Organophosphorus hydrolase-poly-β-cyclodextrin as a stable self-decontaminating bio-catalytic material for sorption and degradation of organophosphate pesticide

Applications of Microbial Organophosphate-Degrading Enzymes to Detoxification of Organophosphorous Compounds for Medical Countermeasures against Poisoning and Environmental Remediation

Mining of organophosphorous (OPs)-degrading bacterial enzymes in collections of known bacterial strains and in natural biotopes are important research fields that lead to the isolation of novel OP-degrading enzymes. Then, implementation of strategies and methods of protein engineering and nanobiotechnology allow large-scale production of enzymes, displaying improved catalytic properties for medical uses and protection of the environment. For medical applications, the enzyme formulations must be stable in the bloodstream and upon storage and not susceptible to induce iatrogenic effects. This, in particular, includes the nanoencapsulation of bioscavengers of bacterial origin. In the application field of bioremediation, these enzymes play a crucial role in environmental cleanup by initiating the degradation of OPs, such as pesticides, in contaminated environments. In microbial cell configuration, these enzymes can break down chemical bonds of OPs and usually convert them into less toxic metabolites through a biotransformation process or contribute to their complete mineralization. In their purified state, they exhibit higher pollutant degradation efficiencies and the ability to operate under different environmental conditions. Thus, this review provides a clear overview of the current knowledge about applications of OP-reacting enzymes. It presents research works focusing on the use of these enzymes in various bioremediation strategies to mitigate environmental pollution and in medicine as alternative therapeutic means against OP poisoning.

Cyclodextrin-enhanced photo-induced fluorescence of tau-fluvalinate, molecular modelling of inclusion complexes and determination in natural waters

The effect of adding organized supramolecular systems such as β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) on the photochemically-induced fluorescence (PIF) spectral properties of tau-fluvalinate (TFV) in aqueous solutions was examined. The influence of pH, UV irradiation time and photoproduct stability on the cyclodextrin-enhanced photochemically-induced fluorescence intensity was also investigated. The spectral changes associated with the inclusion process yielded values for the formation constants of TFV inclusion complexes between 450 and 640 M-1, which were calculated using the nonlinear iterative regression approach least squares. In addition, host-guest interaction was clearly determined by PIF enhancement and a 1 : 1 stoichiometry was found for the β-CD and HP-β-CD complexes formed with TFV. The negative free energy (ΔG°) value indicated that the reaction of TFV with cyclodextrins was thermodynamically favorable. Furthermore, the structures of inclusion complexes of TFV with cyclodextrins were elucidated by 3-21G ab initio calculations. The limits of detection and quantification obtained ranged between 1.3 and 4.0 ng mL-1 and from 4.4 to 13.0 ng mL-1 in β-CD and HP-β-CD media, respectively. The analytical application in tap and river water samples yielded satisfactory mean recoveries ranging from 98.12 to 102.97%. Due to its sensitivity and ease of use, this method can be reliably applied to routine analysis.

Critical review on organophosphate esters in water environment: Occurrence, health hazards and removal technologies

Organophosphate esters (OPEs), which are phosphoric acid ester derivatives, are anthropogenic substances that are widely used in commerce. Nevertheless, there is growing public concern about these ubiquitous contaminants, which are frequently detected in contaminated water sources. OPEs are mostly emitted by industrial operations, and the primary routes of human exposure to OPEs include food intake and dermal absorption. Because of their negative effects on both human health and the environment, it is clear that innovative methods are needed to facilitate their eradication. In this study, we present a comprehensive overview of the existing characteristics and origins of OPEs, their possible impacts on human health, and the merits, drawbacks, and future possibilities of contemporary sophisticated remediation methods. Current advanced remediation approaches for OPEs include adsorption, degradation (advanced oxidation, advanced reduction, and redox technology), membrane filtration, and municipal wastewater treatment plants, degradation and adsorption are the most promising removal technologies. Meanwhile, we proposed potential areas for future research (appropriate management approaches, exploring the combination treatment process, economic factors, and potential for secondary pollution). Collectively, this work gives a comprehensive understanding of OPEs, providing useful insights for future research on OPEs pollution.

A supramolecular catalyst based on sodium alginate and viologen calix[4]resorcinol for the room temperature hydrolysis of paraoxon

Properties of paraoxon, such as poor water solubility, low rate of natural decomposition, ability to accumulate in soil and wastewater, lead to the fact that paraoxon is found in various agricultural products and textiles. In this regard, the search for effective ways of paraoxon degradation becomes an extremely urgent problem, which can be solved by creating catalysts by mimicking paraxonase. In this work, a complex of physicochemical methods was used to study the supramolecular interactions of sodium alginate, which has a calcium-binding ability similar to paraxonase, with viologen calix[4]resorcinol and to reveal the nature of the intermolecular interactions between them resulting in the spontaneous formation of nanoparticles. Before proceeding to the investigation of the binding ability of obtained nanoparticles to paraoxon, the encapsulating effect of nanoparticles on a number of model substrates of different solubility (doxorubicin hydrochloride, quercetin and oleic acid) was studied. The kinetics of paraoxon hydrolysis reaction using these nanoparticles was studied at room temperature in an aqueous medium by spectrophotometric method. The rate of this reaction increases with increasing concentration of stable nanoparticles having hydrophobic domains that ensure paraoxon immobilization. The results obtained allow considering the supramolecular polysaccharide/calixarene system as an effective biomimetic catalyst.

