A kind of Angelica dahurica polysaccharide silver nanoparticles and its preparation method and application

Abstract

The present invention provides a radix angelicae polysaccharide silver nanoparticles and a preparation method and application thereof, and belongs to the field of biological technology. The present invention first uses dried radix angelicae to prepare radix angelicae crude polysaccharide, then removes protein in the radix angelicae crude polysaccharide with a Sevag mixed solution, and then adds a silver nitrate solution to prepare radix angelicae crude polysaccharide silver nanoparticles. The present invention finds through experiments that the radix angelicae polysaccharide silver nanoparticles prepared by the present invention have excellent antibacterial and antioxidant functions, and can produce significant synergistic effects when used in combination with tetracycline.

Description

Technical Field

[0001] The invention belongs to the technical field of biology, and in particular relates to a kind of Angelica dahurica polysaccharide silver nanoparticles and a preparation method and application thereof. Background Art

[0002] Duhuo is a traditional Chinese medicine with a pungent and bitter taste and a slightly warm nature. It enters the kidney and bladder meridians and has the effects of dispelling wind and dampness, relieving numbness and relieving pain. It is used for wind-cold-dampness arthritis, pain in the waist and knees, headache caused by the hidden wind of Shaoyin, and headache caused by wind-cold and dampness. Modern pharmacological studies have found that Duhuo has certain anti-inflammatory and analgesic effects, and can play a pharmacological role in anti-rheumatoid arthritis by inhibiting cyclooxygenase. Polysaccharides, as one of the active ingredients of traditional Chinese medicine, have multiple biological activities such as immune enhancement, anti-inflammatory, and antioxidant, but there are few reports on the pharmacological activities of Duhuo polysaccharides extracted from the traditional Chinese medicine Duhuo.

[0003] With the development of nanotechnology, the preparation and application of silver nanoparticles have been widely studied. Studies have reported that silver nanoparticles have antibacterial effects, promote the growth of tissue cells, accelerate wound healing, and reduce the formation of scars. However, the safety window for the use of silver nanoparticles in humans and animals is narrow. Studies have found that silver nanoparticles may produce neurotoxicity in mice, and toxic chemical reagents such as sodium borohydride are often used in their synthesis process, which causes waste of reagents and even causes the possibility of environmental pollution, thereby greatly limiting their preparation and application. The present invention uses the Angelica dahurica polysaccharide extracted from the natural Chinese medicine Angelica dahurica to reduce silver nitrate, prepare the Angelica dahurica polysaccharide silver nanoparticles in a green way, explore its antioxidant activity, and provide theoretical and technical support for the research of new antioxidant drugs.

[0004] With the widespread use of antibiotics, bacterial resistance continues to increase, super-resistant bacteria emerge in an endless stream, and antibacterial treatment faces difficulties. The combined use of drugs and antibiotics can exert the synergistic antibacterial effect of drugs and reduce the risk of rapid secondary drug resistance of bacteria. The present invention uses the combined use of Angelica dahurica polysaccharide silver nanoparticles and tetracycline to explore the synergistic antibiotic antibacterial activity of Angelica dahurica polysaccharide silver nanoparticles, providing a preliminary theoretical basis for reducing the use of antibiotics and reducing the resistance of drug-resistant bacteria, and laying a research foundation for the development of new antibacterial drugs. Summary of the invention

[0005] The purpose of the present invention is to provide a kind of Angelica dahurica polysaccharide silver nanoparticles having both antibacterial and antioxidant functions.

[0006] To achieve the above object, the present invention provides a kind of Angelica dahurica polysaccharide silver nanoparticles having both bactericidal function and antioxidant function. The preparation method of Angelica dahurica polysaccharide silver nanoparticles is as follows:

[0007] (1) Place the dried Angelica dahurica in a container, add 95% ethanol solution to cover the medicinal material, soak at room temperature for 12 hours, condense and reflux for 4 hours, and then put the residue into an oven to dry;

[0008] (2) Soak 200 g of dried Angelica dahurica residue in 4 times its volume of ultrapure water for 12 hours, extract at 70°C for 2 hours, collect the filtrate, repeat the decoction twice, combine the three decoctions, concentrate to 150 mL by rotary evaporator, add 4 times its volume of anhydrous ethanol, stir while adding, and let stand overnight;

[0009] (3) centrifuging at 4000 rpm for 10 min to separate the precipitate, and freeze-drying in vacuum to obtain the crude polysaccharide of Angelica dahurica;

[0010] (4) The freeze-dried Angelica dahurica polysaccharide was reconstituted with 300 mL of ultrapure water to prepare a 1.5% Angelica dahurica polysaccharide solution, and 100 mL of Sevag mixed solution was added. After magnetic stirring, the mixture was allowed to stand for two hours to separate the layers, and the upper layer was retained. This was repeated eight times.

