Synthesis, characterization, and application of microbe-triggered controlled-release kasugamycin-pectin conjugate

Photothermal controlled-release microcapsule pesticide delivery systems constructed with sodium lignosulfonate and transition metal ions: construction, efficacy and on-demand pesticide delivery

BACKGROUND

Widespread application of controlled-release pesticide delivery systems is a feasible and effective method to improve the utilization efficiency of pesticides. However, owing to the high cost and complicated preparation technologies of controlled-release pesticide delivery systems, their applications in agricultural production have been seriously hindered.

RESULTS

This study aimed to construct inexpensive photothermally controlled-release pesticide delivery systems using chitosan (CS) and sodium lignosulfonate (LS) as the wall materials, and a coordination assembly strategy of LS with transition metal ions to encapsulate a model pesticide, avermectin (AVM). The resulting complex or nanoparticle photothermal layers in these systems effectively achieved photothermal conversions, and replaced the use of common photothermal agents. In the prepared pesticide-delivery systems, two systems had remarkable photothermal conversion performance and photothermal stabilities with a photothermal conversion efficiency (η) of 24.03% and 28.82%, respectively, under 808 nm, 2 W near-infrared irradiation. The slow-release and ultraviolet-shielding performance of these two systems were markedly enhanced compared with other formulations. The insecticidal activities of these two systems against Plutella xylostella under irradiation with light-emitting diode (LED)-simulated sunlight were also enhanced by 5.20- and 5.06-fold, respectively, compared with that without irradiation of LED-simulated sunlight.

CONCLUSION

Because of their convenient preparations, inexpensive and renewable raw materials, and excellent photothermally controlled-release performance, these on-demand pesticide delivery systems might have significant potential in improving the utilization efficiency of pesticides in modern agriculture. © 2024 Society of Chemical Industry.

The Use and Impact of Antibiotics in Plant Agriculture: A Review

Growers have depended on the specificity and efficacy of streptomycin and oxytetracycline as a part of their plant disease arsenal since the middle of the 20th century. With climate change intensifying plant bacterial epidemics, the established success of these antibiotics remains threatened. Our strong reliance on certain antibiotics for devastating diseases eventually gave way to resistance development. Although antibiotics in plant agriculture equal to less than 0.5% of overall antibiotic use in the United States, it is still imperative for humans to continue to monitor usage, environmental residues, and resistance in bacterial populations. This review provides an overview of the history and use, resistance and mitigation, regulation, environmental impact, and economics of antibiotics in plant agriculture. Bacterial issues, such as the ongoing Huanglongbing (citrus greening) epidemic in Florida citrus production, may need antibiotics for adequate control. Therefore, preserving the efficacy of our current antibiotics by utilizing more targeted application methods, such as trunk injection, should be a major focus. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Acidifying Spray Suspensions of Oxytetracycline and Kasugamycin Enhances Their Effectiveness for Fire Blight Control in Apple and Pear

The stability of the fire blight control material, oxytetracycline, in water is strongly affected by pH, increasing with increasing acidity. From 2017 to 2021, pear and apple orchard trials were conducted to evaluate if acidic amendments to oxytetracycline sprays improve fire blight control. Compared with the water-treated control, infection suppression after two bloom applications of an acidified commercial oxytetracycline formulation averaged 85.9 ± 0.4% compared with 72.2 ± 1.7% without an acidifier, but individual trials frequently had insufficient statistical power to separate among acidified and non-acidified antibiotic treatments. Across trials, a significant linear relationship was observed for regression of relative infection suppression from oxytetracycline (hydrochloride formulation) on spray tank pH. Similar relationships were observed for oxytetracycline (calcium complex formulation) and kasugamycin (P values were 0.055 and 0.069, respectively). Also based on regression, acidified oxytetracycline and kasugamycin suppressed epiphytic populations of Erwinia amylovora on flowers to a greater degree than the antibiotic only. As spray suspensions, commercial oxytetracycline formulations at label rate and amended with citric acid (1.2 g/liter) in well water had pH values near 3.4, but after spraying, the pH of flowers washed in deionized water (1 ml/flower) measured in a range of 5.2 to 5.5 compared with a pH range of 5.8 to 6.0 after a treatment of oxytetracycline only. In pear fruit finish trials, sprays acidified with citric acid-based materials had negligible effects on fruit russeting. Based on a serological assay, the detectable residual of oxytetracycline on apple foliage was increased by co-application with citric acid compared with a non-acidified control.

