A nano-bandage for preserving cut flowers

Abstract

This invention discloses a nano-bandage for preserving cut flowers, belonging to the field of horticultural technology. The nano-bandage consists of a polymer carrier and a bactericide encapsulated therein. The polymer is a mixture of PEG and PDMAEMA. By adjusting the mass fraction and total concentration of PDMAEMA, the particle size of the nanoparticles can be controlled, and their surface can be positively charged. It is prepared using microfluidic co-assembly technology, where the drug-containing organic phase and aqueous phase are instantaneously mixed and purified by dialysis. This nano-bandage actively targets and persistently accumulates on the negatively charged cut surface of fresh cut flowers using electrostatic interactions, forming a physical barrier. It also synergistically inhibits microbial infection through slow-release bactericide and charge adsorption, while its nano-size does not affect vascular function. This invention achieves precise and long-lasting protection for cut flower wounds, significantly extending vase life with extremely low dosage, and has the advantages of high efficiency, safety, and intelligent adjustability.

Description

Technical Field

[0001] This invention relates to the field of horticultural technology, and more specifically to a nano-bandage for preserving cut flowers. Background Technology

[0002] Cut flowers are a core commodity in the flower industry, widely used in ceremonies, social events, and indoor and outdoor decorations, possessing significant economic and cultural value. With the expansion of the consumer market, the global cut flower industry continues to grow. However, most cut flower varieties have a short post-harvest lifespan, easily experiencing problems such as hindered blooming, color fading, wilting, and even rotting, severely restricting their circulation and value realization.

[0003] The main reason for the shortened vase life of cut flowers is that microorganisms (mainly bacteria and fungi) invade the vascular system through stem cuts, multiply rapidly to form biofilms, causing physical blockage and physiological toxicity of the vascular bundles. This hinders the upward transport of water and nutrients, ultimately leading to wilting and premature aging of the cut flowers. Currently, the industry commonly uses the method of directly adding chemical fungicides (such as 8-hydroxyquinoline and silver thiosulfate) to vase preservation solutions to inhibit microbial growth. While this method has some effect, it has significant drawbacks: First, the fungicide disperses in the solution, resulting in a low effective concentration at the cut site, requiring higher doses and potentially posing risks of plant toxicity and environmental residues. Second, traditional fungicides are easily degraded or inactivated, with a short duration of effectiveness, failing to provide long-term protection for the cut. Third, some highly effective fungicides (such as silver salts) are expensive, limiting their large-scale application.

[0004] In recent years, nanotechnology has provided new ideas for cut flower preservation. For example, nano-silver, due to its broad-spectrum and highly effective antibacterial properties, has been used in preservative solutions. However, the preparation cost of nano-silver is high, and the persistence of silver ions in the environment poses potential ecological risks, thus limiting its application. Polymer nanoparticles, as an emerging nanocarrier, have advantages such as precise controllability of particle size and surface properties, good biocompatibility, and the ability to load various active ingredients. Theoretically, by designing specific particle sizes and surface charges, the adsorption, retention, and transport behavior of nanoparticles in plant cut tissues can be controlled. However, current technologies have not fully explored the application potential of polymer nanoparticles in the field of cut flower preservation, especially failing to develop a nanomaterial system that can intelligently target and persistently reside in the cut, providing both a "band-aid"-like physical barrier and slow-release bactericidal function.

[0005] Therefore, to address the aforementioned problems, this invention provides a nano-bandage for preserving cut flowers. By using specific polymers (polyethylene glycol and N,N-dimethylaminoethyl methacrylate) as carriers to encapsulate low-dose bactericides and precisely controlling the particle size and surface positive charge of the nanoparticles, they can target, enrich, and persistently adhere to the negatively charged cut surface of the cut flower stem based on electrostatic interactions, forming a nano-protective layer with physical barrier and slow-release bactericidal functions. This effectively and persistently prevents microbial infection and significantly extends the vase life of cut flowers without affecting water and nutrient absorption. Summary of the Invention

[0006] The purpose of this invention is to provide a nano-bandage for preserving cut flowers, filling a gap in current technology.

[0007] The objective of this invention is achieved through the following technical solution: The purpose of this invention is to provide a nano-bandage for preserving cut flowers, its preparation method and application, in order to solve the problems of poor targeting of bactericides, short duration of effect, easy generation of toxicity and environmental pollution in existing preservation technologies.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A nano-bandage for preserving cut flowers, the nano-bandage being composed of a polymer and a bactericide, with the bactericide encapsulated using the polymer as a carrier.

