Fluorescent lateral flow chromatography detection method of salmonella antibody based on perovskite quantum dots and magnetic nanoparticles

Abstract

The invention belongs to the field of salmonella detection, and discloses a fluorescent lateral flow chromatography detection method for detecting salmonella, which realizes sensitive detection of salmonella through combination of CsPbBr3 (at) SiO2 with excellent fluorescence performance and Fe3O4 with magnetic response capability. The problems that in the prior art, real-time on-site antibody detection is long in time consumption, labor-consuming, high in cost, unable to quantify and the like are solved. The fluorescent probe IPNs capable of specifically recognizing salmonella is obtained by coating the outside of perovskite quantum dots with silicon dioxide, and meanwhile, the surfaces of Fe3O4 nanoparticles are modified with salmonella antibodies to prepare the magnetic probe IMNs. The former provides a fluorescence signal, and the latter realizes rapid separation of bacteria, so that the detection is more sensitive, rapid and convenient, and is suitable for various scenes. Human eyes are highly sensitive to green fluorescence, preliminary qualitative detection can be realized without a fluorescence detector, the method is suitable for field detection, and the method is excellent in specificity, anti-interference capability and repeatability and has potential in actual detection.

Description

Technical Field

[0001] The invention relates to the field of salmonella detection, and in particular to a fluorescent lateral flow chromatography detection method for salmonella antibodies based on perovskite quantum dots and magnetic nanoparticles. Background Art

[0002] Salmonella is one of the most common pathogens that causes acute gastroenteritis, diarrhea, and abdominal cramps. For infants and the elderly with weak immune systems, its infection can even be fatal. Salmonella is a Gram-negative bacterium belonging to the Enterobacteriaceae family. It is a foodborne pathogen of humans and animals. It easily contaminates meat, eggs, milk and other foods. It has strong transmission ability and is difficult to prevent and control. Salmonella has an extremely low infection limit (1 CFU / mL) and a high prevalence rate. It is most often transmitted by eating contaminated food. In addition, it can also be transmitted between humans and animals. This puts higher demands on the prevention and control of Salmonella contaminants, and restrictions on Salmonella have been tightened for many years. Given the serious threat of Salmonella to human health, effective identification and rapid detection of Salmonella are of great significance for preventing outbreaks of foodborne diseases. Many detection methods for Salmonella have been developed, including microbial culture methods, polymerase chain reaction, loop-mediated isothermal amplification test, enzyme-linked immunosorbent assay, and sensors. Traditional microbial culture methods are time-consuming, labor-intensive, and complicated to operate, and cannot meet the needs of on-site testing. Existing rapid detection methods also have many disadvantages, such as requiring laboratories equipped with expensive equipment and well-trained laboratory personnel, which is not friendly to areas with limited resources. Therefore, it is particularly important to develop new detection methods that have short operation time, are portable and easy to operate. Summary of the invention

[0003] The purpose of the present invention is to solve the above-mentioned problems in the prior art that instant on-site detection of antibodies is time-consuming, labor-intensive, costly, and cannot be quantified. Perovskite quantum dots coated with silica shells and magnetic Fe3O4 nanoparticles are used as markers for flow immunoassay, respectively, to provide a detection method with high sensitivity, simple operation, low cost, and excellent specificity, anti-interference ability and repeatability.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] The preparation method of the immune CsPbBr3@SiO2 nanoparticle probe and the immune Fe3O4 nanoparticle probe comprises the following steps:

[0006] 1) Preparation of precursor solution: Weigh lead bromide and cesium bromide and add them to a beaker containing N,N-dimethylformamide, then add a certain amount of oleylamine and oleic acid, and then heat and stir for a period of time to obtain a clear solution. Take a certain amount of the above solution and add a certain amount of ammonia solution to it to obtain a precursor solution.

[0007] 2) Preparation of CsPbBr3@SiO2 nanoparticles (PNs): Under vigorous stirring, a certain amount of the precursor solution prepared in step 1) is quickly added to toluene containing a certain amount of TMOS. The solution immediately turns yellow and shows bright green fluorescence under 365nm ultraviolet flashlight. After a period of time, the stirring speed is adjusted, and the reaction is stopped after being kept at a certain temperature for a period of time. The obtained sample is centrifuged and washed, and then washed alternately with ethanol and water and redispersed in ethanol to obtain CsPbBr3@SiO2 nanoparticles (PNs).