A high adhesion co-assembly based on myclobutanil and tannic acid for sustainable plant disease management

BACKGROUND

Pesticides are irreplaceable inputs for protecting crops from pests and improving crop yield and quality. Self-assembly nanotechnology is a promising strategy by which to develop novel nano-formulations for pesticides. Nano-formulations improve the effective utilization of pesticides and reduce risks to the environment because of their eco-friendly preparation, high drug loading, and desirable physicochemical properties. Here, to enhance the utilization efficiency of myclobutanil (MYC) and develop a novel nano-formulation, carrier-free co-assembled nanoparticles (MT NPs) based on MYC and tannic acid (TA) were prepared by noncovalent molecular interactions using a green preparation process without any additives.

RESULTS

The results showed that the prepared spherical nanoparticles had good stability in neutral and acidic aqueous solutions, low surface tension (40.53 mN m-1 ), high rainfastness, and good maximum retention values on plant leaves. Release of active ingredients from MT NPs could be regulated by altering the molar ratio of subassemblies in the co-assembly and the pH of the environment. Antifungal experiments demonstrated that MT NPs had better activities against Alternaria alternata and Fusarium graminearum [half-maximal effective concentration (EC50 ) = 6.40 and 77.08 mg/L] compared with free MYC (EC50  = 11.46 and 124.82 mg/L), TA (EC50  = 251.19 and 503.81 mg/L), and an MYC + TA mixture (EC50  = 9.62 and 136.21 mg/L). These results suggested that MYC and TA incorporated in the co-assembled nanoparticles had a synergistic antifungal activity. The results of a genotoxicity assessment indicated that MT NPs could reduce the genotoxicity of MYC to plant cells.

CONCLUSION

Co-assembled MT NPs with synergistic antifungal activity have outstanding potential for the management of plant diseases. © 2023 Society of Chemical Industry.

Fabrication of Enzyme-Responsive Prodrug Self-Assembly Based on Fluazinam for Reducing Toxicity to Aquatic Organisms

Prodrug-based nanodrug delivery systems were drug formulations by covalently conjugating drugs with inversely polar groups via a cleavable bond to self-assemble into nanoparticles for efficient drug delivery. To improve the utilization efficiency of fluazinam (FZN), enzyme-responsive prodrugs were prepared by conjugating FZN with different alkyl aliphatic acids through a nucleophilic substitution reaction and subsequently self-assembled into nanoparticles (FZNP NPs) without using any harmful adjuvant. The obtained FZNP NPs exhibited excellent efficacies against Sclerotinia sclerotiorum as a result of improved physicochemical properties, including low surface tension, high retention, and enhanced photostability. The LC50 values of FZNP NPs toward zebrafish were 3-8 times that of FZN, which illustrated that the FZNP NPs reduced the detriments of FZN to the aquatic organisms while retaining good biological activity. Therefore, prodrug self-assembly technology would offer a potential method for improving the utilization efficiency of pesticides and lowering the risks to the ecological environment.

A pectin-based photoactivated bactericide nanosystem for achieving an improved utilization rate, photostability and targeted delivery of hematoporphyrin

Photoactivated pesticides have many advantages, such as high activity, low toxicity, and no drug resistance. However, poor photostability and a low utilization rate limit their practical application. Herein, the photosensitizer hematoporphyrin (HP) was used as a photoactivated pesticide, covalently linked with pectin (PEC) via ester bonds, to prepare an amphiphilic polymer pro-bactericide, and subsequently self-assembled in aqueous solutions to obtain an esterase-triggered nanobactericide delivery system. The fluorescence quenching effect due to the aggregation of HP in nanoparticles (NPs) enabled the inhibition of photodegradation of HP in this system. Esterase stimulation could trigger HP release and increase its photodynamic activity. Antibacterial assays have shown that the NPs had potent antibacterial capacity, almost completely inactivating bacteria after 60 min of exposure to light. The NPs had good adherence to the leaves. Safety assessment indicated that the NPs have no obvious toxic effects on plants. Antibacterial studies on plants have shown that the NPs have excellent antibacterial effects on infected plants. These results provide a new strategy for obtaining a photoactivated bactericide nanosystem with a high utilization rate and good photostability and targeting ability.

