Lignin-based pesticide controlled release micro-nanoparticles with multiple stimuli response and preparation method thereof

Abstract

The present application belongs to the technical field of agricultural bio-based slow-release carriers and pesticide formulations, and relates to a kind of lignin-based pesticide controlled-release micro-nanoparticles with multiple stimuli response and a preparation method thereof, lignin and hydrochloric acid dopamine are dissolved in buffer solution in proportion, an oxidizing agent is added thereto, stirred and reacted to obtain a lignin-polydopamine composite solution, which is purified by dialysis in water, dried to obtain a lignin-polydopamine solid powder; the lignin-polydopamine solid powder and abamectin are mixed in an organic solvent in a mass ratio of 1-5:1, then water is added in portions while stirring, the polarity of the system is changed, and the lignin-polydopamine micro-nanoparticle drug-loaded particles loaded with abamectin are precipitated, which are dried to obtain the present application. The abamectin delivery system has multiple environmental responsiveness, long-acting leaf adhesion function and controllable release characteristics.

Description

Technical Field

[0001] This invention belongs to the field of agricultural bio-based slow-release carriers and pesticide formulations, specifically relating to a lignin-based pesticide controlled-release micro / nanoparticle with multiple stimulus responses and its preparation method. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Precise, efficient, and green application of pesticides is a core challenge for the sustainable development of modern agriculture. Traditional pesticide formulations, such as abamectin, generally suffer from problems such as rapid photodegradation, weak leaf adhesion, uncontrollable release, and low utilization, leading to frequent application, increased costs, and serious environmental residues and ecotoxicity.

[0004] Furthermore, the biological microenvironment during pest and disease occurrence (such as the pH of the pest's gut, specific enzymes secreted by plant wounds or pathogens) and natural environmental factors (diurnal temperature variation) together constitute a multi-trigger release scenario, urgently requiring the development of multi-response systems capable of simultaneously responding to pH, biological enzymes, and temperature. However, most existing vectors only have the ability to respond to a single environmental signal (such as pH or temperature), making it difficult to adapt to the complex and ever-changing environment in the field. Summary of the Invention

[0005] To address the common problems of existing pesticide controlled-release carriers, such as limited environmental response dimensions, complex preparation processes, and weak adhesion to leaf surfaces, this invention provides lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses and their preparation method. This invention's abamectin intelligent delivery system, derived from natural sources and possessing multiple environmental responses, long-lasting leaf adhesion, and controllable release characteristics, has significant scientific value and application prospects for overcoming the common technical bottlenecks of traditional pesticides, such as low utilization rates, short duration of action, and mismatch between release behavior and pest and disease occurrence patterns under complex field conditions.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses, comprising the following steps:

[0008] Lignin and dopamine hydrochloride were dissolved in a buffer solution in a certain proportion, an oxidant was added, and the mixture was stirred to react and obtain a lignin-polydopamine composite solution. The solution was purified by dialysis in water and dried to obtain lignin-polydopamine solid powder.

[0009] The lignin-polydopamine solid powder and abamectin amine were mixed in an organic solvent at a mass ratio of 1 to 5:1. Water was then added in portions while stirring to change the polarity of the system, causing micro-nano drug-loaded particles of abamectin to precipitate out. The micro-nano drug-loaded particles were then dried to obtain the final product.

[0010] Secondly, the present invention provides lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses, prepared by the aforementioned preparation method.

[0011] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows:

[0012] (1) The lignin-based pesticide controlled-release micro / nanoparticles prepared in this invention possess multiple environmental stimulus response characteristics, realizing intelligent and precise pesticide release behavior. These micro / nanoparticles can simultaneously respond to various environmental signals commonly found in the field. Under alkaline conditions in the insect's gut or under the conditions of laccase secreted by plant pathogens, the lignin-polydopamine complex structure can undergo chemical bond breakage or conformational changes, accelerating pesticide release. Under elevated temperature conditions, the system can further regulate the release rate through diffusion. This "pH-enzyme-temperature" synergistic response mechanism enables pesticide release to match the occurrence patterns of pests and diseases and environmental changes, significantly improving the targeting and timeliness of pesticide application.

