various fields of research such as in (bio)chemistry or material science. By choosing suitable organic groups in the framework of these materials, their surface properties such as polarity, optical/electrical characteristics and adsorption capacity can be tuned. This critical review provides an overview of the current state of the art in the developments and applications of some PMO nanomaterials in diverse fields of research. This is placed in the context of four leading areas of PMO nanomaterials, including chiral PMOs, plugged PMO nanomaterials, Janus PMOs and PMO-based nanomotors. The review briefly discusses the recent and key findings on these PMO nanomaterials as well as their potential applications for future developments.