[0009] Preferably, the polymer used is a mixture of polyethylene glycol (PEG) and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), wherein the mass fraction of PDMAEMA is greater than 0% and less than or equal to 100%, and the total polymer concentration is 0.005~0.5 mg / mL. By adjusting the mass fraction of PDMAEMA and the total polymer concentration, the particle size of the nano-bandage can be precisely controlled to be 63.2 nm~820 nm, and the surface potential to be 0 mV~47.19 mV with a positive charge. This design allows the nanoparticles to actively target and firmly adhere to the negatively charged cut surface of the flower stem through electrostatic attraction, forming a physical protective layer, while the positive charge itself also helps to adsorb negatively charged microorganisms.

[0010] Preferably, the mass fraction of PDMAEMA is further preferably 10% to 100% to optimize the positive charge strength and stability of the nanoparticles.

[0011] Preferably, the bactericide is at least one of 8-hydroxyquinoline, 8-hydroxyquinoline citrate, isothiazolinone, ciprofloxacin, or norfloxacin. These bactericides can be effectively encapsulated within nanoparticles to achieve slow, sustained release, prolong the duration of action, and reduce the direct exposure dose of the bactericide.

[0012] The present invention also provides a method for preparing the above-mentioned nano-bandage for preserving cut flowers, comprising the following steps: S1. Preparation of Stream 1: Dissolve the bactericide and polymer in an organic solvent to form an organic phase stream; S2, Preparation of Stream 2: Providing an aqueous stream; S3, Nano-co-assembly: Equal volumes of the stream 1 and the stream 2 are simultaneously injected into a microfluidic mixer for mixing; S4. Purification: The nanoparticle mixture obtained in step S3 is placed in a dialysis device for dialysis to remove organic solvents and impurities, thereby obtaining the nano-bandage.

[0013] Preferably, in step S1, the organic solvent is tetrahydrofuran; the concentration of the bactericide in stream 1 is 0.001~0.2 mg / mL, and the total concentration of the polymer is 0.005~0.5 mg / mL. This concentration range is crucial to ensuring the formation of stable nanoparticles and effective drug loading.

[0014] Preferably, in step S2, the aqueous stream is ultrapure water or PBS buffer with various pH values ​​(preferably 4.0~8.0). Different pH environments can be used to adjust the charged state of the polymer and the formation of nanoparticles.

[0015] Preferably, in step S3, the flow rate injected into the mixer is 2~50 mL / min. By controlling the flow rate, the intensity of mixing can be adjusted, thereby affecting the particle size and uniformity of the nanoparticles.

[0016] Preferably, in step S4, the aqueous dialysis solution used for dialysis is ultrapure water or PBS buffer with a pH of 4.0 to 8.0, and the dialysis time is 12 to 14 hours to ensure complete removal of organic solvents.

[0017] This invention further provides the application of the aforementioned nano-bandage in preventing microbial infection of cut flower wounds caused by bacteria such as Staphylococcus aureus. The positive charge of the nano-bandage can efficiently adsorb bacteria, and combined with the slow-release bactericide, synergistically destroy the bacterial cell membrane, achieving excellent antibacterial effect.

[0018] This invention also provides a specific application of the aforementioned nano-bandage in cut flower preservation. The nano-bandage is dispersed in a vase solution (preservative solution) at a concentration of 0.001~0.1 mg / mL. When the cut end of the cut flower stem is immersed in this solution, the positively charged nano-bandage rapidly accumulates and adheres to the cut surface and nearby vascular tissue through electrostatic attraction, forming a nano-protective layer similar to a bandage. This protective layer can both physically block the invasion of microorganisms in the environment and actively kill attached microorganisms through slow-release bactericides. Furthermore, due to its nano-size, it hardly clogs the vascular bundles and does not affect the normal absorption of water and nutrients by the cut flower, thus significantly extending its vase life. Depending on the needs, nutrients such as sucrose or plant growth regulators such as salicylic acid and gibberellin can be added to the preservative solution to synergistically enhance the preservation effect.

[0019] Finally, the present invention provides a method for preserving cut flowers by immersing the cut end of the cut flower stem in a preservative solution containing the aforementioned nano-bandage.