[0013] (2) The micro- and nano-particles prepared in this invention possess both excellent leaf surface adhesion and environmental stability, significantly improving the field retention and duration of action of pesticides. The catechol structure of polydopamine can firmly bind to the leaf surface through hydrogen bonding, coordination, and covalent interactions, giving the particles strong bioadhesion. At the same time, the aromatic structure of lignin and polydopamine molecules, together with the phenolic hydroxyl groups, constitute a network for ultraviolet absorption and free radical quenching, effectively slowing down the photodegradation of pesticides. This composite carrier enhances leaf surface adhesion while significantly improving the system's resistance to rain erosion and photostability, thereby reducing pesticide loss due to environmental factors and extending the effective action time in the field. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, 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.

[0015] Figure 1 Scanning electron microscope image of abamectin / lignin-polydopamine micro / nanoparticles prepared in Example 1;

[0016] Figure 2 This is a scanning electron microscope image of the adhesion effect of abamectin / lignin-polydopamine micro / nanoparticles prepared in Example 1 on cabbage leaves;

[0017] Figure 3The cumulative release curves of the abamectin / lignin-polydopamine micro / nanoparticles prepared in Example 1 under different pH conditions are shown.

[0018] Figure 4 The cumulative release curves of the abamectin / lignin-polydopamine micro / nanoparticles prepared in Example 1 under different temperature conditions are shown.

[0019] Figure 5 The cumulative release curves of the abamectin / lignin-polydopamine micro / nanoparticles prepared in Example 1 under different laccase concentrations are shown.

[0020] Figure 6 The image shows a comparison of the photodegradation resistance of the avermectin / lignin-polydopamine micro / nanoparticles prepared in Example 1, the avermectin / lignin micro / nanoparticles prepared in Comparative Example 1, and the avermectin / polydopamine solid powder prepared in Comparative Example 2. Detailed Implementation

[0021] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] To address the technical problems mentioned in the background section, this invention provides a method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses, comprising the following steps:

[0023] Lignin and dopamine hydrochloride were dissolved in a buffer solution in a certain proportion, an oxidant was added, and the mixture was stirred to react and obtain a lignin-polydopamine composite solution. The solution was purified by dialysis in water and dried to obtain lignin-polydopamine solid powder.

[0024] The lignin-polydopamine solid powder and abamectin amine were mixed in an organic solvent at a mass ratio of 1 to 5:1. Water was then added in portions while stirring to change the polarity of the system, causing micro-nano drug-loaded particles of abamectin to precipitate out. The micro-nano drug-loaded particles were then dried to obtain the final product.

[0025] Lignin is a natural aromatic polymer found in plant cell walls, typically present as a byproduct in papermaking and biomass processing. It boasts advantages such as abundant availability, low cost, and certain UV absorption and biocompatibility. Polydopamine, a biomimetic adhesive material, exhibits excellent surface adhesion and photostability, and can interact with various biological or pesticide molecules to form a protective layer. However, current technologies have not effectively combined the advantages of both to construct a composite drug delivery system that combines multi-stimulus response release, leaf adhesion, excellent photostability, simple processing, and controllable cost. This invention not only significantly enhances the adhesion persistence on leaf surfaces through the introduction of polydopamine but also utilizes its synergistic effect with lignin to endow the carrier with multi-responsive release characteristics to pH changes, laccase catalysis, and temperature fluctuations. This allows for precise control of pesticide release behavior in terms of time, space, and dosage, providing an integrated solution to address the current problems of "rapid loss, chaotic release, and short effective period" in pesticide use.

[0026] Lignin-polydopamine (an amphiphilic composite carrier) and hydrophobic avermectin are dissolved together in an organic solvent (such as acetonitrile) to form a homogeneous solution. Upon addition of water, the polarity of the system increases significantly, and the hydrophobic structure of the carrier (lignin aromatic ring, polydopamine hydrophobic segment) undergoes intermolecular aggregation, simultaneously encapsulating the hydrophobic avermectin molecule. The aggregated carrier-drug complex remains stable due to hydrophobic interactions and precipitates out, yielding micro / nano drug-loaded particles after drying. Water addition must be carried out under stirring and the reaction must be continued for 1–3 hours to ensure uniform particle dispersion and prevent agglomeration.

