Preparation method and application of a quantitative detection sensor based on magnetic fluorescent nanosystem

Abstract

The present invention belongs to the technical field of food safety detection, specifically relating to a method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem and its use. First, a magnetic nanomaterial and a fluorescent material (AuNCs) are synthesized, followed by the preparation of an MN@PEI@AuNCs composite material. Finally, by combining the composite with a Staphylococcus aureus antibody (Ab), a quantitative detection sensor based on the magnetic fluorescent nanosystem is prepared. The constructed quantitative detection sensor based on the magnetic fluorescent nanosystem can accurately detect Staphylococcus aureus. The correlation coefficient of the fluorescence rapid detection prediction model can reach 0.9869, and the detection limit can reach 4.7663×10 ‑11 CFU / mL; and the pre-treatment of the Staphylococcus aureus quantitative detection sensor prepared by the present invention is simple, the detection process is easy to operate, the detection speed is fast, and the detection results are intuitively visible.

Description

Technical Field

[0001] The present invention belongs to the technical field of food safety detection, and in particular relates to a preparation method and application of a quantitative detection sensor based on a magnetic fluorescent nanosystem. Background Art

[0002] Foodborne pathogens, characterized by their wide transmission, high toxicity, and high frequency of contamination, have become the leading cause of food safety incidents. Staphylococcus aureus (S. aureus) is a common foodborne pathogen, widely found in food ingredients and production environments. Furthermore, S. aureus metabolites can produce a variety of human toxins (hemolysins, enterotoxins, etc.) and invasive enzymes (plasma coagulase, fibrinolytic enzymes), which can cause pneumonia, pericarditis, and even sepsis. Methicillin-resistant S. aureus has become the third most common source of infection after HIV and hepatitis B virus. Therefore, the prevention and control of S. aureus in food is of paramount importance.

[0003] Although the existing standard method for Staphylococcus aureus overcomes the challenges of counting and quantification caused by the extremely small size of single bacteria and the extremely similar appearance of single colonies, it is limited by cumbersome operational processes such as bacterial proliferation and species identification. The quantitative detection time for a single batch of Staphylococcus aureus takes 3-5 days, and it is highly dependent on laboratory equipment and requires high professional operation, which cannot meet the market demand for rapid detection of Staphylococcus aureus. Summary of the Invention

[0004] In view of the steps of the prior art, the present invention first provides a method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem, and the technical solution adopted is as follows:

[0005] (1) Synthesis of magnetic nanomaterials (MN)

[0006] FeCl3·6H2O and FeCl2·4H2O were dissolved in ultrapure water to obtain a mixed solution, which was then deoxygenated under a nitrogen atmosphere. After deoxygenation, ammonia was added dropwise to adjust the pH of the solution, and the solution was stirred for a period of time. After the stirring was completed, the solution was naturally cooled to room temperature and aged with a black precipitate. After aging, the solution was filtered, washed, and dried to obtain a magnetic nanomaterial, which was recorded as MN.

[0007] (2) Synthesis of fluorescent materials (AuNCs solution)

[0008] HAuCl4 and reduced glutathione were mixed and stirred at a certain temperature. After the stirred mixed solution was cooled to room temperature, a fluorescent material solution was obtained, which was recorded as AuNCs solution and stored in the dark for future use.

[0009] (3) Preparation of MN@PEI@AuNCs composites

[0010] The magnetic nanomaterial (MN) prepared in step (1) is dissolved in ultrapure water to obtain a MN solution; the polyethyleneimine solution is added to the MN solution for mixing and incubation, and after incubation, the precipitate is collected by centrifugation, and then washed by centrifugation with ultrapure water. After washing, the precipitate is collected to obtain the MN@PEI composite material;

[0011] The MN@PEI composite material is then redissolved in ultrapure water to obtain an MN@PEI composite material aqueous solution, to which the AuNCs solution prepared in step (2) is added, mixed and incubated, and then washed by centrifugation with ultrapure water. After washing, the precipitate is collected to obtain the MN@PEI@AuNCs composite material;

[0012] (4) Synthesis of Ab-MN@PEI@AuNCs

[0013] The MN@PEI@AuNCs composite material prepared in step (3) is added to water to obtain a MN@PEI@AuNCs solution. Staphylococcus aureus antibody (Ab) is added to the MN@PEI@AuNCs solution. After mixed incubation, an Ab-MN@PEI@AuNCs solution is obtained, which is a quantitative detection sensor based on a magnetic fluorescent nanosystem.