[0020] The working mechanism of this invention is as follows: Nano-bandages with different charges can be obtained by using polymers with different mass fractions. Nano-bandages with different particle sizes can be obtained by adjusting the total polymer concentration. The stems of cut flowers are mainly composed of cellulose and pectin, therefore the cut surface of fresh cut flowers is negatively charged. When the nano-bandage is negatively charged, it repels the stem, causing the negatively charged nanoparticles to be transported upwards along the xylem vascular bundles. The smaller the particle size, the faster the transport rate. Therefore, this type of bandage is difficult to accumulate on the cut surface for a long time, making it difficult to achieve an antibacterial effect on the cut surface, resulting in an unsatisfactory effect. Conversely, when the nano-bandage is positively charged, it attracts the negatively charged stem. Except for a small number of nanoparticles that are transported upwards along the vascular bundles a short distance due to capillary action, most nanoparticles accumulate on and around the cut surface of the fresh cut flower, forming a layer of nano-"bandage". Changing the particle size has no significant effect on the aggregation state of the positively charged nanoparticles. The presence of the bandage can prevent bacteria and fungi from forming a biofilm on the cut surface; in addition, since bacteria and fungi are negatively charged, they are easily adsorbed by the positively charged bandage. Physical adsorption and slow release of the loaded bactericide will disrupt the integrity of the bacterial cell membrane, thus playing a bactericidal role; at the same time, since the nanoparticles are very small in size, they have almost no impact on the cut flowers' absorption of water and other substances.

[0021] Due to the application of the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. This invention pioneers a new mechanism for targeted and long-lasting preservation of cut flowers. By imparting a controllable positive charge to nanoparticles, they can actively and rapidly accumulate and permanently adhere to the negatively charged cut surfaces of fresh cut flowers, forming a physical "nanobandage". This transforms the traditional "systemic drug delivery" mode into "precise local treatment" of key areas, resulting in a more direct and longer-lasting preservation effect.

[0022] 2. This invention achieves a perfect balance between high-efficiency antibacterial effect and low-dose medication. By encapsulating low-dose bactericides in nanocarriers and releasing them slowly, combined with the physical adsorption of the positive charge of the nanoparticles and the membrane disruption effect, a triple synergistic antibacterial mechanism of "physical barrier + charge adsorption + chemical slow release" is formed. This significantly reduces the amount of bactericide used while achieving better preservation effect and reducing chemical residues and toxicity risks.

[0023] 3. This invention possesses the characteristics of an intelligent and adjustable universal platform. By adjusting the polymer composition and concentration, the particle size and surface charge of nanoparticles can be flexibly and precisely controlled to adapt to the preservation needs of different cut flower varieties. The carrier platform has strong compatibility and can encapsulate various bactericides, nutrients or plant growth regulators, realizing modular customization and expansion of functions.

[0024] 4. The nano-bandage provided by this invention significantly extends the vase life of cut flowers without affecting their normal physiological functions; the nanoscale size ensures that it will not block the vascular bundles when forming a protective layer, ensuring the normal transport of water and nutrients and avoiding secondary stress that may be caused by preservation treatment.

[0025] 5. The preparation process of this invention is simple, low-cost and environmentally friendly. It adopts mature microfluidic co-assembly and dialysis technology, and the process is controllable and reproducible. The main raw material is a biocompatible synthetic polymer, which significantly reduces the cost and environmental risk compared with metal materials such as nano-silver. When applied, it only needs to be added to ordinary bottle-insertion solution without changing the industrial process. It is easy to use and promote. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, some of the drawings in the following description are some embodiments of the present invention. For those skilled in the art, other drawings can be made based on these drawings without creative effort.

[0027] Figure 1 These are the particle size and STEM image of the nano-bandage prepared in Example 1 of this invention; Figure 2 These are the particle size and STEM image of the nano-bandage prepared in Example 2 of this invention; Figure 3 These are the particle size and STEM image of the nano-bandage prepared in Example 3 of this invention; Figure 4 These are the particle size and STEM image of the nano-bandage prepared in Comparative Example 1 of this application; Figure 5These are the potential maps of the nano-bandages prepared in Examples 1 to 3 and Comparative Example 1 of this invention; Figure 6 This is a near-infrared two-zone live imaging distribution map of the nano-bandages prepared in Examples 1 to 3 and Comparative Example 1 of this invention on the stems of cut flowers; Figure 7 This is a graph showing the uptake rate of the nano-bandages prepared in Examples 1 to 3 and Comparative Example 1 on the stems of cut flowers. Figure 8 This refers to the cumulative amount of the nano-bandages prepared in Examples 1 to 3 and Comparative Example 1 applied to the stems of cut flowers. Figure 9 This demonstrates the antibacterial effect of the nano-bandages prepared in Examples 1-3 and Comparative Example 1 of this invention. Figure 10 This is the application of the nano-bactericidal bandage prepared in Example 4 of the present invention in the preservation of cut flowers. Detailed Implementation

[0028] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific implementation schemes are now described in detail.