Self-demise of soft rot bacteria by activation of microbial predators by pectin-based carriers

Soft rot pectobacteria (SRP) are phytopathogens of the genera Pectobacterium and Dickeya that cause soft rots on a wide range of crops and ornamental plants. SRP produce plant cell wall degrading enzymes (PCWDEs), including pectinases. Bdellovibrio and like organisms are bacterial predators that can prey on a variety of Gram-negative species, including SRP. In this research, a low methoxyl pectin (LMP)-based immobilization system for B. bacteriovorus is established. It takes advantage that pectin residues induce PCWDE secretion by the pathogens, bringing upon the release of the encapsulated predators. Three commercial LMPs differing in the degree of esterification (DE) and amidation (DA) were tested as potential carriers, by examining their effect on SRP growth, enzymes secretion and substrate breakdown. A clear advantage was observed for pectin 5 CS with the lowest DE and DA content. The degradation of 5 CS pectin-based carriers was further optimized by reducing cross-linker and pectin concentration, by adding gelatin and by dehydration. This resulted in SRP-induced disintegration of the carrier within 72 h. The released encapsulated predator caused a large decrease in SRP population while its own significantly increased, demonstrating the efficiency of this system in which the pathogen brings about its own demise.

Versatile functionalization of pectic conjugate: From design to biomedical applications

Pectin exists extensively in nature and has attracted much attention in biological applications for its unique chemical and physical characteristics. Functionalized pectin, especially pectic conjugates, has given many possibilities for pectin to improve its properties and bioactivity as well as to deliver active molecules. To better exploit this strategy of pectic functionalization, this review presents in detail the structural modifications of pectin, different synthetic methods, and design strategies of pectic conjugates involving both traditional chemical and "green" approaches. Here, the research ideas and applications of pectic prodrugs as well as the development of preparation based on pectic conjugates are reviewed, with emphasis on crosslinking systems of functionalized pectin and nanosystems based on self-assembly techniques. We hope this review will provide comprehensive and valuable information for the functionalization and systematization of the pectic conjugate from synthesis to application.

Synthesis, characterization and application of emamectin-alkaline lignin conjugate with photolysis resistance and systemic translocation

Controlled release formulations (CRFs) are a key technical approach for the sustainable development of pesticides. In this study, a CRF conjugate (emamectin-alkaline lignin, EB-AL) was successfully prepared using alkaline lignin as the substrate, with amide bond connecting emamectin and alkaline lignin. The structure and morphology of the conjugate were characterized using IR, ¹HNMR, elemental analysis, SEM and TG. The release of EB-AL showed that the conjugate maintained its original structure when released in 50 % methanol-water and soil column, and the amide bond remained intact. The anti-photolysis test revealed that EB-AL had a 3.5 times higher photolysis half-life T_0.5 than the general emamectin suspension concentrate (EB-SC). Bioactivity tests in the greenhouse demonstrated that EB-AL possessed a longer insecticidal duration and good biosafety. Ostrinia nubilalis lethality rate remained above 70 % for 19 days, while EB-EC, the control, had a rate of <50 % after 11 days of application. Additionally, EB-AL conjugate demonstrated excellent systemic translocation in plants, likely due to its ability to mediate alkaline lignin.

Prodrug Based on Ionic Liquids for Dual-Triggered Release of Thiabendazole

The application of triggered release pesticides can provide active ingredient release at required environmental conditions, reduce environmental problems, and toxicity to nontarget organisms. In this work, a novel prodrug that responds to water and enzymes as release triggers for thiabendazole was prepared. The release behaviors under different conditions, bioactivity against Penicillium italicum, and acute toxicity to Danio rerio of prodrugs were investigated. The results showed that the prodrug had remarkable water- and enzyme-triggered release properties, and the correlation coefficients (r ²) fitted by the Weibull model were all >0.99. Meanwhile, the prodrug showed improved antifungal efficacy against Penicillium italicum and reduced toxicity to Danio rerio. Overall, the prodrug developed offers an efficient way to triggered release pesticides, control fungal, and reduce the risk of harm to aquatic organisms.