[0011] (5) After being concentrated by a rotary evaporator, the polysaccharide is dried by a vacuum freeze dryer to obtain the deproteinized polysaccharide;

[0012] (6) Prepare a 1.0 mg / mL Angelica dahurica polysaccharide solution, filter 2 mL through a 0.2 μm microporous filter membrane and place in a 10 mL vial. Slowly add 2 mL of a 1 mM silver nitrate solution under magnetic stirring, and stir in the dark for 6 hours to obtain Angelica dahurica polysaccharide silver nanoparticles.

[0013] Preferably, the bactericidal function is to inhibit Escherichia coli and Staphylococcus aureus.

[0014] Preferably, the antioxidant function is to inhibit DPPH, ABTS + ·、Hydroxy free radicals.

[0015] Secondly, the present invention provides the use of Angelica dahurica polysaccharide silver nanoparticles in the preparation of a drug having both antibacterial and antioxidant functions.

[0016] Preferably, the Angelica dahurica polysaccharide silver nanoparticles are prepared by the preparation method of Angelica dahurica polysaccharide silver nanoparticles according to claim 1.

[0017] Preferably, the bactericidal function is to inhibit Escherichia coli and Staphylococcus aureus;

[0018] The antioxidant function is to inhibit DPPH, ABTS + ·、Hydroxy free radicals.

[0019] Secondly, the present invention provides the use of Angelica dahurica polysaccharide silver nanoparticles in the preparation of an antibacterial enhancer for tetracycline.

[0020] Preferably, the Angelica dahurica polysaccharide silver nanoparticles are prepared by the preparation method of Angelica dahurica polysaccharide silver nanoparticles according to claim 1; and the antibacterial enhancer increases the inhibitory effect of tetracycline on Escherichia coli.

[0021] In addition, the present invention provides an antibacterial composition for inhibiting Escherichia coli, wherein the antibacterial composition is composed of tetracycline and Angelica dahurica polysaccharide silver nanoparticles.

[0022] Preferably, the Angelica dahurica polysaccharide silver nanoparticles are prepared by the preparation method of Angelica dahurica polysaccharide silver nanoparticles according to claim 1;

[0023] The minimum concentration of tetracycline in the antibacterial composition is 0.4 μg / mL;

[0024] The minimum concentration of Angelica dahurica polysaccharide silver nanoparticles in the antibacterial composition is 12 μg / mL.

[0025] The beneficial effects of the present invention are:

[0026] The present invention prepares a kind of Angelica dahurica polysaccharide silver nanoparticles with excellent antibacterial and antioxidant functions, which can not only inhibit Escherichia coli and Staphylococcus aureus, but also significantly remove DPPH and ABTS + and hydroxyl radicals;

[0027] At the same time, the present invention found that when the Angelica dahurica polysaccharide silver nanoparticles are used in combination with tetracycline, a synergistic effect can be produced on the inhibition of Escherichia coli, while the Angelica dahurica polysaccharide or silver nanoparticles do not have this effect when used alone. Therefore, the present invention creatively prepares the Angelica dahurica polysaccharide silver nanoparticles and tetracycline into a composition to increase the antibacterial effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The color change of the solution system during the synthesis process of Angelica dahurica polysaccharide and silver nitrate;

[0029] Figure 2 This is the particle size distribution result of Angelica dahurica polysaccharide silver nanoparticles;

[0030] Figure 3 This is the Congo red test result of Angelica dahurica polysaccharide;

[0031] Figure 4 This is the XRD spectrum of Angelica dahurica polysaccharide silver nanoparticles;

[0032] Figure 5 The SEM image and energy spectrum of Angelica dahurica polysaccharide;

[0033] Figure 6 The SEM image and energy spectrum of Angelica dahurica polysaccharide silver nanoparticles;

[0034] Figure 7This is the result of Angelica dahurica polysaccharide silver nanoparticles scavenging DPPH free radicals;