[0029] The present invention will be further described below with reference to embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0030] Example 1 See appendix Figure 1 Appendix Figure 5 ~Appendix Figure 9 This embodiment provides a positively charged nano-bandage with an average particle size of approximately 110 nm; the addition of laboratory-synthesized fluorescent dye IR790 facilitates the tracking of the nano-bandage.

[0031] ①The preparation method of the nano-bandage includes the following steps: S1. Under light-protected conditions, 8-hydroxyquinoline (8-HQ), polymer PEG, PDMAEMA, and IR790 were dissolved in tetrahydrofuran. The concentration of 8-HQ was 0.05 mg / mL, the total concentration of polymer PEG and PDMAEMA was 0.5 mg / mL, the mass fraction of PDMAEMA in the polymer was 25%, and the concentration of IR790 was 8 μM. The above tetrahydrofuran solution was used as stream 1, and an equal volume of PBS (pH=6.6) was used as stream 2.

[0032] S2. Inject equal volumes of stream 1 and stream 2 into the two-channel mixer simultaneously for mixing at an injection rate of 30 mL / min to obtain a nanoparticle mixture.

[0033] S3. The nanoparticle mixture obtained in step S2 is dialyzed in PBS (pH=6.6) for 12 hours to remove organic solvents and impurities, resulting in IR790-labeled nano-bandages for preserving cut flowers.

[0034] Near-infrared II imaging has a deeper penetration depth, less background scattering and autofluorescence, and a higher signal-to-noise ratio, enabling the acquisition of higher resolution images; therefore, the study used the aforementioned near-infrared II dye IR790 as a tracer, with an excitation wavelength of 790 nm and an emission wavelength of 800 nm to 1000 nm.

[0035] The above experiment was repeated three times. The three parallel samples of the nano-bandage were analyzed using a Zetasizer and scanning electron microscope. The average particle size and STEM images of the nano-bandage are attached. Figure 1 As shown, its average Zeta potential is as follows: Figure 5 As shown.

[0036] ②The adsorption effect of the nano-bandage is shown in the following experiment: The flowers used in this experiment were purchased from Pingji Flower Market in Shanghai. Healthy, disease-free, and uniformly sized and mature 'Rosa chinensis' cut flowers were selected. The cut flowers were trimmed to a total stem length of 35cm, and 5cm of stem was taken from the end of the trimmed stem.

[0037] Take 1 mL of the above-prepared nano-bandage solution into a cuvette; for easy tracing, cut the above 5 cm stem longitudinally and immediately insert it into the cuvette containing the nano-bandage; use a near-infrared II in vivo imaging system to observe in real time the position of nano-bandages of different particle sizes in the fresh cut flowers of Carola roses; cut three 5 cm stem sections and repeat the above experiment three times.

[0038] The distribution of nano-bandages on cut flower stems, as recorded in real time by a near-infrared II imaging system, was analyzed. The results are shown in the attached figure. Figure 5 ~Appendix Figure 7 As shown, due to capillary action, the nano-bandage rises along the xylem vascular bundles, but due to electrostatic attraction, it remains near the incision. After 1 minute, the nano-bandage remains within 8 mm of the incision and remains essentially unchanged. Therefore, this nano-bandage can be adsorbed around stem incisions.

[0039] ③ The antibacterial effect of the nano-bandage on the plate is shown in the following experiment: First, the bacterial culture in the cryopreservation tube was revived to obtain plates with independent colonies; a single Staphylococcus aureus with clear boundaries was taken and added to 10 mL of liquid LB medium, and incubated on a shaker for 8 h; sterile PBS (pH=7.4) was used as a control group; 10 μL of the incubated bacterial culture was taken and diluted 10 μL in sterile PBS and the nano-bandage solution prepared in Example 1, respectively. 6 Take 20 μL of the diluted bacterial solution, spread it onto a plate, seal it, and place it in an incubator; repeat the bactericidal effect experiment three times; after 12 hours, observe under a microscope, count the bacteria from the three experiments, and calculate the average inhibition rate; Figure 9 As shown, the nano-bandage prepared in Example 1 has a significant bactericidal effect, with an average antibacterial rate of 85.6%.

[0040] Example 2 See appendix Figure 2 Appendix Figure 5 ~Appendix Figure 9 This embodiment provides a positively charged nano-bandage with an average particle size of approximately 205 nm; the addition of laboratory-synthesized fluorescent dye IR790 facilitates the tracking of the nano-bandage.

