Preparation method and application of poly D-mannose nano-selenium

Abstract

The invention relates to a preparation method and application of poly (D-mannose) nano-selenium, explores the potential of the poly (D-mannose) nano-selenium in inhibiting the activity of various common food-borne pathogenic bacteria and the formation of biofilms, and provides scientific basis and technical support for the application of the poly (D-mannose) nano-selenium in the fields of food preservation and food safety. The preparation method comprises the following steps: 1) uniformly mixing a poly D-mannose solution and a sodium selenite solution at a certain speed to form a mixed solution; 2) slowly dropwise adding an ascorbic acid solution into the mixed solution prepared in the step 1) to promote generation of poly D-mannose-selenium nanoparticles; (3) carrying out dialysis treatment, so as to obtain pure poly D-mannose-selenium nanoparticles; the poly D-mannose-selenium nano-particles prepared by the invention have remarkable inhibitory activity on various food-borne pathogenic bacteria, particularly have a remarkable inhibitory effect on formation of biofilms of staphylococcus aureus and bacillus cereus, and are innovations on the preparation method and application of the poly D-mannose nano-selenium.

Description

1. Technical Field

[0001] The invention relates to the technical field of nano material preparation and biological application thereof, in particular to a preparation method of poly D-mannose nano selenium and application thereof. 2. Background Technology

[0002] With the rapid development of the food industry and the increasing demand for food safety from consumers, the problem of foodborne pathogens has become a major challenge facing the global food safety field. These pathogens, such as Escherichia coli O157:H7, Salmonella typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus cereus, can not only survive and reproduce during food production and processing, but also form biofilms, which greatly increases the risk of food contamination and the difficulty of prevention and control. Traditional food preservation and antibacterial methods, such as the use of chemical preservatives and high-temperature sterilization, can effectively inhibit the growth of pathogens to a certain extent, but may also bring food safety risks, such as chemical residues and destruction of nutrients. Therefore, it is particularly important to develop a new type of food preservation and antibacterial technology that is efficient, safe and environmentally friendly.

[0003] In recent years, nanomaterials have attracted much attention due to their unique physicochemical properties and broad application prospects. Among them, selenium nanoparticles (SeNPs) have shown broad application potential in the field of food science due to their unique physicochemical properties and biological activity. However, selenium nanoparticles are prone to agglomeration during the preparation process, resulting in uneven particle size distribution, affecting their stability and bioavailability. In addition, when selenium nanoparticles are directly used for food preservation, they may cause food safety problems due to their surface properties. To solve the above problems, researchers began to explore the use of polysaccharides to modify the surface of selenium nanoparticles to improve their dispersibility and biocompatibility. Patent application number 202210898248.9 Poly D-mannose prepared by chemical synthesis has a more controllable structure and properties, and functional groups such as hydroxyl groups in its molecular structure can form chemical bonds with selenium atoms on the surface of selenium nanoparticles, thereby achieving effective modification of selenium nanoparticles. Combining poly D-mannose with selenium elements with antibacterial activity to form nanoparticles is expected to become a new and efficient food preservative and antibacterial material. However, the current research on the preparation method of poly D-mannose nanoselenium (Man-SeNPs) and its application in inhibiting the activity of foodborne pathogens and their biofilm formation is still insufficient. Therefore, it is imperative to invent a preparation method of poly D-mannose nanoselenium and its application. III. Summary of the invention

[0004] In view of the above situation, in order to solve the defects of the prior art, the purpose of the present invention is to provide a preparation method and application of poly D-mannose nano-selenium, and to characterize its physical and chemical properties, while exploring its potential in inhibiting the activity of various common foodborne pathogens and their biofilm formation, so as to provide a scientific basis and technical support for its application in the field of food preservation and food safety.

[0005] The technical solution provided by the present invention is that the preparation method of the poly D-mannose nano-selenium comprises the following steps:

[0006] 1) mixing the poly D-mannose solution and the sodium selenite solution at room temperature at a certain speed to form a mixed solution;

[0007] 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) according to the molar ratio of ascorbic acid to sodium selenite, and reacting for a period of time under light-proof conditions to promote the formation of poly D-mannose-selenium nanoparticles (Man-SeNPs);

[0008] 3) placing the reacted solution in a dialysis bag for dialysis treatment to remove unreacted raw materials and small molecule impurities to obtain pure poly D-mannose-selenium nanoparticles.