[0027] Lignin is rich in benzene rings and phenolic hydroxyl groups, which can efficiently absorb ultraviolet light and inhibit the photolysis of avermectin. Lignin can be catalyzed and degraded by laccase secreted by pathogens, destroying the particle structure and accelerating drug release, thus achieving an enzyme response. Under alkaline conditions, phenolic hydroxyl groups are deprotonated, changing the hydrophilicity and hydrophobicity of the particles, promoting drug release, and achieving a pH response.

[0028] The catechol structure of polydopamine can form hydrogen bonds and coordination bonds with hydroxyl / carboxyl groups on the leaf surface, significantly improving particle retention. The protonation state of the amino group changes at different pH values, affecting particle charge distribution and stability, and regulating the release rate. The conjugated structure can absorb ultraviolet light and synergistically protect abamectin with lignin.

[0029] The synergistic effect of the hydrophobic lignin framework and the amphiphilic structure of polydopamine can effectively improve drug loading efficiency and particle stability.

[0030] In some embodiments, the lignin is selected from at least one of alkali lignin, sulfate lignin, enzymatically hydrolyzed lignin, or lignin extracted with organic solvents.

[0031] Alkali lignin is a type of lignin extracted by treating plant fiber raw materials (such as wood and straw) with alkaline solutions (such as NaOH and KOH). It is a major byproduct of alkaline pulping (a traditional process in the papermaking industry). Its molecular structure retains more phenolic hydroxyl groups, making it relatively hydrophilic.

[0032] Sulfate lignin refers to lignin produced during the pulping process using the sulfate method (Kraft method, using a mixture of Na2S and NaOH). It is currently the type of lignin with the largest industrial output. Its molecular structure incorporates sulfur elements (such as thioether bonds) due to the action of sulfides, resulting in strong thermal stability and antioxidant properties.

[0033] Enzymatic hydrolysis of lignin refers to the lignin components remaining during the enzymatic hydrolysis and saccharification of biomass (such as using cellulase to decompose plant fibers to produce fuel ethanol), and is a byproduct of biorefining.

[0034] Organic solvent-extracted lignin refers to lignin extracted using organic solvents (such as single or mixed solvents like ethanol, acetone, and xylene) under mild conditions. It is a product of green extraction processes, and its molecular structure is closest to that of natural lignin, with almost no chemical modification.

[0035] In some embodiments, the buffer solution is a Tris-HCl buffer solution with a pH of 8-9 and a concentration of 0.08-0.12 mol / L.

[0036] The synthesis of polydopamine depends on the oxidative self-polymerization of dopamine in an alkaline environment. pH 8.5 is the optimal pH range for the oxidation and cross-linking of dopamine molecules to form polydopamine. Tris-HCl buffer has excellent buffering capacity in the pH range of 8.0-9.0, and a concentration of 0.08-0.12 mol / L can ensure that the pH value does not fluctuate drastically due to side reactions such as dopamine oxidation and lignin dissolution during the reaction, thus ensuring that the complex reaction of lignin and polydopamine proceeds uniformly and in a controllable manner.

[0037] In some embodiments, the mass ratio of lignin to dopamine hydrochloride is 1~3:1~1.5.

[0038] Preferably, the concentration of lignin dissolved in the buffer solution is 1-5 wt%.

[0039] In some embodiments, the oxidant is selected from at least one of hydrogen peroxide, ammonium persulfate, or laccase.

[0040] The synthesis of polydopamine depends on the oxidative cross-linking reaction of dopamine molecules. Oxidizing agents (such as hydrogen peroxide, ammonium persulfate, and laccase) can provide an oxidative environment to promote the oxidative dehydrogenation of dopamine hydrochloride in an alkaline buffer to form an ortho-benzoquinone intermediate, which in turn generates polydopamine through a self-polymerization reaction.

