Method for enhancing antibacterial activity of nano-silver

Abstract

The invention belongs to the field of nano chemistry, and relates to a method for enhancing the antibacterial activity of nano silver. Comprising the following steps: (1) taking quercetin as a reducing agent, taking hexadecyl trimethyl ammonium bromide as a stabilizer, and reacting with silver nitrate to obtain nano-silver particles Que-coated AgNPs which are coated with quercetin and are positively charged; and (2) incubating the Que (at) AgNPs and a protein to form a Que (at) AgNPs-protein compound, wherein the protein is lysozyme, gamma-globulin or fibrinogen. The antibacterial activity of the nano-silver is obviously improved, meanwhile, the biotoxicity of the nano-silver is reduced, synthesis is convenient, and operation is easy.

Description

Technical Field

[0001] The present invention belongs to the field of nano - chemistry, and particularly relates to a method for enhancing the antibacterial activity of silver nanoparticles. Background Art

[0002] Silver nanoparticles (AgNPs) have strong bacteriostatic and bactericidal effects and broad - spectrum antibacterial activity. It is effective not only against Gram - positive bacteria, Gram - negative bacteria, viruses and fungi, but also has a long - acting antibacterial effect that cannot be compared with traditional antibacterial agents and does not produce drug resistance. The research and application of AgNPs in the field of antibacterial disinfection have received extensive attention and have been on the commercialization path. In emerging nanotechnology projects, the annual output of AgNPs ranks first among all nanomaterials, and its products are widely used in daily life such as food packaging, textiles, electronic products, household appliances, cosmetics, water purification, sprays, etc. With the rapid marketization of AgNPs, the biological toxicity caused by AgNPs has also attracted wide attention. In this regard, on the one hand, the effective concentration of AgNPs can be reduced by enhancing the antibacterial activity of AgNPs, so that AgNPs can also exert effective antibacterial activity at a lower concentration, thereby reducing the biological toxicity of AgNPs. On the other hand, the toxicity caused by continuous accumulation of free Ag + can be reduced. Summary of the Invention

[0003] The present invention proposes a method for enhancing the antibacterial activity of silver nanoparticles. In the present invention, quercetin is coated on the surface of silver nanoparticles to form positively charged Que@AgNPs, and then Que@AgNPs are co - incubated with lysozyme, γ - globulin or fibrinogen to obtain Que@AgNPs - lysozyme / γ - globulin / fibrinogen complexes, which significantly improves the antibacterial activity of silver nanoparticles and reduces the biological toxicity of silver nanoparticles at the same time.

[0004] The technical solution adopted by the present invention is as follows:

[0005] A method for enhancing the antibacterial activity of silver nanoparticles according to the present invention includes the following steps:

[0006] (1) Using quercetin as a reducing agent and cetyltrimethylammonium bromide (CTAB) as a stabilizer, reacting with silver nitrate to obtain positively charged silver nanoparticles Que@AgNPs coated with quercetin;

[0007] Specifically, adding a quercetin solution to a silver nitrate solution, heating to boiling, and waiting for it to cool to room temperature. Then adding CTAB, reacting under stirring, centrifuging multiple times and then redispersing in ultrapure water to obtain positively charged silver nanoparticles Que@AgNPs coated with quercetin.

[0008] (2) Incubate Que@AgNPs with proteins to form Que@AgNPs-protein complexes. Among them, the proteins are lysozyme, γ-globulin or fibrinogen.

[0009] Before incubation, purify Que@AgNPs. Specifically, centrifuge the Que@AgNPs solution obtained in step (1) again, and then wash it with ultrapure water to remove unreacted stabilizer CTAB and unreacted quercetin. The rotation speed of centrifugation is 10,000 rpm, the centrifugation time is 15 minutes, and the centrifugation temperature is 25 °C.

[0010] Step 2 is specifically: incubate the Que@AgNPs solution with the protein solution so that the protein coats on the surface of Que@AgNPs to form Que@AgNPs-protein complexes.

[0011] As a specific scheme, the average particle size of the Que@AgNPs synthesized in step (1) is 64.7 nm. In terms of molar ratio, the dosage ratio of quercetin, silver nitrate and CTAB is (2:3:500) - (5:6:500). The reaction temperature is 25 °C, the reaction time is 12 h; the rotation speed of centrifugation is 10,000 rpm, the centrifugation time is 15 minutes, and the centrifugation temperature is 25 °C.

