Introducing reticular chemistry into agrochemistry

MOF Hybrid for Long-Term Pest Management and Micronutrient Supply Triggered with Protease

Advanced intelligent systems for delivery of pesticides or fertilizers require formulations that allow for long-term efficacy. In this work, a metal-organic framework (MOF) hybrid was developed for long-term pest management and micronutrient supply. Zeolitic imidazolate framework-8 was fabricated for crop micronutrients (Zn²⁺) supply and insecticide dinotefuran (DNF) encapsulation. Polymethylmethacrylate was polymerized in situ to impart the MOF hybrid with sustained cargo delivery. Then, zein was introduced to facilitate protease-triggered cargo release associated with the microenvironment of pests and targeted release. The resulting MOF hybrid exhibited stimulus-responsive, slow-release behaviors. Sustained DNF delivery was achieved over a period of at least 32 days in soil. Compared with that of free DNF, the UV resistance of DNF in the MOF hybrid increased by nearly 10 times, and the insecticidal efficiency increased 33.3% with leaching treatment and 40.1% after incubating in a greenhouse for 14 days. This MOF hybrid provides a controlled, targeted, and sustained delivery formulation for long-term pest management and crop micronutrient supply and has huge application prospects in sustainable agriculture.

Indole/Tetrahydroquinoline as Renewable Natural Resource-Inspired Scaffolds in the Devising and Preparation of Potential Fungicide Candidates

As a continuous effort toward developing novel and highly efficient agrochemicals for integrated management of crop pathogens, two series of oxime ester derivatives from indole and tetrahydroquinoline natural scaffolds were prepared. Guided by the preliminary inhibition rates against ubiquitous and representative fungi, the antifungal profile of the target compounds against Valsa mali was intensively and extensively studied. The tetrahydroquinoline-based derivatives 12a-12r exerted a promising inhibition effect, especially against V. mali. The remarkable compounds 12p (R = 4-OCF₃) and 12r (R = 4-OBn) with EC₅₀ values of 0.81 and 0.47 μg/mL, respectively, have a far more prominent activity than commercial fungicide trifloxystrobin. The biochemistry and physiology responses of V. mali after treatment with target compound 12p was examined, and the fruit body production, hyphae morphology, and organelles were profoundly affected. Moreover, the curative effects of compound 12p on apple detached branches and leaves were 57.69 and 64.84% at 100 μg/mL, respectively, which were even superior to that of trifloxystrobin. Meanwhile, the three-dimensional quantitative structure-activity relationship model [comparative molecular field analysis (CoMFA): q² = 0.823, r² = 0.924, F = 189.781, and standard error of estimation (SEE) = 0.138 and comparative molecular similarity index analysis (CoMSIA): q² = 0.795, r² = 0.904, F = 145.644, and SEE = 0.156] indicated that the antifungal activity of target compounds was facilitated by crucial structural factors, which would render inspiration for further design and discovery of novel fungicidal candidates.

A fluorescence aptasensor based on carbon quantum dots and magnetic Fe3O4 nanoparticles for highly sensitive detection of 17β-estradiol

Trace amounts of 17β-estradiol (E2) in food and the environment poses a threat to human health, which has created the demand for sensitive analytical methods to detect E2. In this study, a novel fluorescent aptasensor was developed for sensitive detection of E2 based on double-chain hybridization between carbon quantum dots-labelled with E2 aptamer (CQDs-aptamer) and Fe₃O₄ nanoparticles modified by complementary DNA (Fe₃O₄-cDNA). Under the optimal conditions, the aptasensor displayed a good linear range of 10^-11-10^-6 M for E2 with the coefficient of determination (R²) of 0.996, and a low detection limit of 3.48 × 10^-12 M was obtained. Besides, the aptasensor showed high selectivity and good reproducibility for E2 detection, which was successfully applied to the sensitive detection of E2 in milk as compared with tap water and lake water with satisfactory recoveries from 85.21% to 114.80%, suggesting the great significance of this aptasensor for detecting food contaminants in the food industry.