[0009] The poly D-mannose is poly mannoses prepared by chemical synthesis method of patent application number 202210898248.9, and the preparation method is: using citric acid as a catalyst, mannose is polymerized to obtain the poly D-mannose, the mass ratio of mannose to citric acid is 100:1-6, and the polymerization reaction conditions are as follows: temperature is 125-175°C; time is 5-60min.

[0010] The poly D-mannose nano-selenium is used in inhibiting the growth of food-borne pathogens and the formation of their biofilms.

[0011] A composition capable of significantly inhibiting the growth of foodborne pathogenic bacteria and the formation of biofilm thereof is obtained by mixing and culturing a poly D-mannose nano-selenium solution with a foodborne pathogenic bacteria suspension.

[0012] The preparation method of the present invention is simple and easy to operate, and effectively solves the problem of easy agglomeration of selenium nanoparticles. The prepared poly D-mannose-selenium nanoparticles have significant inhibitory activity against a variety of foodborne pathogens, especially have a significant inhibitory effect on the biofilm formation of Staphylococcus aureus and Bacillus cereus. It is an innovation in the preparation method of poly D-mannose nano-selenium and its application. IV. Description of the drawings

[0013] Figure 1 These are SeNPs stabilized by poly-D-mannose at different concentrations according to the present invention.

[0014] Figure 2 The absorbance values ​​of SeNPs stabilized by poly-D-mannose at different concentrations of the present invention.

[0015] Figure 3 The particle size distribution, polydispersity index (PDI) and Zeta potential of SeNPs stabilized by poly D-mannose of the present invention at different concentrations. (a) Particle size distribution; (b) Average particle size and polydispersity index (PDI); (c) Zeta potential.

[0016] Figure 4 This is a TEM image of 40 mg / mL poly-D-mannose-stabilized SeNPs of the present invention.

[0017] Figure 5 Surface element analysis of 40 mg / mL poly-D-mannose stabilized SeNPs of the present invention. (a) Element composition of Man-SeNPs; (b) C; (c) O; (d) Se.

[0018] Figure 6 The effects of different concentrations of Man-SeNPs on the growth of pathogens: (a) Escherichia coli O157:H7; (b) Salmonella typhimurium; (c) Pseudomonas aeruginosa; (d) Staphylococcus aureus; (e) Bacillus cereus.

[0019] Figure 7 The color changes of pathogenic bacteria biofilms added with different concentrations of Man-SeNPs of the present invention after MTT staining: (a) Bacillus cereus; (b) Staphylococcus aureus; (c) Salmonella typhimurium; (d) Escherichia coli O157:H7; (e) Pseudomonas aeruginosa. V. Specific implementation methods

[0020] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples.

[0021] Example 1

[0022] The present invention may further include the following steps when implemented:

[0023] 1) 3 mL of a poly D-mannose solution with a concentration range of 40-100 mg / mL was mixed with 5 mL of a sodium selenite solution with a concentration of 20 mmol / L at a speed of 600 rpm / min at room temperature to form a mixed solution;

[0024] 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) in a molar ratio of ascorbic acid to sodium selenite of 6:1, and continuing the reaction for 3 hours under light-proof conditions to promote the formation of poly D-mannose-selenium nanoparticles (Man-SeNPs);

[0025] 3) After the reaction is completed, the resulting solution is placed in a dialysis bag with a molecular weight cutoff of 500 Daltons (Da) and dialyzed for 3-4 days to remove unreacted raw materials and small molecule impurities, and finally pure poly D-mannose-selenium nanoparticles (Man-SeNPs) are obtained.

[0026] Example 2

[0027] The present invention may further include the following steps when implemented:

[0028] 1) 3 mL of a 40 mg / mL poly D-mannose solution and 5 mL of a 20 mmol / L sodium selenite solution were mixed at room temperature at a speed of 600 rpm / min to form a mixed solution;

[0029] 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) in a molar ratio of ascorbic acid to sodium selenite of 6:1, and continuing the reaction for 3 hours under light-proof conditions to promote the formation of poly D-mannose-selenium nanoparticles (Man-SeNPs);

[0030] 3) After the reaction is completed, the resulting solution is placed in a dialysis bag with a molecular weight cutoff of 500 Daltons (Da) and dialyzed for 3-4 days to remove unreacted raw materials and small molecule impurities, and finally pure poly D-mannose-selenium nanoparticles (Man-SeNPs) are obtained.

