A non-surfactant self-templating strategy for mesoporous silica nanospheres: beyond the Stöber method

Seeking Cells, Targeting Bacteria: A Cascade-Targeting Bacteria-Responsive Nanosystem for Combating Intracellular Bacterial Infections

Intracellular bacteria pose a great challenge to antimicrobial therapy due to various physiological barriers at both cellular and bacterial levels, which impede drug penetration and intracellular targeting, thereby fostering antibiotic resistance and yielding suboptimal treatment outcomes. Herein, a cascade-target bacterial-responsive drug delivery nanosystem, MM@SPE NPs, comprising a macrophage membrane (MM) shell and a core of SPE NPs. SPE NPs consist of phenylboronic acid-grafted dendritic mesoporous silica nanoparticles (SP NPs) encapsulated with epigallocatechin-3-gallate (EGCG), a non-antibiotic antibacterial component, via pH-sensitive boronic ester bonds are introduced. Upon administration, MM@SPE NPs actively home in on infected macrophages due to the homologous targeting properties of the MM shell, which is subsequently disrupted during cellular endocytosis. Within the cellular environment, SPE NPs expose and spontaneously accumulate around intracellular bacteria through their bacteria-targeting phenylboronic acid groups. The acidic bacterial microenvironment further triggers the breakage of boronic ester bonds between SP NPs and EGCG, allowing the bacterial-responsive release of EGCG for localized intracellular antibacterial effects. The efficacy of MM@SPE NPs in precisely eliminating intracellular bacteria is validated in two rat models of intracellular bacterial infections. This cascade-targeting responsive system offers new solutions for treating intracellular bacterial infections while minimizing the risk of drug resistance.

Rapid Construction of Double Crystalline Prussian Blue Analogue Hetero-Superstructure

The controllable construction of complex metal-organic coordination polymers (CPs) merits untold scientific and technological potential, yet remains a grand challenge of one-step construction and modulating simultaneously valence states of metals and topological morphology. Here, a thiocyanuric acid (TCA)-triggered strategy is presented to one-step rapid synthesis a double-crystalline Prussian blue analogue hetero-superstructure (PBA-hs) that comprises a Co3[Fe(CN)6]2 cube overcoated with a KCo[Fe(CN)6] shell, followed by eight self-assembled small cubes on vertices. Unlike common directing surfactants, TCA not only acts as a trigger for the fast growth of KCo[Fe(CN)6] on the Co3[Fe(CN)6]2 phase resulting in a PBA-on-PBA hetero-superstructure, but also serves as a flange-like bridge between them. By combining experiments with simulations, a deprotonation-induced electron transfer (DIET) mechanism is proposed for formation of second phase in PBA-hs, differing from thermally and photo-induced electron transfer processes. To prove utility, the calcined PBA-hs exhibits enhanced oxygen evolution reaction performance. This work provides a new method to design of novel CPs for enriching chemistry and material science. This work offers a practical approach to design novel CPs for enriching chemistry and material science.

Tetraalkoxysilane-Assisted Self-Emulsification Templating for Controlled Mesostructured Silica Nanoparticles

Although mesoporous silica nanoparticles (MSNs) have been intensively investigated, their mesostructure and formation mechanism are still a topic of debate. Here, we show that MSNS are generated at the interface of the biphasic water-surfactant-triethanolamine-tetraalkoxysilane (TAOS) quaternary system. The spontaneous microemulsification of the hydrophobic TAOS generates microdroplets and direct micelles that both determine the particle size and the pore size. We confirmed also that the dendritic morphology with conical pores is an intermediate species, which readily transforms into regular MSNs concomitantly with the collapse of the microemulsion due to the continuous consumption of TAOS. The prominent effect of the microemulsion on the mechanism growth as a primary template is thoroughly investigated and named here tetraalkoxysilane-assisted self-emulsification templating.

