Probe for detecting bacteria in air as well as preparation method and application of probe

Abstract

The invention provides a probe for detecting bacteria in air as well as a preparation method and application of the probe. The probe comprises Au-Fe3O4 nanoparticles and a recognition medium combined on the surfaces of the Au-Fe3O4 nanoparticles, and the recognition medium comprises at least one of a mixture of 5 (6)-carboxyl fluorescein and 3-(aminomethyl) phenylboronic acid hydrochloride and a product obtained by taking the 5 (6)-carboxyl fluorescein and the 3-(aminomethyl) phenylboronic acid hydrochloride as reactants. When the probe is used, air is sampled, maltose is added for incubation, a solution possibly containing bacteria after incubation is taken, then the obtained solution is mixed with the probe, and the content of the bacteria in the air can be correspondingly obtained through a fluorescence signal shown by the probe. The content of bacteria in the air can be effectively obtained through the probe. Meanwhile, the probe is simple to prepare and convenient to use, and is favorable for promoting the development of a technology for detecting bacteria in air.

Description

Technical Field

[0001] The present invention relates to the field of biological detection technology, and in particular to a probe for detecting bacteria in the air, and a preparation method and application thereof. Background Art

[0002] Bacteria in the air have a significant impact on human health, industrial production and environmental hygiene. In medical places, such as hospital operating rooms and wards, bacteria in the air may cause serious complications such as postoperative infection in patients, increasing medical risks and costs. In food processing and storage environments, bacterial contamination can cause food to spoil and rot, leading to food safety accidents, endangering consumer health and damaging corporate reputation. In public spaces, such as schools, offices, shopping malls, etc., the spread of bacteria may also cause the spread of various infectious diseases, affecting people's lives and work.

[0003] Traditional methods for detecting bacteria in the air have many limitations. As a classic detection method, the plate culture method is simple and intuitive in principle, but the operation is extremely cumbersome and requires multiple steps such as sampling, inoculation, culture, and colony counting. The entire detection cycle often takes several days, which is difficult to meet the needs of rapid detection. The liquid culture method is also time-consuming and is easily interfered by various factors in the bacterial counting process, resulting in inaccurate counting. Although the PCR technology based on molecular biology has high sensitivity and specificity and can detect low concentrations of bacteria, this technology has strict requirements on experimental equipment and requires expensive instruments such as professional PCR amplifiers. In addition, the experimental operation requires professional technicians to strictly follow the procedures, and the detection cost is high. It is not suitable for large-scale routine testing and on-site rapid testing. Therefore, the development of a simple, rapid, sensitive and low-cost method for detecting bacteria in the air has become an urgent problem to be solved. Summary of the invention

[0004] Based on the above problems, the present invention provides a probe for detecting bacteria in the air, a preparation method thereof, and an application thereof. The probe can realize efficient, accurate, and rapid detection of the bacterial content in the air, and has the advantages of simple operation and low cost, so as to meet the needs of different fields for detecting bacteria in the air and promote the development and application of air bacteria detection technology.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A probe for detecting bacteria in the air, comprising Au-Fe3O4 nanoparticles and an identification medium bound to the surface of the Au-Fe3O4 nanoparticles, wherein the identification medium comprises a mixture of 5(6)-carboxyfluorescein and 3-(aminomethyl)phenylborate hydrochloride, and at least one of products obtained by comprising the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants.

[0007] In some of the embodiments, the identification medium includes a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride, and the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylborate hydrochloride is 1:(0.8-1.2).

[0008] In some of the embodiments, the identification medium includes the product obtained by using the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants, and the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylborate hydrochloride is 1:(1.5-2.5).

[0009] In some of the embodiments, the particle size of the Au-Fe3O4 nanoparticles is 20 nm to 50 nm.

[0010] In some embodiments, the recognition medium is bound to the surface of the Au-Fe3O4 nanoparticles by chemical bonding or physical adsorption.

