Foliar application of glycine-functionalized nanopesticides for effective prevention and control of root-knot nematodes via a targeted delivery strategy.

BACKGROUND: Root-knot nematodes (RKNs) are the highly damaging pests for various crops, and the prevalence of RKNs has posed serious threats to worldwide agricultural harvest, severely affecting global food security and ecosystem health. Traditional pesticide systems on controlling RKNs generally cause environmental hazards and phytotoxicity due to the excessive use of pesticides resulted from low utilization efficiency. And effective approaches with biosafe and efficient features are highly demanded to break away from the dilemma caused by RKNs. RESULTS: In this research, a nanopesticide system with root-targeted delivery function was developed to achieve effective prevention and control of RKNs. The nanocarriers (MSN-KH560-Gly) and the obtained nanopesticides (EB@MSN-KH560-Gly) were proved to be biosafe. Also, this nanopesticide system demonstrated sustained release behavior. The grafting of glycine (Gly) significantly improved the pesticide contents translocating to cucumber roots (about 304.7%). Besides, such root-targeted delivery function resulted in no root nodule in cucumber plants after the foliar application of these nanopesticides (prevention rate of 100%). In addition, the root nodule numbers of the infected cucumber plants decreased by 71.67%. CONCLUSION: Foliar application of these Gly-functionalized nanopesticides achieved effective prevention and control of RKNs due to the root-targeted delivery property inherent in this nanopesticide system, and such root-targeted delivery strategy opens a novel and efficient method to protect crops from RKN invasion and thus facilitates the development of sustainable agriculture. © 2023 Society of Chemical Industry.

Optimizing the method for removing MSNs templates using an ionic liquid ([C4mim]Cl).

The key step in preparing mesoporous silica is to remove the organic template agent, and the most common method used to achieve this goal is high-temperature calcination. However, this method has many disadvantages, one of which is that it reduces the silanol density on the surface of mesoporous silica, which affects its subsequent modification. Ionic liquids (ILs) are often used as extractants. In this work, the 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) IL is considered, and the effects of its concentration, reaction temperature, and reaction time as well as HCl concentration on the extraction rate and silanol density were investigated using an IL extraction template agent (cetyl trimethyl ammonium bromide (CTAB)). The results show that an IL concentration of 10%, a reaction temperature of 120 °C, a reaction time of 12 h, and an HCl concentration of 1% are the best reaction parameters; with these parameters, the extraction rate and the silanol density were found to be 93.19% and 2.23%, respectively. The silanol density of mesoporous silica treated by calcination is only 0.81%. A higher silanol density provides more reaction sites, so that the modified mesoporous silica treated with the IL can be loaded with more Zn ions.

Salicylic acid functionalized zein for improving plant stress resistance and as a nanopesticide carrier with enhanced anti-photolysis ability.

BACKGROUND: There is a serious global problem of salinization of arable land, causing large reduction in world food production. Use of plant hormones is an effective way to reduce damage caused to crops and salt stress. RESULTS: In this study, PEI-EDA was modified with AM-zein and grafted with plant hormone SA (AM-zein-SA) and used as a nano-pesticide carrier to load emamectin benzoate (EB). The use of AM-zein-SA as a nano-pesticide carrier could reduce the damage caused by salt stress to crops. The structure of AM-zein-SA was characterized by FTIR, UV, fluorescence, Raman, and 1H NMR spectroscopic techniques. AM-zein-SA could effectively improve the resistance of EB to ultraviolet radiations, resistance of cucumber to salt stress, and the absorption of EB by plants. The experimental results showed that AM-zein-SA could effectively improve the anti-UV property of EB by 0.88 fold. When treated with 120 mmol NaCl, the germination rate of cucumber seeds under salt stress increased by 0.93 fold in presence of 6.25 mg/L carrier concentration. The POD and SOD activities increased by 0.50 and 1.21 fold, whereas the content of MDA decreased by 0.23 fold. In conclusion, AM-zein-SA nano-pesticide carrier could be used to improve the salt resistance of crops and the adhesion of pesticides to leaves. CONCLUSION: AM-zein-SA, without undergoing any changes in its insecticidal activity, could simultaneously improve the salt stress resistance and salt stress germination rate of cucumber, reduce growth inhibition due to stress under high-concentration salt, and had a good effect on crops. In addition, EB@AM-zein-SA obviously improved the upward transmission rate of EB, as compared with EB. In this study, SA was grafted onto zein-based nano-pesticide carrier, which provided a green strategy to control plant diseases, insects, and pests while reducing salt stress on crops in saline-alkali soil.