[0012] In the present invention, in the process of synthesizing Que@AgNPs in step (1), it is necessary to control the dosage of quercetin and the reaction time and temperature to obtain ideal spherical silver nanoparticles. When the molar ratio of added quercetin to silver nitrate ranges from (2:3) - (5:6) to (4:3) - (5:3), the plasma absorption peak of the obtained Que@AgNPs undergoes a red shift, the hydrodynamic particle size becomes larger, and aggregation is likely to occur. If the stirring reaction temperature is less than 25 °C, CTAB aggregation will occur, and Que@AgNPs cannot be synthesized or the subsequent CTAB cannot be cleaned thoroughly. If the stirring time is too long, the synthesis will fail. When CTAB is not cleaned thoroughly, miscellaneous peaks will appear in the ultraviolet-visible absorption spectrum.

[0013] As a specific scheme, in step (2), in terms of mass, the dosage ratio of Que@AgNPs to the protein is 2:(18 - 270). Specifically, the dosage ratios of Que@AgNPs to the protein are selected as 2:18, 2:45, 2:72, 2:90, 2:108, 2:180, 2:270.

[0014] The present invention also provides quercetin-coated positively charged silver nanoparticles-protein complexes (Que@AgNPs-protein complexes) prepared by the above method.

[0015] The present invention also provides the application of the above-mentioned positively charged quercetin-coated silver nanoparticles-protein complex (Que@AgNPs-protein complex) in the preparation of antibacterial products.

[0016] The beneficial effects of the present invention are as follows:

[0017] (1) As Figure 1 shown, in the present invention, quercetin is used as a reducing agent and CTAB is used as a stabilizer to prepare positively charged quercetin-coated silver nanoparticles Que@AgNPs, and then Que@AgNPs are incubated with lysozyme, γ-globulin or fibrinogen to form Que@AgNPs-protein complexes. First, the positively charged AgNPs show the maximum antibacterial activity against all bacteria through the electrostatic attraction between the negatively charged microbial cell membrane and the positively charged nanoparticles. Second, quercetin, as an active ingredient of traditional Chinese medicine, has good antibacterial activity. Quercetin and AgNPs are actively loaded to form Que@AgNPs, which can exert higher antibacterial activity at a lower concentration of AgNPs, thereby reducing the use concentration of AgNPs and reducing the biological toxicity of AgNPs. At the same time, the antibacterial activity of AgNPs may be regulated by specific protein interactions. By modifying the surface of Que@AgNPs with proteins, the antibacterial activity of AgNPs can be improved.

[0018] (2) In the present invention, lysozyme, γ-globulin or fibrinogen is modified on the surface of Que@AgNPs, which increases the antibacterial activity of silver nanoparticles and can also make Ag + slowly release and control its concentration, thereby minimizing its potential toxicity as much as possible.

[0019] In summary, the present invention improves the antibacterial activity of AgNPs from three aspects: (1) Using CTAB as a stabilizer to prepare positively charged AgNPs, because positively charged AgNPs show the maximum antibacterial activity against all bacteria. (2) Coating quercetin as a reducing agent on the surface of AgNPs to form Que@AgNPs. Since quercetin has strong antibacterial activity, it can increase the antibacterial activity of AgNPs. (3) Modifying lysozyme, γ-globulin or fibrinogen on the surface of Que@AgNPs. The modification of proteins makes Ag + slowly release and control its concentration, further increasing the antibacterial activity of AgNPs while reducing the biological toxicity of AgNPs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart for preparing Que@AgNPs of the present invention and modifying proteins on the surface of Que@AgNPs.

[0021] Figure 2Characterization diagrams of quercetin-coated silver nanoparticles Que@AgNPs in Example 1. UV-visible absorption spectrum of Que@AgNPs (A); TEM image of Que@AgNPs (B); hydrodynamic diameter of Que@AgNPs (C); ζ-potential of Que@AgNPs (D); XRD pattern of Que@AgNPs (E).

[0022] Figure 3 Antibacterial activities of AgNPs and Que@AgNPs against Escherichia coli (A) and Staphylococcus aureus (C) in Example 1. Relative viability of Escherichia coli (B) and Staphylococcus aureus (D) in the presence of AgNPs and Que@AgNPs. Control represents the blank control.