Robust and highly reactive membranes for continuous disposal of chemical warfare agents: Effects of nanostructure and functionality in MOF and nanochitin aerogel composites

Developing appropriate disposal of stockpiles of chemical warfare agents (CWAs) has gained significant attention as their lethal toxicity seriously harms humanity. In this study, a novel green-fabrication method with UiO-66 catalysts and amine-functionalized chitin nanofibers (ChNFs) was suggested to prepare durable and highly reactive membranes for decomposing chemical warfare agents (CWAs) in the continuous flow system. The strong interaction between ChNFs and the UiO-66 led to stable loading of the UiO-66 on the continuous nano-porous channel of the ChNF reactive membrane even with high loading of UiO-66 (70 wt% of UiO-66 in the ChNF substrate). In addition, the Brønsted base functionalities (-NH2 and -NHCOCH3) of the ChNF enhanced the catalytic activity and recyclability of the UiO-66. The resulting 70-ChNF composites can effectively decompose a nerve agent simulant (methyl paraoxon) even after 7 repeatable cycles, which has been not obtained in the previous UiO-66 catalyst. The ChNF/UiO-66 reactive membranes with 1 m2 of the area decomposed 130 g of CWAs within an hour in a continuous flow system. We believe these robust and highly reactive membranes can provide a sustainable and efficient solution for the massive CWA disposal and also contribute to the advancement of functional membrane material science.

Effective remediation and decontamination of organophosphorus compounds using enzymes: From rational design to potential applications

Organophosphorus compounds (OPs) have been widely used in agriculture for decades because of their high insecticidal efficiency, which maintains and increases crop yields worldwide. More importantly, OPs, as typical chemical warfare agents, are a serious concern and significant danger for military and civilian personnel. The widespread use of OPs, superfluous and unreasonable use, has caused great harm to the environment and food chain. Developing efficient and environmentally friendly solutions for the decontamination of OPs is a long-term challenge. Microbial enzymes show potential application as natural and green biocatalysts. Thus, utilizing OP-degrading enzymes for environmental decontamination presents significant advantages, as these enzymes can rapidly hydrolyze OPs; are environmentally friendly, nonflammable, and noncorrosive; and can be discarded safely and easily. Here, the properties, structure and catalytic mechanism of various typical OP-degrading enzymes are reviewed. The methods and effects utilized to improve the expression level, catalytic performance and stability of OP-degrading enzymes were systematically summarized. In addition, the immobilization of OP-degrading enzymes was explicated emphatically, and the latest progress of cascade reactions based on immobilized enzymes was discussed. Finally, the latest applications of OP-degrading enzymes were summarized, including biosensors, nanozyme mimics and medical detoxification. This review provides guidance for the future development of OP-degrading enzymes and promotes their application in the field of environmental bioremediation and medicine.

Molecularly imprinted self-buffering double network hydrogel containing bi-amidoxime functional groups for the rapid hydrolysis of organophosphates

The development of high-performance catalyst materials with high catalytic activity for the hydrolysis of organophosphorus toxicants without additional pH buffer conditions has become an urgent need for practical application. Here, a multifunctional molecularly imprinted polymer double network hydrogel (MIP-DN) material has been prepared by integrating the first polymer network containing the functional group of bi-amidoxime as the catalytic active center and the cationic polymer polyethyleneimine (PEI) with pH buffer function as the main component of the second network. Advantageously, the resultant MIP-DN hydrogel showed excellent catalytic performance without additional pH buffer conditions, exhibiting a half-life of 25 min for the hydrolysis of paraoxon in pure water. Together with multi-functions of high catalytic activity, self-buffering function and excellent processability, the MIP-DN hydrogel prepared in this work provides a new strategy for the preparation of catalytic materials with practical application value toward toxic organophosphates.

Carrier Variety Used in Immobilization of His6-OPH Extends Its Application Areas

Organophosphorus hydrolase, containing a genetically introduced hexahistidine sequence (His6-OPH), attracts the attention of researchers by its promiscuous activity in hydrolytic reactions with various substrates, such as organophosphorus pesticides and chemical warfare agents, mycotoxins, and N-acyl homoserine lactones. The application of various carrier materials (metal-organic frameworks, polypeptides, bacterial cellulose, polyhydroxybutyrate, succinylated gelatin, etc.) for the immobilization and stabilization of His6-OPH by various methods, enables creation of biocatalysts with various properties and potential uses, in particular, as antidotes, recognition elements of biosensors, in fibers with chemical and biological protection, dressings with antimicrobial properties, highly porous sorbents for the degradation of toxicants, including in flow systems, etc. The use of computer modeling methods in the development of immobilized His6-OPH samples provides in silico prediction of emerging interactions between the enzyme and immobilizing polymer, which may have negative effects on the catalytic properties of the enzyme, and selection of the best options for experiments in vitro and in vivo. This review is aimed at analysis of known developments with immobilized His6-OPH, which allows to recognize existing recent trends in this field of research, as well as to identify the reasons limiting the use of a number of polymer molecules for the immobilization of this enzyme.

