Preparation method and application of magnetic relaxation switch biosensor for detecting food-borne pathogenic bacteria based on photolysis hydrogel

Abstract

The invention discloses a preparation method and application of a magnetic relaxation switch biosensor for detecting food-borne pathogenic bacteria based on photolysis hydrogel. The preparation method is characterized by comprising the following steps: (1) preparing a signal unit LAP-MXene (at) AuNPs-ssDNA; 2) preparing a gun head sensing interface; 3) preparing a test solution; (4) detecting food-borne pathogenic bacteria; determining the intensity of corresponding low-field nuclear magnetic resonance signals T2 under the condition of different concentrations of target food-borne pathogenic bacteria by adopting a low-field nuclear magnetic resonance instrument, establishing a quantitative relationship between the concentration of the food-borne pathogenic bacteria and a T2 signal change value (delta T2), and determining the concentration of the food-borne pathogenic bacteria in an unknown sample according to the quantitative relationship; the method has the advantages of high precision and high convenience.

Description

Technical Field

[0001] The present invention relates to a method for detecting foodborne pathogenic bacteria, and in particular to a preparation method and application of a magnetic relaxation switch biosensor for detecting foodborne pathogenic bacteria based on photo-cleavable hydrogel. Background Art

[0002] Pathogenic bacteria are a major problem in food safety, and the sensitive, accurate and rapid detection of pathogenic bacteria has important public health significance. In addition to the conventional plate counting method, many new methods have emerged: spectral methods such as colorimetry, fluorescence and surface enhanced Raman scattering; electrochemical methods such as electrochemistry, electrochemiluminescence and photoelectrochemistry; mass spectrometry, etc. Although the above methods show good performance in terms of sensitivity, specificity and accuracy, tedious sample pretreatment is usually required to eliminate signal interference from complex sample matrices. In contrast, magnetic materials rarely appear in sample matrices, so magnetochemical methods have unique advantages in anti-interference and no need for sample pretreatment.

[0003] Magnetic relaxation switch (MRS) sensors use low-field nuclear magnetic resonance analysis instruments to output signals and quantitatively detect targets through relaxation analysis of water protons. They are widely used in the detection of biomacromolecules, pesticide residues, veterinary drug residues, and pathogenic bacteria. At present, most reported MRS sensors detect targets through the indirect effect of magnetic nanoparticles on the proton state. However, since magnetic nanoparticles may have problems such as heterogeneous dispersion and easy aggregation, the stability and repeatability of the detection results are affected. The detection precision can be greatly improved by detecting the change of water proton state in a homogeneous system. Recently, there has been a biosensing strategy that uses the target-mediated sol-gel transition of hydrogel to directly regulate the relaxation behavior of water molecules and output the signal T2. This inspired us to use the phase transition between hydrogel and sol to construct a homogeneous MRS sensor for high-precision detection of pathogens.

[0004] The present invention uses a pipette tip as a biorecognition container. In the presence of a target, a signal unit LAP-MXene@AuNPs-ssDNA loaded with a large amount of acyl lithium hypophosphite LAP falls from the inner surface of the pipette tip and is injected into the detection liquid. LAP induces the disulfide bond breakage of the hydrogel matrix in the detection liquid under ultraviolet light irradiation, causing the gel to change into a sol state. By detecting the change in relaxation time caused by the change in the gel-sol state, the detection of foodborne pathogens can be achieved. The present invention places the biorecognition reaction process in the pipette tip, simplifies the operation steps, reduces the inevitable operation errors in the process of multiple sample transfers, and can easily achieve high-throughput biorecognition. In addition, the phase transition of the photocontrolled hydrogel is used as the signal output, which is not only separated from the biorecognition process, but also successfully avoids the heterogeneous problem caused by the use of magnetic materials that are easy to self-aggregate in the conventional MRS method, effectively improving the precision of the detection. At present, there is no public research report on the preparation method and application of magnetic relaxation switch biosensors for detecting foodborne pathogens based on photo-cleaved hydrogels at home and abroad. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method and application of a magnetic relaxation switch biosensor for detecting foodborne pathogens based on photo-cleavable hydrogel with high precision and convenient operation.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a preparation method and application of a magnetic relaxation switch biosensor for detecting foodborne pathogens based on photo-cleavable hydrogels. The method is not for the purpose of diagnosis or treatment and comprises the following steps:

[0007] (1) Preparation of signal unit LAP-MXene@AuNPs-ssDNA

[0008] a. Slowly add 40-120 μL 0.1 mol / L HAuCl4 solution into 2-12 mL 1 mg / mL MXene dispersion, stir for 40 min in the dark, centrifuge at 5000-6000 × g, and redisperse in 2-12 mL water to obtain MXene@AuNPs dispersion.

[0009] b. Add 2-8 mg of phenyl (2,4,6-trimethylbenzoyl) lithium phosphate LAP to the MXene@AuNPs dispersion and shake it at room temperature for 4 h. LAP is bound to MXene by electrostatic adsorption to obtain LAP-MXene@AuNPs. Wash it by centrifugation several times and redisperse it in 2-8 mL of water.

[0010] c. Continue to add 0.5-3 mL of 1OD ssDNA dispersion and stir at room temperature for 5 h. The ssDNA is bound to LAP-MXene@AuNPs through the Au-S bond. After centrifugation and washing several times, it is dispersed in 2-8 mL of water to obtain the signal unit LAP-MXene@AuNPs-ssDNA dispersion.

[0011] (2) Preparation of the gun tip sensing interface

[0012] a. Use a pipette tip to absorb the grafting solution and place it under ultraviolet light to obtain a pipette tip with a carboxylated inner surface.