CMC based microcapsules for smart delivery of pesticides with reduced risks to the environment.

Inefficient use of traditional pesticides causes serious environmental pollution. Stimuli-responsive pesticide formulations improve the utilization efficiency of target pests and reduce harm to non-target organisms and the environment. Herein, multi-stimuli-responsive avermectin (AVM) polyurea microcapsules (AVM@CM-SS-PU) are prepared by interfacial polymerization with modified carboxymethyl cellulose CMC-SS-NH2 as the wall material and hexadecane as the temperature-responsive core. The microcapsules are 3.90 µm in size and the encapsulation efficiency of AVM is 88.23 %. The photostability of AVM@CM-SS-PU is 5-times that of AVM solution. The insecticidal effect of AVM solution and AVM emulsifiable concentrate (EC) decreases to 13.3 % and 16.6 %, respectively, after UV irradiation for 180 min, whereas that of AVM@CM-SS-PU still remains at 50.0 %. AVM@CM-SS-PU has better foliar affinity and releases under the stimuli of temperature, glutathione, pH, cellulase, and urease. Hence, it has high insecticidal activity and biosafety. This smart controlled-release pesticide formulation provides a promising solution for green agriculture.

A high-efficient nano pesticide-fertilizer combination fabricated by amino acid-modified cellulose based carriers.

BACKGROUND: As the global population grows, large quantities of agrochemicals are used to secure food demand and there is an urgent need to develop efficient and environmentally friendly pesticides and fertilizers. Compared with traditional pesticides, nanopesticide formulations can achieve better foliar wettability, chemical stability, and water dispersibility without or with the minimal use of organic solvents, in line with the development of sustainable agriculture. RESULTS: In this research, glycidyl methacrylate (GMA) was used as an intermediate and glycine methyl ester (GLY) was used as an organic nitrogen source to modify carboxymethyl cellulose (CMC) to synthesize a pesticide nanocarrier CMC-PGMA-GLY. A nanopesticide EB@CMC-PGMA-GLY (EB@CPG) was formed by the hydrophobic and electrostatic interactions of emamectin benzoate (EB), which had good water dispersion. The good affinity of the composite towards leaves led to the effective moistening of the leaf surface by the pesticide and through the pH control pesticide release. Biological experiments show that nanopesticides can maintain high insecticidal activity and have no toxicity to seed germination. The results of pot experiment showed that the nanocarriers could be used as an organic nitrogen fertilizer to increase the fresh weight of plants by 39.77%. CONCLUSIONS: This environmentally friendly pesticide carrier can be used as a fertilizer to provide sufficient nutrients for crops, opening a new method for the development of sustainable agriculture. © 2021 Society of Chemical Industry.

Preparation of p-amino salicylic acid-modified polysuccinimide as water-based nanocarriers for enhancing pesticide stability and insecticidal activity.

Avermectin (AVM) is a biopesticide with low toxicity and high activity, but has limited use due to its poor water solubility and easy decomposition. A delivery system that can stabilize this biopesticide can play a significant role for improving its biological activity. Herein, water-dispersible functionalized polysuccinimide nanoparticles (PAD) were prepared by a ring-opening reaction and subsequently used to encapsulate AVM via self-assembly to form AVM@PAD nanoparticles with a loading ratio of 10.04 %. The half-life under UV radiation (300 W) of AVM@PAD was three times higher than that of free AVM, demonstrating the excellent protective ability of PAD. In addition, AVM@PAD nanoparticles could sustain the release of AVM for 70 h with a cumulative release rate of 70 %. AVM@PAD nanoparticles also showed a pH-responsive release, and their maximum cumulative release rate was at neutral pH. Moreover, the median lethal concentration (LC50) value of AVM@PAD with respect to Plutella xylostella was 34.50 mg/L, while that of free AVM was 56.05 mg/L. These results showed that the AVM@PAD nanoparticles can potentially and effectively promote drug stability and biological activity in agriculture.