[0041] ①The preparation method of the nano-bandage includes the following steps: S1. Under light-protected conditions, 8-hydroxyquinoline (8-HQ), polymer PEG, PDMAEMA, and IR790 were dissolved in tetrahydrofuran. The concentration of 8-HQ was 0.05 mg / mL, the total concentration of polymer PEG and PDMAEMA was 0.02 mg / mL, the mass fraction of PDMAEMA in the polymer was 25%, and the concentration of IR790 was 8 μM. The above tetrahydrofuran solution was used as stream 1, and an equal volume of PBS (pH=6.6) was used as stream 2.

[0042] S2. Inject equal volumes of stream 1 and stream 2 into the two-channel mixer simultaneously for mixing at an injection rate of 30 mL / min to obtain a nanoparticle mixture.

[0043] S3. The nanoparticle mixture obtained in step S2 is dialyzed in PBS (pH=6.6) for 12 hours to remove organic solvents and impurities, resulting in IR790-labeled nano-bandages for preserving cut flowers.

[0044] The above experiment was repeated three times. The three parallel samples of the nano-bandage were analyzed using a Zetasizer and scanning electron microscope. The average particle size and STEM images of the nano-bandage are attached. Figure 2 As shown, its average Zeta potential is as follows: Figure 5 As shown.

[0045] ②The adsorption effect of the nano-bandage is shown in the following experiment: The flowers used in this experiment were purchased from Pingji Flower Market in Shanghai. Healthy, disease-free, and uniformly sized and mature 'Rosa chinensis' cut flowers were selected. The cut flowers were trimmed to a total stem length of 35cm, and 5cm of stem was taken from the end of the trimmed stem.

[0046] Take 1 mL of the above-prepared nano-bandage solution into a cuvette; for easy tracing, cut the above 5 cm stem longitudinally and immediately insert it into the cuvette containing the nano-bandage; use a near-infrared II in vivo imaging system to observe in real time the position of nano-bandages of different particle sizes in the fresh cut flowers of Carola roses; cut three 5 cm stem sections and repeat the above experiment three times.

[0047] The distribution of nano-bandages on cut flower stems, as recorded in real time by a near-infrared II imaging system, was analyzed. The results are shown in the attached figure. Figure 5 ~Appendix Figure 7 As shown, due to capillary action, the nano-bandage rises along the xylem vascular bundles, but due to electrostatic attraction, the nano-bandage stays near the incision. After 1 minute, the nano-bandage stays within 8 mm of the incision and remains essentially unchanged. Therefore, the nano-bandage can be adsorbed around the stem incision.

[0048] ③ The antibacterial effect of the nano-bandage on the plate is shown in the following experiment: Take a single Staphylococcus aureus colony with clear borders from a plate containing independent colonies, add 10 mL of liquid LB medium, and incubate on a shaker for 8 hours. Take 10 μL of the incubated bacterial solution and dilute it 10 μL in the nano-bandage solution prepared in Example 2. 6 Take 20 μL of the diluted bacterial solution, spread it onto a plate, seal it, and place it in an incubator; repeat the bactericidal effect experiment three times; after 12 hours, observe under a microscope, count the bacteria from the three experiments, and calculate the average inhibition rate; Figure 9 As shown, the antibacterial rate of the nano-bandage prepared in Example 2 was 74.8%, which was lower than that of Example 1.

[0049] Example 3 See appendix Figure 3 Appendix Figure 5 ~Appendix Figure 9 This embodiment provides a positively charged nano-bandage with an average particle size of approximately 575 nm; the addition of laboratory-synthesized fluorescent dye IR790 facilitates the tracking of the nano-bandage.

[0050] ①The preparation method of the nano-bandage includes the following steps: S1. Under light-protected conditions, 8-hydroxyquinoline (8-HQ), polymer PEG, PDMAEMA, and IR790 were dissolved in tetrahydrofuran. The concentration of 8-HQ was 0.05 mg / mL, the total concentration of polymer PEG and PDMAEMA was 0.005 mg / mL, the mass fraction of PDMAEMA in the polymer was 25%, and the concentration of IR790 was 8 μM. The above tetrahydrofuran solution was used as stream 1, and an equal volume of PBS (pH=6.6) was used as stream 2.

[0051] S2. Inject equal volumes of stream 1 and stream 2 into the two-channel mixer simultaneously for mixing at an injection rate of 30 mL / min to obtain a nanoparticle mixture.

