An Ostrinia furnacalis slow-release electrospun fibrous attractant and a preparation method and application thereof

Abstract

This invention discloses a slow-release electrospun fiber sex pheromone for the Asian corn borer, its preparation method, and its application, relating to the field of pest control technology. The method employs coaxial electrospinning technology, using polyhydroxybutyrate (PHB) as the shell and polylactic acid-glycolic acid (PLA) copolymer as the core, loaded with Asian corn borer sex pheromones to prepare a core-shell structured nanofiber membrane. By optimizing the flow rate ratio of the shell and core layers, the resulting fiber membrane exhibits uniform fiber diameter, and the core-shell structure is clearly visible via TEM. FTIR and TGA analyses confirm successful loading of TDA into the fibers. The fiber membrane has a drug loading of 12.09%, an encapsulation efficiency of 78.56%, and an effective release time of up to 138 days, significantly superior to monoaxial fibers, achieving a 42% burst release inhibition rate in the initial release phase. Field trapping trials show that this fiber membrane is more effective at trapping Asian corn borers than monoaxial electrospun fibers and commercially available butyl rubber stopper carriers.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pest control, and particularly relates to a slow-release type electrospun fibrous attractant for Ostrinia furnacalis (Guenée) and a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general context of the present application and does not necessarily constitute an acknowledgement or any form of suggestion that this information forms part of the prior art that is already known to a person of ordinary skill in the art.

[0003] Ostrinia furnacalis (Guenée) is the most important and common pest in corn production in China, which can cause the most damage to corn. The larvae can bore into stems, tassels and ears, causing stem folding and ear folding, and seriously threatening the safety of corn production. Ostrinia furnacalis has become one of the most threatening pests in corn production areas in China. In general years, it can cause 10% to 30% reduction in corn yield, and the rate of damaged plants can be as high as 90% or more in severe cases.

[0004] In production, chemical control is mainly used to control corn borer, which can have adverse effects on natural enemies and other non-target insects. The boring habit of corn borer often leads to unsatisfactory control effect of chemical pesticides, and causes pest resistance and food safety problems. Synthetic insect sex pheromones have the advantages of strong specificity, high safety, no resistance, easy degradation and no harm to natural enemies, making the insect sex pheromone technology widely used in pest integrated management, invasive pest monitoring and endangered insect protection. At present, domestic insect sex pheromone products are only limited to imitation of a few dosage forms from abroad, and the release of sex pheromones is not stable, or the effective period in the field is short, and there is a lack of mature, stable and labor-saving field application device.

[0005] Controlling the effective concentration of insect sex pheromones is crucial for achieving optimal pest control efficacy, and the most effective approach is to load them onto carrier materials to achieve long-term, controllable release. In practical applications, the molecular structure and ratio of multi-component insect sex pheromones are prone to change; increased temperature, light, or rainfall can accelerate the volatilization, oxidation, or degradation of active substances. When designing insect sex pheromone carriers, regulating the release behavior of the composite system and clarifying its release mechanism are the most critical scientific issues, involving release rate, component ratio, duration, distribution of insect sex pheromones within the carrier and intermolecular forces, release dose and insect response threshold, and environmental factors. Currently, rubber, plastics, and microcapsules have become commercially available carriers, primarily loading insect sex pheromones through impregnation, filling, or encapsulation. However, the release time of insect sex pheromones in these traditional carriers is relatively fast in the field, and the release ratio of different compound components (alcohols, aldehydes, esters, etc.) cannot be effectively controlled, severely impacting pest control effectiveness. To address the prominent issues of early burst release and short duration of effect of existing carriers, which hinder efficient and sustained control of field pests, it is urgent to conduct research on the release regulation mechanism of novel controlled-release carriers and their impact on biological activity based on the dosage requirements of insect sex pheromones in the context of controlling field pests. This research will be conducted through carrier structure design strategies to overcome the technical bottleneck of efficient and precise application of insect sex pheromones.

