Cellulose nanoscale sterilizing agent based on wheat straw upgrading and reconstruction, and preparation method and application thereof

Abstract

This invention discloses a cellulose nano-fungicide based on wheat straw regeneration, its preparation method, and its application, belonging to the field of agricultural technology. The fungicide uses wheat straw-derived nanocellulose as a carrier, which, after oxidative modification, is loaded with fungicidal active ingredients and further coated with a tannic acid / chitosan oligosaccharide composite to construct an intelligent drug delivery system with a three-dimensional network structure. Its core advantage lies in its dual pH and cellulase-responsive release characteristics, enabling precise drug release targeting the pathogenic microenvironment of wheat scab. It significantly improves deposition and adhesion performance on leaves and ears, thereby greatly increasing pesticide utilization. It not only effectively inhibits pathogen growth but also reduces the accumulation of mycotoxins in grains. This invention provides an innovative solution for the high-value utilization of agricultural waste and the green control of crop diseases, with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of agricultural technology, and in particular to a cellulose nano-fungicide based on wheat straw recycling, its preparation method, and its application. Background Technology

[0002] Plant fungal diseases account for 70%–80% of crop diseases, often leading to reduced crop yields and quality, seriously threatening global food security and posing a major challenge to achieving sustainable agriculture. Wheat scab, caused by Fusarium graminearum, is an important ear disease. Its infection process involves the secretion of cellulase and organic acids, damaging plant cell walls and leading to the accumulation of mycotoxins such as vomitoxin (DON), further endangering food security and human health.

[0003] Pesticides, as the primary means of crop disease control, can save approximately 30%–40% of grain losses. However, traditional pesticide formulations have significant drawbacks during application: due to issues such as droplet drift, bouncing, rain washout, and degradation of active ingredients, only about 0.1% of the pesticide can act on the target pathogen, resulting in low pesticide utilization, increased control costs, and risks such as environmental pollution, ecotoxicity, and pathogen resistance.

[0004] To improve pesticide utilization efficiency and environmental safety, nanopesticide delivery systems (such as metal-organic frameworks, covalent organic frameworks, and cellulose-based nanomaterials) have attracted widespread attention. These systems demonstrate promising application prospects by enhancing pesticide deposition, improving leaf adhesion, and achieving controlled release. However, existing nanopesticides still face challenges such as complex preparation processes, high costs, mismatch between targeted release mechanisms and disease occurrence cycles, environmental migration, and risk accumulation, which restrict their large-scale commercial application.

[0005] Patent CN119385151A discloses a temperature- and charge-responsive nano-fungicide. It is formed by the self-assembly of positive and negative polymers with pyraclostrobin into spherical particles, with a surface potential adjustable between -4.2 mV and 41.5 mV. Furthermore, its leaf deposition and absorption can be further optimized by temperature variations within the range of 25–55℃. This formulation achieves an efficacy of up to 84% against tomato gray mold, which can reach 88% under controlled temperature conditions. However, the synthesis and purification of the block copolymer carrier used are complex, resulting in high costs for large-scale production, and a lack of systematic evaluation of its environmental migration, degradation, and ecotoxicity.

[0006] Patent CN107258802A discloses a water-soluble composite nano-fungicide. This formulation encapsulates fungicides such as metalaxyl on polybutyl acrylate, forming negatively charged nanoparticles with a particle size of 100–500 nm, aiming to improve agent stability and reduce loss. However, its preparation requires precise pH adjustment, prolonged stirring, high-speed centrifugation, and multiple washings, making the process cumbersome and energy-intensive. Furthermore, it lacks a disease-responsive microenvironment release mechanism and targeted delivery capability to different parts of the crop.

[0007] Patent CN115005219B relates to a fluorescent nano-fungicide with bidirectional conductivity. This system uses fluorescent mesoporous silica as a carrier, modified with glucosamine, and then loaded with thiabendazole. The resulting 10–70 nm particles can move bidirectionally within plants and can be tracked in real time using fluorescence imaging. However, its preparation involves numerous steps and a complex process, including template synthesis, surface modification, activation, and loading, and requires various organic solvents and centrifugal purification, resulting in high costs and limiting its potential for field application.

[0008] In recent years, bacterial cellulose and other nanocelluloses have been regarded as ideal green pesticide carriers due to their unique nanofiber network structure, rich modifiability, good biocompatibility, and environmental degradability. Nanocellulose can be prepared from agricultural biomass (such as straw) and has the potential for resource recycling. Nevertheless, the current cellulose-based nanopesticide systems still lack systematic design for the precise control of crop ear diseases (such as Fusarium head blight), especially in achieving disease microenvironment-responsive drug release, enhancing leaf / ear deposition and resistance to rain washout, and integrating the entire disease cycle management, which still requires further exploration.