[0041] Oxidants can activate functional groups such as phenolic hydroxyl groups and carboxyl groups on lignin molecules through oxidation, causing them to undergo covalent cross-linking or non-covalent interaction with catechol and amino groups of polydopamine, thereby forming a stable lignin-polydopamine composite structure.

[0042] Preferably, the amount of hydrogen peroxide is 1-10% of the lignin mass, the amount of ammonium persulfate is 3-15% of the dopamine hydrochloride mass, and the amount of laccase is 5-10 IU / g lignin.

[0043] In some embodiments, after adding the oxidant, the stirring reaction time is 12-24 h.

[0044] In some embodiments, the dialysis bag used for dialysis purification has a molecular weight cutoff of 800-1200 Da, and the dialysis time is 1-3 days.

[0045] In some embodiments, the organic solvent is selected from at least one of acetonitrile, ethanol, or acetone.

[0046] In some embodiments, the concentration of lignin-polydopamine solid powder dissolved in an organic solvent is 0.5 to 1.5 wt%.

[0047] In some embodiments, the volume ratio of organic solvent to water is 1 to 4:1.

[0048] Preferably, after adding water to the organic solvent, the reaction continues for 1 to 3 hours.

[0049] In some embodiments, the process of precipitating lignin-polydopamine-encapsulated abamectin is carried out under light-protected conditions.

[0050] The conjugated double bonds in the avermectin molecule readily absorb ultraviolet energy and degrade, leading to the loss of the active ingredient. During drug delivery, avermectin is not yet fully encapsulated by the lignin-polydopamine carrier. If exposed to light, it will undergo photolysis, reducing the drug content and efficacy of the final product. Light-protected conditions prevent byproducts of photodegradation during the self-assembly and delivery stage from interfering with the hydrophobic interaction between the lignin-polydopamine and the drug, ensuring effective carrier encapsulation of avermectin and maintaining the structural integrity and drug delivery stability of the micro / nanoparticles.

[0051] In some embodiments, after lignin-polydopamine-loaded avermectin is precipitated, the reaction system is further subjected to a dialysis step, wherein the molecular weight cutoff of the dialysis bag is 800-1200 Da and the dialysis time is 1-3 days.

[0052] Secondly, the present invention provides lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses, prepared by the aforementioned preparation method.

[0053] The present invention will be further described below with reference to the embodiments.

[0054] Example 1

[0055] (1) 1 g of enzymatically hydrolyzed lignin and 1.5 g of dopamine hydrochloride were dissolved in 100 mL of Tris-HCl buffer solution with pH 8.5 and a concentration of 0.1 mol / L. 0.05 mL of hydrogen peroxide (H2O2, 30%) and 0.05 g of ammonium persulfate were added to the resulting mixture and reacted under stirring for 24 h to obtain a lignin-polydopamine solution. The solution was dialyzed in pure water for 2 days using a dialysis bag with a molecular weight of 1000 Da and then freeze-dried to obtain lignin-polydopamine solid powder.

[0056] (2) Under light-protected conditions, 400 mg of lignin-polydopamine solid powder and 400 mg of avermectin from step (1) were added to 80 mL of acetonitrile, mixed, and ultrasonically dispersed. 40 mL of deionized water was added dropwise at a rate of 2 mL / min under stirring to form self-assembled micro / nanoparticles. The reaction mixture was then dialyzed in pure water using a 1000 Da molecular weight dialysis bag for 2 days to completely remove unencapsulated avermectin. The resulting avermectin / lignin-polydopamine micro / nanoparticles were obtained by freeze-drying. The scanning electron microscope image is shown below. Figure 1 As shown, by Figure 1 It can be seen that the main morphology of abamectin / lignin-polydopamine micro-nanoparticles is spherical, but the rough parts of the microspheres adhere to each other to form dimers or small aggregates, with the size mainly distributed in the range of 400 nm to 2 µm.