[0031] Example 3

[0032] The present invention may further include the following steps when implemented:

[0033] 1) 3 mL of a 60 mg / mL poly D-mannose solution and 5 mL of a 20 mmol / L sodium selenite solution were mixed at room temperature at a speed of 600 rpm / min to form a mixed solution;

[0034] 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) in a molar ratio of ascorbic acid to sodium selenite of 6:1, and continuing the reaction for 3 hours under light-proof conditions to promote the formation of poly D-mannose-selenium nanoparticles (Man-SeNPs);

[0035] 3) After the reaction is completed, the resulting solution is placed in a dialysis bag with a molecular weight cutoff of 500 Daltons (Da) and dialyzed for 3-4 days to remove unreacted raw materials and small molecule impurities, and finally pure poly D-mannose-selenium nanoparticles (Man-SeNPs) are obtained.

[0036] Example 4

[0037] The present invention may further include the following steps when implemented:

[0038] 1) 3 mL of 80 mg / mL poly D-mannose solution and 5 mL of 20 mmol / L sodium selenite solution were mixed at room temperature at a speed of 600 rpm / min to form a mixed solution;

[0039] 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) in a molar ratio of ascorbic acid to sodium selenite of 6:1, and continuing the reaction for 3 hours under light-proof conditions to promote the formation of poly D-mannose-selenium nanoparticles (Man-SeNPs);

[0040] 3) After the reaction is completed, the resulting solution is placed in a dialysis bag with a molecular weight cutoff of 500 Daltons (Da) and dialyzed for 3-4 days to remove unreacted raw materials and small molecule impurities, and finally pure poly D-mannose-selenium nanoparticles (Man-SeNPs) are obtained.

[0041] The poly D-mannose nano-selenium prepared by the present invention has great potential in inhibiting the activity of a variety of common foodborne pathogens and their biofilm formation, and has significant inhibitory activity against a variety of foodborne pathogens, especially against the biofilm formation of Staphylococcus aureus and Bacillus cereus. The relevant test data are as follows:

[0042] Unless otherwise specified, the experimental methods used below are all conventional methods. The materials and reagents used can be obtained from commercial sources unless otherwise specified. The poly D-mannose used was prepared chemically in the early stage and a patent has been applied for (application number: 202210898248.9).

[0043] 1. Dispersion effect of poly-D-mannose on SeNPs

[0044] like Figure 1 As shown in the figure, without the addition of poly D-mannose (concentration of 0 mg / mL), selenium nanoparticles (SeNPs) showed obvious agglomeration, causing the particles to settle at the bottom of the container. Subsequently, when poly D-mannose was introduced into the system, the dispersion state of SeNPs was significantly improved. With the gradual increase in the concentration of poly D-mannose, the solution gradually showed higher light transmittance, and the color of the solution turned into a bright orange-red. When the concentration of poly D-mannose reached 40 mg / mL and above, the light transmittance and color characteristics of the solution tended to be stable, indicating that within this concentration range, the dispersion effect of poly D-mannose on SeNPs has reached saturation.

[0045] 2. Characterization of Poly D-Mannose Nanoselenium

[0046] (1) UV-visible absorption spectra of Man-SeNPs

[0047] UV-visible spectroscopy is a crucial, simple and fast technical means to identify the formation of nanoparticles. In the spectral range of 200 to 800 nanometers (nm), dual-wavelength colorimetry is used, and 410nm and 490nm are specially selected as detection wavelengths. By calculating the ratio of absorbance at these two wavelengths (A410 / A490), it can be used as an indicator to evaluate the particle size of poly D-mannose-selenium nanoparticles (Man-SeNPs). Specifically, the larger the ratio of A410 / A490, the smaller the particle size of Man-SeNPs, and its dispersion stability and colloidal stability are correspondingly enhanced. Figure 2 It can be seen that with the gradual increase of poly D-mannose concentration, the absorbance ratio of poly D-mannose-selenium nanoparticles (Man-SeNPs) at wavelength A410 / A490 showed an increasing trend. When the concentration of poly D-mannose increased to 40 mg / mL, the absorbance ratio tended to be stable and no longer changed significantly. This preliminarily shows that poly D-mannose has a significant effect on regulating the particle size of selenium nanoparticles.