Zeolitic Imidazole Framework-90-Based Pesticide Smart-Delivery System with Enhanced Antimicrobial Performance

Multimodal antimicrobial technology is regarded as a promising strategy for controlling plant diseases because it enhances antimicrobial efficacy by blocking multiple pesticide-resistance pathways. In this work, a pH-responsive multimodal antimicrobial system was constructed based on ZIF-90 for the controlled release of kasugamycin (KSM). A series of physicochemical characterizations confirmed the successful fabrication of ZIF-90-KSM. The results indicated that the loading capacity of ZIF-90-KSM for KSM was approximately 6.7% and that the ZIF-90 nanocarriers could protect KSM against photodegradation effectively. The acid pH at the site of disease not only decompose the Schiff base bonds between KSM and ZIF-90, but also completely dissolved the nanocarriers. The simultaneous release of KSM and Zn²⁺ ions was able to achieve multimodal antimicrobial functions during disease occurs. A bioactivity survey indicated that ZIF-90-KSM had superior fungicidal activity and longer duration against Magnaporthe oryzae than KSM aqueous solution. In addition, the phytotoxicity assessment of ZIF-90-KSM on rice plants did not reveal any adverse effects. Therefore, ZIF-90-KSM prepared by Schiff base reaction has great potential for achieving synergistic antifungal functions and provides an eco-friendly approach to manage rice diseases.

CytroCell Micronized Cellulose Enhances the Structural and Thermal Properties of IntegroPectin Cross-Linked Films

Added to grapefruit IntegroPectin in solution, the micronized cellulose CytroCell, coproduct of the IntegroPectin extraction via hydrodynamic cavitation, enhances the structural and thermal properties of the resulting cross-linked composite films. The films become strong but remain highly flexible as no transition glass temperature is observed, whereas the thermal properties are substantially improved. No organic solvent, acid, or base is used from the extraction of the pectin and cellulose biopolymers through filming their nanocomposites, thereby establishing a completely green route to a class of bio-based 2D films (and 3D scaffolds) with numerous potential applications in regenerative medicine, in tissue engineering, and in the treatment of infections.

Self-Assembled Nanoparticles of a Prodrug Conjugate Based on Pyrimethanil for Efficient Plant Disease Management

Self-assembled nanotechnology is a promising strategy for improving the effective utilization of pesticides due to its distinct advantages. Herein, an amide-bonded prodrug conjugate based on pyrimethanil (PYR) and butyric acid (BA) was successfully synthesized by the nucleophilic substitution reaction and subsequently self-assembled into spherical nanoparticles (PB NPs) with an average size of 85 nm through the solvent exchange method without using any toxic adjuvant. The results showed that PB NPs based on PYR and BA had a synergistic antimicrobial activity against S. sclerotiorum on plant leaves due to good photostability, low volatilization, good surface activity, and improved retention. Additionally, PB NPs could be used by plant cells as nutrients to promote the growth of plants and thus reduced the toxicity of PYR to plant. Therefore, this prodrug conjugate self-assembly nanotechnology would provide a promising strategy for improving the effective utilization rates of pesticides and reducing their toxicities to plants.

Preparation and Insecticidal Activity Evaluation of Emamectin-Lignin Sulfonic Acid Conjugate with Antiphotolysis Property

Controlled release formulations (CRFs) are considered an effective way to solve the low bioavailability of traditional pesticides. However, CRFs prepared by coating or encapsulation has the disadvantage of explosive release of the ingredients. Sustained-release pesticides prepared by coupling with a carrier can overcome this shortcoming. In the present study, an emamectin-lignin sulfonic acid conjugate (EB-SL), in which emamectin was connected via sulfonamide bonds with lignin, was prepared using sodium lignosulfonate as the carrier. The structure of the conjugate was characterized by IR, ¹HNMR, and elemental analysis. The sustained-release results showed that EB-SL maintained its original structure when released in pure water and soil columns, and the sulfamide bond did not break. The photolysis test displayed that the photolysis half-life T _0.5 of EB-SL was increased by 1.5 times compared with the emamectin suspending concentrate (EB-SC). Bioactivity tests in the greenhouse showed that EB-SL not only had similar insecticidal toxicity to emamectin emulsion concentrate (EB-EC) against Ostrinia nubilalis but also displayed a longer duration. The lethality of EB-SL on O. nubilalis was maintained at more than 70% across 19 days, whereas EB-EC as the control was less than 50% after 11 days of application.