[0014] Preferably, in step (1), the concentration of FeCl3•6H2O in the mixed solution is 0.2 mol / L, and the concentration of FeCl2•4H2O is 0.1 mol / L; wherein the molar ratio of FeCl3•6H2O to FeCl2•4H2O is 2:1;

[0015] The deoxygenation temperature is 80°C and the time is 25-30 minutes; the mass concentration of the ammonia water is 25%, and the pH value of the solution is adjusted to 10.0; the stirring time is 4 hours; the aging time of the black precipitate is 4 hours; the cleaning is performed by washing with ethanol and ultrapure water three times respectively; the drying temperature is 70°C and the drying time is 24 hours.

[0016] Preferably, in step (2), the concentration of HAuCl4 is 4 mmol / L, and the concentration of reduced glutathione is 6 mmol / L; the volume ratio of HAuCl4 to reduced glutathione is 1:1; the constant temperature is 90°C, the stirring time is 6 hours; and the temperature for storage in the dark is 4°C.

[0017] Preferably, in step (3), the mass concentration of the MN solution is 0.15%, the mass concentration of the polyethyleneimine solution is 0.5%; the volume ratio of the MN solution to the polyethyleneimine solution is 1:4; and the incubation time is 2 h.

[0018] Preferably, in step (3), the MN@PEI composite material is redissolved in ultrapure water at a ratio of 0.1-0.5 g:10 mL; the volume ratio of the MN@PEI composite material aqueous solution to the AuNCs solution is 1:1; and the incubation time is 2 h.

[0019] Preferably, in step (4), the dosage relationship of the MN@PEI@AuNCs solution and the Staphylococcus aureus antibody (Ab) is 1 mL:1 μg, wherein the concentration of the MN@PEI@AuNCs solution is 0.1-0.5 g / mL; and the mixing incubation time is 30 min.

[0020] The present invention also provides a use of a quantitative detection sensor based on a magnetic fluorescent nanosystem for quantitatively detecting Staphylococcus aureus, and the specific steps are as follows:

[0021] (1) Prepare Staphylococcus aureus standard solution:

[0022] Prepare Staphylococcus aureus standard bacterial solution with different concentration gradients;

[0023] (2) Obtaining fluorescence signals

[0024] The magnetic fluorescent nanostructured quantitative detection sensor was mixed with different concentrations of standard Staphylococcus aureus solutions, with each concentration corresponding to one quantitative detection sensor. After mixed incubation, the precipitate, designated MN@PEI@AuNCs@Ab@Staphylococcus, was collected and re-dissolved in PBS buffer to obtain a mixed solution. The fluorescence intensity of the mixed solution at different S. aureus concentrations was measured.

[0025] (3) Establishment of a fluorescence quantitative detection prediction model

[0026] A model is established using the fluorescence intensity of the Staphylococcus aureus standard solution described in step (1) and the corresponding fluorescence intensity in step (2) to obtain a fluorescence rapid detection prediction model for Staphylococcus aureus, which is denoted as F=f(x), where F is the fluorescence intensity and x is the logarithm of the Staphylococcus aureus concentration;

[0027] (4) Sample testing

[0028] The sample solution is mixed with a quantitative detection sensor based on a magnetic fluorescent nanosystem. After mixed incubation, the precipitate is collected and redissolved in PBS buffer to obtain a mixed solution. The fluorescence intensity of the mixed solution is measured and substituted into the model of step (3) to achieve quantitative detection of Staphylococcus aureus in the sample.

[0029] Preferably, in step (1), the concentration range of the Staphylococcus aureus standard bacterial solution is 1×10 -1 ~1×10 -9 .

[0030] Preferably, in step (2), the volume ratio of the Staphylococcus aureus standard bacterial solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:20; the mixed incubation time is 30 min; the volume ratio of the PBS buffer to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:1; the excitation wavelength selected for measuring the fluorescence intensity is 420 nm, and the emission wavelength range is 450-800 nm.