Bacterial remediation of pesticide polluted soils: Exploring the feasibility of site restoration

For decades, reclamation of pesticide contaminated sites has been a challenging avenue. Due to increasing agricultural demand, the application of synthetic pesticides could not be controlled in its usage, and it has now adversely impacted the soil, water, and associated ecosystems posing adverse effects on human health. Agricultural soil and pesticide manufacturing sites, in particular, are one of the most contaminated due to direct exposure. Among various strategies for soil reclamation, ecofriendly microbial bioremediation suffers inherent challenges for large scale field application as interaction of microbes with the polluted soil varies greatly under climatic conditions. Methodically, starting from functional or genomic screening, enrichment isolation; functional pathway mapping, production of tensioactive metabolites for increasing the bioavailability and bio-accessibility, employing genetic engineering strategies for modifications in existing catabolic genes to enhance the degradation activity; each step-in degradation study has challenges and prospects which can be addressed for successful application. The present review critically examines the methodical challenges addressing the feasibility for restoring and reclaiming pesticide contaminated sites along with the ecotoxicological risk assessments. Overall, it highlights the need to fine-tune the available processes and employ interdisciplinary approaches to make microbe assisted bioremediation as the method of choice for reclamation of pesticide contaminated sites.

Feasible Detoxification Coating Material for Chemical Warfare Agents Using Poly(methyl methacrylate)-Branched Poly(ethyleneimine) Copolymer and Metal-Organic Framework Composites

Defense against chemical warfare agents (CWAs) is regarded as a top priority for the protection of humanity, but it still depends on physical protection with severe limitations such as residual toxicity and post-treatment requirement. In this study, a strategically designed functional polymeric substrate was composited with a metal-organic framework catalyst to remove toxicity immediately. A series of PMMA-BPEI copolymers exhibited high processability as a coating and accelerated the catalytic activity of Zr(IV)-based metal-organic framework catalysts (UiO-66). Among them, PMB12_40 composite coating on a cotton fabric, containing a PMMA-BPEI copolymer (PMMA/BPEI = 1/2) and 40% of UiO-66 catalyst, can efficiently decompose nerve agent simulants (methyl-paraoxon) under both liquid phase (t1/2 = 0.14 h) and humidified (t1/2 = 4.8 h) conditions. Moreover, a real agent, GD, was decomposed 100% by PMB12_40 in 4 h at 25 °C and 65% relative humidity. On the basis of superior catalytic activity, the PMB composites are anticipated to be a potential material for active chemical protection coating.

Facile synthesis disposable MOF membrane filter: Growth of NH2-MIL-125 (Ti) on filter paper for fast removal of organophosphorus pesticides in aqueous solution and vegetables

Metal-organic frameworks (MOFs) have great potential to remove pesticide residues. However, the lack of affinity between the materials and target and the process of trivial sample preparation resulted in limited removal efficiency. Here, we report a one-pot method for the fast preparation of NH₂-MIL-125 (Ti)-based filter paper to synthesise NH₂-MIL-125 (Ti)-based filter paper membranes. The NH₂-MIL-125 (Ti)-based filter paper membrane takes advantage of π-π interactions between the organophosphorus pesticides (OPPs) and the benzene ring of MOFs. The affinity of amino groups and metal Ti for phosphorus atoms in the OPPs exhibits rapid removal efficiency for three OPPs, imidan, fenthion, and fenitrothion. The isothermal adsorption results for imidan, fenthion, and fenitrothion were consistent with the Langmuir, Freundlich, and Langmuir models, respectively. The kinetic results for imidan, fenthion, and fenitrothion agreed with the pseudo-second-order kinetic model, and the removal efficiency reached equilibrium within 1 min. There was no significant change in the adsorption capacity of OPPs in different pH solutions (pH = 2-10). Compared with that of MOFs, the NH₂-MIL-125 (Ti)-based filter paper membrane removal efficiency of OPPs is the same, and it also has better removal efficiency in actual spinach samples. As a result, the sample pretreatment procedure was simplified using a low-cost and simple-to-synthesize disposable NH₂-MIL-125 (Ti)-based filter paper membrane, samples' quick separation and the simultaneous fast removal of OPPs.