[0006] Electrospinning is a continuous nanofiber fabrication technology that produces nanofibers with large specific surface area, high porosity, variable pore size, and highly interconnected porous structures. These nanofibers have been widely applied in energy, textiles, environment, food, and pharmaceutical fields. Electrospinning can be used to construct drug delivery systems with rich microstructures and fiber diameters through process improvement, material combination, and physicochemical modification, optimizing drug release behavior and meeting specific drug delivery needs. In recent years, electrospun nanofibers have gradually entered the field of insect sex pheromone applications as a carrier material with great development potential, and are gradually developing into functionalized carriers. Czarnobai De Jorge et al. (2017) used electrospinning to prepare polycaprolactone / polyethylene glycol composite fibers loaded with insect sex pheromones and cypermethrin, exhibiting good sustained killing ability (84 days). Qian et al. (2023) prepared UV-induced treated polyethylene glycol diacrylate / polystyrene electrospun fibers, achieving long-term loading of methyleugenol sex pheromone (8 weeks). Cao et al. (2023) prepared electrospun fibers (7 weeks) from polyhydroxybutyrate materials that could continuously trap beet armyworms in the field, and these fibers exhibited superior degradation performance compared to commercially available carriers. Although the feasibility and research value of using electrospun fibers as insect sex pheromone carriers have been established, practical application issues such as the regulation mechanism of insect sex pheromone release, high production costs, and limited solvent selection have hindered the industrialization of related products.

[0007] Due to the limitations of uniaxial electrospinning for drug-loaded fiber applications, coaxial electrospinning has improved upon traditional uniaxial electrospinning technology. Coaxial electrospinning uses concentric dual-nozzle / multi-nozzle technology instead of a single nozzle, simultaneously spinning two or more polymer solutions. By controlling the interaction between the core and shell phase solutions, core-shell nanofibers are prepared. Core-shell structured fibers are prepared by simultaneously spinning polymer and drug solutions connected to an outer nozzle in the shell fluid layer and an inner nozzle in the core fluid layer, respectively, thus creating drug-loaded fibers with a core-shell structure. Core-shell nanofiber pesticide carriers offer numerous advantages: the spinning solutions for different layers of the core-shell fibers can be composed of polymer materials with varying properties, thereby enhancing polymer biocompatibility and fiber performance. For instance, polymer polysaccharides (starch, chitosan, sodium alginate, etc.) possess advantages such as good biocompatibility and easy material availability, but the performance of nanofibers electrospun alone is relatively poor. Introducing synthetic polymers (PVA, PLA, PCL, etc.) into core-shell nanofibers can improve fiber performance. The burst release behavior of core-shell spun fibers is significantly lower than that of uniaxial spun fibers composed of the same polymer system. Some pesticide active ingredients are susceptible to environmental influences (such as high temperature, pH value, and light) during processing and storage, leading to loss of activity. Therefore, controlling the degradation of active ingredients during processing and storage to prevent degradation or to keep degradation within a controllable range is crucial. Core-shell structured drug-loaded fibers can effectively reduce the Rayleigh-Taylor instability of the core-phase solution through the shell material, protecting the bioactivity of the loaded pesticide from external environmental factors. Furthermore, the release behavior and bioactivity of the active pesticide components in the fiber can be regulated based on the shell material's hydrophilicity / hydrophobicity and biodegradability. Currently, many scholars have explored the application effects of coaxial electrospinning in the pesticide field. However, the preparation process of coaxial electrospun fibers is complex and inefficient, and the spinning process requires precise control of relevant parameters, which to some extent limits its application development. Additionally, the control of burst release and sustained release of drugs still needs improvement.

[0008] Building upon previous research, this project aims to prepare core-shell fibers containing the sex pheromone of the Asian corn borer using electrospinning technology. The study will systematically investigate the effects of different carrier materials and electrospinning process parameters (solvent selection, core-layer polymer ratio, sex pheromone addition amount, voltage, injection rate ratio, etc.) on the morphology, fiber diameter, chemical composition, drug loading, and encapsulation efficiency of the electrospun film. Furthermore, it will evaluate the application potential in the field from the perspectives of thermodynamic properties, mechanical properties, and hydrophobicity, further exploring the release behavior and models of the insect sex pheromone core-shell fibers under different environments, with a focus on their release and biotrapping capabilities in real field conditions. This research is of great significance for promoting the development and application of next-generation insect sex pheromone sustained-release formulations in China and will also drive the application of electrospinning technology in agriculture. Summary of the Invention

[0009] Aiming at the deficiencies of the existing technology, the main object of the present invention is to solve the technical problems such as the early burst release, short effective period, and inability to effectively control the release ratio of different components, which are commonly present in the existing carriers of sex attractants for Asian corn borers.