[0035] Figure 8 Elimination of ABTS by Angelica dahurica polysaccharide silver nanoparticles + ·Results diagram of free radicals;

[0036] Fig. 9 This is the result of Angelica dahurica polysaccharide silver nanoparticles scavenging hydroxyl radicals; DETAILED DESCRIPTION

[0037] Example 1: Preparation of Angelica dahurica polysaccharide silver nanoparticles

[0038] (1) Accurately weigh 200 g of dried Angelica dahurica and place it in a 250 mL round-bottom flask, add ethanol solution (95%) to cover the medicinal material, and soak it at room temperature for 12 hours. After soaking, condense and reflux for 4 hours to remove most of the polyphenols and monosaccharides, and place the filter residue in a 65° C. oven to dry;

[0039] (2) Soak the dried Angelica dahurica residue in 4 times the volume of ultrapure water for 12 hours, extract at 70°C for 2 hours, collect the filtrate, repeat the decoction twice, combine the three decoctions, concentrate to 150 mL using a rotary evaporator, add 4 times the volume of anhydrous ethanol, stir while adding, and let stand overnight;

[0040] (3) centrifugation at 4000 rpm for 10 min to separate the precipitate, and vacuum freeze-drying to obtain the crude polysaccharide of Angelica dahurica;

[0041] (4) The freeze-dried Angelica dahurica polysaccharide was re-dissolved in 300 mL of ultrapure water to prepare a 1.5% Angelica dahurica polysaccharide solution, and 100 mL of Sevag mixed solution (n-butanol: chloroform = 1:4) was added. After magnetic stirring, the mixture was allowed to stand for two hours to separate the layers, and the upper layer was retained. The above operation was repeated 8 times;

[0042] (5) After being concentrated by a rotary evaporator, the mixture was dried by a vacuum freeze dryer to obtain the protein-free H. pubescens polysaccharide (HHDP);

[0043] (6) Take 1.0 mg / mL Angelica dahurica polysaccharide solution, filter 2 mL through a 0.2 μm microporous filter membrane and put it into a 10 mL vial. Slowly add 2 mL of 1 mM silver nitrate solution under magnetic stirring, stir and react for 6 hours in a dark environment to obtain Angelica dahurica polysaccharide silver nanoparticles (Ag@HHDPs). The reaction process is as follows: Figure 1 shown.

[0044] Example 2: Structural characterization of Angelica dahurica polysaccharide and Ag@HHDPs

[0045] 1. Average particle size distribution

[0046] The average particle size of Ag@HHDPs was measured using a laser nanoparticle size analyzer. Figure 2 shown.

[0047] from Figure 2 It can be seen that the particle size of Ag@HHDPs is uniform and concentrated in a narrow area. The average particle size is 63.82nm and the dispersion index PDI is 0.085. Therefore, the synthesized Ag@HHDPs particles have a good nanoscale.

[0048] 2. Congo red test

[0049] 2 mL of Angelica dahurica polysaccharide solution (1 mg / mL) was fully mixed with 2 mL of Congo red (100 μmol / L) solution, and NaOH solution (final concentrations were 0, 0.1, 0.2, 0.3, 0.4 and 0.5 mol / L, respectively) was added. After standing for 15 min, Congo red was used as a control, the wavelength of the UV spectrophotometer was adjusted to 400-600 nm, and scanning was performed to determine the maximum absorption wavelength of the mixed solution under each concentration of NaOH solution. The experimental results are shown in Figure 3 shown.

[0050] from Figure 3 It can be seen that compared with the maximum absorption wavelength of the Congo red solution, the maximum absorption wavelength of the Angelica dahurica polysaccharide solution has red-shifted, which indicates that the Angelica dahurica polysaccharide may have a triple helix structure. Polysaccharides with a triple helix structure can wrap polymers in the cavity of the triple helix polysaccharide structure in water or a highly polar organic solvent, making it easier to prepare nanomaterials.

[0051] 3. XRD analysis

[0052] Place 2 mg of dried Ag@HHDPs on a glass slide, spread it evenly and compact it, and put it into the instrument sample chamber to detect its element peaks. The results are as follows: Figure 5 shown.

[0053] from Figure 4 It can be seen that the diffraction peaks at 30°, 37°, 48°, 59° and 72° of 2θ correspond to the (101), (111), (200), (311) and (222) crystal planes of face-centered cubic silver, respectively. The strong diffraction peaks in the XRD spectrum indicate that the crystallization properties of Ag@HHDPs are relatively perfect, which means that the hard agglomeration phenomenon is relatively weak during the synthesis process.