[0057] Example 2

[0058] (1) Dissolve 1 g of alkali lignin and 1 g of dopamine hydrochloride in 100 mL of Tris-HCl buffer solution with pH 8.5 and concentration of 0.1 mol / L. Add 0.1 mL of hydrogen peroxide (H2O2, 30%) to the resulting mixture and react under stirring for 24 h to obtain a lignin-polydopamine solution. Dialyze the solution in pure water using a dialysis bag with a molecular weight of 1000 Da for 2 days and freeze-dry to obtain lignin-polydopamine solid powder.

[0059] (2) Under light-protected conditions, 400 mg of lignin-polydopamine solid powder and 200 mg of abamectin were added to 40 mL of acetonitrile and mixed and ultrasonically dispersed. Under stirring, 40 mL of deionized water was added dropwise at a rate of 2 mL / min to form self-assembled micro-nanoparticles and react for 2 h. The resulting reaction solution was dialyzed in pure water with a 1000 Da molecular weight dialysis bag for 2 days to completely remove unloaded abamectin and obtained by freeze drying to obtain abamectin / lignin-polydopamine micro-nanoparticles.

[0060] Example 3

[0061] (1) Dissolve 2 g of lignin sulfate and 1 g of dopamine hydrochloride in 100 mL of Tris-HCl buffer solution with pH 8.5 and a concentration of 0.1 mol / L. Add 0.15 g of ammonium persulfate to the resulting mixture and react for 24 h under stirring to obtain a lignin-polydopamine solution. Dialyze the solution in pure water using a dialysis bag with a molecular weight of 1000 Da for 2 days and freeze-dry to obtain lignin-polydopamine solid powder.

[0062] (2) Under light-protected conditions, 400 mg of lignin-polydopamine solid powder and 100 mg of avermectin were added to 80 mL of acetonitrile and mixed and ultrasonically dispersed. Under stirring, 20 mL of deionized water was added dropwise at a rate of 2 mL / min to form self-assembled micro-nanoparticles and react for 2 h. The resulting reaction solution was dialyzed in pure water with a 1000 Da molecular weight dialysis bag for 2 days to completely remove unloaded avermectin and obtained avermectin / lignin-polydopamine micro-nanoparticles by freeze drying.

[0063] Example 4

[0064] (1) Dissolve 3 g of lignin extracted with organic solvent in 300 mL of acetic acid buffer solution with pH 5.0, add 30 IU of laccase, disperse evenly by ultrasonication, add 1 g of dopamine hydrochloride to dissolve, and react for 24 h under stirring to obtain lignin-polydopamine solution. Dialyze the solution in pure water for 2 days using a dialysis bag with a molecular weight of 1000 Da, and freeze-dry to obtain lignin-polydopamine solid powder.

[0065] (2) Under light-protected conditions, 500 mg of lignin-polydopamine solid powder and 100 mg of avermectin were added to 80 mL of acetonitrile and mixed and ultrasonically dispersed. Under stirring, 40 mL of deionized water was added dropwise at a rate of 1 mL / min to form self-assembled micro-nanoparticles and react for 2 h. The resulting reaction solution was dialyzed in pure water for 2 days using a dialysis bag with a molecular weight of 1000 Da to completely remove unloaded avermectin and then freeze-dried to obtain avermectin / lignin-polydopamine micro-nanoparticles.

[0066] Example 5

[0067] (1) 1 g of enzymatically hydrolyzed lignin and 1.5 g of dopamine hydrochloride were dissolved in 100 mL of Tris-HCl buffer solution with pH 8.5 and a concentration of 0.1 mol / L. 0.1 mL of hydrogen peroxide (H2O2, 30%) and 0.1 g of ammonium persulfate were added to the resulting mixture and reacted under stirring for 24 h to obtain a lignin-polydopamine solution. The solution was dialyzed in pure water for 2 days using a dialysis bag with a molecular weight of 1000 Da and then freeze-dried to obtain lignin-polydopamine solid powder.