A CDR-based approach to generate covalent inhibitory antibody for human rhinovirus protease.

Covalent target modulation with small molecules has been emerging as a promising strategy for drug discovery. However, covalent inhibitory antibody remains unexplored due to the lack of efficient strategies to engineer antibody with desired bioactivity. Herein, we developed an intracellular selection method to generate covalent inhibitory antibody against human rhinovirus 14 (HRV14) 3C protease through unnatural amino acid mutagenesis along the heavy chain complementarity-determining region 3 (CDR-H3). A library of antibody mutants was thus constructed and screened in vivo through co-expression with the target protease. Using this screening strategy, six covalent antibodies with proximity-enabled bioactivity were identified, which were shown to covalently target HRV14-3C protease with high inhibitory potency and exquisite selectivity. Compared to structure-based rational design, this library-based screening method provides a simple and efficient way for the discovery and engineering of covalent antibody for enzyme inhibition.

Rosin modified aminated mesoporous silica adsorbed tea tree oil sustained-release system for improve synergistic antibacterial and long-term antibacterial effects.

Tea tree oil, a natural antibacterial compound, cannot be used effectively because of its volatile nature. In this work, a biocompatible carrier was prepared and loaded with tea tree essential oil. The carrier was prepared via the electrostatic or chemical action of aminated mesoporous silica and sodium rosin for achieving a low volatilization rate of tea tree essential oil. A synergistic antibacterial effect was observed between sodium rosin and tea tree essential oil. This method utilized the positive charge of the amino group and the condensation reaction with the carboxyl group to achieve physical and chemical interactions with sodium rosin. Fourier Transform Infrared, Brunauer-Emmet-Teller, Zeta potential, SEM, TEM, and TG were performed to characterize the structure and properties of the samples. Compared to the electrostatic effect, the chemically modified system exhibited a longer sustained release, and the sustained release curve followed the Korsmeyer-Peppas release model. Also, the antibacterial properties of the chemically modified system exhibited better minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) respectively, the MIC and MBC forE. coliwere 0.3 mg ml-1and 0.6 mg ml-1respectively, forS. aureuswere 0.15 mg ml-1and 0.3 mg ml-1respectively. More strikingly, the sample also demonstrated long-term antibacterial performance. Therefore, this work provides a new way for the delivery of volatile antibacterial drugs to achieve sustained-release and long-lasting antibacterial effects.

A stable polyamine-modified zein-based nanoformulation with high foliar affinity and lowered toxicity for sustained avermectin release.

BACKGROUND: A large amount of pesticides that are not deposited on desired locations due to drift and rolling, endangering the ecological environment and human health. Therefore, it is urgent to develop environmentally friendly and foliar affinity formulations. The design and construction of pesticide nano-delivery system is considered to be an effective way to solve this problem. RESULTS: In this research, polyamine-modified zein (AM-zein) was synthesized by incorporating ethylenediamine-terminated polyethyleneimine into zein to improve its stability as a nanocarrier, enhance electrostatic force between the carrier and pesticides and plant foliage. Avermectin (AVM)-loaded nanoparticles, containing a high positive charge, were prepared by the anti-solvent method using AM-zein as carrier. The nanoparticles can be stored for 30 days without any significant change in the particle size and stably dispersed at pH 5-9. Compared to the commercial emulsifiable concentrate (EC), nanoparticles dispersions exhibited better leaf affinity, and the retention of dispersion increased from 7.82 to 13.86 mg/cm2 . Interestingly, we have discovered for the first time that the ultraviolet (UV) barrier effect of zein increases while prolonging the UV exposure time; 30.47% of the encapsulated AVM remained intact after exposure to UV for 60 min, compared to only 17.13% for the EC. Insecticidal activity of AVM nanoparticles did not improve compared to EC, but they demonstrated significantly lower toxicity against zebrafish. CONCLUSION: This research opens up a new idea for improving the stability of zein nanoparticles, providing a novel path to deliver pesticides efficiently and eco-friendly. © 2021 Society of Chemical Industry.

Natural rosin modified carboxymethyl cellulose delivery system with lowered toxicity for long-term pest control.