[0054] 4. SEM-EDS analysis

[0055] 2 mg of dried Angelica dahurica polysaccharide and Ag@HHDPs were taken and their surface morphology and element spectrum were analyzed under a scanning electron microscope after gold spraying. The results were as follows: Figure 5 and Figure 6 shown.

[0056] like Figure 5The Angelica dahurica polysaccharide shown has an irregular flake-like surface morphology structure with a relatively smooth surface; the Ag element is not observed in the energy spectrum.

[0057] like Figure 6 As shown in the figure, Ag@HHDPs presents a smooth ellipsoidal and spherical surface morphology. Some Ag@HHDPs aggregate to produce larger particles, which may be formed by strong interactions during the freeze-drying process. Energy spectrum analysis shows that Ag element can be detected in the energy spectrum of Ag@HHDPs. Comparative analysis shows that Ag@HHDPs is successfully prepared.

[0058] Example 3: In vitro antioxidant activity of Ag@HHDPs

[0059] 1. DPPH free radical scavenging activity detection

[0060] 1 mL of Ag@HHDPs solution with different concentrations (5, 10, 20, 40, 60, 80 μg / mL) was placed in a test tube, and 2 mL of DPPH solution (0.05 mmol / L, anhydrous ethanol as solvent) was added, mixed, and reacted at room temperature in the dark for 30 min. The absorbance (A) was measured at 517 nm. 1 ). Anhydrous ethanol was used as the control group instead of the sample (A 2 ); Anhydrous ethanol instead of DPPH was used as the blank group (A 0 ), with anhydrous ethanol as the zero hole. Calculation of DPPH free radical scavenging rate:

[0061] DPPH free radical scavenging rate = [1-(A 1 -A 0 ) / A 2 ]×100%

[0062] The results are as follows Figure 7 As shown in the figure, the silver nanoparticles of Angelica dahurica polysaccharide (Ag@HHDPs) have a certain scavenging ability against DPPH. In the range of 5-60μg / mL, as the concentration of Ag@HHDPs increases, the scavenging rate of DPPH free radicals increases.

[0063] 2.ABTS + Free radical scavenging activity assay

[0064] Ag@HHDPs was prepared into five concentrations of 1, 0.5, 0.25, 0.125, and 0.0625 mg / mL. ABTS solution was prepared into a concentration of 2 mmol / L with distilled water. 50 mL of the solution was mixed with 200 mL of K 2 S 2 O 8 The solution (70mmol / L) was mixed evenly and placed away from light for 12-16h to obtain ABTS +Solution. Mix ABTS with PBS + The solution was diluted to an absorbance of (0.70±0.02) (Abs=734 nm), the mixed solution was added to a 96-well plate, and the absorbance was measured using an ELISA reader.

[0065] Add 10 μL of the sample of different concentrations to each well of the sample blank, repeat three wells for each concentration, and add 200 μL of ABTS to each well. + The solution was shaken for 6 min and its absorbance at 734 nm (A 2 ); 10 μL of different sample solutions and 200 μL of PBS solution were added to the blank wells, and the absorbance at 734 nm was measured after shaking for 6 min (A 0 ) ; 210 μL ABTS was added to the control wells + · solution, and detect its absorbance at 734 nm (A 1 ) ABTS + Calculation of free radical scavenging rate:

[0066] ABTS + Free radical scavenging rate = [1-(A 2 -A 0 ) / A 1 ]×100%

[0067] The results are as follows Figure 8 As shown, the silver nanoparticles of Angelica dahurica polysaccharide (Ag@HHDPs) have a certain ABTS + In the range of 0.0625-1 mg / mL, as the concentration of Ag@HHDPs increases, ABTS + The clearance rate showed an overall upward trend.