[0048] (2) Particle size distribution, polydispersity index and zeta potential of Man-SeNPs

[0049] The Nano ZS zeta potential and particle size analyzer (Zetasizer system) was used to accurately measure the particle size, polydispersity index (PDI) and Zeta potential of Man-SeNPs. The specific measurement conditions are set as follows: the particle size analysis uses a backscattering angle of 173°, and all measurements are performed at a constant temperature of 25°C to ensure the comparability of the data; the viscosity of the solvent is set to 0.8872 millipascal seconds (mPa·s), the refractive index of the solvent is 1.330, and the refractive index of the material to be tested is set to 1.59. In the experiment, 1mL of Man-SeNPs solution containing different poly D-mannose concentrations was placed in a dedicated sample cell, and the Nano ZS system was used to measure the particle size distribution and Zeta potential of each sample. Each sample was measured three times, and the average value was taken as the final result. Figure 3(a) and (b) show that, without the addition of poly D-mannose, the average particle size of Man-SeNPs was measured to be 2940 nm, and the PDI was 0.36, showing a relatively large particle size distribution range. Subsequently, with the increase in the concentration of poly D-mannose, the particle size of Man-SeNPs showed a trend of gradual decrease until the concentration of poly D-mannose reached 40 mg / mL, when the particle size change tended to be stable and remained at a small and stable level. At the same time, the addition of poly D-mannose also led to a decrease in the PDI value. When the concentration of poly D-mannose was 40 mg / mL, the average particle size of Man-SeNPs was significantly reduced to 89.88 nm, and the PDI was reduced to 0.133, which further confirmed that poly D-mannose can effectively promote the formation of selenium nanoparticles (SeNPs) with smaller particle size and better dispersibility. In addition, the addition of poly D-mannose has limited effect on the Zeta potential of Man-SeNPs particles, such as Figure 3 As shown in (c), the potential value is basically maintained at around -20 mV, indicating that its surface charge stability has not changed significantly.

[0050] (3) Transmission electron microscopy (TEM) observation of the morphology of Man-SeNPs

[0051] A small amount of Man-SeNPs solution was added to a copper mesh pre-installed with a carbon support film. Then, the added solution was allowed to evaporate naturally at room temperature until it was completely dry. After this step was completed, TEM was used as an observation method to perform high-resolution imaging of the Man-SeNPs attached to the dried copper mesh. Through TEM images, the particle size and microscopic morphology of Man-SeNPs nanoparticles were accurately measured and observed. Figure 4 As shown, under TEM observation, Man-SeNPs showed a uniform spherical morphology, with a particle size distribution between 42-109 nm and an average particle size of 80 nm, which was basically consistent with the results measured by the nanoparticle size analyzer.

[0052] (4) Energy dispersive X-ray (EDX) determination of the elemental composition of Man-SeNPs

[0053] The Man-SeNPs solution was freeze-dried to obtain its solid powder form. Then, the freeze-dried powder was evenly and firmly adhered to a dedicated stage using double-sided tape to ensure that the sample surface was flat and evenly distributed. Then, the surface of the Man-SeNPs freeze-dried powder was qualitatively and quantitatively analyzed for elemental composition using an EDX analysis device. Figure 5 It can be seen that the surface element composition of Man-SeNPs is as follows Figure 5 As shown, the composition ratio of Man-SeNPs is C:O:Se=52.53:44.34:3.13.

[0054] 3. Determination of the inhibitory activity of poly D-mannose nanoselenium on foodborne pathogens

[0055] Five common foodborne pathogens, Escherichia coli O157:H7, Salmonella typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus cereus, were taken out from the -80°C frozen state and inoculated on LB (Luria-Bertani) agar plates and placed in a 37°C constant temperature incubator for 24 hours to promote colony growth. A single colony was picked from the plate and inoculated into LB liquid culture medium for two activation cultures to ensure that the pathogens were in an active proliferation state. After activation, the OD of each bacterial solution was adjusted. 600 The value was 0.2, and then a 10-fold dilution (concentration of 1×10 6 CFU / mL). Take 100 μL from the diluted bacterial solution and add it to a 96-well plate. Add different concentration gradients of Man-SeNPs solution prepared with sterile water to each well, and the final concentration range is set to 12.5 μg / mL-400 μg / mL. The group with equal volume of sterile water was set as the negative control group, and the group containing LB culture medium but no pathogens and Man-SeNPs solution was set as the blank control group. Three parallel samples were set for each concentration gradient and control group. Place the 96-well plate containing the pathogen suspension and different concentrations of Man-SeNPs solution in a microplate reader and culture it for 24 hours under continuous shaking conditions. Use the microplate reader to monitor and record the changes in the optical density (OD) value of each well, and draw the growth curves of the five pathogens under different concentrations of Man-SeNPs treatment. Figure 6 As shown in the figure, within the test concentration range of 12.5-400 μg / mL, Man-SeNPs had a significant inhibitory effect on Staphylococcus aureus, and the dose dependence was not significant. For Pseudomonas aeruginosa, the inhibitory effect of Man-SeNPs was not obvious in the early growth stage. After the culture time reached 10 hours, Man-SeNPs began to inhibit the growth of Bacillus cereus, and this inhibitory effect showed a dose-dependent characteristic. Under the same test conditions, Man-SeNPs had no significant inhibitory effect on Escherichia coli O157:H7, Salmonella typhimurium and Bacillus cereus.