[0052] S3. The nanoparticle mixture obtained in step S2 is dialyzed in PBS (pH=6.6) for 12 hours to remove organic solvents and impurities, resulting in IR790-labeled nano-bandages for preserving cut flowers.

[0053] The above experiment was repeated three times. The three parallel samples of the nano-bandage were analyzed using a Zetasizer and scanning electron microscope. The average particle size and STEM images of the nano-bandage are attached. Figure 3 As shown, its average Zeta potential is as follows: Figure 5 As shown.

[0054] ②The adsorption effect of the nano-bandage is shown in the following experiment: The flowers used in this experiment were purchased from Pingji Flower Market in Shanghai. Healthy, disease-free, and uniformly sized and mature 'Rosa chinensis' cut flowers were selected. The cut flowers were trimmed to a total stem length of 35cm, and 5cm of stem was taken from the end of the trimmed stem.

[0055] Take 1 mL of the above-prepared nano-bandage solution into a cuvette; for easy tracing, cut the above 5 cm stem longitudinally and immediately insert it into the cuvette containing the nano-bandage; use a near-infrared II in vivo imaging system to observe in real time the position of nano-bandages of different particle sizes in the fresh cut flowers of Carola roses; cut three 5 cm stem sections and repeat the above experiment three times.

[0056] The distribution of nano-bandages on cut flower stems, as recorded in real time by a near-infrared II imaging system, was analyzed. The results are shown in the attached figure. Figure 5 ~Appendix Figure 7 As shown, due to capillary action, the nano-bandage rises along the xylem vascular bundles, but due to electrostatic attraction, the nano-bandage stays near the incision. After 1 minute, the nano-bandage stays within 8 mm of the incision and remains essentially unchanged. Therefore, the nano-bandage can be adsorbed around the stem incision.

[0057] ③ The antibacterial effect of the nano-bandage on the plate is shown in the following experiment: Take a single Staphylococcus aureus colony with clear borders from a plate containing independent colonies, add 10 mL of liquid LB medium, and incubate on a shaker for 8 hours. Take 10 μL of the incubated bacterial solution and dilute it 10 μL in the nano-bandage solution prepared in Example 3. 6 Take 20 μL of the diluted bacterial solution, spread it onto a plate, seal it, and place it in an incubator; repeat the bactericidal effect experiment three times; after 12 hours, observe under a microscope, count the bacteria from the three experiments, and calculate the average inhibition rate; Figure 9 As shown, the average antibacterial rate of the nano-bandage prepared in Example 3 was 70.4%, which was lower than that of Examples 1 and 2; therefore, when the nano-bandage is positively charged, the smaller the particle size, the stronger the bactericidal ability.

[0058] Example 4

[0059] See appendix Figure 10 This embodiment provides a method for preparing a positively charged nano-bandage and its application in the preservation of cut flowers.

[0060] ①The preparation method of the nano-bandage includes the following steps: S1. Dissolve 8-hydroxyquinoline (8-HQ), polymer PEG and PDMAEMA, and IR790 in tetrahydrofuran. The concentration of 8-HQ is 0.05 mg / mL, the total concentration of polymer PEG and PDMAEMA is 0.5 mg / mL, and the mass fraction of PDMAEMA in the polymer is 25%. The above tetrahydrofuran solution is used as stream 1, and an equal amount of PBS (pH=6.6) is used as stream 2.

[0061] S2. Inject equal volumes of stream 1 and stream 2 into the two-channel mixer simultaneously for mixing at an injection rate of 30 mL / min to obtain a nanoparticle mixture.

[0062] S3. The nanoparticle mixture obtained in step S2 is placed in PBS (pH=6.6) and dialyzed for 12 hours to remove organic solvents and impurities, thus obtaining a nano-bandage for preserving cut flowers.

[0063] ②The experimental results of the application of the nano-bandage in the preservation of cut flowers are as follows: The flowers used in this experiment were purchased from Pingji Flower Market in Shanghai. Healthy, disease-free, and uniformly sized and mature 'Rosa chinensis' cut flowers were selected. The cut flowers were trimmed to a total stem length of 35cm and cut at a 45° angle.

[0064] The experimental group consisted of 200 mL of deionized water containing 0.01 mg / mL nano-bandage, while the control group consisted of 200 mL of deionized water. Both the experimental and control groups were replicated in triplicate, with three fresh-cut flowers in each group. The laboratory temperature was 25℃±2℃, and the humidity was 50%~60%.