[0031] Preferably, in step (4), when the sample is solid, it needs to be processed into a liquid state; specifically, the solid sample is crushed and dissolved in physiological saline according to the dosage relationship of 1-5 g:10 mL to obtain a sample liquid;

[0032] The volume ratio of the sample solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:20; the mixed incubation time is 30 minutes; the volume ratio of the PBS buffer solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:1; the excitation wavelength selected for measuring the fluorescence intensity is 420 nm, and the emission wavelength range is 450~800 nm.

[0033] Effective results of the present invention:

[0034] (1) The quantitative detection sensor based on the magnetic fluorescent nanosystem constructed in the present invention can accurately detect Staphylococcus aureus, and the correlation coefficient of the fluorescence rapid detection prediction model can reach 0.9869.

[0035] (2) The present invention improves the sensitivity of Staphylococcus aureus and can detect single Staphylococcus aureus colonies with a detection limit of 4.7663×10 -11 CFU / mL (fluorescence).

[0036] (3) The sensor for quantitative detection of Staphylococcus aureus prepared by the present invention has simple pretreatment, easy detection process, fast detection speed and intuitively visible detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a linear relationship diagram between different concentrations of Staphylococcus aureus and the fluorescence intensity at 420 nm.

[0038] Figure 2 Figure 2 shows the fluorescence spectra of Ab-MN@PEI@AuNCs in the presence and absence of Staphylococcus aureus. The upper curve is the fluorescence spectrum of Ab-MN@PEI@AuNCs in the presence of Staphylococcus aureus, and the lower curve is the fluorescence spectrum of Ab-MN@PEI@AuNCs in the absence of Staphylococcus aureus.

[0039] Figure 3 This is the experimental result of the COF-based magnetic fluorescence nanosensor for the spiked recovery of Staphylococcus aureus in milk samples. Specific implementation plan

[0040] The present invention is described in detail below through various embodiments; however, these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0041] Chloroauric acid was purchased from Sigma-Aldrich, USA; the resistivity of ultrapure water was 18.2 MΩ; all chemical reagents used were of analytical grade and used without further purification.

[0042] The Staphylococcus aureus antibody (Ab) and reduced glutathione were purchased from Shanghai Sangon Biotechnology Co., Ltd. Example 1:

[0043] (1) Synthesis of magnetic nanomaterials (MN)

[0044] 0.02 mol of FeCl3·6H2O and 0.01 mol of FeCl2·4H2O were dissolved in 100 mL of ultrapure water, respectively. The mixture was deoxygenated at 80°C under a nitrogen atmosphere for 30 minutes, maintaining a molar ratio of 2:1. 25% ammonia was added dropwise to adjust the pH of the solution to 10.0, while stirring continuously throughout the reaction. After 4 hours, the mixture was cooled to room temperature and aged for another 4 hours to form a black precipitate. The precipitate was collected by filtration, washed three times with ethanol and ultrapure water, and dried at 70°C for 24 hours to obtain the synthesized magnetic nanomaterial, designated MN.

[0045] (2) Synthetic fluorescent materials (AuNCs)

[0046] Accurately pipette 20 mL of 4 mM HAuCl4 and 20 mL of 6 mM reduced glutathione, stir and heat at 90°C for 6 h, and cool the solution to room temperature to obtain the AuNCs solution, which is stored at 4°C in the dark for later use.

[0047] (3) Preparation of MN@PEI@AuNCs composites

[0048] The magnetic nanomaterial (MN) prepared in step (1) was dissolved in water to obtain an MN solution; 10 mL of the MN solution with a mass concentration of 0.15% was accurately pipetted, and 40 mL of the polyethyleneimine solution with a mass concentration of 0.5% was added thereto. After incubation for 2 h, the mixture was centrifuged and washed three times with ultrapure water to obtain an MN@PEI composite material; 0.5 g of the MN@PEI composite material was redissolved in 10 mL of ultrapure water, and 10 mL of the AuNCs solution was added thereto. After incubation for 2 h, the mixture was centrifuged and washed three times with ultrapure water to obtain an MN@PEI@AuNCs composite material.