Enhancing Agrichemical Delivery and Plant Development with Biopolymer-Based Stimuli Responsive Core-Shell Nanostructures

The inefficient delivery of agrichemicals in agrifood systems is among the leading cause of serious negative planetary and public health impacts. Such inefficiency is mainly attributed to the inability to deliver the agrichemicals at the right place (target), right time, and right dose. In this study, scalable, biodegradable, sustainable, biopolymer-based multistimuli responsive core-shell nanostructures were developed for smart agrichemical delivery. Three types of responsive core/shell nanostructures incorporated with model agrichemicals (i.e., CuSO₄ and NPK fertilizer) were synthesized by coaxial electrospray, and the resulting nanostructures showed spherical morphology with an average diameter about 160 nm. Tunable agrichemical release kinetics were achieved by controlling the surface hydrophobicity of nanostructures. The pH and enzyme responsiveness was also demonstrated by the model analyte release kinetics (up to 7 days) in aqueous solution. Finally, the efficacy of the stimuli responsive nanostructures was evaluated in soil-based greenhouse studies using soybean and wheat in terms of photosynthesis efficacy and linear electron flow (LEF), two important metrics for seedling development and health. Findings confirmed plant specificity; for soybean, the nanostructures resulted in 34.3% higher value of relative chlorophyll content and 41.2% higher value of PS1 centers in photosystem I than the ionic control with equivalent agrichemical concentration. For wheat, the nanostructures resulted in 37.6% higher value of LEF than the ionic agrichemicals applied at 4 times higher concentration, indicating that the responsive core-shell nanostructure is an effective platform to achieve precision agrichemical delivery while minimizing inputs. Moreover, the Zn and Na content in the leaves of 4-week-old soybean seedlings were significantly increased with nanostructure amendment, indicating that the developed nanostructures can potentially be used to modulate the accumulation of other important micronutrients through a potential biofortification strategy.

Pectin Microspheres: Synthesis Methods, Properties, and Their Multidisciplinary Applications

There is great contemporary interest in using cleaner technologies through green chemistry and utilizing biopolymers as raw material. Pectin is found on plant cell walls, and it is commonly extracted from fruit shells, mostly apples or citrus fruits. Pectin has applications in many areas of commercial relevance; for this reason, it is possible to find available information about novel methods to transform pectin and pursuing enhanced features, with the structuring of biopolymer microspheres being highly cited to enhance its activity. The structuring of polymers is a technique that has been growing in recent decades, due to its potential for diverse applications in various fields of science and technology. Several techniques are used for the synthesis of microspheres, such as ionotropic gelation, extrusion, aerosol drying, or emulsions, with the latter being the most commonly used method based on its reproducibility and simplicity. The most cited applications are in drug delivery, especially for the treatment of colon diseases and digestive-tract-related issues. In the industrial field, it is used for protecting encapsulated compounds; moreover, the environmental applications mainly include the bioremediation of toxic substances. However, there are still many possibilities for expanding the use of this biopolymer in the environmental field.

Effect of Kasugamycin, Oxytetracycline, and Streptomycin on In-orchard Population Dynamics of Erwinia amylovora on Apple Flower Stigmas

