Zno@fe3o4 urchin-like magnetic beads, preparation method and application thereof

Abstract

The application relates to the technical field of nanomaterial preparation, in particular to a ZnO@Fe3O4 urchin-like magnetic bead and a preparation method and application thereof. The method comprises the following steps: preparing a seed layer solution: dissolving zinc acetate dihydrate and sodium hydroxide in anhydrous ethanol; preparing a growth solution: dissolving zinc nitrate hexahydrate, hexamethylenetetramine and polyethylene imine in deionized water and uniformly mixing by ultrasonic; taking magnetic beads and dispersing the magnetic beads in the seed layer solution, ultrasonic mixing for 3-10 min, and then mechanically stirring for 1.5-2.5 h; after stirring, incubating at 130-180 DEG C for 1.5-3 h; collecting the magnetic beads, discarding the solution, and cleaning with deionized water; transferring to the growth solution, ultrasonic mixing for 3-7 min, and then incubating at 80-100 DEG C for 1.5-2.5 h; washing the product and drying. The urchin-like magnetic bead can mechanically break bacteria, is simple and easy to operate, saves cost, is safe and reliable, and makes the bacterial nucleic acid extraction work more efficient.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of nanomaterial preparation, and in particular to a ZnO@Fe3O4 urchin-like magnetic bead and a preparation method and application thereof. BACKGROUND

[0002] Bacteria have a great impact on human activities. On the one hand, humans often use bacteria to make cheese, yogurt and wine, and to manufacture some antibiotics. On the other hand, bacteria are also the pathogen of many diseases, have strong infectivity, and cause great harm to the society. Therefore, it is particularly important to detect bacteria to help us understand and distinguish their properties. Common methods for detecting bacteria include microscopic observation, bacterial culture and bacterial nucleic acid detection. Among them, bacterial nucleic acid detection is the most sensitive method. The most critical step in nucleic acid detection is nucleic acid extraction, and the quality of the extracted nucleic acid is also one of the key factors determining the success or failure of the downstream experiment. Bacteria belong to prokaryotes, and their cell structure is relatively simple, having a tough cell wall composed of peptidoglycan. The first step for extracting bacterial DNA is to destroy this cell wall to release the intracellular nucleic acid content.

[0003] At present, the methods for extracting bacterial genomic DNA include physical method (including heating and boiling and mechanical crushing), enzyme method and chemical method for cell crushing and DNA extraction. The physical method includes heating and boiling and mechanical crushing. The heating and boiling method is to make the bacteria rupture by high temperature, fully expose the nucleic acid, and then precipitate the denatured protein and bacterial fragments by high-speed centrifugation, and the supernatant is the crude nucleic acid extract. The mechanical method is mainly to crush the bacterial cell wall by mechanical force such as ultrasonic crushing, repeated freezing and thawing, microbead oscillation and the like to release the nucleic acid. The enzyme method is to dissolve and crush the bacterial cell wall by biological enzymes such as lysozyme and the like, and then further extract the nucleic acid by centrifugation. The chemical method is to make the protein denatured by adding chemical reagents such as strong alkali NaOH, surfactant SDS (sodium dodecyl sulfonate), CTAB and the like to the bacteria, and then extract the protein impurities by combining with an organic solvent, and then precipitate by adding ethanol, so as to obtain DNA with high purity. At present, the most commonly used method for extracting bacterial genome is the CTAB-phenol chloroform extraction method, and the main extraction steps include collecting bacterial cells, crushing, extraction, precipitation, washing, drying, dissolution and the like. The chemical method based on the kit includes kit centrifugal column method and kit magnetic bead method. The reagents required by the kit centrifugal column method include lysis solution, binding solution, washing solution and elution solution. The lysis solution is first added to release the genomic DNA of the bacteria, then the binding solution is added to change the solution environment, so that the silica gel membrane column can reversibly adsorb the genomic DNA, the protein impurities are removed after rinsing, and then the genomic DNA is obtained by elution with the elution solution. The reagents contained in the kit magnetic bead method are also lysis solution, binding solution, washing solution and elution solution. However, the adsorption principle is different, that is, the microparticles with magnetism can combine with specific antibodies, and can specifically combine with corresponding antigens in liquid phase, and rely on magnetic field to complete separation, so as to achieve the purpose of enriching and purifying samples. However, these methods still have problems such as complex operation, many types of reagents, toxic reagents such as phenol chloroform, low extraction efficiency and the like. The above-mentioned bacterial nucleic acid extraction methods all have certain limitations. The common silica-based magnetic beads need to establish a low-pH high-salt environment when combining with nucleic acid, and the operation is relatively complex. SUMMARY

[0004] The present application provides a kind of ZnO@Fe3O4 sea urchin-shaped magnetic beads and its preparation method and application to solve the above problems.