[0049] (4) Synthesis of Ab-MN@PEI@AuNCs solution

[0050] The MN@PEI@AuNCs composite material was added to water to obtain a 0.5 g / mL MN@PEI@AuNCs solution; 1 mL of the MN@PEI@AuNCs solution was accurately pipetted, and 1 μg of Staphylococcus aureus antibody (Ab) was added thereto. After incubation for 30 minutes, the Ab-MN@PEI@AuNCs solution was obtained, which is a quantitative detection sensor based on the magnetic fluorescent nanosystem.

[0051] The quantitative detection sensor based on the magnetic fluorescent nanosystem is used to quantitatively detect Staphylococcus aureus, and the steps are as follows:

[0052] S1, prepare Staphylococcus aureus standard bacterial solution, the concentration is C1=10 -9 CFU / mL, C2=10 -8 CFU / mL, C3=10 -7 CFU / mL, C4=10 -6 CFU / mL, C5=10 -5 CFU / mL, C6=10 -4 CFU / mL, C7=10 -3 CFU / mL, C8=10 -2 CFU / mL, C9=10 - 1 CFU / mL, and the number of Staphylococcus aureus corresponding to the corresponding concentration of Staphylococcus aureus standard bacterial solution was determined by the traditional plate counting method.

[0053] S2. Obtaining fluorescence signals

[0054] The quantitative detection sensor based on the magnetic fluorescence nanosystem was mixed with standard Staphylococcus aureus solutions of different concentrations. One quantitative detection sensor was added dropwise for each concentration, and the two had a one-to-one correspondence. After incubation for 30 min, the precipitate, namely MN@PEI@AuNCs@Ab@Staphylococcus, was collected by magnetic adsorption and redissolved in 1 mL of PBS buffer. The fluorescence intensity of the buffer solution at different Staphylococcus aureus concentrations was measured using a fluorescence spectrophotometer. The excitation wavelength was 420 nm, and the emission wavelength range was set from 450 to 800 nm. The fluorescence intensities were recorded as F, which were F1=195.0687, F2=297.2948, F3=399.5209, F4=501.7470, F5=603.9731, F6=706.1992, F7=808.4253, F8=910.6514, and F9=1012.8775, respectively. The fluorescence intensity of the equal amount of MN@PEI@AuNCs@Ab solution that was not bound to S. aureus was measured, and the result F0 was recorded as the control group.

[0055] The present invention synthesizes a COF material with a fluorescent signal and adds AuNCs and MN on its surface to form a MN@PEI@AuNCs composite material. The COF-based fluorescence / electrochemical dual-modal nanosensor has a fluorescence emission peak at 420nm, and the logarithm of the fluorescence intensity at 420nm and the concentration of Staphylococcus aureus is within 10 -11 ~10 -1 There is a good linear correlation in the CFU / mL range, and the detection limit can reach 4.7663×10 -11 CFU / mL (fluorescence). Based on the experimental data, a fluorescence rapid detection prediction model and an electrochemical rapid detection model were established: the model was established using different concentrations of Staphylococcus aureus standard solutions and the corresponding fluorescence intensities, such as Figure 1 As shown in the figure, it is a linear relationship diagram between different concentrations of Staphylococcus aureus and the fluorescence intensity at 420nm. The fluorescence rapid detection prediction model of Staphylococcus aureus is F=y=102.2261x+1115.1036, and the correlation coefficient R 2 =0.9869, LOD is 4.7663×10 -11 CFU / mL nM, where F is the fluorescence intensity at 420 nm and x is the logarithm of the concentration of Staphylococcus aureus;

[0056] Figure 2 Figure 2 shows the fluorescence spectra of Ab-MN@PEI@AuNCs in the presence and absence of Staphylococcus aureus. The upper curve is the fluorescence spectrum of Ab-MN@PEI@AuNCs in the presence of Staphylococcus aureus, and the lower curve is the fluorescence spectrum of Ab-MN@PEI@AuNCs in the absence of Staphylococcus aureus.

[0057] S3. Specific sample testing, taking milk as an example:

[0058] (a) Take four samples, record them as S1, S2, S3, S4; add 100 μL of different concentrations (10 -7 , 10 -5 , 10 -3 , 10 -1 CFU / mL) of Staphylococcus aureus standard solution was prepared and stored in a 4°C refrigerator as sample test solutions Y1, Y2, Y3, and Y4.