[0065] As attached Figure 10 As shown, after 6 days, most of the flowers in the control group wilted, bent, and deformed, and a small number of flowers rotted due to gray mold. In contrast, the experimental group using nano-bandage solution as vase liquid had the vast majority of healthy and upright flowers, with only a small number showing slight bending. Therefore, nano-bandage has the effect of extending the vase life of cut flowers.

[0066] Comparative Example 1 See appendix Figure 4 ~Appendix Figure 9 This comparative example provides a negatively charged nano-bandage with an average particle size of approximately 65 nm; the addition of laboratory-synthesized fluorescent dye IR790 facilitates the tracking of the nano-bandage.

[0067] ①The preparation method of the nano-bandage includes the following steps: S1. Under light-protected conditions, 8-hydroxyquinoline (8-HQ), polymer PEG, and IR790 were dissolved in tetrahydrofuran, with the concentration of 8-HQ being 0.05 mg / mL, the concentration of polymer PEG being 0.5 mg / mL, and the concentration of IR790 being 8 μM. The tetrahydrofuran solution was used as stream 1, and an equal volume of ultrapure water was used as stream 2.

[0068] S2. Inject equal volumes of stream 1 and stream 2 into the two-channel mixer simultaneously for mixing at an injection rate of 30 mL / min to obtain a nanoparticle mixture.

[0069] S3. The nanoparticle mixture obtained in step S2 is dialyzed in ultrapure water for 12 hours to remove organic solvents and impurities, and IR790-labeled nano-bandages for preserving cut flowers are obtained.

[0070] The above experiment was repeated three times. The three parallel samples of the nano-bandage were analyzed using a Zetasizer and scanning electron microscope. The average particle size and STEM images of the nano-bandage are attached. Figure 4 As shown, its average Zeta potential is as follows: Figure 5 As shown.

[0071] ②The adsorption effect of the nano-bandage is shown in the following experiment: The flowers used in this experiment were purchased from Pingji Flower Market in Shanghai. Healthy, disease-free, and uniformly sized and mature 'Rosa chinensis' cut flowers were selected. The cut flowers were trimmed to a total stem length of 35cm, and 5cm of stem was taken from the end of the trimmed stem.

[0072] Take 1 mL of the above-prepared nano-bandage solution into a cuvette; for easy tracing, cut the above 5 cm stem longitudinally and immediately insert it into the cuvette containing the nano-bandage; use a near-infrared II in vivo imaging system to observe in real time the position of nano-bandages of different particle sizes in the fresh cut flowers of Carola roses; cut three 5 cm stem sections and repeat the above experiment three times.

[0073] The distribution of nano-bandages on cut flower stems, as recorded in real time by a near-infrared II imaging system, was analyzed. The results are shown in the attached figure. Figure 5 ~Appendix Figure 7 As shown, due to capillary action, the nanoparticles rise along the xylem vascular bundles. Due to electrostatic repulsion, the nanoparticles are continuously absorbed by the stem. After 1 minute, the nano-bandage stays at a height of 16 mm from the incision and continues to rise. By 2 minutes, the nanoparticles have risen to 18 mm. Therefore, the nano-bandage cannot be adsorbed around the stem incision and the effect is poor.

[0074] ③ The antibacterial effect of the nano-bandage on the plate is shown in the following experiment: Take a single Staphylococcus aureus colony with clear borders from a plate containing independent colonies, add 10 mL of liquid LB medium, and incubate on a shaker for 8 hours. Take 10 μL of the incubated bacterial solution and dilute it 10 μL in the nano-bandage solution prepared in Example 3. 6 Take 20 μL of the diluted bacterial solution, spread it onto a plate, seal it, and place it in an incubator; repeat the bactericidal effect experiment three times; after 12 hours, observe under a microscope, count the bacteria from the three experiments, and calculate the average inhibition rate; Figure 9 As shown, the average antibacterial rate of the nano-bandage prepared in Example 4 was 52.7%; therefore, the bactericidal ability of the positively charged nano-bandage is better than that of the negatively charged nano-bandage.