[0008] 3) Surface modification of CsPbBr3@SiO2 nanoparticles: Add a certain amount of 3-aminopropyltriethoxysilane to a certain amount of PNs synthesized in step 2), shake the mixture at a certain speed at room temperature, and incubate for a period of time to convert the hydroxyl groups on the surface of PNs into amino groups. After the reaction is completed, wash with anhydrous ethanol. Then, the successfully aminated PNs are redispersed in N,N-dimethylformamide, a certain amount of succinic anhydride is added, and the mixture is shaken at a certain speed at room temperature and incubated for a period of time. After the reaction is completed, wash with anhydrous ethanol to complete the surface modification of CsPbBr3@SiO2 nanoparticles.

[0009] 4) Preparation of immune CsPbBr3@SiO2 nanoparticles (IPNs): The PNs successfully carboxylated in step 3) were washed with PBS and dispersed in PBS containing EDC and NHS. The mixture was gently shaken at room temperature to activate the carboxyl groups on the surface of the PNs. After incubation for a period of time, they were washed with PBS, then dispersed in PBS and anti-Salmonella monoclonal antibodies were added. After incubation for a period of time at a certain temperature, they were washed with PBS to remove excess antibodies, and after blocking with BSA solution, probes that can specifically capture Salmonella were obtained, which were recorded as IPNs.

[0010] 5) Preparation of immunomagnetic Fe3O4 nanoparticles: Take a certain amount of Fe3O4 nanoparticle (MNs) stock solution and dilute it, wash it with a magnetic separation rack to remove nanoparticles with poor magnetic response, and then redisperse it in PBS containing EDC and NHS, and gently shake the mixture at room temperature to activate the carboxyl groups on the surface of MNs. Then incubate for a period of time, wash it with PBS several times, disperse it in PBS, add anti-Salmonella monoclonal antibodies and incubate it at a certain temperature for a period of time, wash it with PBS again to remove excess antibodies, and block it with BSA solution to obtain immunomagnetic Fe3O4 nanoparticle probes that can specifically capture Salmonella.

[0011] In step 1), the mass of lead bromide is 0.1468 g, the mass of cesium bromide is 0.0851 g, the volume of N,N-dimethylformamide is 10 mL, the volume of oleylamine is 0.6 mL, and the volume of oleic acid is 1.8 mL; the heating temperature is 90° C., the stirring time is 2 h; the concentration of ammonia solution is 2.8%, and the volume is 40 μL.

[0012] In step 2), the volume of the precursor solution synthesized in step 1) is 0.2 mL; the volume of the toluene solution is 10 mL, and the volume of the solute TMOS is 5 μL; the stirring speed is 150 rpm, the heating temperature is 60° C., and the reaction time is 120 min; the centrifugal speed is 9000 rpm, and the time is 5 min; and the volume of ethanol is 10 mL.

[0013] In step 3), the volume of PNs synthesized in step 2) is 5 mL, the volume fraction of 3-aminopropyltriethoxysilane is 10%, the rotation speed is 200 rpm, and the incubation time is 12 h; the number of washings with anhydrous ethanol is 3 times; the volume of N,N-dimethylformamide is 5 mL, the mass of succinic anhydride is 0.08 g, and the incubation time is 3 h.

[0014] In step 4), the pH of the PBS solution used to activate the carboxyl group is 6.8, the concentration is 0.01M, the volume is 5mL, the solute EDC concentration is 2mM, the NHS concentration is 1mM, and the incubation time is 30min; the pH of the PBS solution used to wash excess antibodies is 7.2, the concentration is 0.01M, the volume is 5mL, the mass of the anti-Salmonella monoclonal antibody is 5μg, the incubation temperature is 37°C, and the time is 4h.

[0015] In step 5), the volume of the Fe3O4 nanoparticle (MNs) stock solution is 200 μL, the volume after dilution is 10 mL, and the number of washing times is 3 times; the pH of the PBS solution for activating the carboxyl group is 6.8, the concentration is 0.01 M, the concentration of the solute EDC is 2 mM, the concentration of NHS is 1 mM, and the incubation time is 30 min; the pH of the PBS solution used to wash excess antibodies is 7.2, the concentration is 0.01 M, the volume is 5 mL, the mass of the anti-Salmonella monoclonal antibody is 5 μg, the incubation temperature is 37°C, and the time is 4 h.