[0005] The first object of the present application is to provide a preparation method of ZnO@Fe3O4 sea urchin-shaped magnetic beads, which specifically comprises the following steps:

[0006] S1, preparing seed layer solution: dissolving zinc acetate dihydrate and sodium hydroxide in anhydrous ethanol;

[0007] S2, preparing growth solution: dissolving zinc nitrate hexahydrate, hexamethylenetetramine and polyethyleneimine in deionized water, and ultrasonic mixing;

[0008] S3, disperse the magnetic beads in the seed layer solution, ultrasonic for 3-10 min, and then mechanically stir for 1.5-2.5 h;

[0009] S4, after stirring, incubate at 130-180℃ for 1.5-3 h; collect the magnetic beads after incubation, discard the solution, and wash with deionized water to obtain the magnetic beads with a zinc oxide seed layer attached to the surface;

[0010] S5, transfer the magnetic beads with a zinc oxide seed layer attached to the surface obtained in step S4 to the growth solution, ultrasonic for 3-7 min, and then incubate at 80-100℃ for 1.5-2.5 h;

[0011] S6, finally wash the product with deionized water, and dry to obtain the ZnO@Fe3O4 urchin-shaped magnetic beads.

[0012] Preferably, the ultrasonic in step S3 is performed for 5 min; and the mechanical stirring is performed for 2 h.

[0013] Preferably, the magnetic beads in step S3 are prepared by the following method:

[0014] S31, weigh the ferric chloride hexahydrate, sodium citrate dihydrate and polyethylene glycol, dissolve them in ethylene glycol to form a mixed solution;

[0015] S32, add sodium acetate to the mixed solution of step S31, and stir at room temperature until the sodium acetate is completely dissolved; then place in an autoclave for reaction at a temperature of 180-250℃ for 20-30 h;

[0016] S33, after the reaction is completed, cool to room temperature, rinse with ethanol and deionized water, and dry to obtain the magnetic beads.

[0017] Preferably, in step S31, the amount of ferric chloride hexahydrate added is 2.5-3 g, the amount of sodium citrate dihydrate added is 0.3-0.5 g, and the amount of polyethylene glycol added is 0.45-0.6 g.

[0018] Preferably, in step S32, the amount of sodium acetate added is 3.5-4 g.

[0019] Preferably, in step S32, the reaction is performed at a temperature of 200℃ for 24 h; and the ratio of the amount-of-substance concentrations of the ferric chloride hexahydrate, the sodium citrate dihydrate and the polyethylene glycol is 10:1:0.125.

[0020] Preferably, in step S4, the incubation is performed at a temperature of 150℃ for 2 h.

[0021] Preferably, in step S5, the incubation is performed at a temperature of 90℃ for 2 h.

[0022] The second object of the present application is to provide a preparation method of the ZnO@Fe3O4 urchin-like magnetic beads.

[0023] The third object of the present application is to provide an application of the ZnO@Fe3O4 urchin-like magnetic beads in extracting bacterial nucleic acid.

[0024] Preferably, the ZnO@Fe3O4 urchin-like magnetic beads are added into the bacterial solution, and are oscillated and irradiated under ultraviolet light. The solution is discarded, and the solid is reserved. The impurities are removed by washing. The eluent is added, so that the bacterial nucleic acid is dispersed in the eluent, and the extraction is completed.

[0025] Compared with the prior art, the present application can achieve the following beneficial effects:

[0026] (1) The prepared ZnO@Fe3O4 urchin-like magnetic beads can crush bacteria by mechanical method, and the separated nucleic acid is adsorbed on the magnetic beads by electrostatic adsorption and is enriched in the magnetic field, which can effectively solve the problems existing in the prior art of bacterial nucleic acid extraction, and is simple, easy to operate, cost-saving, safe and reliable, so that the bacterial nucleic acid extraction work can be more efficient.

[0027] (2) The principle that ZnO in the magnetic beads releases active oxygen under ultraviolet irradiation is applied to bacterial lysis, which improves the nucleic acid extraction efficiency.

