Hierarchical Mesoporous Organosilica-Silica Core-Shell Nanoparticles Capable of Controlled Fungicide Release

Samarium- and Ytterbium-Grafted Periodic Mesoporous Silica for Carbon Dioxide Capture and Conversion

Immobilized coordination compounds of Lewis acidic metals are powerful catalytic components of systems for the cycloaddition of CO2 to epoxides that do not require sophisticated coordination frameworks to harness the metal center and modulate its activity. Surface organometallic chemistry (SOMC) is a valuable methodology to prepare well-defined and site-isolated surface complexes and coordination compounds on metal oxides, with ligand environments easily adjustable to a targeted catalytic reaction. In this work, the SOMC methodology is applied to prepare SmII, YbII, and SmIII alkoxide surface complexes on periodic mesoporous (organo)silica of distinct pore symmetry/size for application in the CO2 cycloaddition reaction. The surface complexes are readily accessible by the grafting of the bis(trimethylsilyl)amide precursors LnII[N(SiMe3)2]2(THF)2 (Ln = Sm, Yb) and SmIII[N(SiMe3)2]3, followed by ligand exchange with alcohols (ethanol and neopentanol). The use of periodic mesoporous supports led to hybrid materials with relatively high surface areas and pore sizes, affording good performance in CO2 capture and in the cycloaddition of CO2 to epoxides under mild conditions (60-80 °C, 1-10 bar). In terms of catalytic performance, recyclability, and low amount of added nucleophile TBAX (X = Br, I), the most active materials prepared in this work compare well to a variety of previously reported SOMC-derived surface complexes and to other heterogeneous Lewis acids displaying more elaborate ligand environments.

Biobased, Macro-, and Nanoscale Fungicide Delivery Approaches for Plant Fungi Control

In this report, two polymeric matrix systems at macro and nanoscales were prepared for efficacious fungicide delivery. The macroscale delivery systems used millimeter-scale, spherical beads composed of cellulose nanocrystals and poly(lactic acid). The nanoscale delivery system involved micelle-type nanoparticles, composed of methoxylated sucrose soyate polyols. Sclerotinia sclerotiorum (Lib.), a destructive fungus affecting high-value industrial crops, was used as a model pathogen against which the efficacy of these polymeric formulations was demonstrated. Commercial fungicides are applied on plants frequently to overcome the transmission of fungal infection. However, fungicides alone do not persist on the plants for a prolonged period due to environmental factors such as rain and airflow. There is a need to apply fungicides multiple times. As such, standard application practices generate a significant environmental footprint due to fungicide accumulation in soil and runoff in surface water. Thus, approaches are needed that can either increase the efficacy of commercially active fungicides or prolong their residence time on plants for sustained antifungal coverage. Using azoxystrobin (AZ) as a model fungicide and canola as a model crop host, we hypothesized that the AZ-loaded macroscale beads, when placed in contact with plants, will act as a depot to release the fungicide at a controlled rate to protect plants against fungal infection. The nanoparticle-based fungicide delivery approach, on the other hand, can be realized via spray or foliar applications. The release rate of AZ from macro- and nanoscale systems was evaluated and analyzed using different kinetic models to understand the mechanism of AZ delivery. We observed that, for macroscopic beads, porosity, tortuosity, and surface roughness governed the efficiency of AZ delivery, and for nanoparticles, contact angle and surface adhesion energy were directing the efficacy of the encapsulated fungicide. The technology reported here can also be translated to a wide variety of industrial crops for fungal protection. The strength of this study is the possibility of using completely plant-derived, biodegradable/compostable additive materials for controlled agrochemical delivery formulations, which will contribute to reducing the frequency of fungicide applications and the potential accumulation of formulation components in soil and water.

