The oral pathway is considered as the most common method for drug administration, although many drugs, especially the highly pH- and/or enzymatic biodegradable peptide drugs, are very difficult to ...formulate and achieve a good intestinal absorption. Efficient systematic absorption of an active substance, delivered
via
oral ingestion, is only achievable if the drug (1) is substantially present as a solution in the gastrointestinal tract, (2) is able to penetrate through the intestinal mucus, (3) overcomes the different gastrointestinal barriers, and (4) provides an effective therapeutic dose. Therefore, optimization of oral bioavailability of poorly-soluble drugs still remains a significant challenge for the pharmaceutical industry. Even though numerous conventional drug carriers have successfully solved some of the issues related to oral delivery of poorly-soluble drugs, only few of them met commercialization requirements. These drawbacks have led the scientific world to reconsider its approaches toward targeted drug delivery systems and researchers started looking for alternative
vectorized
carriers. In this area, nanoparticle-based materials have several significant advantages over free and non-formulated drugs. For example, nanosized porous silica carriers allow for more sustained and controlled drug release or improved oral bioavailability. Thus, in the present review, we will highlight the most important features of nanostructured silica drug carriers, such as particle size, particle shape, surface roughness or surface functionalization, and underline the key advantages of these nanosupports. In particular, this article will discuss recent progress and challenges in the area of mesoporous silica nanocarriers used for oral drug delivery. Additional emphasis will be set on the biological and chemical features of the gastrointestinal tract as well as currently tested
nanoformulations
and strategies to avoid drug degradation in the gastrointestinal environment.
Mesoporous silica nanocarriers are discussed as potential oral drug delivery systems, focusing on their advantages and limitations, and future perspectives.
Metal-organic frameworks (MOFs) are commended as photocatalysts for H
evolution and CO
reduction as they combine light-harvesting and catalytic functions with excellent reactant adsorption ...capabilities. For dynamic processes in liquid phase, the accessibility of active sites becomes a critical parameter as reactant diffusion is limited by the inherently small micropores. Our strategy is to introduce additional mesopores by selectively removing one ligand in mixed-ligand MOFs via thermolysis. Here we report photoactive MOFs of the MIL-125-Ti family with two distinct mesopore architectures resembling either large cavities or branching fractures. The ligand removal is highly selective and follows a 2-step process tunable by temperature and time. The introduction of mesopores and the associated formation of new active sites have improved the HER rates of the MOFs by up to 500%. We envision that this strategy will allow the purposeful engineering of hierarchical MOFs and advance their applicability in environmental and energy technologies.
The term “engineered zeolitic materials” refers to a class of materials with a rationally designed pore system and active‐sites distribution. They are primarily made of crystalline microporous ...zeolites as the main building blocks, which can be accompanied by other secondary components to form composite materials. These materials are of potential importance in many industrial fields like catalysis or selective adsorption. Herein, critical aspects related to the synthesis and modification of such materials are discussed. The first section provides a short introduction on classical zeolite structures and properties, and their conventional synthesis methods. Then, the motivating rationale behind the growing demand for structural alteration of these zeolitic materials is discussed, with an emphasis on the ongoing struggles regarding mass‐transfer issues. The state‐of‐the‐art techniques that are currently available for overcoming these hurdles are reviewed. Following this, the focus is set on core–shell composites as one of the promising pathways toward the creation of a new generation of highly versatile and efficient engineered zeolitic substances. The synthesis approaches developed thus far to make zeolitic core–shell materials and their analogues, yolk–shell, and hollow materials, are also examined and summarized. Finally, the last section concisely reviews the performance of novel core–shell, yolk–shell, and hollow zeolitic materials for some important industrial applications.
Engineered zeolitic materials are of great importance for catalysis or selective adsorption. These modern materials are made by the combination of zeolites as the main building blocks and other secondary components to form composite structures. Herein, critical aspects related to synthesis and modification of zeolitic core–shell materials, yolk–shell, and hollow materials are summarized.
Dry reforming of methane is gaining great interest owing to the fact that this process efficiently converts two greenhouse gases (CH4 and CO2) into synthesis gas (CO + H2), which can be further ...processed into liquid fuels and chemicals. Herein, a perovskite-derived nanostructured Ni/La2O3 material is reported as an efficient and stable catalyst for this reaction. High-surface-area LaNiO3 perovskite precursor is first synthesized by the method of nanocasting using ordered mesoporous silica SBA-15 as a hard template. The resulting nanostructured perovskite was found to possess high specific surface area as obtained from the BET method (150 m2 g–1). The reduction behavior of the nanocast perovskite was monitored by performing the temperature-programmed reduction of hydrogen (TPR-H2). It has been found that the complete destruction of perovskite structure occurs below 700 °C, leading to the formation of highly dispersed Ni0 in La2O3, as observed in the XRD pattern of the material after reduction. Similar behavior was observed for the LaNiO3 perovskite synthesized using the conventional citrate process. However, the specific surface area of the former material was found to be much higher than that of the latter (50 m2 g–1), which obviously resulted from the mesoporous architecture of the nanocast LaNiO3. It was found that the nanostructured Ni/La2O3 obtained from the reduction of the nanocast LaNiO3 exhibited high activity for the conversion of the reactant gases (CH4 and CO2) compared to the catalyst obtained from conventional perovskite, under the reaction conditions used in the present study. Particularly, no coke formation was observed for the mesoporous catalyst under the present conditions of operation, which in turn reflects the enhanced stability of the catalyst obtained from the nanocast LaNiO3. The improved performance of the nanostructured catalyst is attributed to the accessibility of the active sites resulting from the high specific surface area and the confinement effect leading to the stabilization of Ni nanoparticles.