[0011] A method for preparing the probe for detecting bacteria in the air comprises the following steps:

[0012] preparing the Au-Fe3O4 nanoparticles;

[0013] The recognition medium is combined with the surface of the Au-Fe3O4 nanoparticles.

[0014] In some of the embodiments, the Au-Fe3O4 nanoparticles are prepared by a co-precipitation method.

[0015] In some embodiments, the identification medium includes a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride;

[0016] The step of combining the identification medium with the surface of the Au-Fe3O4 nanoparticles comprises:

[0017] The 5(6)-carboxyfluorescein, the 3-(aminomethyl)phenylborate hydrochloride and the Au-Fe3O4 nanoparticles are mixed in a buffer solution for reaction.

[0018] In some embodiments, the identification medium includes the product obtained by using the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants;

[0019] The preparation of the identification medium comprises: performing an amidation reaction or a peptide formation reaction of the amino group and the carboxyl group with the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride, and purifying;

[0020] The step of combining the identification medium with the surface of the Au-Fe3O4 nanoparticles comprises:

[0021] The recognition medium and the Au-Fe3O4 nanoparticles are mixed and reacted in a buffer solution.

[0022] An application of the probe for detecting bacteria in air in detecting bacteria in air comprises the following steps:

[0023] The air is sampled using a culture medium; maltose is added to the sampled culture medium for incubation, the incubated product is subjected to solid-liquid separation, the liquid phase obtained by the solid-liquid separation is mixed with the probe, and the bacterial content in the sampled air is obtained through the fluorescent signal displayed by the probe.

[0024] Beneficial Effects

[0025] The probe of the present invention can realize efficient, accurate and rapid detection of the bacterial content in the air, and at the same time has the advantages of simple operation and low cost, so as to meet the needs of different fields for air bacteria detection and promote the development and application of air bacteria detection technology. DETAILED DESCRIPTION

[0026] One embodiment of the present invention provides a probe for detecting bacteria in the air. The probe includes Au-Fe3O4 nanoparticles and an identification medium bound to the surface of the Au-Fe3O4 nanoparticles, and the identification medium includes a mixture of 5(6)-carboxyfluorescein and 3-(aminomethyl)phenylborate hydrochloride, and at least one of products obtained by including the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants. The probe can achieve efficient, accurate and rapid detection of the bacterial content in the air, and has the advantages of simple operation and low cost, so as to meet the needs of different fields for air bacteria detection and promote the development and application of air bacteria detection technology.

[0027] In some embodiments, the identification medium includes a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylboronic acid hydrochloride, and the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylboronic acid hydrochloride is 1:(0.8-1.2). When the identification medium includes a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylboronic acid hydrochloride, the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylboronic acid hydrochloride can be appropriately selected within the range of 1:(0.8-1.2). For example, the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylboronic acid hydrochloride can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc.

[0028] In some embodiments, the identification medium includes the product obtained by reacting 5(6)-carboxyfluorescein and 3-(aminomethyl)phenyl boron hydrochloride as reactants, and the molar ratio of 5(6)-carboxyfluorescein to 3-(aminomethyl)phenyl boron hydrochloride is 1:(1.5-2.5). When the identification medium includes the product obtained by reacting 5(6)-carboxyfluorescein and 3-(aminomethyl)phenyl boron hydrochloride as reactants, the molar ratio of 5(6)-carboxyfluorescein to 3-(aminomethyl)phenyl boron hydrochloride can be 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, etc.

[0029] In some embodiments, the particle size of the Au-Fe3O4 nanoparticles is 20nm to 50nm. The particle size of the Au-Fe3O4 nanoparticles within this range can provide a suitable number of binding sites for the recognition medium, thereby promoting the binding of the recognition medium to the Au-Fe3O4 nanoparticles. Optionally, the particle size of the Au-Fe3O4 nanoparticles can be 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc.