[0059] (b) The milk samples were pretreated to make the concentration of Staphylococcus aureus in the samples 10 -8 CFU / mL, 10 -6 CFU / mL, 10 -4 CFU / mL, 10 -2CFU / mL. After that, the milk sample was filtered through a 0.22μm filter membrane and the filtrate was collected. Then, the operation of step S2 was followed, except that the filtrate was replaced with the standard solution of Staphylococcus aureus of different concentrations and added dropwise to the quantitative detection sensor. After the addition, the fluorescence intensity was measured and substituted into the constructed equation to detect Staphylococcus aureus in the milk sample. Each sample was measured three times and the average value was taken to achieve visual detection of Staphylococcus aureus in the test object. The specific results are shown in Figure 3 , Figure 3 This is the experimental result of the COF-based magnetic fluorescence nanosensor for the spiked recovery of Staphylococcus aureus in milk samples.

[0060] The results showed that the S. aureus concentration in the samples calculated using the fluorescence intensity regression equation was not significantly different from that determined by the traditional method. The recoveries ranged from 49.92% to 106.19%, with an RSD less than 5%, demonstrating that the sensor has good accuracy, stability, and feasibility for detecting S. aureus in milk samples. In summary, the magnetic fluorescence nanosystem-based quantitative detection sensor can be used for the accurate and rapid detection of S. aureus in milk.

[0061] The Ab-MN@PEI@AuNCs composite material prepared by the present invention has a fluorescent response to Staphylococcus aureus. Figure 3 The results show that, when combined with microfluidic technology, it can realize the detection of single Staphylococcus aureus with accurate results; and by comparing the test results with the control group, it can weaken the false positive or false negative results caused by external interference, further improving the accuracy and reliability of Staphylococcus aureus detection.

[0062] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although this specification has described the present invention in detail with reference to the above embodiments, it should be understood by those skilled in the art that the present invention may still be modified or replaced by equivalents. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem, characterized in that: Here are the steps: (1) Synthesis of magnetic nanomaterials; FeCl3·6H2O and FeCl2·4H2O were dissolved in ultrapure water to obtain a mixed solution, which was then deoxygenated under a nitrogen atmosphere. After deoxygenation, ammonia water was added dropwise to adjust the pH of the solution, and the solution was stirred for 4 hours. After stirring, the solution was naturally cooled to room temperature and aged with a black precipitate. After aging, the solution was filtered, washed, and dried to obtain a magnetic nanomaterial, which was recorded as MN. (2) Synthetic fluorescent materials; HAuCl4 and reduced glutathione were mixed and stirred at 90°C. The mixed solution was cooled to room temperature to obtain a fluorescent material solution, which was recorded as AuNCs solution and stored in the dark for future use. (3) Preparation of MN@PEI@AuNCs composites; The magnetic nanomaterial prepared in step (1) is dissolved in ultrapure water to obtain an MN solution; the MN solution is taken, and a polyethyleneimine solution is added thereto for mixing and incubation, and after incubation, a precipitate is collected by centrifugation, and then washed by centrifugation with ultrapure water, and the precipitate is collected after washing to obtain an MN@PEI composite material; the mass concentration of the MN solution is 0.15%, and the mass concentration of the polyethyleneimine solution is 0.5%; and the volume ratio of the MN solution to the polyethyleneimine solution is 1:4; The MN@PEI composite material is then redissolved in ultrapure water to obtain an MN@PEI composite material aqueous solution, to which the AuNCs solution prepared in step (2) is added, mixed and incubated, and then washed by centrifugation with ultrapure water. After washing, the precipitate is collected to obtain the MN@PEI@AuNCs composite material; the amount ratio of the MN@PEI composite material redissolved in ultrapure water is 0.1-0.5 g: 10 mL; the volume ratio of the MN@PEI composite material aqueous solution to the AuNCs solution is 1:1; (4) The MN@PEI@AuNCs composite material prepared in step (3) is added to water to obtain a MN@PEI@AuNCs solution. The MN@PEI@AuNCs solution is taken, and Staphylococcus aureus antibody Ab is added thereto. After mixed incubation, the Ab-MN@PEI@AuNCs solution is obtained, which is a quantitative detection sensor based on a magnetic fluorescent nanosystem; wherein the dosage relationship of the MN@PEI@AuNCs solution and the Staphylococcus aureus antibody is 1 mL: 1 μg, and the concentration of the MN@PEI@AuNCs solution is 0.1-0.5 g / mL.