A Review of Persulfate Activation by Magnetic Catalysts to Degrade Organic Contaminants: Mechanisms and Applications

All kinds of refractory organic pollutants in environmental water pose a serious threat to human health and ecosystems. In recent decades, sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted extensive attention in the removal of these organic pollutants due to their high redox potential and unique selectivity. This review first introduces persulfate activation by magnetic catalysts to degrade organic contaminants. We present the advances and classifications in the generation of sulfate radicals using magnetic catalysts. Subsequently, the degradation mechanisms in magnetic catalysts activated persulfate system are summarized and discussed. After an integrated presentation of magnetic catalysts in SR-AOPs, we discuss the application of persulfate activation by magnetic catalysts in the treatment of wastewater, landfill leachate, biological waste sludge, and soil containing organic pollutants. Finally, the current challenges and perspectives of magnetic catalysts that activated persulfate systems are summarized and put forward.

Concurrent elimination and stepwise recovery of Pb(II) and bisphenol A from water using β-cyclodextrin modified magnetic cellulose: adsorption performance and mechanism investigation

Coexistence of heavy metals and endocrine disrupting compounds in polluted water with competitive adsorption behavior necessitates design of tailored adsorbents. In this work, β-cyclodextrin modified magnetic rice husk-derived cellulose (β-CD@MRHC) which can provide independent functional sites for effectively binding the above two types of contaminants was synthesized and used for Pb(II) and BPA elimination in both unit and multivariate systems. Characterizations results confirmed successful β-CD grafting and Fe₃O₄ loading, and the β-CD@MRHC had excellent magnetic property for its effectively recovery from water, which was not affected by the adsorption of pollutants. The β-CD@MRHC possessed superior adsorption performance with maximal Pb(II)/BPA uptake of 266.2 or 412.8 mg/g, severally, and the adsorption equilibrium was fleetly reached in 30 and 7.5 min. Moreover, the β-CD@MRHC could accomplish synergetic Pb(II) and BPA elimination through averting their competitive behaviors owing to diverse capture mechanisms for Pb(II) (ion exchange, complexation and electrostatic attraction) and BPA (hydrogen bonding and host-guest inclusion). Furthermore, after three cycles of step-wise desorption, the binding of Pb(II) as well as BPA byβ-CD@MRHC dropped slightly in dualistic condition. In summary, β-CD@MRHC was a promising tailored adsorbent to practical application for simultaneously removing heavy metals and organic matters from wastewater with high-performance magnetic recovery.

A hybrid nanobiocatalyst with in situ encapsulated enzyme and exsolved Co nanoclusters for complete chemoenzymatic conversion of methyl parathion to 4-aminophenol

Combination of enzymatic and chemical reactions provides tremendous possibilities for chemoenzymatic cascade processes. However, constructing efficient hybrid catalysts still faces great challenges. Herein, we develop a hybrid catalyst by in situ encapsulating organophosphorus hydrolase (OPH) into a Zn-doped Co-based ZIF (0.8CoZIF) via biomimetic mineralization for the chemoenzymatic cascade conversion of methyl parathion to 4-nitrophenol and then 4-aminophenol. The exsolved Co nanoclusters in Zn/Co-ZIF are found to catalyze 4-nitrophenol reduction into 4-aminophenol in the presence of sodium borohydride (NaBH₄). The as-synthesized OPH@0.8CoZIF catalyzes the complete conversion of 95 μM methyl parathion at nearly 100% 4-aminophenol production in the presence of 50 mM NaBH₄ within 15 min, which is 1/4 that of the physical mixture of OPH and 0.8CoZIF, benefiting from the MP accumulation and substrate channeling in the hybrid catalyst. The maximum cascade conversion rate of MP to 4-AP reaches 8.07 μmol·min^-1·g-catalyst^-1, which is higher than most of the reported chemoenzymatic cascade catalysts. Therefore, the hybrid nanocatalyst containing Co-ZIF-based catalyst and OPH is successfully fabricated and enables to catalyze the complete conversion of a toxic pollutant like methyl parathion into a non-toxic resource like 4-aminophenol for recycling in useful chemical synthesis through efficient one-pot cascade reactions.

Sorption/Desorption and Kinetics of Atrazine, Chlorfenvinphos, Endosulfan Sulfate and Trifluralin on Agro-Industrial and Composted Organic Wastes

The use of pesticides presents a risk to terrestrial and aquatic ecosystems. For this reason, the development of strategies to prevent and restore pollution is of the greatest interest, including the adsorption to organic matter. The aim of the present study was to investigate the sorption/desorption and kinetics of atrazine, chlorfenvinphos, endosulfan sulfate, and trifluralin onto several raw organic wastes by batch experiments. Three kinetic models were used to fit the obtained sorption kinetics data and two to fit the obtained adsorption isotherm data; both the Freundlich and pseudo-second-order kinetic models described the sorption isotherms well. The desorption study revealed hysteresis in all cases, showing strong, and not completely reversible, adsorption in most cases, with the exception of atrazine-sawdust and chlorfenvinphos-sawdust and chicken manure combinations, for which responses were weak and irreversible. The best kinetic, adsorption and desorption constants were achieved for the hydrophobic pesticides. With respect to sorption-desorption rates, orujillo was found to be the best adsorbent for atrazine, while composted urban solid waste was more suitable for trifluralin and endosulfan sulfate. Sorption constants and simple correlations indicated that, not only the organic matter content, but also the nature of the organic matter itself, and the pesticide and adsorbent properties, determine pesticide sorption-desorption. The use of wastes as efficient and cheap adsorbents for reducing the risk of pesticide pollution is proposed.