[0010] The technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a slow-release electrospun fiber sex attractant for Asian corn borers.

[0011] The sex attractant is a core-shell structured nanofiber membrane. The shell layer material is polyhydroxybutyrate (PHB), and the core layer material is poly (lactic-co-glycolic acid) (PLGA). The core layer is loaded with the sex pheromone of Asian corn borers (TDA). The core-shell structured nanofiber membrane has a three-stage release characteristic: in the first stage, it is released through the swelling of the core layer PLGA and the microporous diffusion of the shell layer; in the second stage, a gel-like structure is formed to reduce the release rate; in the third stage, complete release is achieved through the degradation of the PHB / PLGA skeleton. The three-stage release characteristic of the core-shell structured nanofiber membrane described in the present invention is verified by fitting with the Ritger-Peppas model (0.45 < n < 0.89) and release curve experiments.

[0012] Furthermore, the drug loading amount of the fiber membrane is 5% - 20%, and the encapsulation efficiency is 50% - 90%.

[0013] Furthermore, the active ingredient of the TDA is (Z,E)-12-tetradecenyl acetate, and the mass ratio of Z / E is (20 - 30) : (80 - 70).

[0014] Even further, the drug loading amount is 10% - 15%, the encapsulation efficiency is 70% - 85%, and the mass ratio of Z / E is 22 - 26 : 78 - 74.

[0015] Furthermore, both the PHB and PLGA are biodegradable materials.

[0016] The second aspect of the present invention provides a method for preparing the slow-release electrospun fiber sex attractant for Asian corn borers described in the first aspect, including the following steps: Dissolve PLGA in an organic solvent, add TDA, and stir evenly to obtain the core layer spinning solution; Dissolve PHB in an organic solvent to obtain the shell layer spinning solution; Adopt coaxial electrospinning technology, use the shell layer spinning solution as the outer layer and the core layer spinning solution as the inner layer, and perform electrospinning through a concentric nozzle to form a core-shell structured nanofiber membrane; Dry the obtained fiber membrane to obtain the slow-release sex attractant.

[0017] Furthermore, the mass-volume concentration of PHB in the shell spinning solution is 0.05~0.10 g / mL, and the solvent is chloroform; the mass-volume concentration of PLGA in the core spinning solution is 0.1~0.3 g / mL, and the solvent is a mixture of chloroform and DMF, with a volume ratio of chloroform to DMF of 6:4~8:2.

[0018] Furthermore, the mass ratio of TDA to PLGA in the core spinning solution is 1:1 to 1:3.

[0019] Furthermore, the parameters of the coaxial electrospinning are as follows: shell flow rate 0.3~0.8 mL / h, core flow rate 0.05~0.20 mL / h, positive electrode voltage 10~20 kV, negative electrode voltage 1~5 kV, receiving distance 20~30 cm, temperature 20~30℃, and humidity 40%~60%.

[0020] Furthermore, the molecular weight of the PLGA is 1×10⁻⁶. 4 ~2×10 5 The molecular weight of the PHB is 5 × 10⁻⁶. 5 ~1×10 6 .

[0021] The third aspect of this invention provides the application of the slow-release electrospun fiber sex pheromone of the Asian corn borer described in the first aspect in the control of the Asian corn borer.

[0022] Furthermore, the application involves placing the pheromone in a trap and placing it in a field where Asian corn borers are active to trap adult Asian corn borers.