[0028] (3) The complex operation of establishing a low-pH high-salt environment for combining nucleic acid based on silicon-based magnetic beads is overcome, and the steps of nucleic acid extraction are simplified, which is conducive to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a process schematic diagram of the preparation of the ZnO@Fe3O4 urchin-like magnetic beads according to the embodiment of the present application.

[0030] Figure 2 is a transmission electron microscope image of the ZnO@Fe3O4 urchin-like magnetic beads according to the embodiment of the present application.

[0031] Figure 3 is a process schematic diagram of the extraction of bacterial nucleic acid by the ZnO@Fe3O4 urchin-like magnetic beads according to the embodiment of the present application.

[0032] Figure 4 is an electrophoresis result diagram of the extraction of nucleic acid in Escherichia coli by the ZnO@Fe3O4 urchin-like magnetic beads according to the embodiment of the present application; wherein A represents the Escherichia coli solution without adding magnetic beads; and B represents adding 0.25 mg of ZnO@Fe3O4 urchin-like magnetic beads. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0034] In order to make the objectives, technical solutions, and advantages of the present application clearer, further detailed descriptions will be given below in combination with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application.

[0035] Embodiment 1

[0036] The embodiment is a preparation method of ZnO@Fe3O4 urchin-shaped magnetic beads, which specifically comprises the following steps:

[0037] S1, preparing a seed layer solution: dissolving zinc acetate dihydrate and sodium hydroxide in anhydrous ethanol;

[0038] S2, preparing a growth solution: dissolving zinc nitrate hexahydrate, hexamethylenetetramine, and polyethyleneimine in deionized water, and ultrasonically mixing; the purpose of adding polyethyleneimine is to inhibit the lateral growth of zinc oxide, so as to make it grow into urchin shape;

[0039] S3, dispersing the magnetic beads in the seed layer solution, ultrasonically for 5 min, and then mechanically stirring for 2 h; the ultrasonic is to disperse the magnetic beads and prevent aggregation, and the stirring is to cover the surface of the magnetic beads with the seed layer;

[0040] S4, placing the stirred solution in a high-pressure reaction kettle, and then placing it in an oven, and incubating at 150°C for 2 h; after incubation, the magnetic beads are adsorbed by a magnetic stand, the solution in the tube is discarded, and the magnetic beads are washed with deionized water for 2 times to obtain the magnetic beads with the surface attached with a zinc oxide seed layer; the high-temperature incubation in the oven is to make the seed layer on the surface of the magnetic beads more closely attached, and the temperature and time are optimized;

[0041] S5, transferring the obtained magnetic beads with the surface attached with a zinc oxide seed layer into 20 mL of the growth solution, and ultrasonically for 5 min; pouring the reaction solution into a polytetrafluoroethylene liner, and placing it in a high-pressure reaction kettle, and incubating in a 90°C oven for 2 h; the ultrasonic is to prevent the aggregation of the magnetic beads, and the 2 h in the 90°C oven is to make the zinc oxide on the surface of the magnetic beads grow, and the temperature and time are optimized;

[0042] S6, finally washing the product with deionized water for several times, drying, obtaining ZnO@Fe3O4 urchin-shaped magnetic beads, and resuspending in anhydrous ethanol, and storing at 4°C (a process diagram of the preparation is shown in Figure 1 ).

[0043] The preparation method of the magnetic beads in step S3 specifically comprises the following steps:

[0044] S31, iron chloride hexahydrate (2.70 g, 10 mM), sodium citrate dihydrate (0.40 g, 1 mM) and polyethylene glycol (0.5 g, 0.125 mM) were weighed and dissolved in 70 mL of ethylene glycol to form a mixed solution;

[0045] S32, after adding sodium acetate (3.854 g, 47 mM) to the mixed solution of step S31, the mixture was stirred at room temperature for more than 30 min to make it completely dissolved; then it was transferred to a 50 mL stainless steel autoclave lined with polytetrafluoroethylene, and the autoclave was placed in a preheated oven for reaction at 200℃ for 24 h;

[0046] S33, after the reaction was completed, the black sample was cooled to room temperature, collected and transferred to a centrifuge tube, then washed with ethanol and deionized water for several times, and dried to obtain magnetic beads.

[0047] The transmission electron microscopy (TEM) image of the urchin-like magnetic beads based on ZnO@Fe3O4 prepared by the above method is shown in the following figure Figure 2 As can be seen from the electron microscopy image, the prepared magnetic beads are oval urchin-like, the ZnO grown on the surface is rod-like structure, and the particle size is uniform, about 1.2 μm.