A review on remediation technologies using functionalized Cyclodextrin

Modern lifestyle and alleviated anthropogenic activities have increased the pollutant load, ultimately causing stress on the environment. In industrialization, many harmful compounds are released into the environment polluting air, water, and soil, triggering adverse impacts on the ecosystem and human beings. Therefore, the development of advanced remediation technologies turns out as a significant environmental priority. Less polar cyclic oligosaccharide Cyclodextrin (CD) with cavity binding organic compounds attracted attention by helping effectively as environmental application. The formation of inclusion complexes and modified Cyclodextrin by cross-linking or surface modification enhances their capacity to abate pollutant effectively from the environment. Modification results in the formation of several novel materials such as CD-based composites, nanocomposites, crosslinked polymer or hydrogels, potent cross-linkers, CD-based membranes, and CD immobilized supports. Several environmental remediation technologies based on Cyclodextrin and modified Cyclodextrin have been discussed in detail in this review. Various environmental applications of Cyclodextrin and its derivatives have been discussed, along with their formation, properties, and characterization. Effective removal of organic pollutants, inorganic pollutants, micropollutants, volatile compounds etc., has been explained using several remediation technologies. Based on CD innocuity, this is referred to as the green process. The reversible equilibrium corresponded by the inclusion phenomenon sets a significant trend in the field of CD environmental application to develop techniques by incorporating supramolecular chemistry as well as irreversible methods such as biodegradation and advanced oxidation. It helps in the complete removal of pollutants and ultimately recycling the CD.

Mechanical Bond Approach to Introducing Self-Adaptive Active Sites in Covalent Organic Frameworks for Zinc-Catalyzed Organophosphorus Degradation

Mechanically interlocked molecules (MIMs) with discrete molecular components linked through a mechanical bond in space can be harnessed for the operation of molecular switches and machines, which shows huge potential to imitate the dynamic response of natural enzymes. In this work, rotaxane compounds were adopted as building monomers for the synthesis of a crown-ether ring mechanically intercalated covalence organic framework (COF). This incorporation of MIMs into open architecture implemented large amplitude motions, whose wheel slid along the axle in response to external stimulation. After impregnation with Zn²⁺ ions, the relative locations of two zinc active sites (crown-ether coordinated Zn(II) and bipyridine coordinated Zn(II)) are endowed with great flexibility to fit the conformational transformation of an organophosphorus agent during the hydrolytic process. Notably, the resulting self-adaptive binuclear zinc center in a crown-ether-threaded COF network is endowed with a record catalytic ability, with a rate over 85.5 μM min^-1 for organophosphorus degradation. The strategy of synthesis for porous artificial enzymes through the introduction of mechanically bound crown ether will enable significant breakthroughs and new synthetic concepts for the development of advanced biomimetic catalysts.

Overview of a bioremediation tool: organophosphorus hydrolase and its significant application in the food, environmental, and therapy fields

In the past decades, the organophosphorus compounds had been widely used in the environment and food industries as pesticides. Owing to the life-threatening and long-lasting problems of organophosphorus insecticide (OPs), an effective detection and removal of OPs have garnered growing attention both in the scientific and practical fields in recent years. Bacterial organophosphorus hydrolases (OPHs) have been extensively studied due to their high specific activity against OPs. OPH could efficiently hydrolyze a broad range of substrates both including the OP pesticides and some nerve agents, suggesting a great potential for the remediation of OPs. In this review, the microbial identification, molecular modification, and practical application of OPHs were comprehensively discussed.Key points• Microbial OPH is a significant bioremediation tool against OPs.• Identification and molecular modification of OPH was discussed in detail.• The applications of OPH in food, environmental, and therapy fields are presented.

Robust Nanocellulose/Metal-Organic Framework Aerogel Composites: Superior Performance for Static and Continuous Disposal of Chemical Warfare Agent Simulants

Environment-friendly and robust nanocellulose/metal-organic framework aerogel composites were prepared for effective detoxification of chemical warfare agent simulants both in static and dynamic continuous flow systems. For this, we fabricated a durable porous composite of the UiO-66 catalyst and TEMPO-oxidized cellulose nanofibers (TOCN) to examine as a detoxification filter. Even with over 50 wt % UiO-66, the obtained cellulose aerogel composites exhibited high stability without leaking of UiO-66 for 4 weeks under an aqueous state. The cellulose aerogel composite with 54 wt % UiO-66 showed a quite high surface area (483 m² g^-1) despite the presence of TOCN, which caused fast degradation of methyl paraoxon (MPO), a nerve agent simulant, with a 0.7 min half-life in an aqueous solution with N-ethylmorpholine buffer. This aerogel composite was then examined as the detoxification filter in the continuous flow system under a 7.2 mL h^-1 flow rate, which surprisingly decomposed 53.7 g of MPO within 1 h with 1 m² of the effective area.