[0023] Compared with the related technologies known to the inventors, one of the technical solutions of the present invention has the following beneficial effects: This invention successfully prepared a TDA-loaded PHB / PLGA electrospun film via coaxial electrospinning. The core-shell fiber carrier exhibits uniform fiber diameter, good fiber morphology, and a distinct core-shell structure, and demonstrates good compatibility and co-spinning properties with the Asian corn borer sex pheromone. The fiber membrane also possesses good toughness. The core-shell fiber membrane PPT showed a pheromone loading of 12.09% for the Asian corn borer sex pheromone, with an encapsulation efficiency of 78.56%, and also exhibited certain hydrophobicity and opacity. In terms of release performance, the core-shell fiber effectively inhibited the early burst release of TDA and extended the release time to 138 days, significantly superior to the release time of monoaxial fibers. Field trapping trials revealed that the overall attraction effect of the Asian corn borer core-shell fiber sex pheromone on the target pest was superior to that of PLGA monoaxial fibers and commercially available butyl rubber carriers, and it also exhibited sustained effectiveness. Furthermore, the polymers PHB and PLGA used to prepare the core-shell fibers are both fully biodegradable materials, meeting both the requirements for degradation and the slow-release mechanism in field applications. They have broad application prospects in the field of integrated pest management and are expected to provide new approaches for the development of green pesticides and the control of pesticide pollutants. Attached Figure Description

[0024] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 Schematic diagram of drug loading and release mechanism via electrospinning.

[0026] Figure 2 Chemical structure diagram of the sex pheromone of the Asian corn borer.

[0027] Figure 3 : Schematic diagram of electrospun fiber membrane (a: PLT; b: PPL; c: PPT).

[0028] Figure 4 SEM images of electrospun fibers (a: PPL; b: PPT; c: PLT).

[0029] Figure 5 TEM images of electrospun core-shell fibers (a, b: PPT; c: PLT).

[0030] Figure 6 FTIR images and chemical structures of electrospun core-shell fibers.

[0031] Figure 7 TGA curves of electrospun fibers.

[0032] Figure 8 Release curve of electrospun fiber.

[0033] Figure 9 : Field trapping effect of electrospun fibers. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0037] Experimental materials and instruments Test materials Shell: Polyhydroxybutyrate (PHB), Mn: 750000; Core layer: Polylactic acid-glycolic acid copolymer (PLGA), Mw: 110000; Solvents: one or more of chloroform, dichloromethane, acetone, and N,N-dimethylformamide (DMF); Asian corn borer sex pheromone (TDA), 91.5%, with the active ingredient being (Z, E)-12-tetradecene-1-ol acetate (see... Figure 2 The Z / E mass ratio is 24:76. (Provided by Shandong Academy of Pesticide Sciences); Experimental instruments Table 1 Main Instruments for the Experiment

[0038] Principle of electrospinning solution preparation Polymer molecular weight and solvent solubility parameters determine the state of the polymer solution, directly affecting its spinnability. Besides polymer molecular weight and solvent type, the concentration and conductivity of the polymer solution also influence spinnability. Electrospinning is only possible when the polymer solution concentration is appropriate and the polymer chains are sufficiently entangled. Generally, reducing viscosity and surface tension is beneficial for the formation of finer nanofibers. Additionally, adding surfactants can achieve the same effect; when the solvent viscosity is too low, electrospinning is impossible; when the viscosity is too high, the filaments are difficult to eject from the nozzle. The polymer's conductivity also affects the electrospinning effect. Insulating polymers, due to their lack of conductivity, are difficult to electrospin into filaments. However, if the polymer electrospinning solution is too conductive, Taylor cones cannot be formed. Therefore, it is necessary to select a polymer solution or melt with appropriate conductivity as the electrospinning target. Based on extensive preliminary experimental research, the following solvents were ultimately selected: Uniaxial electrospinning: Dissolve 2.0 g of PLGA in 10 mL of chloroform / DMF solvent at a ratio of 7:3 (v / v), and add 0.2 g of TDA.

[0039] Coaxial electrospinning: Dissolve 0.7 g of PHB in 10 mL of chloroform solvent as the shell solution; dissolve 0.4 g of PLGA in 2 mL of chloroform / DMF solvent at a ratio of 7:3 (v / v) as the core solution, and add 0.2 g of TDA.

[0040] The specific electrospinning solution preparation is shown in Table 2.