[0056] 4. Determination of the inhibitory activity of poly D-mannose nanoselenium on biofilm of foodborne pathogens

[0057] The effects of Man-SeNPs on the biofilms of Escherichia coli O157:H7, Salmonella typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus cereus were measured below the minimum inhibitory concentration (MIC) of Man-SeNPs. The specific method is as follows: First, the five pathogens stored in glycerol cryovials were streaked on TSB (Tryptic Soy Broth) solid culture medium to purify and restore their activity. Subsequently, a single colony was picked from the culture medium and inoculated into TSB liquid culture medium, and cultured in a shaking incubator overnight at 37°C to ensure that the pathogens fully grew to the logarithmic growth phase. By adjusting the bacterial solution concentration to OD 600 = 0.2, and then dilute it 10 times, take 90 μL (concentration is 1×10 6 CFU / mL) was added to the predetermined wells in the 96-well plate. Then, 10 μL of Man-SeNPs solution of different concentrations dissolved in sterile water was added to each well containing bacterial liquid. Four replicate wells were set for each treatment group, the bacterial suspension treated with sterile water was set as the negative control group, and the culture medium with sample but no bacterial suspension was set as the blank control group. The 96-well plate was placed in a 37°C constant temperature incubator and cultured for 24 hours to promote the formation of biofilm.

[0058] After the incubation, the culture supernatant in each well was removed, and the 96-well plate was washed four times with 120 μL sterile PBS buffer to ensure that the non-adherent bacteria were completely removed to reduce interference with subsequent experiments. Subsequently, 100 μL of 0.5 mg / mL MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-DiphenyltetrazoliumBromide, tetramethyl azodiazole salt) solution was added to each well to stain the bacteria adhering to the bottom and wall of the well plate, and incubated at 37°C in the dark for 3 hours to allow MTT to be reduced to formazan crystals by living cells. After the incubation, the MTT solution was carefully removed, and 100 μL of DMSO (Dimethyl Sulfoxide) was added to each well, and the formazan crystals in the bacteria were fully dissolved in DMSO by slow shaking for 10 minutes. Finally, the absorbance of each well was measured at a wavelength of 490 nm using a microplate reader. The absorbance value of the negative control group was used as a benchmark, and its biofilm formation rate was set as 100%. The biofilm formation rate under treatment with different concentrations of Man-SeNPs solution was calculated. The calculation formula was: Biofilm formation rate = (OD sample / OD negative )×100%, where OD sample is the absorbance value of the treatment group, OD negative is the absorbance value of the negative control group.

[0059] like Figure 7 As shown in Table 1, Man-SeNPs had the most significant inhibitory effect on Staphylococcus aureus biofilm, and complete inhibition was achieved at a minimum inhibitory concentration (MIC) of 8.1 μg / mL. For Bacillus cereus biofilm, Man-SeNPs also showed strong inhibitory activity, and showed non-dose-dependent inhibition in the concentration range of 8.1-130 μg / mL. At a concentration of 8.1 μg / mL, the biofilm formation rate was reduced to 5.76%. For Escherichia coli O157:H7, the inhibitory effect of Man-SeNPs did not change significantly with increasing concentration, and the biofilm formation rate was 18.16% at the highest tested concentration of 130 μg / mL. For Salmonella typhimurium, Man-SeNPs had limited inhibitory effect at low concentrations, but as the concentration increased to 130 μg / mL, the biofilm formation rate dropped significantly to 27.09%, showing a certain concentration-dependent inhibition trend. For Pseudomonas aeruginosa, the inhibitory effect of Man-SeNPs was not significant. Even at the highest concentration of 130 μg / mL, the biofilm formation rate was still as high as 68.83%, indicating that its ability to inhibit the biofilm of this species is limited.