[0068] (2) Under light-protected conditions, 300 mg of lignin-polydopamine solid powder and 100 mg of avermectin were added to 80 mL of acetonitrile and mixed and ultrasonically dispersed. Under stirring, 40 mL of deionized water was added dropwise at a rate of 3 mL / min to form self-assembled micro-nanoparticles and react for 2 h. The resulting reaction solution was dialyzed in pure water with a 1000 Da molecular weight dialysis bag for 2 days to completely remove unloaded avermectin and obtained avermectin / lignin-polydopamine micro-nanoparticles by freeze drying.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that in step (2), the lignin-polydopamine solid powder is replaced with enzymatically hydrolyzed lignin powder, and everything else is the same as in Example 1.

[0071] 400 mg of enzymatically hydrolyzed lignin powder and 400 mg of avermectin were added to 80 mL of acetonitrile and mixed and ultrasonically dispersed. Under stirring, 40 mL of deionized water was added dropwise at a rate of 2 mL / min to form self-assembled micro / nanoparticles and react for 2 h. The resulting product was dialyzed in pure water using a 1000 Da molecular weight dialysis bag for 2 days to completely remove unencapsulated avermectin and then freeze-dried to obtain avermectin / lignin micro / nanoparticles.

[0072] Comparative Example 2

[0073] 1 g of dopamine hydrochloride was dissolved in 100 mL of Tris-HCl buffer solution with pH 8.5 and a concentration of 0.1 mol / L. After stirring at room temperature for 24 h, the mixture was centrifuged, washed, and dried to obtain polydopamine.

[0074] 400 mg of polydopamine was dissolved in 40 mL of deionized water and then added dropwise to 80 mL of acetonitrile solution containing 400 mg of avermectin while stirring. The reaction was stirred at room temperature for 24 h. The resulting reaction solution was dialyzed in pure water for 2 days using a dialysis bag with a molecular weight of 1000 Da to completely remove unencapsulated avermectin. The resulting solution was then freeze-dried to obtain avermectin / polydopamine solid powder.

[0075] Performance Test 1:

[0076] The 50 mg abamectin / lignin-polydopamine micro / nanoparticles prepared in Example 1 were dispersed in 10 mL of water to prepare a suspension. Then, 1.5*3 cm cabbage leaves were immersed in the micro / nanoparticle suspension for 15 seconds using tweezers. The leaves were then removed, air-dried, and appropriately sized dried leaves were cut for SEM imaging. The results are as follows. Figure 2 As shown, by Figure 2 It is known that cabbage leaves have a complex leaf surface morphology with wrinkles, stomata and grooves, while abamectin / lignin-polydopamine micro-nanoparticles are mainly enriched around the stomata and in the grooves, showing excellent leaf surface adhesion.

[0077] Performance Test 2:

[0078] Suspensions were prepared by dispersing 50 mg of the avermectin / lignin-polydopamine micro / nanoparticles prepared in Examples 1-5, the avermectin / lignin micro / nanoparticles prepared in Comparative Example 1, and the avermectin / polydopamine solid powder prepared in Comparative Example 2 in 10 mL of water. Then, cabbage leaves were cut into strips, and their surface area (S) was measured.

[0079] The leaf strip was placed in the suspension for 15 seconds using tweezers, then removed and suspended above a beaker until no more droplets fell. The mass (m) of the micro / nano particles attached to the leaf was determined by calculating the change in the mass of the beaker before and after the experiment. The amount of micro / nano particles adhered to the leaf (mg / cm³) was calculated. 2 The results are shown in Table 1:

[0080] Table 1. Measurement of adhesion amount of different samples on cabbage leaves

[0081]

[0082] Compared to Example 1, Comparative Example 1 prepared avermectin / lignin micro / nanoparticles without polydopamine grafting. Compared to Comparative Example 1, the adhesion amount of the avermectin / lignin-polydopamine micro / nanoparticles in Example 1 increased by approximately 172.2%. Therefore, grafting polydopamine can significantly improve the adhesion effect of micro / nanoparticles on leaf surfaces.

[0083] Comparative Example 2, compared to Example 1 above, provides a method for preparing a single avermectin / polydopamine solid powder. Compared to Comparative Example 2, the adhesion amount in Example 1 is increased by approximately 69%, due to... Figure 6 The results showed that the UV photolysis resistance of Example 1 increased by 17.42% after 96 h. Therefore, the presence of lignin can improve the photolysis resistance of avermectin compared with single avermectin / polydopamine solid powder.