The increasing world-wide demand for food has prompted the development of efficient and environmentally friendly pesticide formulations. In this article, we have prepared CMC-g-PRSG carrier based on two compounds from natural materials carboxymethyl cellulose (CMC) and rosin (RS). The model pesticide avermectin (AVM) was encapsulated through hydrophobic interaction, and self-assembled to form nanopesticide AVM@CMC-g-PRSG with an average particle size of 167 nm. The prepared nanopesticide displays enhanced dispersibility and stability of AVM in water, and can effectively adhere to the leaves to prevent loss. The release rate of AVM encapsulated in the nanocarrier can be controlled by adjusting pH, and AVM half-life under ultraviolet radiation shows a 3-fold increase allowing control of pests for prolonged periods of time in practical applications. Biological safety tests showed that AVM@CMC-g-PRSG effectively reduces the toxicity of AVM to aquatic animals. Therefore, the cheap and degradable carrier CMC-g-PRSG can improve the effect of hydrophobic pesticides.

Preparation and Characterization of Zein-Based Nanoparticles via Ring-Opening Reaction and Self-Assembly as Aqueous Nanocarriers for Pesticides.

Herein, we prepared and compared two water-soluble amphiphilic zein-based nanocarrier systems with avermectin (AVM) payload to enhance pesticide's water-dispersity, foliage wettability, adhesion, anti-UV, and pH-responsive controlled release property. Ethylene glycol diglycidyl ether (EGDE) and diethanolamine (DEA) were utilized to conjugate with hydrophobic zein via a ring-opening reaction and then encapsulated with AVM via a hydrophobic interaction to fabricate a nanopesticide marked as AVM@Zein-EGDE/DEA. For the sake of further improving the nanocarrier's performance, sodium carboxymethyl cellulose (CMC) was grafted with methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) to form a kind of copolymer CMC-g-P(HEMA-MMA), which was applied to conjugate with Zein-EGDE via a ring-opening reaction. Likewise, another nanopesticide system named AVM@Zein-EGDE/CMC-g-P(HEMA-MMA) was obtained through hydrophobic interactions as well as the electrostatic effect. Various techniques were utilized to confirm chemical interaction, thermal behavior, structural characteristics, and stability. The results showed that AVM encapsulated in Zein-EGDE/CMC-g-P(HEMA-MMA) possessed a larger particle size with an average value of 180-254 nm than AVM loaded in Zein-EGDE/DEA with 144-175 nm but had better stability in aqueous solution. Also, AVM loaded in Zein-EGDE/CMC-g-P(HEMA-MMA) enhanced the encapsulation efficiency, and both of them exhibited excellent pH-responsive sustained release behavior. Besides, the former improved wettability on a cucumber leaf surface and enhanced adhesion ability compared to AVM@Zein-EGDE/DEA because of CMC-g-P(HEMA-MMA) with hydrophobic segments. Similarly, anti-UV performance was also enhanced owing to CMC-g-P(HEMA-MMA) as an additional protective layer. More importantly, the encapsulation of Zein-EGDE/DEA and Zein-EGDE/CMC-g-P(HEMA-MMA) as protective barriers for AVM still retained a similar toxicity level. Overall, we demonstrated the proof of concept for the application of amphiphilic zein-based nanomaterials as aqueous nanocarriers for hydrophobic pesticides.

Carboxymethyl chitosan grafted trisiloxane surfactant nanoparticles with pH sensitivity for sustained release of pesticide.

A trisiloxane surfactant (TSS) was grafted onto an intermediate, formed by the reaction of allyl glycidyl ether (AGE) with carboxymethyl chitosan (CMCS), to obtain amphiphilic CMCS-AGE-TSS. Avermectin (AVM) was used as a model pesticide and CMCS-AGE-TSS@AVM nanoparticles were prepared by self-assembly. The structures and morphologies of the nanoparticles were studied by FT-IR and 1H NMR spectroscopy, XRD, SEM, TGA, DSC, and DLS techniques. The average particle size of CMCS-AGE-TSS@AVM was 210 nm, with encapsulation efficiency of 66 %. With increase in TSS content, the contact angle on the leaf surface decreased from 73.62° for CMCS to 49.32° for CMCS-AGE-TSS. The half-life of AVM encapsulated in the polymer shell increased from 45 min to 83 min. Moreover, sustained release of the drug showed a significant response to pH. Finally, the difference in toxicities between CMCS-AGE-TSS@AVM and pure AVM was not significant.