We assessed the effect of three antibiotics (streptomycin, oxytetracycline, and kasugamycin) on populations of the fire blight pathogen Erwinia amylovora on apple flower stigmas during three field seasons. Application timing relative to E. amylovora presence on flower stigmas had little impact on population dynamics and subsequent disease incidence. Although E. amylovora populations on water-treated flowers increased to 10^6-7 cfu flower^-1 after 4 to 5 days during each experiment, the antibiotics streptomycin and kasugamycin caused statistically significant reductions in stigma populations by as many as 4 to 5 logs over a 4- to 5-day period during two of the three experiments. In contrast, the effect of oxytetracycline on E. amylovora populations on stigmas was more variable, with reductions in E. amylovora populations only observed during one of the three experiments. In agreement with the population data, the disease incidence was significantly higher for oxytetracycline-treated flowers compared with the other antibiotic treatments during 2 of 3 years. Statistical analyses of the effects of weather parameters on antibiotic activity revealed that solar radiation and temperature negatively impacted the activity of both kasugamycin and oxytetracycline. We further assessed the potential for photodegradation of formulated kasugamycin (Kasumin 2L) and found that Kasumin 2L was susceptible to degradation in vitro after exposure to a 16-h photoperiod of daily light integrals (DLIs) varying from 6 to 35 mol⋅m^-2⋅d^-1. We further determined that exposure to three consecutive 16-h photoperiods of DLIs of 23 or 35 mol⋅m^-2⋅d^-1 reduced the available concentration of Kasumin 2L (assessed using a bioassay) from 100 μg⋅ml^-1 to 10 to 20 μg⋅ml^-1. Our results correlate the superior blossom blight control efficacy of kasugamycin and streptomycin with significant population reductions in E. amylovora on apple flower stigmas but indicate that, similar to oxytetracycline, kasugamycin is vulnerable to photodegradation, which would suggest that further considerations are necessary when applying this antibiotic.

Binary Pectin-Chitosan Composites for the Uptake of Lanthanum and Yttrium Species in Aqueous Media

Rare-earth elements such as lanthanum and yttrium have wide utility in high-tech applications such as permanent magnets and batteries. The use of biopolymers and their composites as adsorbents for La (III) and Y (III) ions were investigated as a means to increase the uptake capacity. Previous work has revealed that composite materials with covalent frameworks that contain biopolymers such as pectin and chitosan have secondary adsorption sites for enhanced adsorption. Herein, the maximum adsorption capacity of a 5:1 Pectin-Chitosan composite with La (III) and Y (III) was 22 mg/g and 23 mg/g, respectively. Pectin-Chitosan composites of variable composition were characterized by complementary methods: spectroscopy (FTIR, ¹³C solids NMR), TGA, and zeta potential. This work contributes to the design of covalent Pectin-Chitosan biopolymer frameworks for the controlled removal of La (III) and Y (III) from aqueous media.

Novel fabrication of a yeast biochar-based photothermal-responsive platform for controlled imidacloprid release

For improving the utilization efficiency of pesticides, we developed a novel pesticide delivery particle (YINCP@EC) with a core–shell structure based on yeast biochar, imidacloprid (IMI), ammonium bicarbonate (NH₄HCO₃), calcium alginate (CA), and ethyl cellulose (EC). Therein, yeast biochar, IMI and NH₄HCO₃ were absorbed in the network-structured of CA to obtain YINCP through hydrogen bonds. The resulting composite was granulated using an ion gelation technique and then coated with EC to form YINCP@EC. In this platform, yeast biochar serving as a photothermal agent can efficiently convert sunlight energy into thermal energy, thereby triggering NH₄HCO₃ decomposition into CO₂ and NH₃ that can break through the EC coating and facilitate IMI release. In addition, the influence of yeast biochar content, pH, and coexisting ions was systematically studied to evaluate the release behavior of IMI from YINCP@EC. Moreover, the hydrophobic EC shell endowed YINCP@EC with high stability in aqueous solution for at least 60 days. Consequently, this novel composite with simple preparation, low cost and remarkable photothermal-responsive properties has a huge application potential in agriculture.

The yeast biochar-based platform exhibited excellent photothermal conversion capability, and realized light-triggered controlled release of IMI.

Fabrication and Characterization of Ceftizoxime-Loaded Pectin Nanocarriers

Ceftizoxime (C13H12N5NaO5S2)is a parenteral, third-generationcephalosporin antibiotic used to treat bacterial infections including ear, nose, and throat infections. In this work, pectin has been used as a nanocarrier for ceftizoxime due to its high biocompatibility and non-toxicity with tunable surface properties. Ceftizoxime-loaded pectin nanocarriers (CPN) were successfully synthesized by the solvent displacement method. Optimization of nanoformulation was done by response surface methodology using Design-Expert software. The optimized formulation examined various in-vitro characterizations such as particle size, morphology, and FTIR studies. TEM results revealed irregular shape nanoparticles within the range of 29-110 nm. The in-vitro drug release using the dialysis method was performed after 24h where nanoformulation showed sustained drug release. Drug-loaded nanoparticles revealed good antimicrobial activity against Bacillus cereus, Bacilluspolymyxa, Enterobacteraerogenes, andPseudomonasaeruginosa.