[0016] The immune CsPbBr3@SiO2 nanoparticle probe and immune Fe3O4 nanoparticle are quantitatively applied in detecting Salmonella. The application method is as follows:

[0017] After a series of standard concentrations of Salmonella solutions were mixed and incubated with a certain amount of INSs, the fluorescence intensity value of the supernatant and the logarithm of the Salmonella concentration were measured after magnetic enrichment, and a standard curve between the fluorescence intensity value of the supernatant and the concentration of Salmonella was established for quantitative detection.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] The present invention provides a new method for detecting Salmonella, namely, using CsPbBr 3 @SiO 2 Excellent fluorescence performance provides sensitive fluorescence signals for detection. 3 O 4 The magnetic response ability of perovskite quantum dots is used to capture pathogens, and the combination of the two realizes sensitive detection of Salmonella. The present invention utilizes the excellent fluorescence properties of perovskite quantum dots and coats them with a layer of silicon dioxide, which not only ensures that the fluorescence of perovskite is not disturbed by the external environment, but also performs functional biological modification on the surface of silicon dioxide to obtain fluorescent probe IPNs that can specifically identify Salmonella. 3 O 4 The surface of the nanoparticles is also modified with antibodies against Salmonella to obtain magnetic probes IMNs. One of these two probes provides a good fluorescent signal, and the other can quickly separate bacteria, making the detection more sensitive, fast, and convenient, and more suitable for a variety of scenarios. Since the human eye is highly sensitive to green fluorescence, a preliminary qualitative judgment of the experimental results can be made without a fluorescence detector, which is suitable for on-site detection. In addition, this method has excellent specificity, anti-interference ability, and repeatability, and has achieved ideal detection results in simulated complex actual samples. Therefore, this method has great potential in actual detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The present invention provides a schematic diagram of the lateral flow immunoassay detection principle based on IPNs and IMNs.

[0021] Figure 2 The present invention provides pictures of CsPbBr3@SiO2 under ultraviolet flashlight and sunlight, fluorescence emission spectra of CsPbBr3 and CsPbBr3@SiO2, XRD pattern of CsPbBr3@SiO2 and water stability test of CsPbBr3@SiO2.

[0022] Figure 3 The transmission electron microscope image of CsPbBr3@SiO2 in the present invention, the HR-TEM image of a single CsPbBr3@SiO2 and the EDX element mapping of Cs, Pb, Br, Si, O and their superimposed layers are given.

[0023] Figure 4 The Zeta potential of CsPbBr3@SiO2 after amination and carboxylation, the fluorescence emission spectra of PNs and IPNs after incubation and washing with Cy3-labeled secondary antibodies, and the transmission electron microscopy images of IPNs incubated with Salmonella are given.

[0024] Figure 5 The infrared spectrum of the Fe3O4 nanoparticles of the present invention and the transmission electron microscope image after incubation of IMNs with Salmonella are given.

[0025] Figure 6 The relationship between the concentration of added antibodies and the fluorescence intensity and the relationship between the concentration of BSA and the fluorescence intensity in the present invention are given.

[0026] Figure 7 Transmission electron microscope images of the IPNs and IMNs after incubation with Salmonella, HR-TEM images of the IPNs and IMNs after incubation with Salmonella, and EDX element mappings of Cs, Pb, Br, Si, Fe, N and their superimposed layers are given.

[0027] Figure 8 The fluorescence spectra of the supernatants of the magnetic separation of the MNs and PNs, IMNs and IPNs mixed with Salmonella, and the interpolation of the fluorescence intensity of the supernatants of the magnetic separation of IMNs and IPNs mixed with different bacteria and the blank control are given.

[0028] Fig. 9 The linear curves of the IPNs and IMNs for detecting Salmonella are given.