[0009] Therefore, developing an environmentally friendly cellulose nano-fungicide based on agricultural biomass, possessing microenvironment-responsive drug release capabilities, significantly enhancing pesticide targeting and retention performance, is of great significance for achieving green and sustainable control of wheat scab. Summary of the Invention

[0010] To address the technical problems existing in the prior art, this invention provides a cellulose nano-fungicide based on wheat straw regeneration, its preparation method, and its application. The preparation process is simple and low-cost. The resulting fungicide can respond to the disease microenvironment, achieving targeted and efficient delivery, and exhibits good environmental compatibility, demonstrating excellent control effects even at low concentrations.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0012] On one hand, this invention provides a cellulose nano-bactericide that is a three-dimensional network nanocarrier of oxidized cellulose nanoparticles loaded with bactericidal active ingredients and coated with a tannic acid / chitosan oligosaccharide composite coating; specifically, it is assembled from oxidized cellulose nanoparticles, bactericidal active ingredients, tannic acid, and chitosan oligosaccharides through hydrogen bonding and electrostatic interactions. The bactericidal active ingredients are adsorbed on the surface of oxidized cellulose through hydrogen bonding, while tannic acid and chitosan oligosaccharides form a coating layer on the surface of the oxidized cellulose nanoparticles loaded with bactericidal active ingredients through electrostatic interactions. The average fiber diameter of the cellulose nano-bactericide ranges from 20 to 100 nm, the drug loading is 24.06%, and it is dispersed in a network structure in water.

[0013] Preferably, the bactericidal active ingredient is one or more of carbendazim, tebuconazole, prothioconazole, and cyazofamid, with carbendazim (CBZ) being the most preferred; the nanocellulose is one or more of bacterial cellulose, cellulose nanocrystals, and cellulose nanofibers, with bacterial cellulose (BC) being the most preferred.

[0014] On the other hand, the present invention also provides a method for preparing the above-mentioned cellulose nano-bactericide, comprising the following steps:

[0015] (1) Preparation of nanocellulose: Using WSTH as a carbon source, Acetobacter xylinum was inoculated and allowed to ferment statically. The generated bacterial cellulose membrane was collected, and purified bacterial cellulose was obtained after alkali treatment, washing, and freeze-drying.

[0016] Alternatively, cellulose nanocrystals can be obtained by hydrolyzing wheat straw with sulfuric acid.

[0017] Alternatively, cellulose nanofibers can be obtained by high-pressure homogenization using wheat straw as raw material;

[0018] (2) Preparation of oxidized nanocellulose: The nanocellulose obtained in step (1) is selectively oxidized in a TEMPO / NaBr / NaClO system, and oxidized nanocellulose is obtained by dialysis and freeze drying; the addition ratio of nanocellulose, water, TEMPO, NaBr and NaClO is 1 g:200 mL:0.06 g:5 g:46 mL.

[0019] (3) Preparation of cellulose nano-bactericide: Dissolve the oxidized nanocellulose obtained in step (2) in water, add the solution of bactericidal active ingredients under stirring, and obtain oxidized nanocellulose loaded with bactericidal active ingredients after sonication and stirring; add tannic acid solution and chitosan oligosaccharide solution in sequence, vortex mix evenly and freeze dry to obtain powdered cellulose nano-bactericide.

[0020] The concentration of the water-soluble oxidized nanocellulose is 5-10 g / L, preferably 8-10 g / L; the concentration of the bactericidal active ingredient solution is 5-10 g / L, preferably 8-10 g / L; and the concentrations of tannic acid and chitosan oligosaccharide are both 24 mmol / L.

[0021] The addition ratio of the oxidized nanocellulose solution, the bactericidal active ingredient solution, the tannic acid solution, and the chitosan oligosaccharide solution is 0.33 mL: 0.67 mL: 10 μL: 10 μL.

[0022] Furthermore, this invention also provides the application of the aforementioned cellulose nano-fungicide in the control of wheat scab. For the control of wheat scab, this cellulose nano-fungicide can achieve efficient deposition and adhesion on the leaf surface and ear, improving pesticide utilization; at the same time, it significantly inhibits the growth of scab fungus and reduces the accumulation of mycotoxins in the grains; this cellulose nano-fungicide is safe for the environment and non-target organisms, demonstrating good environmental friendliness.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) This invention provides a cellulose nano-bactericide prepared from agricultural biomass wheat straw as raw material. It is prepared by microbial fermentation, mild oxidation and biomimetic interface modification (tannic acid / chitosan oligosaccharide coating). The process is green and low cost, realizing the upgrading and recycling of agricultural waste.

[0025] (2) The cellulose nano-bactericide prepared by the present invention has a three-dimensional nanofiber network structure and a "Velcro-shaped" surface, which can be tightly bound to the waxy layer on the surface of wheat leaves / ears through physical interlocking and hydrogen bonding, significantly improving pesticide deposition (the deposition amount on leaves / ears increases by 72.51% / 109.28% respectively) and resistance to rainwater erosion.

[0026] (3) The cellulose nano-fungicide prepared by the present invention has dual pH / cellulase response release characteristics. It can achieve on-demand release (combination of initial burst release and subsequent slow release) in the acidic, cellulase-rich microenvironment of Fusarium head blight infection. It effectively destroys the mycelial membrane of Fusarium graminearum, inhibits the expression of key genes in glycolysis, and reduces the content of vomitoxin (DON) in grains by 84.32%, achieving high-efficiency control of Fusarium head blight at low concentrations (inhibition rate >95%).