[0041] Table 2. Electrospinning Solution Preparation Table

[0042] Example 1: Preparation of coaxial electrospun core-shell fiber membrane PPT Dissolve 0.7 g PHB in 10 mL chloroform and stir at 500 r / min for 8 h at room temperature to obtain the shell solution. Dissolve 0.4 g PLGA in 2 mL chloroform / DMF (7:3, v / v), add 0.2 g TDA, and stir at 500 r / min for 4 h at room temperature to obtain the core solution.

[0043] Using coaxial electrospinning, such as Figure 1, the core-shell fibers prepared by coaxial electrospinning technology require the use of a special concentric circular needle. The mechanical process parameters of coaxial electrospinning are set as follows: nozzle 21 G (inner diameter 0.5 mm, outer diameter 0.8 mm); positive electrode voltage 15 kV; negative electrode voltage 2 kV; distance between the needle and the receiver 28 cm; temperature 25°C; humidity 46%. After drying at room temperature for 24 h, a coaxial electrospinning core-shell fiber membrane was prepared and named PPT. The unloaded coaxial electrospinning fiber membrane was used as a control and named PPL.

[0044] Example 2: Preparation of uniaxial electrospinning fiber membrane PLT Dissolve 2.0 g of PLGA in 10 mL of chloroform / DMF (7:3, v / v), add 0.2 g of TDA, and stir at 500 r / min at room temperature for 4 h. Uniaxial electrospinning was used, as Figure 1 , the mechanical process parameters of uniaxial electrospinning are set as follows: needle diameter 21 G (diameter 0.8 mm); flow rate 0.5 mL / min; positive electrode voltage 11 kV; negative electrode voltage 2 kV; distance between the needle and the receiver 25 cm; temperature 25°C; humidity 45%. After drying at room temperature for 24 h, a uniaxial electrospinning fiber membrane was prepared and named PLT.

[0045] Example 3: Performance testing and results (1) Influence of flow rate on core-shell fibers The prepared core-shell solution was filled into the inner and outer needle syringes connected to the needle for electrospinning respectively, and the drug-loaded fibers were collected into a film through a grounded receiver. In the preparation of core-shell fibers by coaxial electrospinning, the flow rate ratio of the shell layer and the core layer is one of the key factors for adjusting the fiber structure and drug loading amount. In this study, the core-shell fibers were optimized by adjusting the flow rate of the core-shell solution. The results are shown in Table 3. When the shell liquid flow rate is 0.50 mL / h and the core liquid flow rate is 0.10 mL / h, the core-shell fibers with the best morphology can be obtained.

[0046] Table 3 Influence of core-shell flow rate on core-shell fibers

[0047] (2) Fiber morphology characteristics Nanofiber membrane morphology: Figure 3 shows the morphology of three nanofiber membranes prepared by different electrospinning processes. The uniaxial electrospun fiber membrane PLT has a relatively smooth surface without protrusions or depressions, and the fiber membrane has strong toughness. The drug-loaded coaxial electrospun core-shell fiber membrane PPT has a relatively smooth surface and strong material toughness, and its morphology is similar to that of the unloaded coaxial electrospun fiber membrane PPL. All materials used exhibit a continuous spinnable film-forming structure, possess good spinnability, and show good compatibility and co-spinning properties with the Asian corn borer sex pheromone.

[0048] Electron microscopy images of nanofiber membranes: The electrospun fibers were adhered to the sample stage with conductive adhesive and then subjected to gold sputtering using an ion sputtering system. The surface morphology of the core-shell fiber membrane was observed using scanning electron microscopy (SEM). The fiber diameter in the SEM images was measured using ImageJ software to statistically analyze the average fiber diameter of different samples (see Table 4). PLGA-loaded uniaxial electrospun fiber membranes (PLT) prepared by uniaxial electrospinning technology. Figure 4 c) The fibers are uneven in thickness. Compared with the fibers of uniaxial electrospun fiber membrane PLGA, the unloaded coaxial electrospun fiber membrane PPL ( Figure 4 (a) and drug-loaded coaxial electrospun core-shell fiber membranes PPT ( Figure 4 b) There are no obvious defects in the structure, the fiber diameter is uniform, and the core layer PLGA loaded with TDA is effectively wrapped by the shell layer PHB.