Highly Dispersed Pt Catalysts on Hierarchically Mesoporous Organosilica@Silica Nanoparticles with a Core-Shell Structure for Polycyclic Aromatic Hydrogenation

Hydrogenation of naphthalene can effectively reduce the content of aromatics in oil and generate high-value products. A series of Pt-based aluminum-modified core-shell-structured hierarchically periodic mesoporous organosilica@mesoporous silica nanoparticles (Pt/Al-x-PMOs@MSNs) were successfully synthesized and tested for the hydrogenation properties, with preferable mass transfer of macromolecular reactants in the pores and increasing the total acidity of the catalysts. Moreover, the physicochemical properties of the core-shell-structured Pt-based catalysts were systematically analyzed using various characterization techniques. At 300 °C, the naphthalene conversion on the Pt/Al-10-PMOs@MSNs catalyst reached up to 100%, the selectivity of trans-decalin reached 83.9%, and the rate constants (k₁, k₂) and TOF were 13.2 × 10^-6 mol·g^-1·s^-1, 1.7 × 10^-7 mol·g^-1·s^-1, and 218.8 h^-1, respectively. In the presence of sulfur, the naphthalene hydrogenation over the Pt/Al-10-PMOs@MSN catalyst first decreased to around 40% and then recovered to the original level, which originated from the synergistic effect of the texture and chemical properties over the Pt/Al-10-PMOs@MSNs with an excellent performance.

Recent advanced development of metal-loaded mesoporous organosilicas as catalytic nanoreactors

Ordered periodic mesoporous organosilicas have been widely applied in adsorption/separation/sensor technologies and the fields of biomedicine/biotechnology as well as catalysis. Crucially, surface modification with functional groups and metal complexes or nanoparticle loading has ensured high efficacy and efficiency. This review will highlight the current state of design and catalytic application of transition metal-loaded mesoporous organosilica nanoreactors. It will outline prominent synthesis approaches for the grafting of metal complexes, metal salt adsorption and in situ preparation of metal nanoparticles, and summarize the catalytic performance of the resulting mesoporous organosilica hybrid materials. Finally, the potential prospects and challenges of metal-loaded mesoporous organosilica nanoreactors are addressed.

Anisotropic and Amphiphilic Mesoporous Core-Shell Silica Microparticles Provide Chemically Selective Environments for Simultaneous Delivery of Curcumin and Quercetin

Porous silica materials are often used for drug delivery. However, systems for simultaneous delivery of multiple drugs are scarce. Here we show that anisotropic and amphiphilic dumbbell core-shell silica microparticles with chemically selective environments can entrap and release two drugs simultaneously. The dumbbells consist of a large dense lobe and a smaller hollow hemisphere. Electron microscopy images show that the shells of both parts have mesoporous channels. In a simple etching process, the properly adjusted stirring speed and the application of ammonium fluoride as etching agent determine the shape and the surface anisotropy of the particles. The surface of the dense lobe and the small hemisphere differ in their zeta potentials consistent with differences in dye and drug entrapment. Confocal Raman microscopy and spectroscopy show that the two polyphenols curcumin (Cur) and quercetin (QT) accumulate in different compartments of the particles. The overall drug entrapment efficiency of Cur plus QT is high for the amphiphilic particles but differs widely between Cur and QT compared to controls of core-shell silica microspheres and uniformly charged dumbbell microparticles. Furthermore, Cur and QT loaded microparticles show different cancer cell inhibitory activities. The highest activity is detected for the dual drug loaded amphiphilic microparticles in comparison to the controls. In the long term, amphiphilic particles may open up new strategies for drug delivery.

Self-transformation synthesis of hierarchically porous benzene-bridged organosilica nanoparticles for efficient drug delivery

Herein, a feasible outside-in hydrothermal self-transformation strategy is presented to fabricate hierarchically porous benzene-bridged organosilica nanoparticles (HPBONs), and detailed mechanistic investigations were performed to study the formation of hierarchically porous nanostructures. The obtained HPBONs consisted of a mesoporous core (2.3 nm) and a large mesoporous flocculent shell (12.6 nm), which corresponded to an overall diameter of ∼ 200 nm and good water dispersibility, respectively. Owing to the unique hierarchically porous structure and high surface area (877 m²/g), HPBONs showed a high coloading capacity for the hydrophilic drug doxorubicin (DOX) and the hydrophobic photosensitizer chlorin e6 (Ce6) (355 µg/mg, 38 µg/mg, respectively) and acid-responsive DOX drug release (42.62%), leading to precise chemo-photodynamic therapy in vitro, as the cytotoxicity assay revealed 70% killing of breast cancer (MCF-7) cells. This research provides a new method to construct hierarchically porous organosilica-based nanodelivery systems.