Over the past few years, silica‐based nanotheranostics have demonstrated their great potential for nano/biomedical applications. However, the uncontrollable and difficult degradability of their pure ...silica framework and long‐time in vivo retention still cause severe and unpredictable toxicity risks. Therefore, it is highly desirable to design and synthesize materials with safer framework structures and compositions. To this aim, the introduction of disulfide bonds into the silica framework can not only maintain high stability in physiological conditions, but also achieve a stimuli‐responsive biodegradation triggered by intracellular reducing microenvironment in living cells, especially in cancer cells. Once nanotheranostics with disulfide (i.e., thioether)‐bridged silsesquioxane framework are taken up by tumor cells via passive or active targeting, the disulfide bonds in the hybrid silica matrix can be cleaved by a high concentration of intracellular glutathione, enabling redox‐triggered biodegradation of the nanosystems for both concomitant release of the loaded therapeutic cargo and in vivo clearance. It is envisioned that such hybrid materials comprised of disulfide‐bridged silsesquioxane frameworks can become promising responsive and biodegradable nanotheranostics. This review summarizes the recent advances in the synthesis of hybrid organosilicas with disulfide‐bridged silsesquioxane frameworks, and discuss their redox‐triggered biodegradation behaviors combined with their biocompatibility and nanobiomedical applications.
An overview of the designed synthesis of nanomaterials consisting of disulfide‐bridged organosilica frameworks, their intracellular redox‐triggered biodegradation behaviors, and emerging nanobiomedical applications is provided in this feature article.
Oral ingestion remains as the most convenient route of administration for the application of pharmaceuticals since it is non-invasive and does not require trained personnel to administer the drugs. ...Despite significant progress in novel oral drug delivery platforms over the past few decades, the oral delivery of macromolecules (particularly for peptides and proteins) is one of the major challenges faced by the biopharmaceutical industry. This is even more important since a large number of biologic drugs have been available in the past decade which typically require intravenous administration. Recently, silica nanoparticles have emerged as multifunctional, biocompatible and biodegradable inorganic nanocarriers with enormous potential as an oral drug delivery platform for various therapeutics including macromolecules. Their unique structural composition facilitates the loading of large therapeutic payloads at desired loading capacities for a controlled and site-specific oral delivery. Here, we review first the physiological challenges for oral delivery of peptides and proteins. Next, we discuss silica-based functional materials for oral delivery of macromolecules and highlight their evolving role not only as an encapsulant but as a permeation enhancer as well. Lastly, we also discuss potential strategies for future translation of these novel materials to the clinic.
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An Au/TiO2 nanostructure was constructed to obtain a highly efficient visible‐light‐driven photocatalyst. The design was based on a three‐dimensional ordered assembly of thin‐shell Au/TiO2 hollow ...nanospheres (Au/TiO2‐3 DHNSs). The designed photocatalysts exhibit not only a very high surface area but also photonic behavior and multiple light scattering, which significantly enhances visible‐light absorption. Thus Au/TiO2‐3 DHNSs exhibit a visible‐light‐driven photocatalytic activity that is several times higher than conventional Au/TiO2 nanopowders.
Order makes a difference: A three‐dimensional ordered assembly of thin‐shell Au/TiO2 hollow nanospheres exhibits not only a very high surface area but also photonic behavior and multiple light scattering. The designed materials show significantly enhanced visible‐light absorption and a visible‐light‐driven photocatalytic activity several times higher than those of conventional Au/TiO2 nanopowders.
A versatile synthetic method based on solvothermal technique has been developed for the fabrication of TiO2 nanocrystals with different shapes such as rhombic, truncated rhombic, spherical, dog-bone, ...truncated and elongated rhombic, and bar. The central features of our approach are the use of water vapor as hydrolysis agent to accelerate the reaction and the use of both oleic acid and oleylamine as two distinct capping surfactants which have different binding strengths to control the growth of the TiO2 nanoparticles. We also show that the presence of an appropriate amount of water vapor along with the desired oleic acid/oleylamine molar ratio plays a crucial role in controlling size and shape of TiO2 nanocrystals.
The present study is concerned with the nanocasting preparation of Co3O4 nanostructures employing two-dimensional (2D) hexagonal SBA-15 and three-dimensional (3D) cubic KIT-6 as hard templates. The ...influence of framework connectivity of the parent silica and loading of the cobalt source are studied in detail. Structures can be tailored as isolated or randomly organized Co3O4 nanowires or as highly ordered mesoporous Co3O4 networks retaining the symmetry of the silica parent using 2D hexagonal parent materials. Applying cubic KIT-6 silica with suitable wall thickness and degree of framework interconnectivity as a template, we can vary the pore size of mesostructured Co3O4 from 3 nm up to values as high as 10 nm. To verify the influence of surface properties and texture, we employed different mesoporous silicas that were conventionally calcined at 550 °C and equivalent silica materials microwave treated in the presence of a concentrated H2O2/HNO3 mixture. The parent silica materials and the resulting Co3O4 were characterized in detail at different steps during the templating route by nitrogen physisorption measurements and powder X-ray diffraction. Transmission electron microscopy and scanning electron microscopy investigations were performed to visualize the structure and morphology of the nanocast materials, and thermogravimetry−differential thermal analyses (TG−DTA) were done to follow the formation of Co3O4. With our method, preparation of nanocast Co3O4 is highly reproducible, regardless of template shapes and sizes, which makes the pathway much more versatile for a great variety of templates.
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