[0030] In some embodiments, the recognition medium is bonded to the surface of the Au-Fe3O4 nanoparticles by chemical bonding or physical adsorption. Chemical bonding or physical adsorption can stably bond the recognition medium to the surface of the Au-Fe3O4 nanoparticles, so that the probe maintains a stable structure.

[0031] One embodiment of the present invention provides a method for preparing the probe for detecting bacteria in the air, comprising the following steps: preparing the Au-Fe3O4 nanoparticles. Binding the identification medium to the surface of the Au-Fe3O4 nanoparticles. The preparation method is simple and easy, and a probe with excellent performance can be obtained without relying on complex processes and expensive equipment.

[0032] In some embodiments, the Au-Fe3O4 nanoparticles are prepared by coprecipitation. Optionally, the preparation of the Au-Fe3O4 nanoparticles includes the following steps: weighing ferric chloride (FeCl3) and chloroauric acid (HAuCl4), dissolving them in deionized water, stirring them thoroughly until they are completely dissolved, and preparing a mixed metal salt solution. Under stirring conditions, the mixed solution is added dropwise to a pre-prepared sodium hydroxide (NaOH) solution at a slow and steady rate. During the dropwise addition process, the temperature of the reaction system is controlled at 60°C using a thermostat, and the pH value of the solution is monitored in real time to maintain the stability of the reaction conditions. The reaction time is 2h, and the stirring state is always maintained during the reaction to allow the reaction to proceed fully. After the reaction is completed, a black precipitate is generated, which is transferred to a centrifuge tube and centrifuged and washed multiple times with deionized water (e.g., centrifuged for 5 minutes each time at a speed of 8000rpm) until a small amount of washing liquid is taken and no white precipitate is generated after the addition of silver nitrate solution, indicating that the chloride ions have been completely removed. Finally, the washed precipitate was transferred to a drying dish and dried in a constant temperature oven at 80°C for 12 hours to obtain Au-Fe3O4 nanoparticles. The particle size of the prepared nanoparticles was about 30 nm as determined by a particle size analyzer.

[0033] In some embodiments, the recognition medium includes a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride. Binding the recognition medium to the surface of the Au-Fe3O4 nanoparticles includes: mixing the 5(6)-carboxyfluorescein, the 3-(aminomethyl)phenylborate hydrochloride and the Au-Fe3O4 nanoparticles in a buffer solution.

[0034] Optionally, the buffer solution is phosphate buffered saline (PBS, pH=7.4).

[0035] Further optionally, the identification medium is bound to the surface of the Au-Fe3O4 nanoparticles, including: weighing 5(6)-carboxyfluorescein and 3-(aminomethyl)phenyl boron hydrochloride in a molar ratio of 1: (0.8-1.2), dissolving the two in a phosphate buffer solution (PBS, pH=7.4), and using an ultrasonic oscillator for ultrasonic treatment for 30 minutes to fully disperse the substances in the solution. Then, the Au-Fe3O4 nanoparticles are slowly added to the above solution, and stirred for 4 hours at room temperature to allow the identification medium to fully react and bind to the surface of the Au-Fe3O4 nanoparticles. After the reaction is completed, the reaction solution is transferred to a centrifuge, centrifuged at a speed of 10,000 rpm for 15 minutes, and the bottom precipitate is collected. The precipitate is washed 3 times with a PBS solution to remove unbound 5(6)-carboxyfluorescein and 3-(aminomethyl)phenyl boron hydrochloride and other impurities, and finally a probe for airborne bacteria detection is obtained.

[0036] In some embodiments, the recognition medium includes a product obtained by using the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenyl boron hydrochloride as reactants. The preparation of the recognition medium includes: subjecting the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenyl boron hydrochloride to amidation reaction or peptide formation reaction of the amino and carboxyl groups, and purifying. Binding the recognition medium to the surface of the Au-Fe3O4 nanoparticles includes: mixing the recognition medium and the Au-Fe3O4 nanoparticles in a buffer solution.