[0027] (4) The cellulose nano-bactericide prepared by the present invention has carrier components (oxidized nanocellulose, tannic acid, chitosan oligosaccharide) that are all derived from natural biodegradable materials. It can be gradually degraded in the environment through the action of microorganisms and enzymes. It is safe for crops and soil microbial communities, does not affect seed germination and seedling growth, and has high environmental compatibility.

[0028] (5) This invention integrates agricultural waste resource utilization, intelligent design of nanocarriers, disease microenvironment response release and food safety protection in the whole chain. It provides a simple preparation, highly efficient targeted delivery, environmentally friendly and sustainable full life cycle management strategy for Fusarium head blight. It achieves the comprehensive goal of "reducing dosage, increasing efficiency, reducing toxicity and promoting growth" with low pesticide usage and has broad prospects for farmland promotion. Attached Figure Description

[0029] Figure 1 Scanning electron microscope images of bacterial cellulose and bacterial cellulose nano-bactericide prepared in Example 1;

[0030] Figure 2 Scanning electron microscopy images of the bacterial cellulose nanoparticle bactericide prepared in Example 1 in cellulase solutions at pH 7, pH 5, pH 3 and pH 7+;

[0031] Figure 3 The cumulative release curves of the bacterial cellulose nano-bactericide prepared in Example 1 were obtained by fitting the release kinetic curves using zero-order model, first-order model, Higuchi model and Ritger-Peppas model.

[0032] Figure 4 Images showing the droplet impact behavior of the cellulose nano-fungicides prepared for water, Comparative Example 2, and Examples 1-3 on wheat leaves;

[0033] Figure 5 Scanning electron microscope images of the fungicide of Example 1, the fungicide of Comparative Example 1, and the blank on the wheat leaf surface, and their morphology after rinsing.

[0034] Figure 6 Images showing the in vitro bactericidal activity of Examples 1-3, Comparative Examples 1-3, and a blank sample;

[0035] Figure 7 Images showing the control effects of the cellulose nano-bactericides of Examples 1-2, Comparative Examples 1-2, and the blank on diseased wheat grains;

[0036] Figure 8 The effects of the cellulose nano-bactericides of Examples 1-2, Comparative Examples 1-2, and blank on wheat plant growth are shown. Detailed Implementation

[0037] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0038] Unless otherwise specified, all reagents and materials used in this invention are commercially available.

[0039] Bacterial cellulose was prepared by the following method: using WSTH as a carbon source, *Acetobacter xylinum* was inoculated and allowed to ferment statically. The resulting bacterial cellulose membrane was collected, treated with alkali, washed, and freeze-dried to obtain purified bacterial cellulose. Details are as follows:

[0040] WSTH was obtained by drying, pulverizing, acid / enzymatic hydrolysis, and adsorption of wheat straw. Its monosaccharide composition was xylose 5.13 g / L. -1 4.57 g L of glucose -1 1.03 g / L of arabinose -1 The bacterial cellulose fermentation medium was Hestrin-Schramm (HS) medium, containing 1% glucose, 1% bacterial peptone, 0.75% yeast extract, and 0.5% KH₂PO₄, denoted as HS-Glu medium. HS-WSTH medium was prepared by replacing glucose with WSTH while maintaining the total monosaccharide content at 1%, with other components remaining unchanged. For BC synthesis, *Gluconacetobacter xylinus* was cultured in LB medium at 30°C for 24 hours, washed, and resuspended in sterile water to ~10 °C. 7 mL -1 Then, the cells were inoculated into HS-WSTH medium at 1% (v / v). After static incubation at 25°C for 72 hours, bacterial cellulose membranes were obtained. The membranes were then treated with 0.5 M NaOH at 100°C for 30 minutes to lyse the cells. After washing to neutrality, the membranes were freeze-dried to constant weight to obtain purified bacterial cellulose.

[0041] Cellulose nanocrystals were prepared by the following method: Cellulose nanocrystals were obtained from wheat straw through sulfuric acid hydrolysis; details are as follows:

[0042] Cellulose nanocrystals were prepared from wheat straw using the following steps: 10 g of pulverized and sieved wheat straw powder (40-60 mesh) was dewaxed by Soxhlet extraction with toluene / ethanol (2:1) for 24 h. After drying, the powder was treated with 700 mL of 1.4% NaClO2 solution (pH adjusted to 3-4) at 70℃ for 5 h to remove lignin. After washing, the powder was treated with 400 mL of 5% KOH solution at room temperature for 24 h, followed by treatment at 90℃ for 2 h to remove hemicellulose, yielding purified cellulose fibers. 5 g of the fibers were added to 250 mL of 55% sulfuric acid solution and hydrolyzed in an ultrasonic water bath at 60℃ for 90 min. The reaction was terminated with ice water, and the fibers were centrifuged and washed until neutral. The solution was then dialyzed for 72 h (molecular weight cutoff 3000 Da) to remove residual acid. Finally, the solution was ultrasonically dispersed for 30 min to obtain a cellulose nanocrystal suspension, which was then refrigerated for later use.