[0029] Fig.10 The present invention provides a picture of the supernatant of the actual sample detection under 365nm ultraviolet flashlight irradiation and a bar graph of the actual sample detection. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0031] Figure 1 The schematic diagram of the lateral flow immunoassay detection based on IPNs and IMNs is given. 3 It can exist stably in water for a long time, and then its surface is modified to obtain fluorescent nanoprobe IPNs, which can also be used for Fe 3 O 4 Nanoparticles are modified to obtain magnetic nanoprobes IMNs. After incubation of IPNs and IMNs with Salmonella, a sandwich structure is formed. When an external magnet is added, the sandwich structure complex is captured, and only IPNs that are not bound to bacteria remain in the supernatant. The greater the bacterial concentration, the fewer IPNs will remain in the supernatant, and the weaker the fluorescence intensity will be. Therefore, the quantitative detection of bacterial concentration can be achieved by detecting the fluorescence intensity in the supernatant.

[0032] Figure 2 The present invention provides pictures of CsPbBr3@SiO2 under ultraviolet flashlight and sunlight, fluorescence emission spectra of CsPbBr3 and CsPbBr3@SiO2, XRD pattern of CsPbBr3@SiO2 and water stability test of CsPbBr3@SiO2. Figure 2 (a) is a picture of PNs aqueous solution under 365nm ultraviolet light and natural light. PNs are well dispersed in water and have bright green fluorescence under ultraviolet light. 3 It is very sensitive to solutions such as ethanol and water. It will immediately decompose and lose fluorescence when in water. The prepared PNs can emit bright green fluorescence in water, indicating that the formed silica protective shell has a strong effect on CsPbBr 3 The kernel has a very good protective effect. Figure 2 (b) is CsPbBr 3 and CsPbBr 3 @SiO 2 The fluorescence emission spectrum of CsPbBr 3 , CsPbBr 3 @SiO 2 The fluorescence emission spectrum of CsPbBr has a significant blue shift, and the fluorescence intensity has decreased significantly. The silica coating will cause the fluorescence spectrum to blue shift. The thicker the shell, the more obvious the blue shift. There are two main factors for the decrease in fluorescence intensity. One is that some CsPbBr 3It was not completely coated by silica and was removed by washing with ethanol and water. Another reason is that during the synthesis stage, the addition of a small amount of ammonia water would cause the newly generated CsPbBr 3 was directly quenched. Figure 2 (c) CsPbBr 3 @SiO 2 The XRD spectrum of CsPbBr 3 It is a cubic phase with a small and broad shoulder in the range of 2θ = 20-30°, which is attributed to the presence of amorphous silica. Figure 2 (d) is CsPbBr 3 @SiO 2 Comparison of fluorescence emission spectra before and after 15 days of synthesis shows that after 15 days of synthesis, the peak value of the fluorescence spectrum slightly red-shifted and the fluorescence intensity slightly increased. The red-shift of the peak value is attributed to the aggregation of nanoparticles, which makes the particles larger. The slight increase in fluorescence intensity is mainly due to the evaporation of water, which increases the overall concentration of the solution. After 15 days, CsPbBr 3 @SiO 2 The fact that the original fluorescence intensity can still be maintained indicates that it has a high degree of stability, which provides conditions for subsequent applications.

[0033] Figure 3 The transmission electron microscope image of CsPbBr3@SiO2 in the present invention, the HR-TEM image of a single CsPbBr3@SiO2 and the EDX element mapping of Cs, Pb, Br, Si, O and their superimposed layers are given. The prepared CsPbBr3@SiO2 is observed by transmission electron microscopy, and it can be seen from Figure 3 (a) It can be seen that the CsPbBr3@SiO2 nanoparticles are spherical, with an overall size of about 95nm, a core size of about 25nm, and a shell thickness of about 35nm. Figure 3 (b) Its HR-TEM image, Figure 3 (c) to (h) are the element distribution diagrams of Cs, Pb, Br, Si, and O, respectively. It can be seen that CsPbBr3 is the core and is wrapped by silica.

[0034] Figure 4 The Zeta potential of CsPbBr3@SiO2 after amination and carboxylation, the fluorescence emission spectra of PNs and IPNs after incubation and washing with Cy3-labeled secondary antibodies, and the transmission electron microscopy images of IPNs and Salmonella incubation are given. 3 @SiO 2 After amination and carboxylation, the Zeta potential was tested. Figure 4 (a) It can be seen that its potential changes alternately between positive and negative, indicating the successful modification of amination and carboxylation. Figure 4(b) is the fluorescence emission spectrum of PNs and IPNs after incubation and washing with Cy3-labeled secondary antibodies. As shown in the figure, IPNs has an absorption peak at 568nm, which proves that the antibody of Salmonella has been successfully modified on PNs. After incubating IPNs with Salmonella, transmission electron microscopy was used to observe, as shown in Figure 4 As shown in (c), IPNs can specifically recognize and bind to Salmonella, which indicates the successful preparation of the fluorescent probe.