[0049] Table 4 Fiber Diameter

[0050] Nanofiber membrane structure characteristics: To investigate the distribution characteristics of TDA in core-shell fibers and verify the formation of the core-shell structure, transmission electron microscopy (TEM) was used for observation. The samples were collected during electrospinning; a copper mesh was agitated along the spinning path for 3-5 seconds to collect the samples for TEM observation. Figure 5 The TEM image clearly shows the core-shell structure formed by coaxial electrospinning.

[0051] (3) Chemical composition analysis: Fourier transform infrared spectroscopy (FTIR) analysis: The molecular structure and chemical composition of the core-shell fibers were analyzed using Fourier transform infrared spectroscopy (FTIR). Appropriate amounts of uniaxial electrospun fiber membranes (PLT) loaded with Asian corn borer sex pheromones, coaxial electrospun core-shell fiber membranes (PPT), coaxial electrospun fiber membranes (PPL) without insect sex pheromones, and Asian corn borer sex pheromone technical grade were pulverized, mixed, and compressed into tablets. The analysis was performed at a resolution of 4 cm⁻¹. -1 Between 600 and 4000 cm -1 Measurements were performed within the spectral range. FTIR results are as follows: Figure 6As shown, in the range of 800~1500 cm -1 Within the range of 1600–1850 cm⁻¹, the FTIR spectra of coaxial electrospun core-shell fiber membranes (PPT) and unloaded coaxial electrospun fiber membranes (PPL) are essentially the same, which is related to CH stretching, CH bending vibration, and CO stretching. -1 The characteristic peak is attributed to the asymmetric C=O stretching vibration, and variations in the intensity of the characteristic peak can also be observed in the PLT and PPT spectra. 2854 cm⁻¹ -1 and 2925cm -1 The peak at that point corresponds to the stretching vibrations of -CH3 and -CH2 in the TDA. The loading of the TDA causes this peak to appear in the FTIR spectra of the PLT and PPT.

[0052] Thermogravimetric analysis (TGA): The thermodynamic properties of nanofibers were analyzed using a thermogravimetric analyzer (TGA). 5 mg of each sample was placed in the crucible of the TGA analyzer. Under nitrogen atmosphere, the temperature was gradually increased from 30°C to 400°C at a rate of 10°C / min. The fiber weight as a function of temperature was measured. Figure 7 It can be seen that initial weight loss of the Asian corn borer sex pheromone technical was observed at 210.6℃. At this temperature, both PLT uniaxial fibers and PPT coaxial fibers also showed initial weight loss. However, at 271.5℃, PPL fibers without Asian corn borer sex pheromones showed initial weight loss. PPT and PPL coaxial fibers began to show a rapid weight loss process from 279.2℃ (Td (5%)), and the weight loss trend slowed down at 300℃. This was due to the introduction of the second component PLGA into the coaxial spun fibers by PHB fibers. The thermal decomposition (Td) of TDA technical material showed a gradual weight loss process from 226.4℃ Td (5%) to 297.4℃ Td (90%); the thermal decomposition (Td) of PLT fiber showed a gradual weight loss process from 279.2℃ Td (5%) to 375.0℃ Td (85%); the thermal decomposition (Td) of PPL fiber showed a gradual weight loss process from 279.2℃ Td (5%) to 363.5℃ Td (90%); and the thermal decomposition (Td) of PPT fiber showed a gradual weight loss process from 279.2℃ Td (5%) to 363.5℃ Td (95%).

[0053] In summary, FTIR analysis of the molecular structure and chemical composition of core-shell fibers and TGA analysis of their thermodynamic properties demonstrate that TDA is loaded into PLT and PPT fibers.