[0084] Performance Test 3:

[0085] 1 mL of the avermectin / lignin-polydopamine suspension (5 mg / mL) from Example 1 was dispersed in 10 mL of water, and the pH of the system was adjusted to 3, 7, and 11 using hydrochloric acid and sodium hydroxide solutions, respectively. Each pH sample was transferred to a dialysis bag (molecular weight cutoff 1000 Da), immersed in a glass bottle containing 100 mL of ethanol / water solution (50 / 50 v / v), and incubated at 25°C in the dark with constant shaking at 100 rpm. At predetermined time points (2, 4, 8, 12, 24, 36, 48, 60, 72, and 100 h), 1 mL of the release medium was sampled. After each sampling, an equal volume of fresh ethanol / water solution (50 / 50, v / v) was added to maintain a constant total volume of the release medium. After filtration through a 0.22 µm filter membrane, the avermectin concentration was analyzed by high-performance liquid chromatography (HPLC) at 245 nm. The cumulative release rate of avermectin was calculated, and cumulative release curves under different pH conditions were plotted. The results are shown below. Figure 3 As shown; by Figure 3 It was found that after 100 h, the cumulative release rates of avermectin in acidic (pH=3), neutral (pH=7), and alkaline (pH=11) media were 76.7%, 59.9%, and 90.3%, respectively. This significant pH-responsive characteristic enables targeted release into the midgut fluid of lepidopteran larvae.

[0086] Performance Test 4:

[0087] One mL of the avermectin / lignin-polydopamine suspension (5 mg / mL) from Example 1 was dispersed in 10 mL of water and then transferred to a dialysis bag (molecular weight cutoff 1000 Da). The dialysis bag was immersed in a glass bottle containing 100 mL of ethanol / water solution (50 / 50 v / v) and incubated at 25°C, 35°C, and 45°C in the dark with constant shaking at 100 rpm. At predetermined time points (2, 4, 8, 12, 24, 36, 48, 60, 72, and 100 h), 1 mL of the release medium was sampled. After each sampling, an equal volume of fresh ethanol / water solution (50 / 50 v / v) was added to maintain a constant total volume of the release medium. After filtration through a 0.22 µm filter membrane, the avermectin concentration was analyzed by high-performance liquid chromatography (HPLC) at 245 nm. The cumulative release rate of avermectin was calculated, and cumulative release curves under different temperature conditions were plotted. The results are shown below. Figure 4 As shown; by Figure 4 It was found that after 100 hours, the cumulative release rates of abamectin reached 59.9%, 90.3%, and 97.9% at 25℃, 35℃, and 45℃, respectively. This significant temperature-responsive characteristic allows for on-demand release of the drug during the daytime when pests are feeding and active.

[0088] Performance Test 5:

[0089] 1 mL of the avermectin / lignin-polydopamine suspension (5 mg / mL) from Example 1 was dispersed in 10 mL of water. Laccase was added to achieve concentrations of 1 U / mL and 2 U / mL, respectively. The solutions were then transferred to dialysis bags (molecular weight cutoff 1000 Da). The dialysis bags were immersed in a glass bottle containing 100 mL of ethanol / water solution (ethanol to water volume ratio 1:1) and incubated at 25°C in the dark with uniform shaking at 100 rpm. At predetermined time points (2, 4, 8, 12, 24, 36, 48, 60, 72, and 100 h), 1 mL of the release medium was sampled. After each sampling, an equal volume of fresh ethanol / water solution (50 / 50, v / v) was added to maintain a constant total volume of the release medium. After filtration through a 0.22 µm filter membrane, the avermectin concentration was analyzed by high-performance liquid chromatography at 245 nm. The cumulative release rate of avermectin was calculated, and cumulative release curves were plotted under different laccase concentrations. The results are as follows: Figure 5 As shown; by Figure 5 The cumulative release rates of abamectin in media with laccase concentrations of 0 U / mL, 1 U / mL, and 2 U / mL were 59.9%, 65.5%, and 84.6%, respectively. This significant enzyme-responsive characteristic enables precise targeted release into many plant pathogenic fungi and insect gut microbiota.