[0035] Figure 5 The infrared spectrum of the Fe3O4 nanoparticles of the present invention and the transmission electron microscope image after incubation of IMNs with Salmonella are given. 3 O 4 Nanoparticles were tested by infrared spectroscopy. Figure 5 (a) It can be seen that the infrared spectrum at 3370cm -1 The characteristic OH peak appears at 1650cm -1 A C=O characteristic peak appears at the MNs, indicating that MNs have carboxyl groups and do not need to be modified. After activation, they are connected to Salmonella antibodies. After incubating IMNs with Salmonella and observing them under a transmission electron microscope, it can be seen that IMNs can recognize Salmonella and bind to it, which indicates the successful preparation of the magnetic nanoprobe.

[0036] Figure 6 The relationship between the concentration of the added antibody and the fluorescence intensity and the relationship between the concentration of BSA and the fluorescence intensity are given in the present invention. Figure 6 As shown in (a), as the amount of added antibody increases, the fluorescence intensity decrease value of the positive sample does not increase continuously compared with the negative sample. Adding too much antibody will lead to the hook effect, which will affect the sensitivity of the detection. Therefore, 1 μg mL -1 The optimal condition is the antibody amount of 1 μg mL -1 Under the condition of , different concentrations of BSA were selected to block the redundant sites on the probe to reduce nonspecific adsorption. As shown in Figure (b), compared with the negative sample, the fluorescence intensity decrease of the positive sample reached the maximum when the BSA concentration was 1%. If the BSA concentration was too low, the site blocking would be incomplete and nonspecific adsorption would be serious. If the BSA concentration was too high, the recognition site would also be affected by the blocking, thus reducing the sensitivity. Therefore, 1% BSA concentration was selected as the optimal blocking concentration.

[0037] Figure 7The transmission electron micrographs of the IPNs and IMNs after incubation with Salmonella, the HR-TEM images after incubation with Salmonella, and the EDX element mappings of Cs, Pb, Br, Si, Fe, N and their superimposed layers are given. The enriched products obtained by magnetic adsorption after incubation of IPNs and IMNs with Salmonella are redispersed in water and observed by transmission electron microscopy, as shown in FIG. Figure 7 As shown in (a), IMNs and IPNs specifically recognize and bind to Salmonella. Figure 7 (b) to (l) also proved this point from the perspective of elemental analysis. Therefore, we can believe that the weakening of the fluorescence intensity of the supernatant is because some IPNs are magnetically adsorbed to the bottom after binding with Salmonella, and thus the relationship between the fluorescence intensity of the supernatant and the concentration of Salmonella can be established.

[0038] Figure 8 The fluorescence spectra of the supernatants of the magnetic separation of MNs and PNs, IMNs and IPNs mixed with Salmonella, and the interpolation of the fluorescence intensity of the supernatants of the magnetic separation of IMNs and IPNs mixed with different bacteria and the blank control are given. Figure 8 As shown in (a), it can be seen that it is almost the same as the negative sample, so its nonspecific adsorption can be ignored. After incubation with Pseudomonas aeruginosa, hemolytic Streptococcus, Enterobacter sakazakii, Listeria monocytogenes, and Staphylococcus aureus, the fluorescence intensity of the supernatant was measured. The results compared with Salmonella are shown in Figure 8 As shown in (b), it can be seen that IPNs and IMNs have specificity in recognizing bacteria, which is attributed to the specific binding between antigen and antibody.

[0039] Fig. 9 The linear curves of the IPNs and IMNs of the present invention for detecting Salmonella are given. After determining the detection conditions and various factors of the probe, a series of standard concentrations of Salmonella solutions are incubated with IMNs and IPNs, and the relationship between the fluorescence intensity value of the supernatant measured after magnetic enrichment and the logarithmic value of the Salmonella concentration is shown in the following figure: Fig. 9 As shown in the figure, the fluorescence intensity of the supernatant is related to the concentration of Salmonella at 1×10 2 ~1×10 8 CFU·mL -1 The lowest detection concentration was 1×10 2 CFU·mL -1 The regression equation for detecting Salmonella is y=337.35-17.26·x.