[0037] Optionally, the recognition medium includes the product obtained by using the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenyl boron hydrochloride as reactants. The preparation of the recognition medium includes: step (1) adding 5(6)-carboxyfluorescein to a phosphate buffer solution with a pH of 4.5 to 7.2, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) and stirring at 25°C to 35°C for 10 to 30 minutes; step (2) adding 3-(aminomethyl)phenyl boron hydrochloride and adjusting the pH of the reaction system to 7 to 8 and stirring the reaction for 2 to 5 hours; step (3) purifying the product.

[0038] Optionally, the method for purifying the product in step (3) is purification through a non-polar solid phase extraction column, the non-polar solid phase extraction column is a C18 extraction column; the elution solvent is a gradient solvent of dimethyl sulfoxide and n-hexane or a gradient solvent of dimethyl sulfoxide and n-pentane.

[0039] The molar ratio of 5(6)-carboxyfluorescein to 3-(aminomethyl)phenylborate hydrochloride is 1:(1.5-2.5). The amount of 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 40 mg / mL-80 mg / mL of the reaction solution, and the amount of N-hydroxysuccinimide is 40 mg / mL-80 mg / mL of the reaction solution.

[0040] Another embodiment of the present invention provides an application of the probe for detecting bacteria in the air in detecting bacteria in the air, comprising the following steps: sampling the air using a culture medium; adding maltose to the sampled culture medium for incubation, performing solid-liquid separation on the incubated product, mixing the liquid phase obtained by the solid-liquid separation with the probe, and obtaining the bacterial content in the sampled air through the fluorescent signal displayed by the probe.

[0041] Optionally, sampling the air using a culture medium includes: using an impact method, using a suitable air sampling device (such as an Anderson sampler) to sample the air, setting a sampling flow rate (such as 28.3L / min) and a sampling time (such as 5min to 15min) according to different detection environments and requirements, and collecting the bacteria in the air onto the culture medium. A natural sedimentation method can also be used, with a time of 5 minutes.

[0042] Adding maltose to the culture medium after sampling for incubation includes: transferring the culture medium after sampling to a PBS solution containing a certain concentration of maltose (such as 1%), and incubating for a certain time (such as 30 minutes) at a suitable temperature (such as 37°C). Maltose can specifically interact with specific structures on the surface of bacteria, promote the release of bacteria from the sampling medium into the solution, and improve the detectability of bacteria.

[0043] The incubated product is subjected to solid-liquid separation, the liquid phase obtained by the solid-liquid separation is mixed with the probe, and the bacterial content in the sampled air is obtained through the fluorescent signal displayed by the probe, including: taking 1 ml of the liquid phase obtained by solid-liquid separation, adding an appropriate amount (such as 100 μl) of the probe prepared by the present invention, mixing well, and detecting the fluorescent signal on a fluorescence spectrophotometer. Because certain components on the surface of bacteria (such as polysaccharides, etc.) will specifically interact with the recognition medium on the surface of the probe, this interaction will cause the fluorescent signal of the probe to change. The bacterial content in the air can be obtained by using a pre-established standard curve of fluorescent signal and bacterial content.

[0044] Example 1

[0045] (1) Preparation of Au-Fe3O4 nanoparticles: Weigh ferric chloride (FeCl3) and chloroauric acid (HAuCl4), dissolve them in deionized water, stir thoroughly until completely dissolved, and prepare a mixed metal salt solution. Under stirring conditions, add the mixed solution dropwise to the pre-prepared NaOH solution at a slow and steady rate. During the dropwise addition process, the temperature of the reaction system is controlled at 60°C using a thermostat, and the pH value of the solution is monitored in real time to maintain the stability of the reaction conditions. The reaction time is 2 hours, and the stirring state is always maintained during the reaction to allow the reaction to proceed fully. After the reaction is completed, a black precipitate is generated, which is transferred to a centrifuge tube and centrifuged and washed several times with deionized water, each time for 5 minutes at a speed of 8000 rpm, until a small amount of washing liquid is taken and no white precipitate is generated after adding the silver nitrate solution, indicating that the chloride ions have been completely removed. Finally, the washed precipitate is transferred to a drying dish and dried in a constant temperature oven at 80°C for 12 hours to obtain Au-Fe3O4 nanoparticles. Detected by a particle size analyzer, the particle size of the prepared nanoparticles was about 30 nm.