Silica nanoparticles: Biomedical applications and toxicity

Silica nanoparticles (SiNPs) are composed of silicon dioxide, the most abundant compound on Earth, and are used widely in many applications including the food industry, synthetic processes, medical diagnosis, and drug delivery due to their controllable particle size, large surface area, and great biocompatibility. Building on basic synthetic methods, convenient and economical strategies have been developed for the synthesis of SiNPs. Numerous studies have assessed the biomedical applications of SiNPs, including the surface and structural modification of SiNPs to target various cancers and diagnose diseases. However, studies on the in vitro and in vivo toxicity of SiNPs remain in the exploratory stage, and the toxicity mechanisms of SiNPs are poorly understood. This review covers recent studies on the biomedical applications of SiNPs, including their uses in drug delivery systems to diagnose and treat various diseases in the human body. SiNP toxicity is discussed in terms of the different systems of the human body and the individual organs in those systems. This comprehensive review includes both fundamental discoveries and exploratory progress in SiNP research that may lead to practical developments in the future.

Recent Advances in Synthetic and Natural Biomaterials-Based Therapy for Bone Defects

Synthetic and natural biomaterials are a promising alternative for the treatment of critical-sized bone defects. Several parameters such as their porosity, surface, and mechanical properties are extensively pointed out as key points to recapitulate the bone microenvironment. Many biomaterials with this pursuit are employed to provide a matrix, which can supply the specific environment and architecture for an adequate bone growth. Nevertheless, some queries remain unanswered. This review discusses the recent advances achieved by some synthetic and natural biomaterials to mimic the native structure of bone and the manufacturing technology applied to obtain biomaterial candidates. The focus of this review is placed in the recent advances in the development of biomaterial-based therapy for bone defects in different types of bone. In this context, this review gives an overview of the potentialities of synthetic and natural biomaterials: polyurethanes, polyesters, hyaluronic acid, collagen, titanium, and silica as successful candidates for the treatment of bone defects.

Pyromellitic diamide-diacid bridged mesoporous organosilica nanospheres with controllable morphologies: a novel PMO for the facile and expeditious synthesis of imidazole derivatives

In this work, novel pyromellitic diamide-diacid bridged mesoporous organosilica (PMAMOS) nanospheres with controllable morphologies and Brønsted acid catalytic centers were designed and prepared through a convenient method by altering the addition sequence of precursors, solvent, and aging time. The obtained PMAMOSs demonstrate high surface areas and uniform pore sizes. FESEM, HRTEM, BET, EDX, XRD, FTIR and TGA analyses were performed to characterize and examine the effective factors for the preparation of PMAMOS nanospheres. Due to the appropriate physicochemical properties including Brønsted acid centers, suitable surface area and thermal stability of the PMAMOS nanosphere material, it was explored in the three-component reaction of benzyl or benzoin, ammonium acetate, and different aldehyde derivatives as a case study of multicomponent reactions. Corresponding imidazole derivatives were obtained in EtOH under reflux conditions in high to quantitative yields and short reaction times. It was also shown that the heterogeneous solid acid can be reused at least five times with negligible loss of its catalytic activity, indicating the appropriate stability and high activity of the newly introduced mesoporous organosilica.

Controllable synthesis of porous tubular carbon by a Ag+-ligand-assisted Stöber-silica/carbon assembly process

Herein, in this study, we utilized Ag+-ligand interactions for critically regulating the morphology of carbon by the Stöber-silica/carbon co-assembly method for the first time. Tetraethyl orthosilicate (TEOS) and resorcinol/formaldehyde (RF) assemble upon dictation by Ag+ and pyridyl-functionalized surfactants, producing porous carbon tubes (RF1) with a high surface area of 696 m2 g-1 and accessible mesopores ∼15 nm in size. Furthermore, when using tetrapropyl orthosilicate (TPOS) with a slower hydrolysis rate than that of TEOS, carbon tubes (RF2) with enhanced uniformity and a surface area as high as 2112 m2 g-1 are generated. Additionally, when using dopamine hydrochloride instead of RF as a carbon precursor, tubular polydopamine (TDA) with lengths of tens of microns is fabricated, which exhibits excellent catalytic activity toward oxygen reduction reactions in alkaline solutions due to its unique structural feature, a high surface area of 1350 m2 g-1, metallic silver remains of 8.3 wt%, and a rich nitrogen content of 3.6 wt%. This work sheds light on the engineering of a micellar soft template and synthesizing novel nanostructures by the extension of the Stöber method.