[0023] Figure 4 For the Que@AgNPs-lysozyme complex (A 1 ) in Example 2, the Que@AgNPs-γ-globulin complex (B 1 ) and the Que@AgNPs-fibrinogen complex (C 1 ), surface plasmon resonance peak intensity diagrams. Relationship between the change in absorption intensity (ΔA) of the Que@AgNPs-lysozyme complex (A 2 ), the Que@AgNPs-γ-globulin complex (B 2 ) and the Que@AgNPs-fibrinogen complex (C 2 ) and the protein concentration.

[0024] Figure 5 Variation diagrams of the ζ-potential of the Que@AgNPs-lysozyme complex, the Que@AgNPs-γ-globulin complex and the Que@AgNPs-fibrinogen complex with the concentrations of lysozyme, γ-globulin and fibrinogen in Example 2. c(lysozyme) = c(γ-globulin) = c(fibrinogen) = 4.5×10 -8 mol L -1 , 9.0×10 -8 mol L -1 , 1.35×10 -7 mol L -1 , 4.5×10 -7 mol L -1 , 6.0×10 -7 mol L -1 , 9.0×10 -7 mol L -1 or 1.35×10 -6 mol L -1 .

[0025] Figure 6 For the bacteriostatic activities of Que@AgNPs, Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen against Escherichia coli (A) and Staphylococcus aureus (B) in Example 2, they increase with the increase in the concentration of Que@AgNPs. In the presence of Que@AgNPs, Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen, the relative viability of Escherichia coli (C) and Staphylococcus aureus (D) decreases with the increase in the concentration of Que@AgNPs. c(lysozyme) = c(γ-globulin) = c(fibrinogen) = 45 mg L -1 . Control represents the blank control.

[0026] Figure 7 For the antibacterial activities of Que@AgNPs, Que@AgNPs-lysozyme (A, B), Que@AgNPs-γ-globulin (C, D), and Que@AgNPs-fibrinogen (E, F) against Escherichia coli and Staphylococcus aureus with the increase in the concentration of lysozyme / γ-globulin / fibrinogen in Example 2. In the groups of Que@AgNPs, Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen, c(Que@AgNPs) = 2 mg L -1 , and 18, 45, 72, 90, 108, 180, 270 mg L in the figure -1 represent the concentrations of lysozyme, γ-globulin, and fibrinogen.

[0027] Figure 8 For the relative viabilities of Escherichia coli and Staphylococcus aureus in the presence of Que@AgNPs, Que@AgNPs-lysozyme (A, B), Que@AgNPs-γ-globulin (C, D), and Que@AgNPs-fibrinogen with the increase in the concentration of lysozyme / γ-globulin / fibrinogen in Example 2. In the groups of Que@AgNPs, Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen, c(Que@AgNPs) = 2 mg L -1 , and 18, 45, 72, 90, 108, 180, 270 mg L in the figure -1 represent the concentrations of lysozyme, γ-globulin, and fibrinogen. Detailed implementation mode

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will clearly describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0029] Example 1

[0030] The method for enhancing the antibacterial activity of nano-silver in this example includes the following steps:

[0031] Add 0.5 mL of 4.6×10 -2 mol L -1 quercetin solution to 5.9×10 -4 mol L -1 50 mL of AgNO 3 solution, heat to boiling, and wait for it to cool to room temperature. Then add 1.82 g of CTAB, stir at 25°C for 12 h, centrifuge at 10000 rpm for 15 minutes at 25°C, and then redisperse in ultrapure water to obtain positively charged Que@AgNPs. Centrifuge the Que@AgNPs solution again at 10000 rpm for 15 minutes at 25°C, and then wash it three times with ultrapure water to remove the unreacted stabilizer CTAB and unreacted quercetin. The characterization diagrams of the obtained Que@AgNPs are as Figure 2 shown. As Figure 2 shown in Figure 2 A, the surface plasmon resonance (SPR) absorption peak of Que@AgNPs is located at 442 nm and is symmetric, indicating that the prepared Que@AgNPs have uniform sizes, a particle size of approximately 68 nm, and are spherical; as Figure 2 shown in Figure 2 B, the transmission electron microscope (TEM) image shows that the morphology of Que@AgNPs is close to spherical, with good dispersibility, and the average particle size is about 64.7 nm; as Figure 2As shown in Figure E, X-ray diffraction (XRD) analysis shows that Que@AgNPs exhibits five characteristic peaks at 38.14°, 44.36°, 64.50°, 77.43°, and 79.48°, which belong to the (111), (200), (220), (311), and (222) crystal planes of face-centered cubic (fcc) silver crystals, respectively.