Uptake of Methylene Blue from Aqueous Solution by Pectin–Chitosan Binary Composites

To address the need to develop improved hybrid biopolymer composites, we report on the preparation of composites that contain chitosan and pectin biopolymers with tunable adsorption properties. Binary biopolymer composites were prepared at variable pectin–chitosan composition in a solvent directed synthesis, dimethyl sulfoxide (DMSO) versus water. The materials were characterized using complementary methods (infrared spectroscopy, thermal gravimetric analysis, pH at the point-of-zero charge, and dye-based adsorption isotherms). Pectin and chitosan composites prepared in DMSO yielded a covalent biopolymer framework (CBF), whereas a polyelectrolyte complex (PEC) was formed in water. The materials characterization provided support that cross-linking occurs between amine groups of chitosan and the –COOH groups of pectin. CBF-based composites had a greater uptake of methylene blue (MB) dye over the PEC-based composites. Composites prepared in DMSO were inferred to have secondary adsorption sites for enhanced MB uptake, as evidenced by a monolayer uptake capacity that exceeded the pectin–chitosan PECs by 1.5-fold. This work provides insight on the role of solvent-dependent cross-linking of pectin and chitosan biopolymers. Sonication-assisted reactions in DMSO favor CBFs, while cross-linking in water yields PECs. Herein, composites with tunable structures and variable physicochemical properties are demonstrated by their unique dye adsorption properties in aqueous media.

Chitosan-Based Coacervate Polymers for Propolis Encapsulation: Release and Cytotoxicity Studies

Chitosan-DNA (CS-DNA) and Chitosan-Pectin (CS-P) hydrogels were formulated as a sustained drug delivery carrier for drug delivery. For this, hydrogels were prepared by emulsion technique: mixing aqueous phase of the CS and DNA or P solution with benzyl alcohol using a high-performance dispersing instrument. Green Propolis (GP) was incorporated by imbibition: hydrogels were placed in GP aqueous solution (70 µg/mL) for 2 h. The specimens were freeze-dried and then characterized using different techniques. In vitro cell viability and morphology were also performed using the MG63 cell line. The presence of P was evidenced by the occurrence of a strong band at 1745 cm-1, also occurring in the blend. DNA and CS-DNA showed a strong band at 1650 cm-1, slightly shifted from the chitosan band. The sorption of GP induced a significant modification of the gel surface morphology and some phase separation occurs between chitosan and DNA. Drug release kinetics in water and in saliva follow a two-step mechanism. Significant biocompatibility revealed that these hydrogels were non-toxic and provided acceptable support for cell survival. Thus, the hydrogel complexation of chitosan with DNA and with Pectin provides favorable micro-environment for cell growth and is a viable alternative drug delivery system for Green Propolis.

Dual-Functionalized Pesticide Nanocapsule Delivery System with Improved Spreading Behavior and Enhanced Bioactivity

The prevention and control of pests and diseases are becoming increasingly difficult owing to extensive pesticide resistance. The synergistic use of pesticides for disease control is an effective way of slowing pesticide resistance, reducing the number of pesticide applications, and protecting the environment. In this study, a dual-functionalized pesticide nanocapsule delivery system loaded with two active ingredients (AIs)—validamycin and thifluzamide—was developed to prevent and control rice sheath blight; the nanocapsule system was based on a water–oil–water double emulsion method combined with high-pressure homogenization technology. Our results showed that the dual-functionalized pesticide nanocapsules were monodisperse spheres with a mean particle size of ~260 nm and had good storage stability. Compared with commercial formulations, the dual-functionalized pesticide nanocapsules exhibited good foliar spread owing to their small size, which is beneficial for reducing the loss of pesticides on the leaves. The 50% median effect concentration and synergistic ratio against Rhizoctonia solani of the dual-functionalized pesticide nanocapsules and commercial formulation were 0.0082 and 0.0350 μg/mL, and 2.088 and 0.917, respectively. These findings indicate that the bioactivity of the dual-functionalized system was significantly better than that of the commercial formulations and that the dual-functionalized system demonstrated a clear synergistic effect between the two AIs. The system presented here is simple, fast, and capable of dual-pesticide loading with significant synergistic effects. Our findings could help to facilitate the improvement of pesticides efficiency and the slowing of pesticide resistance.