Preparation of efficient, stable, and reusable copper-phosphotriesterase hybrid nanoflowers for biodegradation of organophosphorus pesticides

Phosphotriesterase (PTE) is considered to be a good biodegradation agent for organophosphorus pesticides. However, the instability of the free PTE limits its application. In this study, the free PTE was hybridized with copper ions (Cu²⁺) to enhance its catalytic stability and activity. The acquired particles were freeze-dried after precipitation with PO₄^3- at 4 °C for 72 h. Scanning electron microscopy showed that the Cu-PTE complexes formed flower-like nanoparticles after hybridization. The characteristic peaks of both the enzyme and metal material were revealed by Fourier transform-infrared spectroscopy. X-ray diffraction analysis indicated that PTE was encapsulated in the Cu₃(PO₄)₂·3H₂O based hybrid nanoflowers. Compared with free PTE, the catalytic activity of Cu-PTE hybrid nanoflowers was significantly increased about 2.2 fold. The catalytic efficiency (k_cat/V_max) of Cu-PTE hybrid nanoflowers was 1.76 fold than that of free PTE. The stability of the immobilized PTE under thermal and pH conditions was improved and the tolerance of it to organic solvents was also enhanced. Moreover, the Cu-PTE hybrid nanoflowers still exhibited 72.3 % relative activity after ten consecutive reactions. In general, this is the first time to use copper based hybrid nanoflowers to immobilize PTE, and the immobilized enzyme shows excellent performance on OPs degradation. The Cu-PTE hybrid nanoflowers may have great potential in the biodegradation of organophosphorus compounds in future.

[Recent developments of pesticide adsorbents based on cyclodextrins]

The invention and application of pesticides have greatly increased the yield of crops, greatly contributing to ensuring people's basic livelihoods and gradually improving their livelihoods to a well-off level. However, foods, water sources, and soil, containing high levels of pesticide residues, result in increasingly serious pollution. Pesticide residues usually have the characteristics of micro toxicity, difficult biodegradation, and bioaccumulation, and thus pose serious threat to living organisms and ecosystems. In recent years, pesticide pollution has earned worldwide focus. Thus, methods for the efficient detection of trace pesticides and reduction of the harm caused by pesticide pollution are urgently required. Researchers have used catalysis, electrochemistry, membrane separation, adsorption, and other methods to enrich pesticides from complex matrices. Among these, adsorbents have attracted much attention owing to their advantages of simple operation steps, rapid treatment process, and low amounts of organic solvents required. Research on adsorption materials has always been a very active field, and is also the key to the success of separation and enrichment of pesticides from complex matrices. Development of adsorbents with the advantages of simple synthesis, environment-friendliness, high stability, and strong reusability is of great significance. There has been some progress in the field of pesticide adsorption using supramolecular compounds. Cyclodextrin is a macrocyclic compound with a cavity after crown ether, which can form inclusion complexes via host guest interactions as the main body. Cyclodextrin can also be modified by etherification, esterification, oxidation, and other chemical reactions to improve its adsorption performance. Pesticides can be classified into organic and inorganic substances. One of the most widely used inorganic fungicides is the Bordeaux solution, whose main component is Cu2+. Organic fungicides, insecticides, herbicides, and plant growth regulators are basically organic molecules, whose hydroxyl and carboxyl groups can form complexes with Cu2+. As a matrix, cyclodextrin not only increases the surface area of the materials, but also provides the binding sites of hydroxyl and carboxyl groups, which guarantees efficient enrichment of Cu2+. Organic pesticides with high polarity, high electron density, and strong hydrophobicity could be better adsorbed. In this paper, the application of cyclodextrin-based adsorbents in pesticide adsorption was reviewed, and on this basis, reference to future development directions and application prospects were provided. The adsorption capacity of individual pesticide adsorbents based on cyclodextrin, as reviewed in this paper, is not high enough. Therefore, improving the adsorption capacity is currently a major research target. Some of the above-mentioned adsorbents have unclear degradation mechanisms and can easily cause secondary pollution. Therefore, the development of environment-friendly pesticide adsorbents that are easy to regenerate is a promising research direction for the future. After adsorption, some detection methods are used to determine whether the pesticide residues are up to the standard; however, the detection instruments are expensive. Therefore, the development of a combined detection mechanism that can reduce workload and cost is a promising research direction. Finally, the development of smart cyclodextrin-based adsorbents is also an efficient and rapid method to reduce the cost of detecting residual pesticide concentrations and the risk of pesticide pollution. For example, intelligent materials, whose color changes can be observed by the naked eye, not only adsorb pesticides, but also respond according to the concentration of residual pesticides.