[0048] Example 2

[0049] The preparation method of the urchin-like magnetic beads based on ZnO@Fe3O4 in this embodiment specifically includes the following steps:

[0050] S1, preparing a seed layer solution: dissolving zinc acetate dihydrate and sodium hydroxide in anhydrous ethanol;

[0051] S2, preparing a growth solution: dissolving zinc nitrate hexahydrate, hexamethylenetetramine and polyethyleneimine in deionized water and ultrasonically mixing;

[0052] S3, taking the magnetic beads and dispersing them in the seed layer solution, ultrasonically for 3 min, and then mechanically stirring for 2.5 h;

[0053] S4, placing the stirred solution in a high-pressure reaction kettle, then placing it in an oven, and incubating at 180℃ for 1.5 h; after incubation, the magnetic beads were adsorbed by a magnetic stand, the solution in the tube was discarded, and the magnetic beads were washed with deionized water for 2 times to obtain magnetic beads with a zinc oxide seed layer attached to the surface;

[0054] S5, transferring the obtained magnetic beads with a zinc oxide seed layer attached to the surface to 20 mL of the growth solution, and ultrasonically for 5 min; pouring the reaction solution into a polytetrafluoroethylene liner, and placing it in a high-pressure reaction kettle, and incubating in a 90℃ oven for 2 h;

[0055] S6, finally washed the product several times with deionized water, dried, to obtain ZnO@Fe3O4 urchin-like magnetic beads, resuspended in anhydrous ethanol, 4℃ preservation.

[0056] The preparation method of the magnetic beads in step S3 specifically comprises the following steps:

[0057] S31, weighed ferric chloride hexahydrate (3g, 10mM), sodium citrate dihydrate (0.5g, 1mM) and polyethylene glycol (0.5g, 0.125mM) were dissolved in 80mL ethylene glycol to form a mixed solution;

[0058] S32, after adding sodium acetate (3.6g, 47mM) to the mixed solution of step S31, the mixture was stirred at room temperature for more than 30min to make it completely dissolved; then transferred to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, the autoclave was placed in a preheated oven, and reacted at 210℃ for 20h;

[0059] S33, after the reaction was completed, it was cooled to room temperature, the black sample was collected and transferred to a centrifuge tube, then washed with ethanol and deionized water for several times, dried to obtain magnetic beads.

[0060] Example 3

[0061] The preparation method of the ZnO@Fe3O4 urchin-like magnetic beads in this embodiment specifically comprises the following steps:

[0062] S1, prepare a seed layer solution: dissolve zinc acetate dihydrate and sodium hydroxide in anhydrous ethanol;

[0063] S2, prepare a growth solution: dissolve zinc nitrate hexahydrate, hexamethylenetetramine and polyethyleneimine in deionized water and ultrasonically mix;

[0064] S3, take the magnetic beads and disperse them in the seed layer solution, ultrasonically for 3min, then mechanically stir for 2.5h;

[0065] S4, place the stirred solution in a high-pressure reaction kettle, then put it in an oven, incubate at 130℃ for 2.5h; after incubation, adsorb the magnetic beads with a magnetic stand, discard the solution in the tube, wash with deionized water for 2 times, to obtain magnetic beads with a zinc oxide seed layer attached to the surface;

[0066] S5, transfer the obtained magnetic beads with a zinc oxide seed layer attached to the surface to 20mL of the growth solution, ultrasonically for 5min; pour the reaction liquid into a polytetrafluoroethylene liner, put it in a high-pressure reaction kettle, incubate in a 100℃ oven for 1.5h;

[0067] S6, finally washed the product several times with deionized water, dried, to obtain ZnO@Fe3O4 urchin-like magnetic beads, resuspended in anhydrous ethanol, 4℃ preservation.

[0068] The preparation method of the magnetic beads in step S3 specifically comprises the following steps:

[0069] S31, weigh ferric chloride hexahydrate (3g, 10mM), sodium citrate dihydrate (0.5g, 1mM) and polyethylene glycol (0.5g, 0.125mM) and dissolve them in 80mL of ethylene glycol to form a mixed solution;

[0070] S32, after adding sodium acetate (3.6g, 47mM) to the mixed solution of step S31, stir the mixture at room temperature for more than 30min to completely dissolve it, then transfer it to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and place the autoclave in a preheated oven for reaction at 210℃ for 20h;

[0071] S33, after the reaction is completed, cool it to room temperature, collect the black sample, transfer it to a centrifuge tube, then rinse it with ethanol and deionized water for several times, dry it, and obtain the magnetic beads.