[0040] Fig.10The images of the supernatant of the actual sample detection under 365nm ultraviolet flashlight and the bar graph of the actual sample detection are given. In order to explore whether IPMs and IMNs can be used in actual samples, a chopping board and a kitchen knife are selected to simulate actual samples. Fig.10 (a) and (b) are pictures of the supernatant of the water used to wash the sterilized and contaminated cutting boards and knives after the standard experimental steps were carried out under the irradiation of a 365nm ultraviolet flashlight. It can be clearly seen that the fluorescence intensity of the water used to wash the contaminated cutting boards and knives is weaker than that of the negative. Fig.10 (c) is a bar graph of its fluorescence intensity. Substituting the measured fluorescence intensity value into the standard equation, the concentration of Salmonella on the cutting board is 1.67×10 6 CFU·mL -1 , the concentration of Salmonella on the knife was 6.3×10 7 CFU·mL -1 , although the concentration of bacteria added is the same.

Claims

1. A fluorescent lateral flow chromatography detection method for Salmonella antibodies based on perovskite quantum dots and magnetic nanoparticles, characterized in that The following steps are involved: After a series of standard concentrations of Salmonella solutions were mixed and incubated with a certain amount of immune CsPbBr3@SiO2 nanoparticles and immune Fe3O4 nanoparticles, the fluorescence intensity of the supernatant measured after magnetic enrichment and the logarithm of the Salmonella concentration were used to establish a standard curve between the fluorescence intensity of the supernatant and the concentration of Salmonella for quantitative detection. 2 ~1×10 8 CFU·mL -1 The minimum detection concentration was 1×10 2 CFU·mL -1 The regression equation for detecting Salmonella is y=337.35-17.26·x.

2. The fluorescent lateral flow chromatography detection method for Salmonella antibodies using perovskite quantum dots and magnetic nanoparticles as claimed in claim 1, characterized in that The synthesis steps of the immune CsPbBr3@SiO2 nanoparticle probe and the immune Fe3O4 nanoparticle probe include the following processes: 1) Preparation of precursor solution: Weigh lead bromide and cesium bromide and add them to a beaker containing N,N-dimethylformamide, then add a certain amount of oleylamine and oleic acid, and then heat and stir for a period of time to obtain a clear solution. Take a certain amount of the above solution and add a certain amount of ammonia solution to it to obtain a precursor solution. 2) Preparation of CsPbBr3@SiO2 nanoparticles (PNs): Under vigorous stirring, a certain amount of the precursor solution prepared in step 1) is quickly added to toluene containing a certain amount of TMOS. The solution immediately turns yellow and shows bright green fluorescence under 365nm ultraviolet flashlight. After a period of time, the stirring speed is adjusted, and the reaction is stopped after being kept at a certain temperature for a period of time. The obtained sample is centrifuged and washed, and then washed alternately with ethanol and water and redispersed in ethanol to obtain CsPbBr3@SiO2 nanoparticles (PNs). 3) Surface modification of CsPbBr3@SiO2 nanoparticles: Add a certain amount of 3-aminopropyltriethoxysilane to a certain amount of PNs synthesized in step 2), shake the mixture at a certain speed at room temperature, and incubate for a period of time to convert the hydroxyl groups on the surface of PNs into amino groups. After the reaction is completed, wash with anhydrous ethanol. Then, the successfully aminated PNs are redispersed in N,N-dimethylformamide, a certain amount of succinic anhydride is added, and the mixture is shaken at a certain speed at room temperature and incubated for a period of time. After the reaction is completed, wash with anhydrous ethanol to complete the surface modification of CsPbBr3@SiO2 nanoparticles. 4) Preparation of immune CsPbBr3@SiO2 nanoparticles (IPNs): The PNs successfully carboxylated in step 3) were washed with PBS and dispersed in PBS containing EDC and NHS. The mixture was gently shaken at room temperature to activate the carboxyl groups on the surface of the PNs. After incubation for a period of time, they were washed with PBS, then dispersed in PBS and anti-Salmonella monoclonal antibodies were added. After incubation for a period of time at a certain temperature, they were washed with PBS to remove excess antibodies, and after blocking with BSA solution, probes that can specifically capture Salmonella were obtained, which were recorded as IPNs. 5) Preparation of immunomagnetic Fe3O4 nanoparticles: Take a certain amount of Fe3O4 nanoparticle (MNs) stock solution and dilute it, wash it with a magnetic separation rack to remove nanoparticles with poor magnetic response, and then redisperse it in PBS containing EDC and NHS, and gently shake the mixture at room temperature to activate the carboxyl groups on the surface of MNs. Then incubate for a period of time, wash it with PBS several times, disperse it in PBS, add anti-Salmonella monoclonal antibodies and incubate it at a certain temperature for a period of time, wash it with PBS again to remove excess antibodies, and block it with BSA solution to obtain immunomagnetic Fe3O4 nanoparticle probes that can specifically capture Salmonella.