[0068] 3. Hydroxyl radical scavenging activity assay

[0069] Add 1 mL 9.0 mmol / L FeSO 4 , 1 mL 9.0 mmol / L salicylic acid-ethanol solution, 1 mL Ag@HHDPs solutions of different concentrations (5, 10, 20, 40, 60, 80 μg / mL), 1 mL 3% H 2 O 2 The solution was heated at 37°C for 60 min and the absorbance at 510 nm (A 1 ); replace the Ag@HHDPs solution with an equal volume of distilled water and measure its absorbance (A 0 ); replace 3% H 2 O 2 Solution, operate in the same way, and measure its absorbance (A 2). Calculation of hydroxyl radical scavenging rate:

[0070] Hydroxyl radical scavenging rate = [A 0 -(A 1 -A 2 )] / A 0 ×100%

[0071] The results are as follows Fig. 9 The results show that the silver nanoparticles of Angelica dahurica polysaccharide (Ag@HHDPs) have a certain ability to scavenge hydroxyl radicals. As the concentration of Ag@HHDPs increases, the scavenging rate of hydroxyl radicals increases. When the concentration of Ag@HHDPs is 60μg / mL, its free radical scavenging ability is the highest. After that, as the concentration of Ag@HHDPs increases, its hydroxyl radical scavenging rate enters a plateau period.

[0072] Example 4: Antibacterial testing

[0073] 1.MIC detection

[0074] E. coli (ATCC25922) was cultured in a shaker for 18 h, and then the McFarland turbidity was adjusted to 0.5 with MHB and diluted 10 2 50 μL of MH medium was added to columns 1-12 of a round-bottom 96-well culture plate; 1024 μg / mL tetracycline, 2048 μg / mL Angelica dahurica polysaccharide silver nanoparticle solution, 4096 μg / mL Angelica dahurica polysaccharide, and 2048 μg / mL silver nanoparticle solution were diluted 10 times, and 50 μL of each was added to columns 1-10 of a round-bottom 96-well culture plate; 100 μL of the diluted Escherichia coli was added to columns 1-11; after mixing, the mixture was transferred to a 37°C incubator in the dark and cultured for 18-22 hours before observation. The results are shown in Table 1.

[0075] Table 1 Antibacterial effects of tetracycline, Angelica dahurica polysaccharide silver nanoparticles, Angelica dahurica polysaccharide and silver nanoparticles

[0076]

[0077] "+" indicates bacterial growth; "-" indicates sterile growth

[0078] From the results in Table 1, it can be seen that tetracycline, Angelica dahurica polysaccharide silver nanoparticles, and silver nanoparticles can inhibit the growth of Escherichia coli at concentrations of 2 μg / mL, 64 μg / mL, and 64 μg / mL, respectively; however, Angelica dahurica polysaccharide has no antibacterial effect at a concentration of 1024 μg / mL, and is assumed to have no antibacterial effect.

[0079] 2. Chessboard method of combined medication

[0080] Escherichia coli (ATCC 25922) was cultured in a shaker for 18 h, and then the McFarland turbidity was adjusted to 0.5 with MHB and diluted 10 2 times, set aside. Dilute the silver nanoparticles of Angelica dahurica polysaccharide from 1024μg / mL to 6 concentrations, and dilute tetracycline from 512μg / mL to 10 concentrations. Add 50μL of MH medium to a round-bottom 96-well culture plate; add 50μL of silver nanoparticles of Angelica dahurica polysaccharide from high to low concentrations in rows 1-6, and add 50μL of tetracycline from high to low concentrations in columns 1-10; add 50μL of diluted bacterial solution in columns 1-11 and rows 1-6; mix well, transfer to a 37℃ incubator away from light and culture for 18-22h. The same steps were used to observe the combined use of tetracycline and Angelica dahurica polysaccharide, and tetracycline and silver nanoparticles.

[0081] After tetracycline and Angelica dahurica polysaccharide silver nanoparticles were used together, the MICs of the two were 0.5μg / mL and 16μg / mL, respectively. According to FIC=MIC of combined drug A / MIC of single drug A+MIC of combined drug B / MIC of single drug B, the FIC was calculated to be 0.5≤0.5, indicating that the two drugs had a synergistic effect. Since the FIC result was 0.5, which was at the critical position between synergistic effect and additive effect, further combined drug experiments were conducted to verify it. Angelica dahurica polysaccharide silver nanoparticles were diluted to 56, 48, 40, 32, and 28μg / mL, and tetracycline was prepared to 4, 3.6, 3.2, 2.8, 2.4, and 2.0μg / mL. The operation of combined use of tetracycline and Angelica dahurica polysaccharide silver nanoparticles was the same as described above. The results showed that the MICs of tetracycline and Angelica dahurica polysaccharide silver nanoparticles were 0.4μg / mL and 12μg / mL, respectively. FIC=MIC of combined drug A / MIC of drug A alone+MIC of combined drug B / MIC of drug B alone, FIC=0.3875≤0.5.