Synthesis of mesoporous silica post-loaded by methyl eugenol as an environment-friendly slow-release bio pesticide.

Salicylaldimine, furfuralimine and benzaldehyde imine were adopted to modify mesoporous silica (MCM) respectively denoted as Sal-MCM, Fur-MCM and Ben-MCM before loading methyl eugenol (Me) for pesticide delivery. Me was adsorbed by Schiff base mesoporous silica without destructing regular hexagonal pore structure verified by the characterization results. DSC result implied that Me in amorphous state which was distributed in the pores of the mesoporous silica. The loading content of Me-Sal-MCM, Me-Fur-MCM and Me-Ben-MCM 67.89%, 73.34% and 73.84% which was higher than Me-MCM without modification (67.35%).Because the electrostatic interaction and π-π interaction between Schiff base and Me strengthened the adsorption capacity of the carrier. And the electrostatic interaction played a more important role in interaction between Me and Schiff base modified mesoporous silica. As a result, Schiff base modified sustained release system also has significantly longer sustained release time with a sequence of Me-Sal-MCM > Me-Ben-MCM > Me-Fur-MCM in release speed in negative correlation with the electric potential sequence. The behaviors of their sustained release performance can be fitted by First order kinetic model before Schiff base modification. After modification, their sustained release behaviors were consistent with Korsmeyer-Peppas equation with non-Fickian diffusion mechanism indicating that main impact on the release process after modification was no longer mainly controlled by the difference of the concentration. Finally, the highest lure rate of the modified MCM (Me-Fur-MCM) equals to the 73% of the pure Me due to its highest BET surface area and strongest interaction with Me among the three Schiff base modified samples. Therefore, the environment-friendly slow-release bio pesticide with long service life was prepared to reduce the damage on the environment caused by pesticide.

Long-lasting anti-bacterial activity and bacteriostatic mechanism of tea tree oil adsorbed on the amino-functionalized mesoporous silica-coated by PAA.

Tea tree oil (TTO) is an efficient natural antibacterial agent. However, the bacteriostatic effect of TTO does not prevail for a long period because of the volatile nature of the oil. Therefore, a novel sustained-release formulation of TTO should be developed for improving the applicability of TTO. Herein, the mesoporous silica was selected for constructing a carrier for TTO. Mesoporous silica is non-toxic, easy to modify and exhibited an adjustable pore size. First, the mesoporous silica was modified by an aminated silane coupling agent (NH2-MCM-41). Then, the polyacrylic acid (PAA) was bonded by electrostatic bonds (PAA-NH2-MCM-41), which imparted the sustained-release effect in the TTO, supported in the mesoporous silica channel (TTO/PAA-NH2-MCM-41). The prepared bacteriostatic agent can achieve long-term sustained-release properties. At room temperature (26 ℃), the release rate of TTO after 11 h release reached 50 %. However, the release rate of TTO from TTO/PAA-NH2-MCM-8 reached only 42 % after 24 h. Furthermore, the sustained release behavior of TTO/PAA-NH2-MCM-41 was consistent with the Korsmeyer-Peppas kinetic model. Compared to TTO, TTO/PAA-NH2-MCM-41 exhibited a stable and sustained bacteriostatic effect even after 50 days in a natural environment. The minimum inhibitory concentration (MIC) value of the TTO/PAA-NH2-MCM-41 against Escherichia coli (E. coli) was 0.37∼0.44 mg/mL. TTO altered the cell morphology of E. coli and broke the integrity of the cell membrane, leading to cell death.

Carboxymethyl cellulose capsulated zein as pesticide nano-delivery system for improving adhesion and anti-UV properties.