[0090] Performance Test 6:

[0091] 1 mL of avermectin suspension (5 mg / mL) was added to a 6 cm culture dish containing 5 mL of deionized water. The dish was then covered and gently shaken to ensure uniform dispersion. The dish was irradiated at 40 cm from a 30 W UV lamp for 6, 12, 24, 36, 60, and 96 h. After each irradiation, the contents of the culture dish were dissolved in anhydrous ethanol, sonicated, and diluted to 50 mL. The resulting solution was filtered through a 0.22 µm filter and analyzed by high-performance liquid chromatography (HPLC) at 245 nm to determine the avermectin concentration. The cumulative residual amount of avermectin was calculated, and the photosynthesis resistance curve was plotted. The results are shown below. Figure 6 As shown.

[0092] Depend on Figure 6 It was found that avermectin has poor photostability, with only 22.47% remaining after 96 hours of UV irradiation. In contrast, the avermectin / lignin micro / nanoparticles in Comparative Example 1 showed the best UV resistance, with a cumulative avermectin residue of 88.72% after 96 hours. This is because lignin is rich in benzene rings and phenolic hydroxyl groups, which efficiently absorb ultraviolet light and prevent avermectin decomposition. Although the cumulative residue of the avermectin / lignin-polydopamine micro / nanoparticles in Example 1 after 96 hours of UV irradiation was 86.21%, slightly lower than that of the avermectin / lignin micro / nanoparticles alone, it was still better than the avermectin / polydopamine solid powder in Comparative Example 2, indicating that lignin provides the main protective effect in the UV resistance test of avermectin.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses, characterized in that: Includes the following steps: Lignin and dopamine hydrochloride were dissolved in a buffer solution in a certain proportion, an oxidant was added, and the mixture was stirred to react and obtain a lignin-polydopamine composite solution. The solution was purified by dialysis in water and dried to obtain lignin-polydopamine solid powder. The lignin-polydopamine solid powder and abamectin are mixed in an organic solvent at a mass ratio of 1 to 5:

1. Water is then added in portions while stirring to change the polarity of the system, causing the lignin-polydopamine-loaded abamectin micro-nano drug-carrying particles to precipitate out. The micro-nano drug-carrying particles are then dried to obtain the final product. The lignin is selected from at least one of alkali lignin, sulfate lignin, enzymatically hydrolyzed lignin, or lignin extracted with organic solvents.

2. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: The buffer solution is a Tris-HCl buffer solution with a pH of 8-9 and a concentration of 0.08-0.12 mol / L.

3. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: The oxidant is selected from at least one of hydrogen peroxide, ammonium persulfate, or laccase; the amount of hydrogen peroxide is 1-10% of the lignin mass, the amount of ammonium persulfate is 3-15% of the dopamine hydrochloride mass, and the amount of laccase is 5-10 IU / g lignin.

4. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: The dialysis bag used for dialysis purification has a molecular weight cutoff of 800-1200 Da, and the dialysis time is 1-3 days.

5. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: The organic solvent is selected from at least one of acetonitrile, ethanol, or acetone.

6. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: The concentration of lignin-polydopamine solid powder dissolved in organic solvent is 0.5~1.5 wt.

7. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: The volume ratio of organic solvent to water is 1 to 4:

1.

8. The method for preparing lignin-based pesticide controlled-release micro / nanoparticles with multiple stimulus responses according to claim 1, characterized in that: After lignin-polydopamine-encapsulated abamectin is precipitated, the reaction system is further subjected to a dialysis step. The molecular weight cutoff of the dialysis bag is 800-1200 Da, and the dialysis time is 1-3 days.

9. A lignin-based pesticide controlled-release micro / nanoparticle with multiple stimulus responses, characterized in that: It is prepared by any of the preparation methods described in claims 1 to 8.

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