Low molecular weight polylactic acid as a matrix for the delayed release of pesticides

Invasion of Trifolium repens L. aggravated by biodegradable plastics: adjustable strategy for foraging N and P

The invasion of alien plant and the pollution caused by soil microplastics have emerged as significant ecological threats. Recent studies have demonstrated aggravating effect of non-biodegradable microplastics on plant invasion. However, the impact of biodegradable microplastics (BMPs) on plant invasion remains unclear. Therefore, it is imperative to explore the impact of BMPs on plant invasion. In this study, a 30-day potting experiment with Trifolium repens L. (an invasive plant) and Oxalis corniculata L. (a native plant) was conducted to evaluate the influence of BMPs on T. repens's invasion. The findings revealed that BMPs results in a reduction in available N and P contents, thereby facilitating the colonization of arbuscular mycorrhizal fungi on T. repens 's roots. Consequently, T. repens adjusted its N and P foraging strategy by increasing P absorption ratio, and enhancing the accumulation of N and P in leaves. This ultimately led to the decrease of relative neighbor effect index of T. repens, indicating an aggravated invasion by T. repens. This study significantly enhances and expands the understanding of mechanisms by which microplastics aggravate plant invasion.

Considering degradation kinetics of pesticides in plant uptake models: proof of concept for potato

BACKGROUND

Degradation kinetics of pesticides in plants are crucial for modeling mechanism-based pesticide residual concentrations. However, due to complex open-field conditions that involve multiple pesticide plant uptake and elimination processes, it is difficult to directly measure degradation kinetics of pesticides in plants. To address this limitation, we proposed a modeling approach for estimating degradation rate constants of pesticides in plants, using potato as a model crop. An operational tool was developed to backward-estimate degradation rate constants, and three pesticides were selected to perform example simulations.

RESULTS

The simulation results of thiamethoxam indicated that the growth dynamics of the potato had a significant impact on the degradation kinetic estimates when the pesticide was applied during the early growth stage, as the size of the potato determined the uptake and elimination kinetics via diffusion. Using mepiquat, we demonstrated that geographical variations in weather conditions and soil properties led to significant differences in the dissipation kinetics in both potato plants and soil, which propagated the variability of the degradation rate constant. Simulation results of chlorpyrifos differed between two reported field studies, which is due to the effect of the vertical distribution of the residue concentration in the soil, which is not considered in the majority of recent studies.

CONCLUSIONS

Our proposed approach is adaptable to plant growth dynamics, preharvest intervals, and multiple pesticide application events. In future research, it is expected that the proposed method will enable region-specific inputs to improve the estimation of the degradation kinetics of pesticides in plants. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Electrospinning of PLA Nanofibers: Recent Advances and Its Potential Application for Food Packaging

Poly(lactic acid), also abbreviated as PLA, is a promising biopolymer for food packaging owing to its environmental-friendly characteristic and desirable physical properties. Electrospinning technology makes the production of PLA-based nanomaterials available with expected structures and enhanced barrier, mechanical, and thermal properties; especially, the facile process produces a high encapsulation efficiency and controlled release of bioactive agents for the purpose of extending the shelf life and promoting the quality of foodstuffs. In this study, different types of electrospinning techniques used for the preparation of PLA-based nanofibers are summarized, and the enhanced properties of which are also described. Moreover, its application in active and intelligent packaging materials by introducing different components into nanofibers is highlighted. In all, the review establishes the promising prospects of PLA-based nanocomposites for food packaging application.

Constructing slow-release formulations of herbicide metribuzin using its co-extrusion with biodegradable polyester poly-ε-caprolactone

Different technologies to prepare long term pesticide forms include polymer coating, preparing composites and encapsulating pesticides in nanoparticles. A simple and low-cost method was proposed to obtain slow-release formulations by co-extrusion of a pesticide with a biodegradable polymer at a temperature above the melting points of both components. A herbicide metribuzin and low-melting polyester poly-ε-caprolactone were chosen for this work. Formulations containing 10%, 20%, and 40% herbicide were prepared. During 7 days of their exposition in water, it was released from 81% to 96% of initially loaded metribuzin; the highest release was detected for 40%-loaded forms. Biodegradation of the constructs and pesticide release were further studied in the model soil. Degradation rates of the specimens increased with an increase in pesticide content, from 9% to 20% over 14 weeks for the 10%/20%-loaded and the 40%-loaded specimens, respectively. The release of metribuzin reached, respectively, 37-38% and 55%. The herbicide content in soil was lower due to its partial degradation in soil; it reached 23-25% and 33%, respectively, from initially loaded into the polymer matrix. Release kinetics of metribuzin in water as in soil best fitted the First-order model. The used approach is promising for obtaining long-term release formulations for soil applications.