3. The synthesis step of the immuno CsPbBr3@SiO2 nanoparticle probe for the fluorescent lateral flow chromatography detection method of Salmonella antibodies using perovskite quantum dots and magnetic nanoparticles as claimed in claim 2, characterized in that In step 1), the mass of lead bromide is 0.1468 g, the mass of cesium bromide is 0.0851 g, the volume of N,N-dimethylformamide is 10 mL, the volume of oleylamine is 0.6 mL, and the volume of oleic acid is 1.8 mL; the heating temperature is 90° C., the stirring time is 2 h; the concentration of ammonia solution is 2.8%, and the volume is 40 μL.

4. The step of synthesizing the immuno CsPbBr3@SiO2 nanoparticle probe for the fluorescent lateral flow chromatography detection method of Salmonella antibodies using perovskite quantum dots and magnetic nanoparticles as claimed in claim 2, characterized in that In step 2), the volume of the synthesized precursor solution is 0.2 mL; The volume of the toluene solution was 10 mL, the volume of the solute TMOS was 5 μL; the stirring speed was 150 rpm, the heating temperature was 60° C., the reaction time was 120 min; the centrifugal speed was 9000 rpm, the time was 5 min; and the volume of ethanol was 10 mL.

5. The step of synthesizing the immuno CsPbBr3@SiO2 nanoparticle probe for the fluorescent lateral flow chromatography detection method of Salmonella antibodies using perovskite quantum dots and magnetic nanoparticles as claimed in claim 2, characterized in that In step 3), the volume of the synthesized PNs was 5 mL, the volume fraction of 3-aminopropyltriethoxysilane was 10%, the rotation speed was 200 rpm, and the incubation time was 12 h; The number of washings with anhydrous ethanol was 3 times; the volume of N,N-dimethylformamide was 5 mL, the mass of succinic anhydride was 0.08 g, and the incubation time was 3 h.

6. The step of synthesizing the immuno CsPbBr3@SiO2 nanoparticle probe for the fluorescent lateral flow chromatography detection method of Salmonella antibodies using perovskite quantum dots and magnetic nanoparticles as claimed in claim 2, characterized in that In step 4), the pH of the PBS solution used to activate the carboxyl group is 6.8, the concentration is 0.01M, the volume is 5mL, the solute EDC concentration is 2mM, the NHS concentration is 1mM, and the incubation time is 30min; the pH of the PBS solution used to wash excess antibodies is 7.2, the concentration is 0.01M, the volume is 5mL, the mass of the anti-Salmonella monoclonal antibody is 5μg, the incubation temperature is 37°C, and the time is 4h.

7. The step of synthesizing the immune Fe3O4 nanoparticle probe for the fluorescent lateral flow chromatography detection method of Salmonella antibodies using perovskite quantum dots and magnetic nanoparticles as claimed in claim 2, characterized in that In step 5), the volume of the Fe3O4 nanoparticle (MNs) stock solution is 200 μL, the volume after dilution is 10 mL, and the number of washing times is 3 times; the pH of the PBS solution for activating the carboxyl group is 6.8, the concentration is 0.01 M, the concentration of the solute EDC is 2 mM, the concentration of NHS is 1 mM, and the incubation time is 30 min; the pH of the PBS solution used to wash excess antibodies is 7.2, the concentration is 0.01 M, the volume is 5 mL, the mass of the anti-Salmonella monoclonal antibody is 5 μg, the incubation temperature is 37°C, and the time is 4 h.

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