Recent Trends in Morphology-Controlled Synthesis and Application of Mesoporous Silica Nanoparticles

The outstanding journey towards the investigation of mesoporous materials commences with the discovery of high surface area porous silica materials, named MCM-41 (Mobil Composition of Matter-41) according to the inventors' name Mobile scientists in the United States. Based on a self-assembled supramolecular templating mechanism, the synthesis of mesoporous silica has extended to wide varieties of silica categories along with versatile applications of all these types in many fields. These silica families have some extraordinary structural features, like highly tunable nanoscale sized pore diameter, good Brunauer-Emmett-Teller (BET) surface areas, good flexibility to accommodate different organic and inorganic functional groups, metals etc., onto their surface. As a consequence, thousands of scientists and researchers throughout the world have reported numerous silica materials in the form of published articles, communication, reviews, etc. Beside this, attention is also given to the morphology-oriented synthesis of silica nanoparticles and their significant effects on the emerging fields of study like catalysis, energy applications, sensing, environmental, and biomedical research. This review highlights a consolidated overview of those morphology-based mesoporous silica particles, emphasizing their syntheses and potential role in many promising fields of research.

In situ semi-transformation from heterometallic MOFs to Fe-Ni LDH/MOF hierarchical architectures for boosted oxygen evolution reaction

Metal-organic frameworks (MOFs) with large surface area, abundant coordination metal centers and tunable structures are regarded as promising electrocatalysts for the water splitting reaction. However, the less accessible active sites and poor stability of MOFs hinder their potential practical applications. Hierarchical double-layer hydroxide (LDH)/MOF electrocatalysts that combine the advantages of two materials are expected to overcome these drawbacks. Herein, we develop a simple and universal strategy, in situ pseudomorphic transformation, to construct hierarchical LDH/MOF electrocatalysts. Accordingly, ultra-thin Fe-Ni LDH nanosheets are in situ produced in the heterometallic MOF during the transformation process. Profiting from the abundant metal sites and the extended electron transport channel from the inserted ultra-thin LDH arrays, the hierarchical Fe-Ni LDH/MOFs exhibit striking electrochemical activities for the oxygen evolution reaction (OER). In particular, the as-synthesized Fe-Ni LDH/MOF-b2 delivers the best OER performance, exhibiting an ultralow overpotential (255 mV at 10 mA cm^-2), minimum Tafel slope (24 mV dec^-1) and outstanding cycling durability. Meanwhile, the evolution process of the hierarchical Fe-Ni LDH/MOF has been monitored with the controllable in situ semi-transformation strategy. This also provides an opportunity to decipher the original active species for the OER process. Mechanism analysis indicates that the bimetallic MOF and bimetallic LDH are both active species, and the excellent OER performance of hierarchical Fe-Ni LDH/MOF could be attributed to the effect of "a whole greater than the sum of the parts".

Comprehensive understanding of the synthesis and formation mechanism of dendritic mesoporous silica nanospheres

The interest in the design and controlled fabrication of dendritic mesoporous silica nanospheres (DMSNs) emanates from their widespread application in drug-delivery carriers, catalysis and nanodevices owing to their unique open three-dimensional dendritic superstructures with large pore channels and highly accessible internal surface areas. A variety of synthesis strategies have been reported, but there is no basic consensus on the elucidation of the pore structure and the underlying formation mechanism of DMSNs. Although all the DMSNs show a certain degree of similarity in structure, do they follow the same synthesis mechanism? What are the exact pore structures of DMSNs? How did the bimodal pore size distributions kinetically evolve in the self-assembly? Can the relative fractions of small mesopores and dendritic large pores be precisely adjusted? In this review, by carefully analysing the structures and deeply understanding the formation mechanism of each reported DMSN and coupling this with our research results on this topic, we conclude that all the DMSNs indeed have the same mesostructures and follow the same dynamic self-assembly mechanism using microemulsion droplets as super templates in the early reaction stage, even without the oil phase.