[0043] Cellulose nanofibers were prepared by the following method: Cellulose nanofibers were obtained by high-pressure homogenization using wheat straw as raw material; details are as follows:

[0044] Cellulose nanofibers were prepared from wheat straw using the following steps: Wheat straw powder (40-60 mesh) was pulverized and sieved, then dewaxed using a Soxhlet extract of toluene / ethanol (2:1) for 24 h. After drying, the powder was treated with a 1.4% NaClO2 solution (pH adjusted to 3-4) at 70℃ for 5 h to remove lignin. Then, it was treated with a 5% KOH solution at room temperature for 24 h, followed by treatment at 90℃ for 2 h to remove hemicellulose, yielding purified cellulose fibers. An appropriate amount of these fibers was dispersed in deionized water to prepare a 1% suspension. After pre-dispersion using a high-speed stirrer, the suspension was introduced into a high-pressure homogenizer and homogenized 20-30 times at 100 MPa until a uniform gel-like suspension was formed. This cellulose nanofiber suspension was then stored in a refrigerator for later use.

[0045] This invention provides a cellulose nano-bactericide based on wheat straw recycling, its preparation method, and its application. Specific embodiments are as follows.

[0046] Example 1

[0047] A method for preparing a cellulose nano-bactericide includes the following steps:

[0048] 1.0 g of bacterial cellulose prepared from fermented wheat straw was dispersed in 200 mL of water. 0.06 g of TEMPO and 5.0 g of NaBr were added, and the pH was adjusted and maintained at 10.0 with sodium hydroxide solution. 46 mL of 8wt% sodium hypochlorite solution was added dropwise with stirring, and the reaction was carried out at room temperature for 6 hours. During the reaction, the pH was maintained at 10 ± 0.1 with 1 M NaOH. The reaction was quenched with 2 mL of ethanol to obtain an oxidized bacterial cellulose solution. The solution was placed in an activated dialysis bag (MWCO = 12,000) and dialyzed against deionized water at 150 rpm for 48 hours (water changed every 6 hours). Then, it was freeze-dried at -70℃ under vacuum for 2 days to obtain oxidized bacterial cellulose.

[0049] Take 50 mg of oxidized bacterial cellulose, add 5 mL of water to prepare a solution, add 10 mL of 10 g / L carbendazim acetic acid solution while stirring, sonicate for 2 minutes and continue stirring for 6 hours. Centrifuge at 5,000 rpm for 5 minutes to collect the solid, and then freeze-dry at -70℃ for 2 days.

[0050] Take 10 mg of the above-mentioned dried solid and redisperse it in 1 mL of water. Then, add 10 μL of tannic acid solution with a concentration of 24 mmol / L and 10 μL of chitosan oligosaccharide solution with a concentration of 24 mmol / L sequentially, vortexing to mix after each addition. Finally, freeze-dry the suspension to obtain powdered bacterial cellulose nano-bactericide; dilute with water to a carbendazim concentration of 40 mg / L.

[0051] Example 2

[0052] A method for preparing a cellulose nano-bactericide includes the following steps:

[0053] 1.0 g of cellulose nanocrystals was dispersed in 200 mL of water. 0.06 g of TEMPO and 5.0 g of NaBr were added, and the pH was adjusted and maintained at 10.0 with sodium hydroxide solution. 46 mL of 8wt% sodium hypochlorite solution was added dropwise with stirring, and the reaction was carried out at room temperature for 6 hours. During the reaction, the pH was maintained at 10 ± 0.1 with 1 M NaOH. The reaction was quenched with 2 mL of ethanol to obtain an oxidized cellulose nanocrystal solution. The solution was placed in an activated dialysis bag (MWCO = 3,000) and dialyzed against deionized water at 150 rpm for 48 hours (water changed every 7 hours). Then, the solution was freeze-dried at -70℃ under vacuum for 2 days to obtain oxidized cellulose nanocrystals.

[0054] Take 40 mg of oxidized cellulose nanocrystals and add 5 mL of water to prepare a solution. Add 10 mL of 8 g / L tebuconazole acetone solution dropwise while stirring, and stir at room temperature for 4 hours.

[0055] After removing acetone, the mixture was freeze-dried. 10 mg of the dried solid was redispersed in 1 mL of water, and then 10 μL of a 24 mmol / L tannic acid solution and 10 μL of a 24 mmol / L chitosan oligosaccharide solution were added sequentially. The mixture was vortexed and then freeze-dried to obtain powdered cellulose nanocrystal bactericide. This was then diluted with water to a tebuconazole concentration of 40 mg / L.