[0032] Comparison of the antibacterial activities of uncoated quercetin AgNPs and Que@AgNPs is shown as Figure 3 follows. As can be seen from Figure 3 it, when the concentrations of AgNPs and Que@AgNPs are 1 mg / L -1 and when the concentrations of AgNPs and Que@AgNPs are 2 mg / L -1 , there is no significant difference in the relative viability of AgNPs and Que@AgNPs against Escherichia coli. When the concentrations of AgNPs and Que@AgNPs are 5 mg / L -1 , the relative viability of Escherichia coli in the presence of Que@AgNPs is significantly reduced (at this time, Escherichia coli has no growth and the viability is 0). When the concentrations of AgNPs and Que@AgNPs are 1 mg / L -1 , there is no significant difference in the relative viability of AgNPs and Que@AgNPs against Staphylococcus aureus. When the concentrations of AgNPs and Que@AgNPs are 2 mg / L -1 and 5 mg / L -1 , the relative viability of Staphylococcus aureus in the presence of Que@AgNPs is significantly reduced, and when the concentration is 5 mg / L -1 of Que@AgNPs, Staphylococcus aureus has no growth and the viability is 0.

[0033] When the concentrations of AgNPs and Que@AgNPs increase to 10 mg / L -1 , the relative viability of both Escherichia coli and Staphylococcus aureus drops to 0.

[0034] Example 2

[0035] The method for enhancing the antibacterial activity of silver nanoparticles in this example includes the following steps:

[0036] Step (1): Add 0.5 mL of 4.6×10 -2 mol / L -1 quercetin solution to 5.9×10 -4 mol / L -1 50 mL of AgNO 3In the solution, heat it to boiling and wait for it to cool to room temperature. Then add 1.82 g of CTAB, stir at 25 °C for 12 h, centrifuge and redisperse in ultrapure water to obtain positively charged Que@AgNPs. The Que@AgNPs solution is centrifuged again at 10000 rpm for 15 minutes, and then washed three times with ultrapure water to remove the unreacted stabilizer CTAB and unreacted quercetin.

[0037] Step (2): Incubate the Que@AgNPs solution with protein lysozyme, γ-globulin, and fibrinogen solutions for half an hour respectively, and lysozyme, γ-globulin or fibrinogen is coated on the surface of Que@AgNPs to form Que@AgNPs-lysozyme / γ-globulin / fibrinogen complexes.

[0038] As Figure 4 and Figure 5 shown, adding lysozyme ( Figure 4 A) to Que@AgNPs will reduce the intensity of SPR, but there is no obvious blue shift or red shift in the peak position, indicating that lysozyme can only adsorb on the quercetin on the surface of Que@AgNPs and will not affect the properties of the metal surface. As the concentration of lysozyme increases, when the concentration of lysozyme reaches 6.0×10 -7 mol L -1 , the SPR peak intensity tends to be stable, indicating that the adsorption of lysozyme on the surface of Que@AgNPs reaches saturation. For γ-globulin ( Figure 4 B), adding 3.0×10 -7 mol L -1 of γ-globulin results in a significant decrease in the SPR peak intensity. When the concentration of γ-globulin exceeds 3.0×10 -7 mol L -1 , the SPR peak intensity gradually increases, and the peak intensity of γ-globulin shows a "decrease-increase" characteristic, indicating that γ-globulin does not reach adsorption equilibrium on the surface of Que@AgNPs within the studied concentration range. The possible reason is that after γ-globulin contacts Que@AgNPs, at very low concentrations of γ-globulin, the surface of γ-globulin will unfold. Because unfolding is beneficial for covering a larger surface area, a single protein molecule can bind to multiple Que@AgNPs to form crosslinks, generating large Que@AgNPs clusters. As the concentration of γ-globulin increases, the degree of unfolding of γ-globulin at the interface decreases, and the probability of crosslink formation decreases, resulting in a decrease in particle size. After adding fibrinogen to Que@AgNPs, the shape of the SPR peak changes significantly. When the concentration of fibrinogen is less than 9.0×10 -8 mol L -1 , the peak intensity increases. When it is higher than 9.0×10 -8 mol L -1At this time, the peak intensity decreases ( Figure 4 C). This indicates that the adsorption of fibrinogen on Que@AgNPs may affect the ground state complex on the metal surface. When the fibrinogen concentration reaches 9.0×10 -8 mol L -1 it reaches a certain degree of saturation.