In order to further enhance hydrophilicity of zein and achieve nano-scale pesticide system, phosphorylated zein (P-Zein) was incorporated with graft copolymer CMC-g-PDMDAAC by electrostatic interaction, in which carboxymethyl cellulose (CMC) and diallyldimethylammonium chloride (DMDAAC) as monomers. P-Zein/CMC-g-PDMDAAC was applied to encapsulate model pesticide avermectin (AVM) via electrostatic interaction to achieve AVM@P-Zein/CMC-g-PDMDAAC nano-pesticides. The stability, drug loading, anti-ultraviolet, adhesion, sustained-release and toxicity of nano-pesticides presented considerable behavior confirmed via various characteristics. The results indicated that AVM@P-Zein/CMC-g-PDMDAAC had an average particle size of 360 nm, and possessed favorable dispersion performance and excellent anti-ultraviolet property compared to P-Zein. And comparatively, encapsulation efficiency increased up to 82.11%. In addition, adhesion performance of AVM@P-Zein/CMC-g-PDMDAAC on foliage also improved by about 20% compared to P-Zein. Also, AVM@P-Zein/CMC-g-PDMDAAC can intelligently control pesticide release by adjusting monomer ratio and pH values. More importantly, such nano-pesticide system presented no significant difference on toxicity in comparison with bare AVM.

Synthesis, characterization, and comparison of antibacterial effects and elucidating the mechanism of ZnO, CuO and CuZnO nanoparticles supported on mesoporous silica SBA-3.

Silanized iminodiacetic acid (GLYMO-IDA) modified mesoporous silica (G-SBA) was prepared following a co-condensation method. G-SBA/Cu2+, G-SBA/Zn2+ and G-SBA/Cu2+-Zn2+ were obtained through the impregnation method with coordination by GLYMO-IDA. SBA/CuO, SBA/ZnO, and SBA/CuZnO were generated after calcination of G-SBA/Cu2+, G-SBA/Zn2+ and G-SBA/Cu2+-Zn2+. After modification, the amount of metal ion was 6 to 70 times higher than that of the blank mesoporous silica. The diameter of nano-copper oxide particles in mesoporous silica was 4.8 nm. The bacteriostatic rates of SBA/CuO at a copper oxide concentration of 250 ppm against E. coli and S. aureus were 85.87% and 100%, respectively. SBA/CuO and SBA/CuZnO with {111} lattice planes exhibited better antibacterial effects compared to the commercial-grade nano-zinc oxide and nano-copper oxide. When exposed to ultraviolet light, SBA/CuZnO displayed the highest photocatalytic activity and optimal antimicrobial effect. Therefore, SBA/CuZnO can be an alternative to antibiotics because of its non-toxic nature and good antibacterial properties.

Enzyme cum pH dual-responsive controlled release of avermectin from functional polydopamine microcapsules.

Novel enzyme cum pH dual-responsive microcapsule were prepared with an aim to enhance the utilization of pesticides and reduce environmental pollution. The synthetic procedure involved the introduction of urea bonds by forming a covalent bond between isocyanate-functionalized polydopamine (PDA) microcapsules and polyethyleneimine (PEI). The prepared AVM@PDA-IPTS-PEI microcapsules could effectively protect avermectin (AVM) from ultraviolet radiation, and thus decelerate the decomposition rate; the cumulative release showed positive correlations with pH and the urease activity. The AVM release rate was highest at pH 10. At pH 7, the release rate was enhanced after addition of urease, showing improved urease-responsive property under neutral or weak base condition. Especially at pH 7 in presence of urease, the release behavior was in agreement with the Logistic model and able to describe the S-shaped/sigmoidal release profiles, whereas Korsmeyer-Peppas model was better suited in the absence of urease, as the value of K1 was smaller than 0.45, suggesting that the behavior was controlled by Fick's diffusion. AVM@PDA-IPTS-PEI displayed better adhesion property than AVM, and the microcapsule ameliorated foliage wettability. AVM@PDA-IPTS-PEI exhibited the insecticidal property similarly with AVM, which can be used for reducing the applied quantity of pesticides and improving their efficacy.

Coordination bonding-based polydopamine-modified mesoporous silica for sustained avermectin release.