[0082] After tetracycline was used in combination with silver nanoparticles, the MIC of the two were 1μg / mL and 16μg / mL, respectively, 0.5<FIC=0.75<1, and the combination of the two had an additive effect; after tetracycline was used in combination with Angelica dahurica polysaccharide, the MIC of tetracycline was still 2μg / mL, and Angelica dahurica polysaccharide still had no antibacterial effect.

[0083] The above results show that when the silver nanoparticles of Angelica dahurica polysaccharide are combined with tetracycline to inhibit Escherichia coli, the two produce a synergistic effect, while tetracycline and silver nanoparticles, and tetracycline and Angelica dahurica polysaccharide have no synergistic effect after combined use. In summary, the combined use of silver nanoparticles of Angelica dahurica polysaccharide and tetracycline can significantly improve the bactericidal effect, and the present invention can provide preliminary theoretical and technical support for the research on reducing the use of antibiotics and reducing the drug resistance of drug-resistant bacteria.

Claims

1. A kind of Angelica dahurica polysaccharide silver nanoparticles having both bactericidal and antioxidant functions, characterized in that: The preparation method of preparing the Angelica dahurica polysaccharide silver nanoparticles with 200g of dried Angelica dahurica residue is as follows: (1) Place the dried Angelica dahurica in a container, add 95% ethanol solution to cover the medicinal materials, soak at room temperature for 12 hours, condense and reflux for 4 hours, and then put the residue into an oven to dry; (2) Take 200 g of dried Angelica dahurica residue and soak it in 4 times the volume of ultrapure water for 12 hours, extract it at 70°C for 2 hours, collect the filtrate, repeat the decoction twice, combine the three decoctions, concentrate to 150 mL using a rotary evaporator, add 4 times the volume of anhydrous ethanol, stir while adding, and let it stand overnight; (3) Centrifuge at 4000 rpm for 10 min to separate the precipitate, and freeze-dry in vacuum to obtain the crude polysaccharide of Angelica dahurica; (4) Dissolve the freeze-dried Angelica dahurica polysaccharide in 300 mL of ultrapure water to prepare a 1.5% Angelica dahurica polysaccharide solution, add 100 mL of Sevag mixed solution, stir magnetically and let stand for two hours to separate the layers, retain the upper layer, and repeat 8 times; (5) After being concentrated using a rotary evaporator, the extract was dried using a vacuum freeze dryer to obtain the protein-free Angelica dahurica polysaccharide; (6) Prepare a 1.0 mg / mL Angelica dahurica polysaccharide solution, filter 2 mL of the solution through a 0.2 μm microporous filter membrane and place it in a 10 mL vial. Slowly add 2 mL of a 1 mM silver nitrate solution under magnetic stirring. Stir and react for 6 hours in the dark to obtain Angelica dahurica polysaccharide silver nanoparticles.

2. The use of Angelica dahurica polysaccharide silver nanoparticles in the preparation of drugs with antibacterial function, characterized in that: The Angelica dahurica polysaccharide silver nanoparticles are prepared by the preparation method of Angelica dahurica polysaccharide silver nanoparticles according to claim 1; The antibacterial function is to inhibit Escherichia coli.

3. The use of Angelica dahurica polysaccharide silver nanoparticles in the preparation of an antibacterial enhancer for tetracycline, characterized in that: The Angelica dahurica polysaccharide silver nanoparticles are prepared by the Angelica dahurica polysaccharide silver nanoparticles preparation method according to claim 1; the antibacterial enhancer increases the inhibitory effect of tetracycline on Escherichia coli; In the antibacterial enhancer, the minimum concentration of Angelica dahurica polysaccharide silver nanoparticles is 12 g / mL; When the antimicrobial enhancer is used, the minimum concentration of tetracycline is 0.4 g / mL.

4. An antibacterial composition for inhibiting Escherichia coli, characterized in that: The antibacterial composition is composed of tetracycline and Angelica dahurica polysaccharide silver nanoparticles; The Angelica dahurica polysaccharide silver nanoparticles are prepared by the preparation method of Angelica dahurica polysaccharide silver nanoparticles according to claim 1; The minimum concentration of tetracycline in the antibacterial composition is 0.4 μg / ml; The minimum concentration of Angelica dahurica polysaccharide silver nanoparticles in the antibacterial composition is 12 μg / ml.

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