[0056] Example 3

[0057] A method for preparing a cellulose nano-bactericide includes the following steps:

[0058] 1.0 g of cellulose nanofibers were dispersed in 200 mL of water. 0.06 g of TEMPO and 5.0 g of NaBr were added, and the pH was adjusted and maintained at 10.0 with sodium hydroxide solution. 46 mL of 8wt% sodium hypochlorite solution was added dropwise with stirring, and the reaction was carried out at room temperature for 6 hours. During the reaction, the pH was maintained at 10 ± 0.1 with 1 M NaOH. The reaction was quenched with 2 mL of ethanol to obtain an oxidized cellulose nanofiber solution. The solution was placed in an activated dialysis bag (MWCO = 3,000) and dialyzed against deionized water at 150 rpm for 48 hours (water changed every 8 hours). Then, the solution was freeze-dried at -70℃ under vacuum for 2 days to obtain oxidized cellulose nanofibers.

[0059] Take 25 mg of oxidized cellulose nanofibers and add 5 mL of water to prepare a solution. Add 10 mL of a 5 g / L prothioconazole ethanol solution while stirring, and stir at room temperature for 3 hours.

[0060] After removing the ethanol, the mixture was freeze-dried. 10 mg of the dried solid was redispersed in 1 mL of water, and then 10 μL of a 24 mmol / L tannic acid solution and 10 μL of a 24 mmol / L chitosan oligosaccharide solution were added sequentially. The mixture was vortexed and then freeze-dried to obtain powdered cellulose nanofibers as a fungicide. This was then diluted with water to a prothioconazole concentration of 40 mg / L.

[0061] The physicochemical properties of the prepared Examples 1-3 were tested, including microstructure and zeta potential. The relevant test methods are as follows.

[0062] Microscopic morphology determination: The cellulose nano-bactericidal sample solutions from Examples 1-3 were dropped onto the clean silicon wafer surface. After natural drying, they were subjected to gold sputtering in an ion sputtering instrument to enhance conductivity. Subsequently, the surface morphology and microstructure were observed using a scanning electron microscope at an accelerating voltage of 5 kV. The results are shown in the figure. Figure 1 .like Figure 1 As shown, the cellulose nano-bactericide exhibits a network-like microstructure, with the fiber surface covered by a tannic acid / chitosan oligosaccharide membrane, and the fiber diameter is approximately 45 nm.

[0063] Zeta potential measurement: The zeta potential of Examples 1-3 was measured at 25±0.1℃ using a Malvern Nano ZS90 dynamic light scattering instrument. Each sample was tested 5 times and the average value was taken. The results are shown in Table 1.

[0064] Table 1. Zeta potential of cellulose nano-bactericides

[0065]

[0066] As shown in Table 1, the zeta potential of the cellulose nano-bactericide of the present invention is all below -30 mV, indicating that the nano-bactericide has a large electrostatic repulsion force, can be fully dispersed in the solution, reduces precipitation caused by agglomeration or flocculation, and has good stability.

[0067] The prepared samples from Examples 1-3 were subjected to response release experiments, and the relevant test methods are as follows.

[0068] At pH 3, 5, 7 and 1 mg mL -1 The cumulative release of the bactericidal active ingredient from cellulose nanoparticles was evaluated in the presence of cellulase. Briefly, 10 mg of cellulose nanoparticles were placed in a 3 kDa MWCO dialysis bag, immersed in 60 mL of methanol-PBS (30:70 v / v) release medium, and stirred at 150 rpm in a 25°C water bath. At preset time points, 1 mL aliquots were taken for HPLC analysis and replaced with an equal volume of fresh methanol-PBS. All experiments were repeated three times. Release kinetics were fitted using zero-order, first-order, Higuchi, and Ritger-Peppas models. The cumulative release percentage (CRP) was calculated using equation (1):

[0069] (1)

[0070] Where V e =1 mL (sampling volume), C n [mg mL -1 [ ] represents the concentration of the bactericidal active ingredient at time n, V0 = 60 mL (initial volume), M i [mg] represents the initial bactericidal active ingredient loading in 10 mg of cellulose nano-bactericide.

[0071] The results are as follows Figure 2-3 As shown in Table 2.

[0072] like Figure 2 As shown, scanning electron microscopy images reveal that some of the tannic acid / chitosan oligosaccharide shell dissolves in a pH 5 solution, while most of the tannic acid / chitosan oligosaccharide shell disintegrates when the pH drops to 3, exposing carbendazim completely to the surface of the fiber bundles. Similarly, in a pH 7 solution containing cellulase, the bacterial cellulose network is hydrolyzed into short rods, which also accelerates the release of carbendazim.

[0073] like Figure 3As shown, the images illustrate the cumulative release curves and release kinetic fitting models of carbendazim from cellulose nanoparticles in different pH and cellulase solutions. The cumulative release rate increased from 47.48% (pH 7) to 57.98% (pH 7 + cellulase), 65.63% (pH 5), and 96.69% (pH 3). These results indicate that the cellulose nanoparticles rapidly release carbendazim in the acidic and cellulase-rich microenvironment of Fusarium head blight infection, achieving precise targeted delivery and long-term control of Fusarium head blight. In contrast, carbendazim release is slow in uninfected and off-target sites, effectively reducing off-target toxicity and environmental pollution.

[0074] Table 2. Fitting results of four release kinetic models for cellulose nano-bactericides.

[0075]

[0076] Mt / Mz represents the amount of carbendazim released at time t. k represents the kinetic constant.