2. The method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem according to claim 1, characterized in that: In step (1), the concentration of FeCl3•6H2O in the mixed solution is 0.2 mol / L, and the concentration of FeCl2•4H2O is 0.1 mol / L; wherein the molar ratio of FeCl3•6H2O to FeCl2•4H2O is 2:1; The deoxygenation treatment temperature is 80°C and the time is 25-30 minutes; the mass concentration of the ammonia water is 25%, and the pH value of the solution is adjusted to 10.0; the black precipitate aging time is 4 hours; the cleaning is washed three times with ethanol and ultrapure water respectively; the drying temperature is 70°C and the drying time is 24 hours.

3. The method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem according to claim 1, characterized in that: In step (2), the concentration of HAuCl4 is 4 mmol / L, and the concentration of reduced glutathione is 6 mmol / L; the volume ratio of HAuCl4 to reduced glutathione is 1:1; the stirring time is 6 h; and the temperature for storage in the dark is 4°C.

4. The method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem according to claim 1, wherein: In step (3), the incubation time is 2 h.

5. The method for preparing a quantitative detection sensor based on a magnetic fluorescent nanosystem according to claim 1, wherein: In step (4), the mixed incubation time is 30 min.

6. Use of a quantitative detection sensor based on a magnetic fluorescent nanosystem prepared according to any one of claims 1 to 5 for quantitative detection of Staphylococcus aureus, characterized in that: Here are the steps: (1) Prepare Staphylococcus aureus standard solution: Prepare Staphylococcus aureus standard bacterial solution with different concentration gradients; (2) Obtaining fluorescence signals The magnetic fluorescent nanostructured quantitative detection sensor was mixed with different concentrations of standard Staphylococcus aureus solutions, with each concentration corresponding to one quantitative detection sensor. After mixed incubation, the precipitate, designated MN@PEI@AuNCs@Ab@Staphylococcus, was collected and re-dissolved in PBS buffer to obtain a mixed solution. The fluorescence intensity of the mixed solution at different S. aureus concentrations was measured. (3) Establishment of a fluorescence quantitative detection prediction model A model is established using the fluorescence intensity of the Staphylococcus aureus standard solution described in step (1) and the corresponding fluorescence intensity in step (2) to obtain a fluorescence rapid detection prediction model for Staphylococcus aureus, which is denoted as F=f(x), where F is the fluorescence intensity and x is the logarithm of the Staphylococcus aureus concentration; (4) Sample testing The sample solution is mixed with a quantitative detection sensor based on a magnetic fluorescent nanosystem. After mixed incubation, the precipitate is collected and redissolved in PBS buffer to obtain a mixed solution. The fluorescence intensity of the mixed solution is measured and substituted into the model of step (3) to achieve quantitative detection of Staphylococcus aureus in the sample.

7. The use according to claim 6, characterized in that In step (1), the concentration range of the Staphylococcus aureus standard bacterial solution is 1×10 -1 ~1×10 -9 .

8. The use according to claim 6, characterized in that In step (2), the volume ratio of the Staphylococcus aureus standard bacterial solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:20; the mixed incubation time is 30 minutes; the volume ratio of the PBS buffer solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:1; The excitation wavelength used to measure the fluorescence intensity was 420 nm, and the emission wavelength range was 450–800 nm.

9. The use according to claim 6, characterized in that In step (4), when the sample is solid, it needs to be processed into a liquid state; specifically, the solid sample is crushed and dissolved in physiological saline according to the dosage relationship of 1-5g:10mL to obtain a sample liquid; The volume ratio of the sample solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:20; the mixing and incubation time is 30 minutes; the volume ratio of the PBS buffer solution to the quantitative detection sensor based on the magnetic fluorescent nanosystem is 1:1; The excitation wavelength used to measure the fluorescence intensity was 420 nm, and the emission wavelength range was 450–800 nm.

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