[0072] The preparation method of the magnetic beads in step S3 specifically comprises the following steps:

[0073] S1, weigh ferric chloride hexahydrate (2.5g, 10mM), sodium citrate dihydrate (0.4g, 1mM) and polyethylene glycol (0.35g, 0.125mM) and dissolve them in 70mL of ethylene glycol to form a mixed solution;

[0074] S2, after adding sodium acetate (3.6g, 47mM) to the mixed solution of step S1, stir the mixture at room temperature for more than 30min to completely dissolve it, then transfer it to a 50mL stainless steel autoclave lined with polytetrafluoroethylene, and place the autoclave in a preheated oven for reaction at 195℃ for 28h;

[0075] S3, after the reaction is completed, cool it to room temperature, collect the black sample, transfer it to a centrifuge tube, then rinse it with ethanol and deionized water for several times, dry it, and obtain the magnetic beads.

[0076] Example 4

[0077] The prepared ZnO@Fe3O4 urchin-like magnetic beads are used to extract bacterial nucleic acid, and the extraction method comprises the following steps:

[0078] S7, add a small amount of ZnO@Fe3O4 urchin-like magnetic beads to the bacterial solution, shake thoroughly, and irradiate under ultraviolet light;

[0079] S8, discard the solution and retain the solid; wash and remove impurities;

[0080] S9, adding an eluent, dispersing the nucleic acid in the eluent, and completing the extraction of the bacterial nucleic acid.

[0081] Taking E. coli as an example, the nucleic acid in E. coli is extracted by ZnO@Fe3O4 urchin-like magnetic beads, a set of parallel experiments is set, the mass of ZnO@Fe3O4 urchin-like magnetic beads added is 0.25 mg, and E. coli liquid without adding magnetic beads is used as a control to perform gel electrophoresis experiment; the process is as follows:

[0082] 1. Lysis: the prepared ZnO@Fe3O4 urchin-like magnetic beads are added to the centrifuge tube containing the bacterial liquid, and shaken for a period of time. In the process of shaking, the magnetic beads are in full contact with the bacteria, and the ZnO rod structure grown on the surface of the magnetic beads can destroy the bacteria, so that the nucleic acid is released into the bacterial liquid. In the process, the centrifuge tube is irradiated with ultraviolet light, and ZnO releases active oxygen to further kill the bacteria and cause them to release nucleic acid;

[0083] 2. Binding: the ZnO on the surface of the magnetic beads is positively charged, and the nucleic acid in the bacterial liquid is negatively charged. The nucleic acid is adsorbed on the magnetic beads by electrostatic adsorption, and the magnetic beads are enriched on one side of the centrifuge tube under the action of the magnetic field force, and then the solution is poured off;

[0084] 3. Washing: deionized water is added and shaken gently, and the solution is poured off after washing three times. The purpose is to remove bacterial residues and other impurities;

[0085] 4. Elution: the eluent (Tris-HCl 10 mM, EDTA 5 mM) is added to the centrifuge tube containing the magnetic beads. Under the condition of low salt and high pH, the nucleic acid is uniformly dispersed in the eluent. The eluent containing the nucleic acid is sucked out, which is the extracted nucleic acid sample.

[0086] The results are shown in Figure 4 As can be seen from the electrophoresis result graph, before the magnetic beads are added, the E. coli is not lysed and no band is visible. When 0.25 mg of magnetic beads is added, the E. coli is lysed and the supernatant shows obvious bands. The position of the band is consistent with that of the E. coli genome extracted by the kit, indicating that the ZnO@Fe3O4 urchin-like magnetic beads prepared based on ZnO@Fe3O4 can extract the nucleic acid of E. coli.

[0087] The application has the advantages that the application combines the mechanical method and the magnetic bead method, a sea urchin-shaped magnetic bead based on ZnO@Fe3O4 is prepared, nucleic acid separated out is electrostatically adsorbed with the magnetic bead by oscillation and is enriched in a magnetic field. Only the prepared magnetic bead is added into a bacterial solution to oscillate, the bacteria are broken by mechanical force, and various lysis solutions do not need to be added. After the bacteria are broken, the nucleic acid is dispersed in the bacterial solution, the nucleic acid with negative electricity is adsorbed due to the positive electricity of ZnO grown on the surface of the magnetic bead, an eluent is added, the nucleic acid is separated from the magnetic bead, and the purpose of extracting the nucleic acid is achieved. The method is simple and easy to operate, does not need to add some toxic chemical reagents, is safe, has low cost, saves time and effort, has high extraction efficiency, and can be used in a large scale.