Kinetics of slow release of nitrogen fertiliser from multi-layered nanofibrous structures

Fertilisers are essential in modern agriculture to enhance plant growth, crop production and product quality. Recent research has focused on the development of delivery systems designed to prolong fertiliser release. This study introduces a new technology to encapsulate and release molecules of fertilisers by using multi-layered electrospun nanofibre as a carrier. Single-layer poly L-lactic acid (PLLA) nanofibres loaded with urea were fabricated using electrospinning. Triple-layer nanofibrous structures were produced by electrospinning polyhydroxybutyrate (PHB) nanofibres as external layers with PLLA nanofibres impregnated with urea fertiliser as the middle layer. Scanning electron microscopy (SEM) and Fourier transform infrared spectrophotometry (FTIR) were employed to characterize the morphology of electrospun nanofibres. Urea release dynamic was analysed using a total nitrogen instrument (TNM-1). The results indicated that triple-layered urea-impregnated nanofibrous structures led to lower initial rate of nitrogen release and slower release rate of cumulative nitrogen which extended for more than three months. It is concluded that triple-layer nanofibrous structures have the potential for slow release delivery of fertilisers.

PLAGA-PEG-PLAGA Terpolymer-Based Carriers of Herbicides for Potential Application in Environment-Friendly, Controlled Release Systems of Agrochemicals

The present study aimed to develop and prepare new polymer/herbicide formulations for their potential application in environment-friendly, controlled release systems of agrochemicals. Selected biodegradable polymers, including L-Lactide/Glycolide/PEG/Terpolymer (PLAGA-PEG-PLAGA) as well as oligosaccharide-based polymers and their blend with terpolymer, were used to prepare microspheres loaded with two soil-applied herbicides. The degradation process of the obtained polymeric microspheres was evaluated based on (1) their weight loss and surface erosion and (2) the release rate of loaded metazachlor and pendimethalin. The herbicidal effectiveness of the herbicides released to the soil from microspheres was evaluated using the European Weed Research Council (EWRC) rating scale. Moreover, the ecotoxicological effect of herbicide-loaded microspheres buried in soil on the marine bacterial species A. fischeri was assessed. It was found that the gradual degradation rate of microparticles led to the prolonged release of both herbicides that lasted for a few months, i.e., for the entire crop season, which is crucial in terms of agrochemical and environmental protection. Maltodextrin- and dextrin-based microspheres showed higher susceptibility to degradation than terpolymer-based microspheres. The microencapsulation of herbicides protected them from decomposition and excessive leaching into soil and maintained their activity for a longer period than that for non-immobilized herbicides. The ecotoxicological assessment on A. fischeri demonstrated that the proposed microsphere-encapsulated herbicides were less toxic than non-immobilized herbicides.

Constructing sustained-release herbicide formulations based on poly-3-hydroxybutyrate and natural materials as a degradable matrix

BACKGROUND

The purpose of the present study was to develop ecofriendly herbicide formulations. Its main aim was to develop and investigate slow-release formulations of herbicides (metribuzin, tribenuron-methyl, and fenoxaprop-P-ethyl) of different structure, solubility, and specificity, which were loaded into a degradable matrix of poly-3-hydroxybutyrate (P(3HB)) blended with available natural materials (peat, clay, and wood flour).

RESULTS

Differences in the structure and physicochemical properties of the formulations were studied depending on the type of the matrix. Herbicide release and accumulation in soil were associated with the solubility of the herbicide. Fourier-transform infrared spectroscopy showed that no chemical bonds were formed between the components in the experimental formulations. Degradation of the formulations in agro-transformed soil in laboratory conditions was chiefly influenced by the shape of the specimens (granules or pellets) while the effect of the type of filler (peat, clay, or wood flour) was insignificant. The use of granules enabled more rapid accumulation of the herbicides in soil: their peak concentrations were reached after 3 weeks of incubation while the concentrations of the herbicides released from the pellets were the highest after 5-7 weeks. Loading of the herbicides into the polymer matrix composed of the slowly degraded P(3HB) and natural materials enabled both sustained function of the formulations in soil (lasting between 1.5 and ≥3 months) and stable activity of the otherwise rapidly inactivated herbicides such as tribenuron-methyl and fenoxaprop-P-ethyl.

CONCLUSION

The experimental herbicide formulations enabled slow release of the active ingredients to soil. © 2019 Society of Chemical Industry.