[0054] (4) Characterization of drug loading capacity and release performance of core-shell fibers Weigh an appropriate amount of fiber film and place it in a 10 mL volumetric flask. Then, add chloroform and dissolve it by sonication. Finally, analyze the encapsulation efficiency and residual release of the electrospun film by gas chromatography (GC). GC parameters: Column: HP-5 (30m × 0.32mm(id) × 0.25µm); Column temperature: 150℃, hold for 1 min, increase to 180℃ at 5℃ / min, hold for 5 min, increase to 300℃ at 40℃ / min, hold for 10 min; Injector temperature: 300℃; Detector temperature: 300℃; Carrier gas flow rate (mL / min): Carrier gas (N2) 1, Compensating gas (N2) 30, Hydrogen 30, Air 300; Split ratio: 10:1; Injection volume: 1.0. The encapsulation efficiency (Ec) of TDA by the fiber membrane was calculated according to formula (1): Ec(%) = Wn / W×100% (1) Where: Wn is the actual content of TDA in the fiber membrane; W is the amount of TDA added in the spinning solution. The fiber membrane was cut into 50 mg portions and placed in the insect attractant. It was placed in a fume hood with non-directional airflow at room temperature, and samples were taken at different time points. The remaining pheromone content was analyzed by GC. The cumulative release rate was calculated according to formula (2): Wc(%) = mn / m×100% (2) Where: mn is the actual content of TDA released; m is the initial content of TDA. The loading of uniaxial electrospun fiber PLT on the sex pheromone of Asian corn borer was 5.13%, and the encapsulation efficiency was 56.34%, while the loading of core-shell fiber PPT on the sex pheromone of Asian corn borer was 12.09%, and the encapsulation efficiency reached 78.56%. This demonstrates that, compared to uniaxial spun fibers, the coaxial structure reduces the ineffective volatilization of TDA, thereby improving the encapsulation efficiency of TDA in core-shell fibers. Regarding release performance ( Figure 8), The effective release time (90% release) of the uniaxial electrospun fiber PLT is about 64 days, while the effective release time (90% release) of the core-shell fiber PPT can reach 138 days. Moreover, the core-shell fiber effectively inhibits the burst release of TDA. When released for 20 days, the release amount can be effectively inhibited by up to 42%. Therefore, the core-shell fiber prepared by coaxial electrospinning can effectively improve the release behavior of the sex pheromone of the Asian corn borer. As can be seen from the release behavior schematic diagram in Figure 8, different from the dispersion of TDA in uniaxial fibers, the drug-loading system constructed by the core-shell fiber concentrates TDA in the core layer of PLGA, and the shell layer PHB helps to slow down the uneven dispersion of the active ingredient and the burst release of TDA loaded on the fiber surface. By fitting the drug release kinetics of the PPT and PLT nanofiber membranes, including the zero-order model, first-order model, Higuchi model, and Ritger-Peppas model (Table 5), both PPT and PLT best fit the first-order model. After fitting with the Ritger-Peppas equation, the Fick drug release characteristic index n of PLT is less than 0.45, indicating that the release of PLT follows the Fick diffusion mechanism, while the characteristic coefficient of PPT is between 0.45 and 0.89, conforming to non-Fick diffusion, and the release rate is caused by the combined effects of matrix erosion and diffusion. The study on the release mechanism of the core-shell fiber of PPT found that the release curve is divided into three stages according to the release rate of TDA. The first stage is dominated by fiber swelling and the hydrophilicity of the second component polymer PLGA, and TDA diffuses and releases through the micropores in the shell layer; the second stage is diffusion-controlled through the fused membrane structure, and the fiber membrane morphology gradually changes into a gel-like structure, and the TDA release channels decrease, resulting in a continuously low drug release rate; in the third stage, the release of TDA is based on the degradation of the PHB / PLGA polymer and involves chain breakage. In summary, the release behavior of the core-shell fiber extends the effective release time of TDA and inhibits the burst release behavior in the early stage.