[0060] Table 1 Effects of different concentrations of Man-SeNPs on pathogenic bacterial biofilms

[0061]

[0062] V. Conclusion

[0063] In summary, the present invention successfully prepared poly D-mannose nano-selenium (Man-SeNPs) with good dispersibility and uniform particle size through a specific preparation process, effectively solving the problem of easy agglomeration of selenium nanoparticles, and the nano-selenium particles have significant inhibitory activity against a variety of foodborne pathogens, especially against the biofilm formation of Staphylococcus aureus and Bacillus cereus, providing a new solution for the field of food preservation and food safety. In addition, the preparation method of the present invention is simple, easy to operate, suitable for large-scale industrial production, and has broad application prospects.

[0064] It should be pointed out that the above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession can make changes or modify the technical contents disclosed above into equivalent embodiments with equivalent changes without departing from the scope of the technical solution of the present invention, which all fall within the protection scope of the present invention.

Claims

1. A method for preparing poly D-mannose nano-selenium, characterized in that: The preparation method of the poly D-mannose nano-selenium comprises the following steps: 1) Mixing the poly D-mannose solution and the sodium selenite solution at room temperature at a certain speed to form a mixed solution; 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) according to the molar ratio of ascorbic acid to sodium selenite, and reacting for a period of time under light-proof conditions to promote the formation of poly D-mannose-selenium nanoparticles; 3) The reacted solution is placed in a dialysis bag for dialysis treatment to remove unreacted raw materials and small molecule impurities to obtain pure poly D-mannose-selenium nanoparticles.

2. The method for preparing poly D-mannose nano-selenium according to claim 1, characterized in that: The poly D-mannose is poly mannoses prepared by chemical synthesis method of patent application number 202210898248.9, and the preparation method is: using citric acid as a catalyst, mannose is polymerized to obtain the poly D-mannose, the mass ratio of mannose to citric acid is 100:1-6, and the polymerization reaction conditions are as follows: temperature is 125-175°C; time is 5-60min.

3. The method for preparing poly D-mannose nano-selenium according to claim 2, characterized in that: The following steps are involved: 1) 3 mL of poly D-mannose solution with a concentration range of 40-100 mg / mL was mixed with 5 mL of sodium selenite solution with a concentration of 20 mmol / L at a speed of 600 rpm / min at room temperature to form a mixed solution; 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) in a molar ratio of ascorbic acid to sodium selenite of 6:1, and continuing the reaction for 3 h in a light-proof condition to promote the formation of poly D-mannose-selenium nanoparticles; 3) After the reaction is completed, the resulting solution is placed in a dialysis bag with a molecular weight cutoff of 500 Daltons and dialyzed for 3-4 days to remove unreacted raw materials and small molecule impurities to obtain pure poly D-mannose-selenium nanoparticles.

4. The method for preparing poly D-mannose nano-selenium according to claim 3, characterized in that: The following steps are involved: 1) 3 mL of 60 mg / mL poly D-mannose solution and 5 mL of 20 mmol / L sodium selenite solution were mixed at room temperature and at a speed of 600 rpm / min to form a mixed solution; 2) slowly adding the ascorbic acid solution to the mixed solution prepared in step 1) in a molar ratio of ascorbic acid to sodium selenite of 6:1, and continuing the reaction for 3 h in a light-proof condition to promote the formation of poly D-mannose-selenium nanoparticles; 3) After the reaction is completed, the resulting solution is placed in a dialysis bag with a molecular weight cutoff of 500 Daltons and dialyzed for 3-4 days to remove unreacted raw materials and small molecule impurities, and finally pure poly D-mannose-selenium nanoparticles are obtained.

5. Use of poly D-mannose nano-selenium prepared by the preparation method of any one of claims 1 to 4 in inhibiting the growth of foodborne pathogens and the formation of their biofilms.

6. A composition capable of significantly inhibiting the growth of foodborne pathogens and the formation of biofilms thereof, characterized in that: The poly D-mannose nano-selenium solution is mixed and cultured with a foodborne pathogenic bacteria suspension to obtain the product.

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