[0046] (2) Preparation of probe for airborne bacteria detection: 5(6)-carboxyfluorescein and 3-(aminomethyl)phenylborate hydrochloride were weighed in a molar ratio of 1:1, dissolved in a phosphate buffer solution of pH = 7.4, and ultrasonicated for 30 minutes using an ultrasonic oscillator to fully disperse the substances in the solution. Then, Au-Fe3O4 nanoparticles were slowly added to the above solution, and stirred for 4 hours at room temperature to allow the recognition medium to fully react and bind to the surface of the Au-Fe3O4 nanoparticles. After the reaction was completed, the reaction solution was transferred to a centrifuge and centrifuged at 10,000 rpm for 15 minutes to collect the bottom precipitate. The precipitate was washed three times with PBS solution to remove unbound 5(6)-carboxyfluorescein and 3-(aminomethyl)phenylborate hydrochloride and other impurities, and finally a probe for airborne bacteria detection was obtained.

[0047] (3) The application of the probe for detecting bacteria in the air in the detection of bacteria in the air includes the following steps: adopting the impact method, using an impact air sampler based on the Anderson principle to sample the air, setting the sampling flow rate to 28.3L / min and the sampling time to 15min, and collecting the bacteria in the air onto the culture medium. The sampled culture medium is transferred to a PBS solution containing 1% maltose by mass concentration, and incubated at 37°C for 30min. The incubated product is subjected to solid-liquid separation, 1ml of the liquid phase obtained by solid-liquid separation is taken, 100μl of the probe prepared in this embodiment is added, and after sufficient mixing, the fluorescence signal is detected on a fluorescence spectrophotometer. The deviation of the test probe for the detection of Staphylococcus aureus of different concentrations is tested. The results are shown in Table 1.

[0048] Example 2

[0049] Compared with Example 1, the difference of this example is that the preparation method of the probe is different. The preparation method of the probe comprises: step (1) adding 5(6)-carboxyfluorescein to a phosphate buffer with a pH of 4.8, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) and stirring at 30°C for 20 minutes; the amount of 1-ethyl-(3-dimethylaminopropyl)carbodiimide is 50 mg / mL, and the amount of N-hydroxysuccinimide is 50 mg / mL. Step (2) adding 3-(aminomethyl)phenylborate hydrochloride and adjusting the pH of the reaction system to 7.5, stirring and reacting for 3 hours; the molar ratio of 5(6)-carboxyfluorescein to 3-(aminomethyl)phenylborate hydrochloride is 1:2.2. Step (3) purifying the product by a non-polar solid phase extraction column to obtain a solution (elution phase) containing a recognition medium. Then, the Au-Fe3O4 nanoparticles were slowly added to the above solution, and stirred for 4 hours at room temperature to allow the recognition medium to fully react and bind to the surface of the Au-Fe3O4 nanoparticles. After the reaction was completed, the reaction solution was transferred to a centrifuge and centrifuged at 10,000 rpm for 15 minutes to collect the bottom precipitate. The precipitate was washed three times with PBS solution to remove unbound 5(6)-carboxyfluorescein and 3-(aminomethyl)phenylborate hydrochloride and other impurities, and finally a probe for airborne bacterial detection was obtained.

[0050] Comparative Example 1

[0051] Compared with Example 1, the difference of this comparative example is that the identification medium in Example 1 is directly used (not combined with Au-Fe3O4 nanoparticles) to detect bacteria in the air.

[0052] Comparative Example 2

[0053] Compared with Example 2, the difference of this comparative example is that the identification medium in Example 2 (not combined with Au-Fe3O4 nanoparticles) is directly used to detect bacteria in the air.