Microwave-assisted synthesis of β-cyclodextrin functionalized celluloses for enhanced removal of Pb(II) from water: Adsorptive performance and mechanism exploration

Herein, β-cyclodextrin (β-CD) was efficiently grafted onto rice husk-based celluloses using different cross-linking agents of epichlorohydrin (EPI) and glutaraldehyde (GA). By feat of microwave irradiation, the functionalization procedure was completed in 17 min, and the synthesized RHEPIMWβ-CD and RHGAMWβ-CD exhibited fast adsorption equilibrium for Pb(II) within 20 min, excellent monolayer adsorption capacities of 216.06 and 279.08 mg g^-1 across an extensive pH scope of 3.0-6.0, unaffected affinity to Pb(II) during the existence of co-existing ions, superior reusability with over 81% and 87% of Pb(II) uptake sustained for four adsorption-desorption cycles. Thermodynamic parameters implied that the uptake process of Pb(II) occurred spontaneously (-ΔG⁰) with an endothermic characteristic (+ΔH⁰). Furthermore, electrostatic attraction and complexation were demonstrated to enhance the Pb(II) uptake onto the RHEPIMWβ-CD and RHGAMWβ-CD. In fix-bed columns, these two adsorbents also efficiently eliminated Pb(II) under various flow rates with experimental breakthrough curves well simulated by Thomas and Yoon-Nelson models. Significantly, the RHEPIMWβ-CD and RHGAMWβ-CD could effectively purify acid battery effluent containing Pb(II) for meeting regulatory requirement. Overall, the fast fabrication, excellent adsorption and recycling performance facilitate the development of tailored adsorbents for Pb(II) elimination in wastewater.

Enhancing organophosphate hydrolase efficacy via protein engineering and immobilization strategies

Organophosphorus compounds (OPs), developed as pesticides and chemical warfare agents, are extremely toxic chemicals that pose a public health risk. Of the different detoxification strategies, organophosphate-hydrolyzing enzymes have attracted much attention, providing a potential route for detoxifying those exposed to OPs. Phosphotriesterase (PTE), also known as organophosphate hydrolase (OPH), is one such enzyme that has been extensively studied as a catalytic bioscavenger. In this review, we will discuss the protein engineering of PTE aimed toward improving the activity and stability of the enzyme. In order to make enzyme utilization in OP detoxification more favorable, enzyme immobilization provides an effective means to increase enzyme activity and stability. Here, we present several such strategies that enhance the storage and operational stability of PTE/OPH.

Continuous Flow Composite Membrane Catalysts for Efficient Decomposition of Chemical Warfare Agent Simulants

Continuous and safe decomposition of chemical warfare agents (CWAs) is a critical requirement to protect both soldiers and citizens and to eliminate the stockpiles after the cold war. The Zr-based metal-organic framework (Zr-MOF) has been known as the most effective catalyst for decomposing CWAs, especially the most fatal nerve agents, however, its low processability due to the powder form limits its expansion to actual military applications. To this end, the composite membrane catalysts (CMCs) comprising the Zr-MOF (UiO-66 catalyst) and nylon 6 nanofiber (porous supporter) are developed by the simple integration of electrospray and electrospinning, resulting in selective immobilization of UiO-66 on the surface of the nylon 6 nanofibers. These strategical benefits of CMCs gave super catalytic durability including recyclability over five times without decreasing the catalytic activity for the decomposition of methyl paraoxon (MPO), a simulant of the nerve agent, in the presence of N-ethylmorpholine (N-EM), which was not achieved in the original particulate UiO-66. Because of the excellent physical and chemical stabilities of CMCs, the CMC with 56 wt % of UiO-66 (CMC56) decomposed 198 g of MPO within an hour in the continuous flow system with a flow rate of 21.6 mL h^-1. This study highlights the important strategies in designing the feasible membrane-type catalysts with superior catalytic activity and robust durability for decomposing CWAs in the continuous flow system.

Biomimetic Membrane-Structured Nanovesicles Carrying a Supramolecular Enzyme to Cure Lung Cancer

Platforms for enzyme delivery must simultaneously have plasma stability, high catalytic activity, and low/no immunogenicity of the enzyme. Here, we designed a novel biomimetic membrane-structured nanovesicle (BNV) to efficiently carry supramolecular enzymes to meet the above requirements. We complexed l-asparaginase (Aase) with hydroxypropyl-β-cyclodextrin (HPCD) to form a supramolecular amphiphile (AS) by self-assembly via noncovalent reversible interactions. We then used the first synthesized polyethylene glycol (PEG 2 kDa)-decorated hyaluronan (12 kDa) and HPCD to self-assemble a semipermeable biomimetic membrane-structured nanovesicle (BNV) together with AS loading. As compared to native Aase, AS@BNV exhibited superior catalytic activity preservation, improved catalytic activity, better pharmacokinetics in rats, enhanced cytotoxic effects, increased antitumor efficacy, and decreased side effects. The underlying mechanisms, such as the autophagy inhibition action against tumor cells, protein-protein docking of the interaction between Aase-serum albumin, and decreased hepatic enzymatic activity, were investigated. This approach paves the way for new types of powerful biomimetic-, supramolecular-, and nanocarrier-based enzymatic therapies.