[0077] Table 2 shows that the release kinetics of the cellulose nano-fungicide in cellulase solutions at pH 7, pH 5, pH 3, and pH 7+ best match the first-order kinetic model. This indicates that the release of carbendazim from the cellulose nano-fungicide is proportional to the amount of remaining pesticide, follows an exponential decay law, and exhibits non-Fickian behavior controlled by dissolution and diffusion. Furthermore, the release curves show an initial burst release followed by a sustained release. This release design matches the Fusarium head blight infection pattern, ensuring a high initial dose of pesticide to combat early infection while maintaining a sustained release for long-term control. It is important to note that if the disease worsens at this stage, the disintegration of the cellulose nano-fungicide under the acidic or cellulase-stimulated environment of the Fusarium head blight infection will trigger a further burst release of the remaining pesticide.

[0078] To compare and analyze the performance of the cellulose nano-bactericide with Examples 1-3, the following Comparative Examples 1-3 were constructed for control studies.

[0079] Comparative Example 1

[0080] The 80% carbendazim wettable powder purchased from the market was diluted with water to a carbendazim concentration of 40 mg / L and compared with Example 1.

[0081] Comparative Example 2

[0082] The 80% tebuconazole wettable powder purchased from the market was diluted with water to a tebuconazole concentration of 40 mg / L and compared with Example 2.

[0083] Comparative Example 3

[0084] A commercially available 20% prothioconazole suspension was diluted with water to a prothioconazole concentration of 40 mg / L and compared with Example 3.

[0085] The contact angle, adhesion, sludge retention, deposition amount, and deposition process of the pesticide solutions of Examples 1-3 and Comparative Examples 1-3 on the surface of wheat leaves / ears were studied. The relevant test methods are as follows.

[0086] Contact angle: At 25±0.1℃, the static contact angle of the sample droplets on wheat leaves / ears was measured using the seated drop method and an OCA 20 fully automatic optical contact angle measuring instrument. Each sample was tested 5 times and the average value was taken.

[0087] Adhesion and liquid retention: The adhesion and liquid retention of 10 μL droplets on wheat leaves / ears were determined using a DCAT 21 interfacial tensiometer via the ring method. Five tests were performed on each sample and the average value was taken.

[0088] Deposition amount: Wheat leaves / ears were adhered to a 45° inclined glass slide and the sample solution was sprayed on (pressure 3 bar, spray height 60 cm, moving speed 9 cm / s). -1 The amount of sediment is quantified as the mass / area of ​​the drug solution.

[0089] Impact process: The dynamic impact process of droplets on the surface of wheat leaves was recorded using an i-SPEED 220 high-speed camera. Each experiment was repeated at least five times, and the video data was analyzed using i-SPEED Suite professional software.

[0090] Deposition morphology: The microscopic morphology of the nano-fungicide solution after deposition on wheat leaves / ears was observed by scanning electron microscopy.

[0091] Table 3 shows the contact angle, maximum adhesion force, sap retention, and deposition amount of Examples 1-3 and Comparative Examples 1-3 on wheat leaves and ears. The results show that on the hydrophobic surfaces of wheat leaves and ears, Examples 1-3 can reduce the contact angle by more than 40° compared to Comparative Examples 1-3, significantly enhancing the wettability of the pesticide solution, indicating that Examples 1-3 have better surface activity, which is beneficial for deposition on wheat leaves and ears. Compared to Comparative Examples 1-3, the maximum adhesion force of Examples 1-3 on wheat leaves and ears is significantly increased, with the maximum adhesion force of Example 1 increasing from 0.110 mN and 0.115 mN to 0.190 mN (leaves) and 0.191 mN (ears), indicating a stronger interaction between the droplets and the crop surface. This may be attributed to the entanglement of the bacterial cellulose fiber network with the micro-nano structures of the crop surface. Similarly, the sap retention and deposition amount of Examples 1-3 are significantly increased compared to Comparative Examples 1-3, indicating that the droplets tend to be deposited and retained on the crop surface.

[0092] Table 3. Contact angles of water, Examples 1-3 and Comparative Examples 1-3 on wheat leaves and ears.

[0093] Maximum adhesion force, amount of stagnant liquid, and amount of sediment

[0094]

[0095] like Figure 4 As shown, water and Comparative Example 2 could not be effectively deposited on the surface of wheat leaves and were easily broken and splashed, while Examples 1-3 could be deposited on the surface of wheat leaves and had a better dose delivery effect.

[0096] like Figure 5 As shown, the simple surface morphology of wheat leaves served as a blank control. In Comparative Example 1, due to the limited contact area between the micron-sized suspension particles and the waxy layer on the surface of wheat leaves, the particles were easily washed away by rainwater. In contrast, in Example 1, due to the entanglement between the bacterial cellulose nanonetwork and the micro-nano structure of the leaf waxy layer, the nano-bactericide could still be effectively retained after being washed away by rainwater.

[0097] The present invention also compares the fungicidal properties and vomitoxin-inhibiting effects of the pesticide solutions of Examples 1-3 and Comparative Examples 1-3 on Fusarium graminearum, and the relevant test methods are as follows.