[0039] The adsorption of lysozyme / γ-globulin / fibrinogen on the surface of Que@AgNPs will cause changes in the surface net charge, thereby changing its ζ-potential value. Considering the isoelectric point of proteins, at pH 7.40, lysozyme is positively charged, γ-globulin and fibrinogen are both negatively charged, but fibrinogen has more negative charges than γ-globulin. Figure 5 shows the change in the ζ-potential of Que@AgNPs with the increase in the concentration of lysozyme / γ-globulin / fibrinogen. It can be seen that with the addition of lysozyme, the ζ-potential of Que@AgNPs increases significantly. When the concentration of lysozyme is greater than 1.35×10 -7 mol L -1 the ζ-potential basically remains unchanged, indicating that lysozyme reaches the adsorption equilibrium on the surface of Que@AgNPs. This conclusion is consistent with that Figure 4 obtained from the SPR analysis. The slight difference in the concentration of the lysozyme adsorption equilibrium is probably due to the concentration difference between the samples. When the concentration of γ-globulin is 1.35×10 -6 mol L -1 the ζ-potential of Que@AgNPs slightly decreases to 21.8 mV, indicating the formation of a complex between Que@AgNPs and γ-globulin. Adding a lower concentration of fibrinogen to Que@AgNPs results in a significant decrease in the ζ-potential from 41.2 mV to -50.2 mV, indicating an electrostatic interaction between Que@AgNPs and fibrinogen. When the fibrinogen concentration is greater than 9.0×10 -8 mol L -1 its ζ-potential first increases and then remains stable, indicating that fibrinogen reaches the adsorption equilibrium on the surface of Que@AgNPs. This conclusion is also consistent with that Figure 4 obtained from the SPR analysis.

[0040] Determine the change trend of the antibacterial activities of Que@AgNPs, Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen against Escherichia coli and Staphylococcus aureus with the concentration of Que@AgNPs. From Figure 6It can be seen that with the increase in the concentration of Que@AgNPs, the antibacterial activities of Escherichia coli and Staphylococcus aureus co-cultured with Que@AgNPs and Que@AgNPs-protein complexes gradually increased compared with the control group (Control group). When the concentrations of Que@AgNPs were 1 mg L -1 , 2 mg L -1 , and 5 mg L -1 respectively, the antibacterial activities of Que@AgNPs and Que@AgNPs-protein complexes against Escherichia coli were as follows: Que@AgNPs-lysozyme > Que@AgNPs-γ-globulin ≈ Que@AgNPs > Que@AgNPs-fibrinogen, Que@AgNPs-γ-globulin > Que@AgNPs-lysozyme ≈ Que@AgNPs > Que@AgNPs-fibrinogen, and Que@AgNPs-γ-globulin > Que@AgNPs-lysozyme > Que@AgNPs-fibrinogen ≈ Que@AgNPs. Generally speaking, compared with Que@AgNPs, the Que@AgNPs-lysozyme complex significantly improved the antibacterial activity at a low concentration (1 mg L -1 ), while the Que@AgNPs-fibrinogen complex decreased the antibacterial activity. The antibacterial activity of the Que@AgNPs-γ-globulin complex increased at 2 mg L -1 and 5 mg L -1 . For Staphylococcus aureus, when the concentration of Que@AgNPs was 1 mg L -1 , the Que@AgNPs-lysozyme complex had the strongest antibacterial activity against Staphylococcus aureus. The antibacterial activity ranking was: Que@AgNPs-lysozyme > Que@AgNPs-γ-globulin > Que@AgNPs ≈ Que@AgNPs-fibrinogen. When the concentration of Que@AgNPs was 2 mg L -1 , the antibacterial activity ranking was: Que@AgNPs-lysozyme ≈ Que@AgNPs-γ-globulin > Que@AgNPs > Que@AgNPs-fibrinogen. The antibacterial activities of the Que@AgNPs-fibrinogen complex against Escherichia coli and Staphylococcus aureus were lower than those of Que@AgNPs. This may be because a large amount of fibrinogen was adsorbed on the surface of Que@AgNPs, hindering the release of Ag + , and reducing its antibacterial activity. The concentration of Que@AgNPs was 5 mg L -1When the concentration is [specific value], Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen have a complete inhibitory effect on Escherichia coli and Staphylococcus aureus. Therefore, the antibacterial activity of the Que@AgNPs-lysozyme / γ-globulin / fibrinogen complex against Escherichia coli and Staphylococcus aureus is closely related to the concentration of Que@AgNPs.