Facile synthesis of superparamagnetic β-CD-MnFe2O4 as a peroxymonosulfate activator for efficient removal of 2,4- dichlorophenol: structure, performance, and mechanism

In this study, superparamagnetic β-CD-MnFe₂O₄ with a large surface area was synthesized via a facile co-precipitation method, with β-cyclodextrin (β-CD) acting as a coating agent. The as-prepared β-CD-MnFe₂O₄ exhibited better catalytic performance than bare MnFe₂O₄ in terms of activating peroxymonosulfate (PMS) to degrade 2,4-dichlorophenol (2,4-DCP) over a broad pH range of 5-11. Electron spin resonance spectroscopy (ESR) and free radical quenching experiments indicate that various active species (SO₄^-/OH/O₂^-/¹O₂) are generated in the β-CD-MnFe₂O₄/PMS system and that pollutants trapped in the cyclodextrin cavity are quickly degraded. Various reaction parameters of the β-CD-MnFe₂O₄/PMS system and the stability of β-CD-MnFe₂O₄ were also investigated. The results indicate that β-CD-MnFe₂O₄ is promising for use in water purification owing to its excellent magnetic separation and recovery properties and good resistance to humic acid (HA).

Quantitatively controllable fluid flows with ballpoint-pen-printed patterns for programmable photo-paper-based microfluidic devices

Regulating the fluid flow in microfluidic devices enables a wide range of assay protocols for analytical applications. A programmable, photo-paper-based microfluidic device fabricated by using a method of cutting and laminating, followed by printing, is reported. The flow distance of fluid in the photo-paper-based channel was linearly proportional to time. By printing silver nanoparticle (AgNP) and poly[4,5-difluoro-2,2-bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (PTFE) patterns on the surface of a photo-paper-based channel, we were able to either increase or decrease the fluid flow in the fabricated microfluidic devices, while maintaining the linearity in the flow distance-time relation. In comparison to the speed of fluid flow in a pristine channel, by using hydrophilic AgNP patterns, we were able to increase the speed in the channel by up to 15 times while we were able to slow the speed by a factor of 3 when using hydrophobic PTFE dots. We then further demonstrated a single-step protocol for detecting glucose and a multi-step protocol for detecting methyl paraoxon (MPO) with our methods in photo-paper-based microfluidic devices. This approach can lead to improved fluid handling techniques to achieve a wide range of complex, but programmable, assays without the need for any additional auxiliary devices for automated operation.

Persistence of pesticides-based contaminants in the environment and their effective degradation using laccase-assisted biocatalytic systems

Inevitable use of pesticides due to modern agricultural practices and the associated worldwide environmental pollution has called the special attention of the researchers to overcome the persistence, recalcitrance, and multi-faceted toxicity of pesticides-based emerging contaminants. Some restricted use pesticides (RUPs) are highly toxic and carcinogenic chemicals that can be easily accumulated into non-target organisms, including humans, aquatic invertebrates, algae, and microbes. With regard to physicochemical strategies, enzymes-mediated bioremediation is a compelling and meaningful strategy for biodegradation and biotransformation of pesticides into harmless chemical species. Oxidoreductases hydrolases and transferases are among the most representative classes of enzymes pursued and engineered for this purpose. Ligninolytic enzymes, particularly laccases, are of exceptional interest due to high efficiency, specificity, eco-sustainability, and wide-ranging substrates. However, the use of native enzymes is often hindered in industrial processes for the effective removal of refractory compounds by their high cost and susceptibility. Many of these drawbacks can be addressed by enzyme immobilization on some suitable support materials. Increase in stability, reusability, reduction of product inhibition, enhanced activity, specificity, and easier product separation are amid the desirable characteristics of immobilization to construct biocatalysts for continuous systems. This review summarizes recent and up-to-date literature on the use of enzymes, explicitly, free as well as immobilized laccases in the degradation of different pesticides. In the first part, source and occurrence of pesticides in the environment, their types, and associated detrimental effects on the ecosystem/human health are comprehensively described. Afterward, we highlighted the use of different enzymes with a particular emphasis on laccase for the degradation and detoxification of an array of pesticides. Finally, the review is closed with concluding remarks, and possible future direction is proposed in this very important research arena. In conclusion, it is envisioned that effective deployment of laccase-assisted biocatalytic systems for the degradation or removal of diverse pesticides and related contaminants will help to better understand the persistence and removal fate of these hazardous pollutants. Moreover, the current research thrust presented in this review will additionally evoke researcher to engineer robust and sustainable processes to remediate pesticides-contaminated environmental matrices effectively.