[0098] To assess the bactericidal properties of Fusarium graminearum, cellulose nano-bacterial agents were dispersed in water and then added to potato dextrose agar, followed by autoclaving of the culture medium. Five-mm mycelial blocks were cut from Fusarium graminearum colonies, placed in the center of a culture medium plate, and incubated at 25°C for 3 days. The inhibition rate was calculated and the antibacterial effect was evaluated by observing the diameter of the mycelial cake growth.

[0099] To investigate the inhibitory effect of vomitoxin, wheat grains inoculated with Fusarium graminearum spores were treated with a cellulose nano-fungicide and cultured in moist gauze for 7 days. After culture, the grains were dried, ground, extracted with water, centrifuged, and the supernatant was collected. The vomitoxin content in the grains was detected using a DON ELISA kit.

[0100] Table 4 shows the inhibition rates of Examples 1-3 and Comparative Examples 1-3 against Fusarium graminearum and their inhibitory effects on vomitoxin, with the same volume of water treatment serving as a blank control. Due to the nano-effect and the synergistic antibacterial effect of the bactericidal active substances and chitosan oligosaccharides, Examples 1-3 showed better control effects against Fusarium graminearum compared to Comparative Examples 1-3, exceeding 90%, as shown in the attached table. Figure 6 As shown in the attached figure. Meanwhile, Examples 1-2 also showed significantly stronger inhibitory effects on vomitoxin than Comparative Examples 1-2, exceeding 93%, as shown in the attached figure. Figure 7 As shown.

[0101] Table 4. Inhibition rates of Examples 1-3 and Comparative Examples 1-3 against Fusarium graminearum and

[0102] Anti-vomiting toxin effect

[0103]

[0104] Although the application of nano-fungicides has effectively improved the control of Fusarium head blight, concerns remain regarding the safety of nano-pesticides. The environmental friendliness of these nano-pesticides was evaluated by comparing the effects of Examples 1-3 and Comparative Examples 1-3 on wheat seed germination rate, root length, shoot length, seedling length, fresh weight, and chlorophyll content. The relevant test methods are as follows.

[0105] 20 seeds of Jimai 44 were placed in a petri dish with 60 mg ali-L. -1 Treatment with the agent (10 mL) was performed at 25°C (12 h light / dark, 95% relative humidity). Germination rate and root / shoot length were recorded after 3 days. For seedling analysis, 14-day-old wheat seedlings were sprayed with 60 mg ai L. -1 The pesticide was applied, and the plants were cultured for 14 days to measure fresh weight, plant height, and leaf chlorophyll content. The same water was sprayed as the control (CK), and the pesticides used were those from Examples 1-2 and Comparative Examples 1-2, respectively. The results are shown in Table 5.

[0106] Table 5. Effects of Examples 1-2 and Comparative Examples 1-2 on wheat seeds and plants

[0107]

[0108] Table 5 shows that the agent had no significant effect on the germination rate of wheat seeds and the chlorophyll content of wheat seedlings. Comparative Examples 1-2 inhibited the root and shoot length of wheat seeds, while Examples 1-2 had no significant effect on root and shoot length, and Example 1 even promoted them. Furthermore, Comparative Examples 1-2 reduced wheat seedling length and fresh weight, while Examples 1-2 had no significant effect on wheat seedling length and fresh weight, confirming its environmentally friendly properties, as shown in the appendix. Figure 8 As shown.

[0109] To further illustrate the beneficial effects of the present invention, the inventors have also constructed the following comparative examples.

[0110] Comparative Example 4

[0111] In this comparative example, the bacterial cellulose was not oxidized, and the other conditions were the same as in Example 1.

[0112] Comparative Example 5

[0113] In this comparative example, the tannic acid solution was replaced with an equal volume and equimolar concentration of chitosan oligosaccharide solution, and the other conditions were the same as in Example 1.

[0114] Comparative Example 6

[0115] In this comparative example, the chitosan oligosaccharide solution was replaced with an equal volume and equimolar concentration of tannic acid solution, and the other conditions were the same as in Example 1.

[0116] Comparative Example 7

[0117] In this comparative example, chitosan oligosaccharide was replaced with copper chloride, and the other conditions were the same as in Example 1.

[0118] The performance of the bactericides prepared in Comparative Examples 4-7 was tested, and the results are shown in Table 6.

[0119] Table 6. Contact angle, maximum adhesion, sap retention, and deposition of Comparative Examples 4-7 on wheat leaves and ears, as well as their inhibition rate against Fusarium graminearum and their inhibitory effect on vomitoxin.

[0120]

[0121] In Comparative Example 4, the bacterial cellulose was not oxidized, and the cellulose chains were bound to carbendazim via hydrogen bonds, reducing the drug loading on the cellulose chains and affecting the inhibition rate of Fusarium graminearum and the content of vomitoxin. In Comparative Example 5, replacing the tannic acid solution with an equal volume and equimolar concentration of chitosan oligosaccharide solution affected the wetting, adhesion, and deposition behavior of the drug solution. In Comparative Example 6, replacing the chitosan oligosaccharide solution with an equal volume and equimolar concentration of tannic acid solution improved the wetting, adhesion, and deposition behavior, but reduced the efficacy and crop growth-promoting properties. In Comparative Example 7, replacing chitosan oligosaccharide with copper chloride mainly affected crop growth (safety).