[0054] Comparative Example 3

[0055] Compared with Example 1, the difference of this comparative example is that only 5(6)-carboxyfluorescein is used as the recognition medium, and after combining with Au-Fe3O4 nanoparticles, a probe is obtained, and then the probe is used to detect bacteria in the air.

[0056] Comparative Example 4

[0057] The air was tested for bacteria using the traditional plate culture method.

[0058] Table 1

[0059]

[0060]

[0061] In Table 1, relative error=absolute value of the difference between the set concentration of Staphylococcus aureus and the test value / set concentration of Staphylococcus aureus×100%.

[0062] It can be seen from Table 1 that the embodiment has a smaller relative error than the comparative example, indicating that the probe in the embodiment has a higher accuracy in detecting bacteria in the air.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0064] For those skilled in the art, according to the concept of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A probe for detecting bacteria in the air, characterized in that: It includes Au-Fe3O4 nanoparticles and an identification medium bound to the surface of the Au-Fe3O4 nanoparticles, wherein the identification medium includes a mixture of 5(6)-carboxyfluorescein and 3-(aminomethyl)phenylborate hydrochloride, and at least one of the products obtained by including the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants.

2. The probe for detecting bacteria in the air according to claim 1, characterized in that: The identification medium comprises a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride, and the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylborate hydrochloride is 1:(0.8-1.2).

3. The probe for detecting bacteria in the air according to claim 1, characterized in that: The identification medium includes a product obtained by using the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants, and the molar ratio of the 5(6)-carboxyfluorescein to the 3-(aminomethyl)phenylborate hydrochloride is 1:(1.5-2.5).

4. The probe for detecting bacteria in the air according to claim 1, characterized in that: The particle size of the Au-Fe3O4 nanoparticles is 20nm to 50nm.

5. The probe for detecting bacteria in the air according to any one of claims 1 to 4, characterized in that: The identification medium is combined with the surface of the Au-Fe3O4 nanoparticles by chemical bonding or physical adsorption.

6. A method for preparing a probe for detecting bacteria in the air according to any one of claims 1 to 5, characterized in that: The steps include: preparing the Au-Fe3O4 nanoparticles; The recognition medium is combined with the surface of the Au-Fe3O4 nanoparticles.

7. The method for preparing a probe for detecting bacteria in the air according to claim 6, characterized in that: The Au-Fe3O4 nanoparticles are prepared by a co-precipitation method.

8. The method for preparing a probe for detecting bacteria in the air according to any one of claims 6 to 7, characterized in that: The identification medium comprises a mixture of the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride; The step of combining the identification medium with the surface of the Au-Fe3O4 nanoparticles comprises: The 5(6)-carboxyfluorescein, the 3-(aminomethyl)phenylborate hydrochloride and the Au-Fe3O4 nanoparticles are mixed in a buffer solution for reaction.

9. The method for preparing a probe for detecting bacteria in the air according to any one of claims 6 to 7, characterized in that: The identification medium includes the product obtained by using the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride as reactants; The preparation of the identification medium comprises: performing an amidation reaction or a peptide formation reaction of the amino group and the carboxyl group with the 5(6)-carboxyfluorescein and the 3-(aminomethyl)phenylborate hydrochloride, and purifying; The step of combining the identification medium with the surface of the Au-Fe3O4 nanoparticles comprises: The recognition medium and the Au-Fe3O4 nanoparticles are mixed and reacted in a buffer solution.

10. Use of the probe for detecting bacteria in the air according to any one of claims 1 to 5 in detecting bacteria in the air, characterized in that: The following steps are involved: Air sampling using culture medium; Maltose is added to the culture medium after sampling for incubation, and the incubated product is subjected to solid-liquid separation. The liquid phase obtained by the solid-liquid separation is mixed with the probe, and the bacterial content in the sampled air is obtained through the fluorescent signal displayed by the probe.

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