[0075] In summary, combining the systematic experimental data from Examples 1-3 and Comparative Example 1 with the final application verification in Example 4, the nano-bandage technology for cut flower preservation provided by this invention demonstrates comprehensive and significant progress. Specifically, Examples 1-3 and Comparative Example 1, through precise control of polymer composition and concentration, not only successfully prepared nanoparticles with controllable particle size and surface charge, but more importantly, revealed that "positive charge" is the core mechanism for achieving targeted enrichment of nanoparticles at negatively charged cut surfaces, forming a durable "nano-bandage" protective layer. The negatively charged control particles (Comparative Example 1) failed due to electrostatic repulsion, strongly highlighting and proving the uniqueness and necessity of the design principle of this invention. Further plate antibacterial experiments confirmed that the positively charged nano-bandage has a significant inhibitory effect on common pathogens such as Staphylococcus aureus. Finally, Example 4 demonstrated in a practical cut flower vase preservation experiment that adding an extremely low concentration (0.05 mg / mL) of this nano-bandage could keep fresh-cut flowers healthy and upright for 6 days, significantly extending their vase life and directly verifying its excellent final application effect. Therefore, this invention, through a complete logical chain from "material design - mechanism explanation - effect verification," provides an innovative cut flower preservation solution that integrates many advantages such as targeted long-lasting effect, high efficiency and low consumption, intelligent adjustability, ease of use, and environmental friendliness. It overcomes the shortcomings of traditional technologies such as poor targeting of fungicides, short-lasting effect, large dosage, and high potential risks, and has outstanding industrial application value and market prospects.

[0076] The embodiments described above merely illustrate more specific and detailed implementations of the present invention, and should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A nano-bandage for preserving cut flowers, characterized in that, The nano-bandage is composed of a polymer and a bactericide, with the polymer acting as a carrier to encapsulate the bactericide. The polymer is a mixture of polyethylene glycol and poly(N,N-dimethylaminoethyl methacrylate), wherein the mass fraction of poly(N,N-dimethylaminoethyl methacrylate) is greater than 0% and less than or equal to 100%, and the total polymer concentration is 0.005~0.5 mg / mL. By adjusting the mass fraction of poly(N,N-dimethylaminoethyl methacrylate) and the total polymer concentration, the nano-bandage has a particle size of 63.2 nm~820 nm and a surface potential of 0 mV~47.19 mV with a positive charge.

2. The nano-bandage for preserving cut flowers as described in claim 1, characterized in that, The mass fraction of the polymethacrylate-N,N-dimethylaminoethyl ester is 10%~100%.

3. The nano-bandage for preserving cut flowers as described in claim 1, characterized in that, The bactericide is selected from at least one of 8-hydroxyquinoline, 8-hydroxyquinoline citrate, isothiazolinone, ciprofloxacin, or norfloxacin.

4. A method for preparing a nano-bandage for preserving cut flowers as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Preparation of Stream 1: Dissolve the bactericide and polymer in an organic solvent to form an organic phase stream, wherein the concentration of the bactericide is 0.001~0.2 mg / mL and the total concentration of the polymer is 0.005~0.5 mg / mL; S2, Preparation of Stream 2: Providing an aqueous stream; S3, Nano-co-assembly: Equal volumes of the flow stream 1 and the flow stream 2 are simultaneously injected into a microfluidic mixer and instantaneously mixed at a flow rate of 2~50mL / min, so that the polymer and the bactericide co-assemble to form a nanoparticle mixture. S4. Purification: The nanoparticle mixture obtained in step S3 is placed in a dialysis device and dialyzed with aqueous dialysis solution for 12-14 hours to remove organic solvents and small molecule impurities, thereby obtaining the purified nano-bandage dispersion.

5. The preparation method according to claim 4, characterized in that, In step S1, the organic solvent is tetrahydrofuran.

6. The preparation method according to claim 4, characterized in that, In step S2, the aqueous stream is ultrapure water or PBS buffer with a pH of 4.0 to 8.

0.

7. The preparation method according to claim 4, characterized in that, In step S4, the aqueous dialysis solution is ultrapure water or PBS buffer with a pH of 4.0 to 8.

0.

8. The use of the nano-bandage as described in any one of claims 1 to 3 in the preparation of a preservative for preventing microbial infection of cut flower slits caused by Staphylococcus aureus.

9. The application of the nano-bandage as described in any one of claims 1 to 3 in the preservation of cut flowers, characterized in that, The nano-bandage is dispersed in the vase liquid. The nano-bandage utilizes its positive surface charge to accumulate and adhere to the surface and vicinity of the negatively charged cut flower stem through electrostatic interaction, forming a physical barrier and slowly releasing bactericide, thereby extending the vase life of the cut flowers.

10. A method for preserving cut flowers, characterized in that, The procedure includes the following steps: immersing the cut end of the flower stem in a preservative solution containing the nano-bandage as described in any one of claims 1 to 3, wherein the concentration of the nano-bandage is 0.001 to 0.1 mg / mL.

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