Novel graphene oxide/polymer composite membranes for the food industry: structures, mechanisms and recent applications

The membrane can not only be used as food packaging, but also for the separation, fractionation and recovery of food ingredients. Graphene oxide (GO) sheets are a two-dimensional (2 D) material with a unique structure that exhibit excellent mechanical properties, biocompatibility, and flexibility. The corporation of polymer matrix membrane with GO can significantly improve the permeability, selectivity, and antibacterial activity. In this review, the chemical structures of GO, GO membranes and GO/polymer composite membranes are introduced, the permeation mechanisms of molecules through the membranes are discussed and key factors affecting the permeability are presented in detail. In addition, recent applications in the food industry for filtration, bioreactions and active food packaging are analyzed, and limitations and future trends of GO membranes development are also highlighted. GO/polymer composite membranes exhibit excellent permeability, selectivity and strong barrier properties against bacterial and gas permeation. However, current food material filtration and packaging applications of GO/polymer composite membranes are still in the laboratory stage. Future work can focus on the development of large scale uniformly sized GO production, the homogeneous distribution and tight combination of GO in polymer matrixes, the sensing function of GO in packaging, and the verification method of GO toxicology.

Interfacing metal-polyphenolic networks upon photothermal gold nanorods for triplex-evolved biocompatible bactericidal activity

Gold nanorods (GNRs) outstand in photothermal disinfection but are faced with severe surface chemistry and dose relevant biotoxicity. Herein, a naturally green building block, metal-phenolic networks (MPNs), was employed to functionalize GNRs via coordination reaction, yielding a tunable and biocompatible core-shell photothermal nano-bactericide (GNRs@MPNs). The bioactive GNRs@MPNs built with iron and polyphenols (tannic acid, epigallocatechin gallate, and procyanidins) exhibited superior light-to-heat conversion efficiencies with η = 29.29-44.00%, remarkably preceding that of GNRs (η = 12.24%), which could rapidly ablate 99.8% of Escherichia coli O157: H7 and 98.6% of Staphylococcus aureus bacteria in relatively low efficacy doses (10 ppm of Au). Moreover, local heat triggered by GNRs@MPNs accelerated the healing of the cutaneous wound of a mice model infected by methicillin-resistant S. aureus. The facile synthesis, photothermal synergy, polyphenolic bioactivity, and significantly low efficacy dose of GNRs@MPNs empower them satisfactory efficiency and biosafety in the future broad-spectrum photothermal sterilization applications.

Ti3C2Tx MXenes loaded with Au nanoparticle dimers as a surface-enhanced Raman scattering aptasensor for AFB1 detection

Mycotoxin B1 (AFB1) contamination in agricultural products pose a deadlydangertoanimal and human health and its rapid and reliable detection is thus very important. Herein, a ratiometric surface-enhanced Raman scattering (SERS) aptasensor for AFB1 detection was developed, in which 1,2-bis(4-pyridyl) ethylene (BPE) was used to trigger the assembly of Au nanoparticle dimers (AuNP dimers) and form intensive SERS "hot spots", and MXenes nanosheets could load aptamer-modified AuNP dimers due to the hydrogen bonding and the chelation between the phosphate groups of aptamers and the Ti ion of MXenes. With the presence of AFB1 preferentially binding to AFB1 aptamer, AuNP dimers were separated from MXenes nanosheets, leading to a decrease in SERS intensity. Regression analysis in the range from 0.001 to 100 ng·mL^-1 showed the limit of detection (LOD) being 0.6 pg·mL^-1 in standard solution, indicating that the great prospects of the AuNP dimers/MXenes SERS substrate for detecting AFB1.