[0088] It should be understood that the steps can be reordered, added, or deleted using the various forms of flowcharts shown above. For example, the steps described in the present disclosure can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of the present disclosure can be achieved, and the present disclosure is not limited herein.

[0089] The above detailed description does not constitute a limitation on the protection scope of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing ZnO@Fe3O4 urchin-like magnetic beads, characterized in that, Specifically comprising the following steps: S1, preparing a seed layer solution: dissolving zinc acetate dihydrate and sodium hydroxide in anhydrous ethanol; S2, preparing a growth solution: dissolving zinc nitrate hexahydrate, hexamethylenetetramine and polyethyleneimine in deionized water, and ultrasonic mixing; S3, dispersing magnetic beads in the seed layer solution, ultrasonic mixing for 3-10 min, and mechanical stirring for 1.5-2.5 h; the magnetic beads are prepared by the following method: S31, weighing ferric chloride hexahydrate, sodium citrate dihydrate and polyethylene glycol, dissolving them in ethylene glycol to form a mixed solution; S32, adding sodium acetate to the mixed solution of step S31, stirring at room temperature until the sodium acetate is completely dissolved; placing it in an autoclave for reaction, the temperature is 180-250℃, and the reaction time is 20-30 h; S33, after the reaction is completed, cooling to room temperature, washing with ethanol and deionized water, and drying to obtain magnetic beads; S4, after stirring, incubating at 130-180℃ for 1.5-3 h; after incubation, collecting the magnetic beads, discarding the solution, and washing with deionized water to obtain magnetic beads with a zinc oxide seed layer attached to the surface; S5, transferring the magnetic beads with a zinc oxide seed layer attached to the surface obtained in step S4 to the growth solution, ultrasonic mixing for 3-7 min, and then incubating at 80-100℃ for 1.5-2.5 h; S6, finally washing the product with deionized water, drying to obtain ZnO@Fe3O4 urchin-like magnetic beads.

2. The method for preparing ZnO@Fe3O4 urchin-shaped magnetic beads according to claim 1, characterized in that: The ultrasonic mixing in step S3 is for 5 min; the mechanical stirring is for 2 h.

3. The method for preparing ZnO@Fe3O4 urchin-shaped magnetic beads according to claim 1, characterized in that: The amount of ferric chloride hexahydrate added in step S31 is 2.5-3 g, the amount of sodium citrate dihydrate added is 0.3-0.5 g, and the amount of polyethylene glycol added is 0.45-0.6 g.

4. The method for preparing ZnO@Fe3O4 urchin-shaped magnetic beads according to claim 3, characterized in that: The amount of sodium acetate added in step S32 is 3.5-4 g.

5. The method for preparing ZnO@Fe3O4 urchin-shaped magnetic beads according to claim 4, characterized in that: The reaction in step S32 is at a temperature of 200℃ for 24 h; the molar concentration ratio of ferric chloride hexahydrate, sodium citrate dihydrate and polyethylene glycol is 10:1:0.

125.

6. A method for preparing ZnO@Fe3O4 urchin-like magnetic beads according to any one of claims 1-5, characterized in that: The incubation in step S4 is at a temperature of 150℃ for 2 h.

7. The method for preparing ZnO@Fe3O4 urchin-shaped magnetic beads according to claim 6, characterized in that: The incubation in step S5 is at a temperature of 90℃ for 2 h. 8.The ZnO@Fe 3O 4 urchin-like magnetic bead prepared by the method of claim 1, wherein the ZnO@Fe 3O 4 urchin-like magnetic bead is characterized by: The magnetic beads are oval urchin-like with a particle size of 1-2 μm.

9. The use of the ZnO@Fe3O4 urchin-like magnetic beads of claim 8 in extracting bacterial nucleic acids. 10.The application of the ZnO@Fe3O4 magnetic beads in extracting bacterial nucleic acid according to claim 9, characterized in that: The ZnO@Fe3O4 urchin-like magnetic beads are added to the bacterial solution, shaken thoroughly, and irradiated under ultraviolet light; Discarding the solution and retaining the solid; Washing to remove impurities, adding an eluent, and dispersing the bacterial nucleic acids in the eluent to complete the extraction.

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