Effect of Mesoporous Silica Nanoparticles on The Physicochemical Properties of Pectin Packaging Material for Strawberry Wrapping

Citrus peel pectin was used to prepare films (cast with or without glycerol) containing mesoporous silica nanoparticles. Nanoparticles reduced significantly the particle size, and had no effect on the Zeta potential of pectin solutions. Mechanical characterization demonstrates that pectin+nanoparticles containing films slightly increased tensile strength and significantly decreased the Young's modulus in comparison to films made only of pectin. However, elongation at the break increased in the pectin+nanoparticles films cast in the presence of glycerol, while both Young's modulus and tensile strength were reduced. Moreover, nanoparticles were able to reduce the barrier properties of pectin films prepared with or without glycerol, whereas positively affected the thermal stability of pectin films and the seal strength. The 0.6% pectin films reinforced or not with 3% nanoparticles in the presence of 30% glycerol were used to wrap strawberries in order to extend the fruit's shelf-life, over a period of eighty days, by improving their physicochemical properties.

Development of stimuli-responsive nano-based pesticides: emerging opportunities for agriculture

Pesticides and fertilizers are widely used to enhance agriculture yields, although the fraction of the pesticides applied in the field that reaches the targets is less than 0.1%. Such indiscriminate use of chemical pesticides is disadvantageous due to the cost implications and increasing human health and environmental concerns. In recent years, the utilization of nanotechnology to create novel formulations has shown great potential for diminishing the indiscriminate use of pesticides and providing environmentally safer alternatives. Smart nano-based pesticides are designed to efficiently delivery sufficient amounts of active ingredients in response to biotic and/or abiotic stressors that act as triggers, employing targeted and controlled release mechanisms. This review discusses the current status of stimuli-responsive release systems with potential to be used in agriculture, highlighting the challenges and drawbacks that need to be overcome in order to accelerate the global commercialization of smart nanopesticides.

Development of a Chlorantraniliprole Microcapsule Formulation with a High Loading Content and Controlled-Release Property

Microcapsule formulations have been widely developed and used in agriculture to improve pesticide utilization and reduce environmental pollution. However, commercial formulations of chlorantraniliprole (CAP) are only traditional formulations due to poor solubility of CAP in organic solvents. Here, adopting a solid in oil in water (S/O/W) double-emulsion method combined with premix membrane emulsion, we successfully constructed CAP microcapsule formulations with a high loading content. The microcapsule formulations with good light and thermal stability showed a significantly sustained release for a long period, which could be optimally regulated by tuning the surface porosity and size of the porous microcapsules. Bioassay studies showed that control efficacy of the porous microcapsule formulations against Plutella xylostella was superior to that of the commercial formulation. These results demonstrated that such a porous microcapsule delivery system should have great potential for further exploration as a commercial CAP formulation.

Construction and Characterization of a Novel Sustained-Release Delivery System for Hydrophobic Pesticides Using Biodegradable Polydopamine-Based Microcapsules

Microcapsule formulations have been highly desirable and widely developed for effective utilization of pesticides and environmental pollution reduction. However, commercial and traditional microcapsule formulations of λ-cyhalothrin (LC) were prepared by complicated synthesis procedures and thereby specific organic solvents were needed. In this work, LC was encapsulated into versatile, robust, and biodegradable polydopamine (PDA) microcapsules by self-polymerization of dopamine. LC-loaded PDA microcapsules were characterized by transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and thermogravimetric analysis measurements (TGA). LC-loaded PDA microcapsules have uniform morphology with nanoscale, decent LC loading content (>50.0% w/w), and good physicochemical stability and sustained release properties. The bioassay against housefly ( Musca domestica) showed that the bioactivity and long-term efficiency of LC-loaded PDA microcapsules was superior to that of the commercial formulation. All of these results demonstrated that LC-loaded PDA microcapsules could be applied as a commercial LC microcapsule formulation with fewer environmental side effects and higher effective delivery.

Development of novel hydrogels based on Salecan and poly(N-isopropylacrylamide-co-methacrylic acid) for controlled doxorubicin release

We designed a novel semi-interpenetrating polymer network hydrogel for the controlled delivery of doxorubicin.