Synthesis and assessment of CTAB and NPE modified organo-montmorillonite for the fabrication of organo-montmorillonite/alginate based hydrophobic pharmaceutical controlled-release formulation

The research goal of the present study was to develop a carrier for loading and controlled -release of the hydrophobic drug with the combined use of organo-montmorillonite (OMMT) and alginate. The OMMT was synthesized through the intercalation modification of sodium montmorillonite (Na-MMT) with cationic cetyltrimethylammonium bromide (CTAB), nonionic nonylphenol polyoxyethylene ether (NPE) and the mixture of them via simple and convenient wet ball-milling method. Furthermore, the organo-montmorillonite/alginate (OMMT/Alg) composite hydrogel beads with slow and controlled release properties were constructed by using alginate as a coating material under the exogenous cross-linking of calcium ions. The physical and chemical properties of OMMT were comparatively evaluated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analyzer (TGA), BET-specific surface area measurements, and drug adsorption experiments. Experimental results showed that the presence of CTAB was able to facilitate the intercalation of CTAB/NPE into Na-MMT through the cation exchange reaction. And the cationic CTAB and nonionic NPE were adsorbed or intercalated into the MMT lamellar structure through the wet ball-milling process, which could change the hydrophilic nature of Na-MMT and improve its affinity to the hydrophobic drug molecules. In addition, the OMMT/Alg composite hydrogel beads displayed superior sustained-release properties than Na-MMT/Alg, mainly ascribed to the good affinity of OMMT to hydrophobic drug that retarded the drug diffusion. In particular, CTA/NPE-MMT/Alg with the highest loading capacity (LC) and encapsulation efficiency (EE) revealed the optimal controlled performance for the release of hydrophobic ibuprofen. The release followed the Korsmeyer-Peppas model suggested non-Fickian diffusion release mechanism. Based on the high drug loading capacity and excellent controlled drug release properties, the CTA/NPE-MMT/Alg incorporating hydrophobic drugs into hydrophilic matrices could be a highly promising material for use in hydrophobic drug delivery.

Advances in controlled release pesticide formulations: Prospects to safer integrated pest management and sustainable agriculture

As the world is striving hard towards sustainable agricultural practices for a better tomorrow, one of the primary focuses is on effective pest management for enhanced crop productivity. Despite newer and potent chemicals as pesticides, there are still substantial crop losses, and if by any means this loss can be tackled; it will alleviate unwanted excessive use of chemical pesticides. Scientific surveys have already established that pesticides are not being utilized by the crops completely rather a significant amount remains unused due to various limiting factors such as leaching and bioconversion, etc., resulting in an adverse effect on human health and ecosystems. Concerted efforts from scientific diaspora toward newer and innovative strategies are already showing promise, and one such viable approach is controlled release systems (CRS) of pesticides. Moreover, to bring these smart formulations within the domain of current pesticide regulatory framework is still under debate. It is thus, paramount to discuss the pros and cons of this new technology vis-à-vis the conventional agrarian methods. This review deliberates on the developmental updates in this innovative field from the past decades and also appraises the challenges encumbered. Additionally, critical information and the foreseeable research gaps in this emerging area are highlighted.

Low molecular weight poly(lactic acid) microparticles for controlled release of the herbicide metazachlor: preparation, morphology, and release kinetics

The preemergence chloroacetamide herbicide metazachlor was encapsulated in biodegradable low molecular weight poly(lactic acid) micro- and submicroparticles, and its release to the water environment was investigated. Three series of particles, S, M, and L, varying in their size (from 0.6 to 8 μm) and with various initial amounts of the active agent (5%, 10%, 20%, 30% w/w) were prepared by the oil-in-water solvent evaporation technique with gelatin as biodegradable surfactant. The encapsulation efficiencies reached were about 60% and appeared to be lower for smaller particles. Generally, it was found that the rate of herbicide release decreased with increasing size of particles. After 30 days the portions of the herbicide released for its highest loading (30% w/w) were 92%, 56%, and 34% for about 0.6, 0.8, and 8 μm particles, respectively. The release rates were also lower for lower herbicide loadings. Metazachlor release from larger particles tended to be a diffusion-controlled process, while for smaller particles the kinetics was strongly influenced by an initial burst release.

Controlling pesticide release via structuring agropolymer and nanoclays based materials

The potential use of nanoclays for modulating transfer properties of active agents in bio-sourced polymers was explored. For this purpose, new pesticide formulations were designed by combining wheat gluten, ethofumesate (model pesticide) and three montmorillonites (MMT) using a bi-vis extrusion process. Controlled release properties, evaluated through release experiments in water, were discussed in relation to the material formulations and their resulting structure. Partition coefficients were calculated from experimental data and diffusivity values were identified with a Fick's second law mechanistic model. The effect of temperature on release pattern was also evaluated and the activation energy of diffusion was determined. Ethofumesate release was slowed down for all wheat gluten based-formulations as compared to the commercial product. This slow release effect was increased in the presence of hydrophobic MMTs, due to a higher affinity for ethofumesate than for wheat gluten. Contrarily, hydrophilic MMT, displaying a greater affinity for wheat gluten than for ethofumesate seemed ineffective to slow down its release despite the tortuous pathway achieved through a well-exfoliated structure. To conclude, the release mechanisms would be rather governed by pesticide/MMT interactions than MMT/polymer matrix in the case of a hydrophobic pesticide such as ethofumesate and a hydrophilic matrix such as wheat gluten.