[0122] Table 7 Effects of Comparative Examples 4-7 on wheat seeds and plants

[0123]

[0124] As shown in Table 7, Comparative Examples 4 and 5 had little effect on the germination and growth of wheat seeds, but in Comparative Example 7, copper chloride had a significant effect on the germination rate, root length, shoot length and seedling length of seedlings.

[0125] In summary, this invention addresses the need for green control of wheat scab by proposing a cellulose nano-fungicide based on upgraded wheat straw and its preparation method. This fungicide possesses a three-dimensional network structure and a "Velcro-like" surface, significantly enhancing deposition and retention on leaves and ears. It also exhibits dual pH / cellulase response release capabilities, enabling intelligent drug release within the disease microenvironment, effectively inhibiting pathogen growth and reducing toxin accumulation. Its preparation process is simple and low-cost, using raw materials derived from agricultural waste, and boasts high overall environmental compatibility. It achieves the comprehensive goals of "reduced dosage, increased efficiency, reduced toxicity, and promoted growth," facilitating its widespread application in farmland and providing a new pathway for the green and sustainable development of pesticides.

[0126] The above description is a preferred embodiment of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A cellulose nano-fungicide based on wheat straw regeneration, characterized in that, The cellulose nano-bactericide uses oxidized nanocellulose as a carrier, with bactericidal active ingredients as the loading drug, and is coated with a composite coating of tannic acid and chitosan oligosaccharides; the M of the chitosan oligosaccharides... W ≤1000; The oxidized nanocellulose is one or more of oxidized bacterial cellulose, oxidized cellulose nanocrystals, and oxidized cellulose nanofibers. The bactericidal active ingredient is one or more of carbendazim, tebuconazole, prothioconazole, and cyazofamid.

2. A method for preparing a cellulose nano-bactericide based on wheat straw recycling, characterized in that, include: (1) Preparation of nanocellulose; (2) Preparation of oxidized nanocellulose: The nanocellulose prepared in step (1) was oxidized in the 2,2,6,6-tetramethylpiperidine oxide (TEMPO) / NaBr / NaClO system, and then dialyzed and lyophilized to obtain oxidized nanocellulose; (3) Preparation of cellulose nano-bactericide: Dissolve the oxidized nanocellulose prepared in step (2) in water, add the solution of bactericidal active ingredients under stirring, and obtain oxidized nanocellulose loaded with bactericidal active ingredients after sonication and stirring; then add tannic acid solution and chitosan oligosaccharide solution in sequence, vortex mix evenly and freeze dry to obtain powdered cellulose nano-bactericide.

3. The preparation method according to claim 2, characterized in that, In step (1), the nanocellulose is bacterial cellulose, which is prepared by the following method: using wheat straw total hydrolysate (WSTH) as a carbon source, inoculating it with Acetobacter xylinum for static fermentation, collecting the generated bacterial cellulose membrane, and obtaining purified bacterial cellulose after alkali treatment, washing, and freeze drying.

4. The preparation method according to claim 2, characterized in that, In step (1), the nanocellulose is cellulose nanocrystal, which is prepared by the following method: cellulose nanocrystal is obtained by hydrolyzing wheat straw with sulfuric acid.

5. The preparation method according to claim 2, characterized in that, In step (1), the nanocellulose is cellulose nanofibers, which are prepared by the following method: cellulose nanofibers are obtained by high-pressure homogenization using wheat straw as raw material.

6. The preparation method according to claim 2, characterized in that, The specific steps (2) are as follows: dispersing nanocellulose in water, then adding TEMPO and NaBr, adjusting the pH to 10.0±0.5 with sodium hydroxide, then adding 8wt% NaClO solution dropwise while stirring, reacting at room temperature for 6 hours, and then dialyzing and freeze-drying the liquid after the reaction to obtain oxidized bacterial cellulose.

7. The preparation method according to claim 6, characterized in that, The addition ratio of nanocellulose, water, TEMPO, NaBr, and NaClO is 1 g: 200 mL: 0.06 g: 5 g: 46 mL.

8. The preparation method according to claim 2, characterized in that, In step (3), the concentration of the oxidized nanocellulose solution is 5-10 g / L, the concentration of the bactericidal active ingredient solution is 5-10 g / L, the concentration of the tannic acid solution is 24 mmol / L, and the concentration of the chitosan oligosaccharide solution is 24 mmol / L. The addition ratio of the oxidized nanocellulose solution, the bactericidal active ingredient solution, the tannic acid solution, and the chitosan oligosaccharide solution is 0.33 mL: 0.67 mL: 10 μL: 10 μL.

9. The application of the cellulose nano-fungicide based on wheat straw regeneration as described in claim 1, characterized in that, The cellulose nano-fungicide based on upgraded wheat straw is used for the prevention and control of wheat scab.

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