A Novel Cerium(IV)-Based Metal-Organic Framework for CO2 Chemical Fixation and Photocatalytic Overall Water Splitting

Cerium (IV)-based metal-organic frameworks (MOFs) are highly desirable due to their unique potential in fields such as redox catalysis and photocatalysis. However, due to the high reduction potential of Ce^IV species in solution, it is still a great challenge to synthesize Ce^IV -MOFs with novel structures, which are extremely dominated by the hexanuclear Ce-O cluster inorganic building units (IBUs). Herein, a Ce-O IBU chain containing Ce^IV -MOF, CSUST-3 (CSUST: Changsha University of Science and Technology), was successfully prepared using the kinetic stabilization study of UiO-66(Ce)-NDC (H₂ NDC=2,6-naphthalenedicarboxylic acid). Furthermore, owing to the superior redox activity, Lewis acidity and semiconductor-like behavior owing to Ce⁴⁺ , activated CSUST-3 was demonstrated to be an excellent catalyst for CO₂ chemical fixation. One-pot synthesis of styrene carbonate from styrene and CO₂ was achieved under mild conditions (1 atm CO₂ , 80 °C, and solvent free). Moreover, activated CSUST-3 was shown to be a remarkable co-catalyst-free photocatalyst for overall water splitting (OWS), rendering 59 μmol g^-1  h^-1 of H₂ and 22 μmol g^-1  h^-1 of O₂ under simulated sunlight irradiation (Na₂ S-Na₂ SO₃ as sacrificial agent).

A dual AE-GAN guided THz spectral dehulling model for mapping energy and moisture distribution on sunflower seed kernels

Energy and moisture contents are important food chemical attributes. In the current study, a nondestructive Terahertz (THz) time-domain imaging system was first time used for evaluating the energy and moisture distributions of sunflower seed kernels inside shells. For this task, a dual autoencoders (AE)-generative adversarial nets (GAN) spectral dehulling semi-supervised model was developed. The model could automatically learn the kernel information from the latent representations of the spectra of the intact seeds through adversarial learning to achieve feature disentanglement. Results indicated that the generated kernel images had similar features to the original kernel images and high-quality chemical distribution maps for energy and moisture contents of sunflower seed kernels inside shells were successfully obtained. As the current method took the advantage of the characteristics of THz imaging and selected a suitable deep learning algorithm, it has the potential to generalize for imaging other chemical substances of other dry shelled seeds or biological samples (moisture content and thickness below 15% and 5 mm, respectively).

Precision release systems of food bioactive compounds based on metal-organic frameworks: synthesis, mechanisms and recent applications

Controlled release (CR) systems have become a powerful platform for accurate and effective delivery of bioactive compounds (BCs). Metal-organic frameworks (MOFs) are one of the best BCs-loaded carriers for CR systems. In the review, the principles and methods of the design and synthesis of MOFs-CR systems are summarized in detail, the encapsulation of BCs by MOFs and CR mechanisms are explored, and their biological toxicity and biocompatibility are highlighted and applications in the food industry are discussed. In addition, current challenges in this field and possible future development directions are also presented. MOFs have been proven to encapsulate BCs effectively, including gaseous and solid molecules, and control the release of BCs through spontaneous diffusion or stimulus-response. The solubility, stability and biocompatibility of BCs encapsulated by MOFs are greatly improved, which expands their applications in foods. The effective CR of BCs by MOFs-CR systems is beneficial to assist in maintaining or even improving the quality and safety of food, reduce the BCs usage while increasing the bioavailability. Low- or non-biotoxic MOFs, especially bio-MOFs, show greater application prospects in the food industry.

Antifungal Exploration of Quinoline Derivatives against Phytopathogenic Fungi Inspired by Quinine Alkaloids