[0041] The changing trends of the antibacterial activities of Que@AgNPs, Que@AgNPs-lysozyme, Que@AgNPs-γ-globulin, and Que@AgNPs-fibrinogen against Escherichia coli and Staphylococcus aureus with the protein concentration are as Figure 7 and Figure 8 shown. With the increase in the concentration of lysozyme or γ-globulin, their antibacterial activities against Escherichia coli and Staphylococcus aureus are higher than those of Que@AgNPs. For Escherichia coli, the antibacterial activity of the Que@AgNPs-lysozyme complex fluctuates. The antibacterial activity is the strongest when the concentration of lysozyme is 180 mg / L. -1 For Staphylococcus aureus, the antibacterial activity is the strongest when the concentration of lysozyme is 90 mg / L. -1 When the concentration of γ-globulin is 18 mg / L, -1 the antibacterial activity against Escherichia coli is significantly enhanced. When the concentration of γ-globulin is 45 mg / L, -1 the antibacterial activity is significantly weakened, and then with the continuous increase in the concentration of γ-globulin, the antibacterial activity gradually increases. When the concentration of γ-globulin is 108 mg / L, -1 the antibacterial ability against Staphylococcus aureus is the strongest. Regardless of the concentration of fibrinogen, its antibacterial activities against Escherichia coli and Staphylococcus aureus are lower than those of Que@AgNPs.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for enhancing the antibacterial activity of nanosilver, characterized in that: The following steps are involved: (1) Quercetin was used as a reducing agent and hexadecyltrimethylammonium bromide as a stabilizer to react with silver nitrate to obtain quercetin-coated positively charged silver nanoparticles Que@AgNPs; (2) Que@AgNPs were incubated with proteins to form Que@AgNPs-protein complexes, wherein the proteins were lysozyme, γ-globulin or fibrinogen.

2. A method for enhancing the antibacterial activity of nanosilver according to claim 1, characterized in that: Step (1) comprises: The quercetin solution was added to the silver nitrate solution, heated to boiling, cooled to room temperature, and then hexadecyltrimethylammonium bromide was added to react under stirring. After centrifugation, it was dispersed in ultrapure water to obtain quercetin-coated positively charged silver nanoparticles Que@AgNPs.

3. A method for enhancing the antibacterial activity of nanosilver according to claim 1, characterized in that: The molar ratio of quercetin, silver nitrate and cetyltrimethylammonium bromide is (2:3:500) to (5:6:500).

4. The method for enhancing the antibacterial activity of nanosilver according to claim 1, characterized in that: The reaction temperature was 25°C and the reaction time was 12 h.

5. A method for enhancing the antibacterial activity of nanosilver according to claim 2, characterized in that: The centrifugal speed is 10000 rpm, the centrifugal time is 15 minutes, and the centrifugal temperature is 25°C.

6. The method for enhancing the antibacterial activity of nanosilver according to claim 1, characterized in that: Before incubation in step (2), Que@AgNPs were purified.

7. A method for enhancing the antibacterial activity of nanosilver according to claim 6, characterized in that: The purification of Que@AgNPs is as follows: the Que@AgNPs solution obtained in step (1) is centrifuged again, the speed of the re-centrifugation is 10000 rpm, the time of the centrifugation is 15 minutes, and the centrifugation temperature is 25°C.

8. The method for enhancing the antibacterial activity of nano-silver according to claim 1, characterized in that: In step (2), the mass ratio of Que@AgNPs to protein is 2:(18-270).

9. The Que@AgNPs-protein complex prepared by the method according to any one of claims 1 to 8.

10. Use of the Que@AgNPs-protein complex according to claim 9 in the preparation of antibacterial products.

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