[0055] Table 5 Fitting results of the release curves of fiber membranes loaded with the sex pheromone of the Asian corn borer

[0056] (5) Trapping ability of the core-shell fiber The trapping experiment was conducted in July 2025 at the maize experimental base in Songmiao Village, Linyi Town, Linyi County, Dezhou City, Shandong Province. The experiment used uniaxial electrospun fiber PLT and core-shell fiber PPT as the research objects, and commercially available butyl rubber stoppers (BRS) as a control. All carriers contained 1 mg of the active ingredient TDA. The insect attraction of the traps was recorded until the trapping failed, and the duration of trapping and the total number of insects trapped were recorded. Each treatment was repeated in triplicate. As shown in Figure 9, electrospun fibers PLT, PPT, and BRS all maintained long-term attraction to corn borers, indicating that the TDA concentration released by PLT and PPT in the field was within a reasonable range for attracting corn borers and would not inhibit their growth. The traps loaded with PLT, PPT, and BRS pheromones all captured a large number of corn borers in the early stages, indicating that PLT, PPT, and BRS all exhibited a burst release phenomenon in the early stages. In terms of both the number and trapping capacity, PPT captured a total of 229 animals within 40 days, more than BRS (197 animals) and PLT (195 animals). Analyzing the effective trapping time, PPT's effective trapping time reached 40 days, while BRS and PLT's were effective trapping times of 27 days, showing a significant difference in effectiveness compared to BRS and PLT. It is speculated that the fiber geometry and morphology of the coaxial electrospun film improved the release behavior of TDA, optimized the TDA release rate, and thus enhanced the trapping effect.

[0057] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A slow-release electrospun fiber sex attractant for the Asian corn borer, characterized in that, The sex attractant is a core-shell structured nanofiber membrane, with the shell material being polyhydroxybutyrate (PHB) and the core material being polylactic acid-glycolic acid copolymer (PLGA). The core layer is loaded with the Asian corn borer sex pheromone TDA. The core-shell structured nanofiber membrane has a three-stage release characteristic: the first stage is released through the swelling of the PLGA core layer and the diffusion through the micropores of the shell layer; the second stage forms a gel-like structure to reduce the release rate; and the third stage achieves complete release through the degradation of the PHB / PLGA backbone.

2. The slow-release electrospun fiber sex attractant for the Asian corn borer according to claim 1, characterized in that: The drug loading of the fiber membrane is 5%~20%, and the encapsulation rate is 50%~90%; the active ingredient of the TDA is (Z,E)-12-tetradecene-1-ol acetate, and the Z / E mass ratio is (20~30):(80~70).

3. A method for preparing the slow-release electrospun fiber sex pheromone of the Asian corn borer as described in claim 1 or 2, characterized in that, Includes the following steps: PLGA was dissolved in an organic solvent, TDA was added, and the mixture was stirred until homogeneous to obtain the core spinning solution. PHB is dissolved in an organic solvent to obtain a shell spinning solution; Using coaxial electrospinning technology, with the shell spinning solution as the outer layer and the core spinning solution as the inner layer, spinning is carried out through concentric nozzles to form a core-shell structured nanofiber membrane. The obtained fiber membrane is dried to obtain the sustained-release sex attractant.

4. The preparation method according to claim 3, characterized in that: The shell spinning solution contains PHB at a mass-volume concentration of 0.05~0.10 g / mL and chloroform as the solvent; the core spinning solution contains PLGA at a mass-volume concentration of 0.1~0.3 g / mL and a mixture of chloroform and DMF as the solvent, with a volume ratio of chloroform to DMF of 6:4~8:

2.

5. The preparation method according to claim 3, characterized in that: The mass ratio of TDA to PLGA in the core spinning solution is 1:1 to 1:

3.

6. The preparation method according to claim 3, characterized in that: The parameters for the coaxial electrospinning are as follows: shell flow rate 0.3~0.8 mL / h, core flow rate 0.05~0.20 mL / h, positive electrode voltage 10~20 kV, negative electrode voltage 1~5 kV, receiving distance 20~30 cm, temperature 20~30℃, and humidity 40%~60%.

7. The preparation method according to claim 3, characterized in that: The molecular weight of the PLGA is 1×10⁻⁶. 4 ~2×10 5 The molecular weight of the PHB is 5 × 10⁻⁶. 5 ~1×10 6 .

8. The application of the slow-release electrospun fiber sex pheromone for Asian corn borer according to claim 1 or 2 in the control of Asian corn borer.

9. The application according to claim 8, characterized in that: The application involves placing the pheromone in a trap and setting it in a field where Asian corn borers are active, in order to trap adult Asian corn borers.

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