Enlightened from our previous work of structural simplification of quinine and innovative application of natural products against phytopathogenic fungi, lead structure 2,8-bis(trifluoromethyl)-4-quinolinol (3) was selected to be a candidate and its diversified design, synthesis, and antifungal evaluation were carried out. All of the synthesized compounds Aa1-Db1 were evaluated for their antifungal activity against four agriculturally important fungi, Botrytis cinerea, Fusarium graminearum, Rhizoctonia solani, and Sclerotinia sclerotiorum. Results showed that compounds Ac3, Ac4, Ac7, Ac9, Ac12, Bb1, Bb10, Bb11, Bb13, Cb1. and Cb3 exhibited a good antifungal effect, especially Ac12 had the most potent activity with EC₅₀ values of 0.52 and 0.50 μg/mL against S. sclerotiorum and B. cinerea, respectively, which were more potent than those of the lead compound 3 (1.72 and 1.89 μg/mL) and commercial fungicides azoxystrobin (both >30 μg/mL) and 8-hydroxyquinoline (2.12 and 5.28 μg/mL). Moreover, compound Ac12 displayed excellent in vivo antifungal activity, which was comparable in activity to the commercial fungicide boscalid. The preliminary mechanism revealed that compound Ac12 might cause an abnormal morphology of cell membranes, an increase in membrane permeability, and release of cellular contents. These results indicated that compound Ac12 displayed superior in vitro and in vivo fungicidal activities and could be a potential fungicidal candidate against plant fungal diseases.

MOF-based multi-stimuli-responsive supramolecular nanoplatform equipped with macrocycle nanovalves for plant growth regulation

Controllable and on-demand delivery of agrochemicals such as plant hormones is conducive to improving agrochemicals utilization, tackling water and environmental pollution, reducing soil acidification, and realizing the goals of precision agriculture. Herein, a smart plant hormone delivery system based on metal-organic frameworks (MOFs) and supramolecular nanovalves, namely gibberellin (GA)-loaded CLT6@PCN-Q, is constructed through supramolecular host-guest interaction to regulate the growth of dicotyledonous Chinese cabbage and monocotyledonous wheat. The porous nanoscale MOF (NMOF) with a uniform diameter of 97 nm modified by quaternary ammonium (Q) stalks is served as a cargo reservoir, followed by the decoration of carboxylated leaning tower[6]arene (CLT6) based nanovalves on NMOF surfaces through host-guest interactions to fabricate CLT6@PCN-Q with a diameter of ∼101 nm and a zeta potential value of -13.2 mV. Interestingly, the as-fabricated supramolecular nanoplatform exhibits efficient cargo loading and multi-stimuli-responsive release under various external stimuli including pH, temperature, and competitive agent spermine (SPM), which can realize the on-demand release of cargo. In addition, GA-loaded CLT6@PCN-Q is capable of effectively promoting the seeds germination of wheat and stem growth of dicotyledonous Chinese cabbage and monocotyledonous wheat (1.86 and 1.30 times of control groups, respectively). The smart supramolecular nanoplatform based on MOFs and supramolecular nanovalves paves a way for the controlled delivery of plant hormones and other agrochemicals for promoting plant growth, offering new insights and methods to realize precision agriculture. STATEMENT OF SIGNIFICANCE: To achieve controllable and sustainable release of cargos such as agrochemicals, a smart MOF-based multi-stimuli-responsive supramolecular nanoplatform equipped with supramolecular nanovalves was fabricated via the host-guest interaction between quaternary ammonium stalks-functionalized nanoMOFs and water-soluble leaning tower[6]arene. The as-prepared supramolecular nanoplatform with uniform diameter distribution demonstrated good cargo release in response to various external stimuli. The installation of synthetic macrocycles could effectively reduce cargo loss in the pre-treatment process. This type of supramolecular nanoplatform exhibited good promoting effect on seed germination and plant growth dicotyledonous Chinese cabbage and monocotyledonous wheat. As an eco-friendly, controlled, and efficient cargo delivery system, this supramolecular nanoplatform will be a promising candidate in precision agriculture and controlled drug release to attract the broad readership.

Metal-organic frameworks for chemical sensing devices

Metal-organic frameworks (MOFs) are exceptionally large surface area materials with organized porous cages that have been investigated for nearly three decades. Due to the flexibility in their design and predisposition toward functionalization, they have shown promise in many areas of application, including chemical sensing. Consequently, they are identified as advanced materials with potential for deployment in analytical devices for chemical and biochemical sensing applications, where high sensitivity is desirable, for example, in environmental monitoring and to advance personal diagnostics. To keep abreast of new research, which signposts the future directions in the development of MOF-based chemical sensors, this review examines studies since 2015 that focus on the applications of MOF films and devices in chemical sensing. Various examples that use MOF films in solid-state sensing applications were drawn from recent studies based on electronic, electrochemical, electromechanical and optical sensing methods. These examples underscore the readiness of MOFs to be integrated in optical and electronic analytical devices. Also, preliminary demonstrations of future sensors are indicated in the performances of MOF-based wearables and smartphone sensors. This review will inspire collaborative efforts between scientists and engineers working within the field of MOFs, leading to greater innovations and accelerating the development of MOF-based analytical devices for chemical and biochemical sensing applications.