Mesoporous silica nanoparticle (MSN) is a novel vehicle to deliver pesticide. MSN can be modified with different chemical groups to increase its interaction with pesticides. In this study, polydopamine-modified mesoporous silica (MSN-PDA) was prepared through a one-pot method with the addition of dopamine (DA). Copper ions, zinc ions, and iron ions were impregnated on MSN-PDA. In addition, avermectin (AVM) was used as the model drug. We investigated the materials' structure, adsorption and release behaviors, anti-UV properties, as well as their adhesive capability, especially the bridge effect of metal ions, π-π stacking of PDA and electrostatic interaction. The results demonstrated that the above materials possessed spherical morphology with surface areas from 635.833 to 1048.960 m2/g. Except for the zinc ions, the complexation with copper and iron ions not only enhanced materials' UV resistance but also increased their adsorption rate and the loading amount of AVM from 133 mg/g to 248 and 243 mg/g, respectively. At pH 3, 7, and 10, the bridge effect of the metal ions demonstrated a cumulative release rate using MSN-PDA not over 30% for AVM in 180 h, while the cumulative release rate for MSN reached its 50% in 60, 90, and 50 h under different pH values, respectively. We further demonstrated that the adhesive effect of PDA could be decreased by metal ions.

Phosphorylated Zein as Biodegradable and Aqueous Nanocarriers for Pesticides with Sustained-Release and anti-UV Properties.

Zein's prevalent hydrophobic character is one of the major challenges associated with ineffective utilization as an aqueous nanocarrier for pesticides. Herein, we report an effective approach to hydrophilic modification of zein by phosphorylation using nontoxic sodium tripolyphosphate (STP), thereby improving the water-solubility, foliage wettability, and adhesion ability of zein as a nanocarrier for sustained release of pesticides. The procedure relied on zein grafted with STP via N- and O- phosphate bonds and encapsulation of avermectin (AVM) as a hydrophobic model drug using phosphorylated zein (P-Zein), which achieved pH sensitivity to controlled release of AVM in various applicable environments. The chemical interaction between zein and STP was confirmed by Fourier transform infrared, thermogravimetric analysis, and differential scanning calorimetric. Scanning electron microscopy, dynamic light scattering, and zeta potential technique were applied to investigate their structural characteristics and stability, from which it was found that AVM encapsulated in P-Zein (AVM@P-Zein) formed uniform nanoparticles with average sizes in the range of 174-278 nm under different conditions, and had an excellent stability in aqueous solution. Besides, AVM@P-Zein facilitated the wettability on the foliage surface evidenced from contact angle values owing to the amphiphilic character after phosphorylation as well as enhanced the adhesion ability between liquid and leaf, restricting the pesticide runoff. Ultraviolet-visible spectroscopy was employed to explore the anti-UV property and encapsulation as well as release behavior, which revealed that the presence of P-Zein like a shell protects AVM from UV photolysis with encapsulation efficiency of approximately 81.52%, and the release of AVM from P-Zein showed pH-responsive behavior ascribed to protonation and deprotonation of phosphate under various pH conditions fitting to Elovich kinetic model, achieving the relatively more rapid release under acidic conditions. More importantly, AVM@P-Zein retained the toxicity for insecticidal effect.

Soy protein isolate-carboxymethyl cellulose conjugates with pH sensitivity for sustained avermectin release.

Carboxymethyl cellulose (CMC) was grafted onto the surface of soy protein isolate (SPI) to obtain soy protein isolate-carboxymethyl cellulose conjugate (SPC). Avermectin (AVM) was hydrophobically encapsulated as a model drug to obtain SPC@AVM. The reaction between SPI and CMC was confirmed by infrared spectroscopy, thermal analysis and SDS-PAGE electrophoresis. The results of scanning electron microscopy showed that the average particle size of the drug-loaded microspheres was 129 nm and the shape of microspheres changed from block to spherical after the addition of AVM. After encapsulation of AVM, the absolute value of zeta potential was greater than 15 mV, which indicated better stability. Compared to AVM solution, SPC@AVM showed more wettability on the leaf surface and the contact angle on the leaves decreased from 71.64° to 57.33°. The maximum liquid holding capacity increased by 41.41%, from 8.85 to 12.52 mg cm-2, which effectively reduced leaf loss. SPC@AVM also prevented UV photolysis, wherein the half-life was extended from 18 to 68 min when exposed to UV light. Moreover, toxicity tests showed that the encapsulation of AVM was beneficial to retain the insecticidal effect of AVM in the presence of ultraviolet light. The release rate of AVM showed pH responsiveness and the release rate under neutral conditions was faster than acidic and alkaline conditions. Moreover, the process conformed to the Weibull model.