Size Effect of Mesoporous Silica Nanoparticles on Pesticide Loading, Release, and Delivery in Cucumber Plants

Mesoporous silica nanoparticles (MSN) are widely used as pesticide carriers to enhance their effective utilization, since it can promote the solubility and absorption of pesticides by plants. For plants, the particle size of pesticides influences their absorption and efficacy. Herein, is our research work of the size effect of MSN on the loading, release, and delivery behavior of pyraoxystrobin (Pyr) in cucumber plants. The well-ordered Pyr-loaded carbon quantum dots-MSN (Pyr@M) with sizes of 15, 100, and 200 nm were prepared. A comparative study among different particle sizes of Pyr@M was carried out on the aspects of control release performance, loading content, uptake, and transportation performance in cucumber plants. It was found that the loading content increased as the particle size increased. The nanoparticles as carriers increased the solubility of insoluble Pyr, but the nanoparticle size had no clear difference impact on the release rate. The efficiency of the cellular uptake strongly depended on the particle size. The smaller the MSN size, the easier it was to be absorbed and transmitted by cucumber plants. Compared to the free Pyr, the upward transportation rate of Pyr from Pyr@M in plant increased by 3.5 times. These findings provide new theoretical basis to design the MSN pesticide delivery system.

Recent advances and remaining barriers to producing novel formulations of fungicides for safe and sustainable agriculture

BACKGROUND

Fungi have evolved for 1 billion years and due to their adaptability and resilience can be found in multiple habitats around the globe. Among numerous species of fungi, some are pathogenic, and humans have battled since the dawn of organized agriculture to reduce production losses. With the arrival of fungicides many gains have been made in this struggle. However, though fungicides have greatly contributed to substantial increase in agricultural productivity, their over usage has led to both health and environmental repercussions. They remain cornerstone of the agriculture industry, however, development of safer formulations to champion sustainable and eco-friendly agriculture is of great importance, especially in face of a growing global population, climate change and increasing fungal resistance to existing compounds.

SCOPE AND APPROACH

The aim of this review is to present the state of the art in fungicides formulations developed for agrochemistry, also describing recent improvements in their safety, with special focus on fungicides used most against the ten most important fungal pathogens.

KEY FINDINGS AND CONCLUSIONS

The major focus in the field remains to be the improvement of the overall performance of the fungicide formulations. The research trends are also moving towards developing more eco-friendly formulations. However, there are still very few studies assessing nanoformulations toxicity and environmental impact. For example, there is still a limited body of research on the holistic assessment of nanoformulation shells' fate in soil and in the environment after release, as well as redistribution within plants after absorption, with no studies on human or environmental exposure.

Nanoporous hybrid core–shell nanoparticles for sequential release

Silica inside – organosilica outside, and nanoporous throughout: Drug molecules to be released sequentially from novel core–shell nanoparticles select their location (core/shell) autonomously.

Hydrophobicity-responsive engineered mesoporous silica nanoparticles: application in the delivery of essential nutrients to bacteria combating oil spills

Facile chemical modification of mesoporous silica particles allows the production of gated reservoir systems capable of hydrophobicity-triggered release. Applied to the delivery of nutrients specifically to an oil phase, the systems developed have been shown to reliably assist the bacterial degradation of hydrocarbons. The gated system developed, made of C₁₈ hydrocarbon chains, is demonstrated to be in a closed collapsed state in an aqueous environment, yet opens up through solvation by lipophilic alkanes and releases its content on contact with the oil phase.