Bioinspired Nanomodification Strategies: Moving from Chemical-Based Agrosystems to Sustainable Agriculture

Agrochemicals have supported the development of the agricultural economy and national population over the past century. However, excessive applications of agrochemicals pose threats to the environment and human health. In the last decades, nanoparticles (NPs) have been a hot topic in many fields, especially in agriculture, because of their physicochemical properties. Nevertheless, the prevalent methods for fabricating NPs are uneconomical and involve toxic reagents, hindering their extensive applications in the agricultural sector. In contrast, inspired by biological exemplifications from microbes and plants, their extract and biomass can act as a reducing and capping agent to form NPs without any toxic reagents. NPs synthesized through these bioinspired routes are cost-effective, ecofriendly, and high performing. With the development of nanotechnology, biosynthetic NPs (bioNPs) have been proven to be a substitute strategy for agrochemicals and traditional NPs in heavy-metal remediation of soil, promotion of plant growth, and management of plant disease with less toxicity and higher performance. Therefore, bioinspired synthesis of NPs will be an inevitable trend for sustainable development in agricultural fields. This critical review will demonstrate the bioinspired synthesis of NPs and discuss the influence of bioNPs on agricultural soil, crop growth, and crop diseases compared to chemical NPs or agrochemicals.

Recent developments in Raman spectral analysis of microbial single cells: Techniques and applications

The conventional microbial cell analyses are mostly population-averaged methods that conceal the characteristics of single-cell in the community. Single-cell analysis can provide information on the functional and structural variation of each cell, resulting in the elimination of long and tedious microbial cultivation techniques. Raman spectroscopy is a label-free, noninvasive, and in-vivo method ideal for single-cell measurement to obtain spatially resolved chemical information. In the current review, recent developments in Raman spectroscopic techniques for microbial characterization at the single-cell level are presented, focusing on Raman imaging of single cells to study the intracellular distribution of different components. The review also discusses the limitation and challenges of each technique and put forward some future outlook for improving Raman spectroscopy-based techniques for single-cell analysis. Raman spectroscopic methods at the single-cell level have potential in precision measurements, metabolic analysis, antibiotic susceptibility testing, resuscitation capability, and correlating phenotypic information to genomics for cells, the integration of Raman spectroscopy with other techniques such as microfluidics, stable isotope probing (SIP), and atomic force microscope can further improve the resolution and provide extensive information. Future focuses should be given to advance algorithms for data analysis, standardized reference libraries, and automated cell isolation techniques in future.

Synthesis of bimetallic core-shelled nanoparticles modified by 2-mercaptoethanol as SERS substrates for detecting ferbam and thiabendazole in apple puree

Modification of surface-enhanced Raman spectroscopy (SERS) substrates with thiol ligands is an emerging approach in enhancing the stability and sensitivity of metal substrates due to their good affinity with metals such as Au, Ag, and Cu. Thus, in the current study, 2-mercaptoethanol was used to modify the surface of silver-coated gold nanoparticles to develop a novel SERS substrate for the rapid assessment of fungicide residues in fruit samples. Results showed that the substrate could achieve the detection of ferbam and thiabendazole residues in apple puree with limits of detection of approximately 0.0042 and 0.0064 ppm, high coefficients of determination of 0.9946 and 0.9968, good recoveries ranging from 80 to 105 and 81 to 107% and relative standard deviations of 3.5-7.5 and 3.8-7.9 %, respectively. Therefore, the substrate developed could potentially be utilised to assess other toxic agrochemicals in future.