[0013] b. Activate the carboxyl group in the pipette tip and modify the aptamer Apt, and then connect LAP-MXene@AuNPs-ssDNA to prepare the pipette tip sensing interface.

[0014] (3) Preparation of test solution

[0015] Add four-arm thiol-terminated polyethylene glycol 4ARM-PEG-SH solution, hydrogen peroxide H2O2 solution and sodium iodide NaI solution into a 1.5 mL sample bottle and react at room temperature for 35 minutes to obtain a test solution.

[0016] (4) Detection of foodborne pathogens

[0017] a. The sample to be tested is sucked into the functionalized pipette tip and incubated at room temperature. Then the solution in the pipette tip is injected into the test solution and T2 is measured after UV irradiation.

[0018] b. T2 was measured at 35°C with the following parameters: main frequency 19.00MHz, sampling frequency 100kHz, RF delay 0.5ms, waiting time 5000ms, echo time 1.0ms, number of echoes 18000, accumulation times 2, digital gain 3, analog gain 15.0dB. The value of ΔT2 was calculated by the following formula: ΔT2 = T2(positive) – T2(negative). Among them, T2(negative) is the average T2 when there is no foodborne pathogen, and T2(positive) is the average T2 when there is a target foodborne pathogen.

[0019] Furthermore, the specific process of step (2) a is as follows: add 150-250 mg of benzophenone BP and 3-7 mL of acrylic acid AA to 4-8 mL of water, and shake well to obtain a grafting solution. Use a polypropylene pipette tip to absorb 0.5 mL of the grafting solution, wipe off the residual liquid on the outer surface, and place it under a UV lamp (365 nm, 20 W) for 30 minutes. Then drain the solution, absorb enough methanol, and then ultrasonically wash for 30 minutes to remove excess substances. Dry at 60°C to obtain a pipette tip with a carboxylated inner surface.

[0020] Further, the specific process of step (2) b is as follows: 6-18 mg 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride EDC and 4-10 mg N-hydroxysuccinimide NHS are dissolved in 5 mL of water, and the pH is adjusted to 5.0 with 0.01 mol / L hydrochloric acid HCl. 0.5 mL of the above solution is drawn using a carboxylated gun tip, and incubated at room temperature for 2-4 hours to activate the carboxyl group. The liquid is then discharged and washed with water, and 0.5 mL of 0.5 μM aptamer Apt is drawn in, and incubated at room temperature for 2 hours to allow the 5′-terminal amino group of Apt to undergo a coupling reaction with the activated carboxyl group on the inner surface of the gun tip. The liquid is discharged, and 0.5 mL of 2 wt% bovine serum albumin BSA solution is drawn in at 37° C. to block nonspecific binding sites for 0.5-2 hours, and washed with water three times. Finally, 0.5 mL of LAP-MXene@AuNPs-ssDNA dispersion was inhaled and reacted at room temperature for 1 to 3 h. Apt and ssDNA fixed the signal unit on the inner surface of the gun tip through hybridization to obtain the gun tip sensing interface.

[0021] Furthermore, the specific process of step (3) is as follows: add 0.5mL of 1wt% four-arm thiol-terminated polyethylene glycol 4ARM-PEG-SH solution, 0.01mL of 0.5mol / L hydrogen peroxide H2O2 solution and 0.01mL of 1mol / L sodium iodide NaI solution into a 1.5mL sample bottle, react at room temperature for 35min, and obtain a test solution.

[0022] Furthermore, the specific process of step (4) a is as follows: 0.5 mL of the sample to be tested is sucked into the functionalized gun tip, incubated at room temperature for 30 to 60 min to allow Apt to fully capture the target, the solution in the gun tip is injected into the test solution, reacted under ultraviolet light for 10 min, and then T2 measurement is performed.

[0023] Furthermore, the foodborne pathogenic bacteria are selected from Vibrio parahaemolyticus, Vibrio vulnificus, Staphylococcus aureus, Escherichia coli and Salmonella.

[0024] Principle of the invention: The detection principle of the present invention is as follows Figure 1As shown, taking Vibrio parahaemolyticus VP as an example. The signal unit LAP-MXene@AuNPs-ssDNA uses MXene as a carrier, and a large amount of LAP and AuNPs are loaded on its surface, and a large amount of ssDNA is modified on AuNPs through Au-S bonds. The aptamer Apt of VP is modified on the inner surface of the gun tip, which hybridizes with the ssDNA on the signal unit, fixes the signal unit on the inner surface of the gun tip, and obtains the gun tip sensing interface. When the solution containing the target VP is sucked into the gun tip, the Apt on the inner surface of the gun tip specifically binds to VP, releasing the signal unit into the solution in the gun tip, and the solution is then injected into the test liquid in the gel state. Under 365nm ultraviolet light irradiation, the LAP on the signal unit is cleaved to form free radicals, attacking the disulfide bonds in the gel, breaking the disulfide bonds, and the released thiol radicals can also react with the disulfide bonds and break them, accelerating the gel-sol phase transition process, and the original three-dimensional gel structure is quickly broken and transformed into a sol form. In this gel-sol phase transition, water molecules change from being bound by the gel structure to being free. The increase in the degree of freedom of water molecules makes their hydrogen protons more affected by the external magnetic field, that is, the nuclear magnetic resonance response level increases, resulting in an increase in T2. ​​In this system, the greater the concentration of VP, the more Apt is bound, and the more signal units and LAP are exchanged, making the degree of gel-sol transition greater and ΔT2 greater. Based on this, a quantitative detection relationship between ΔT2 and the concentration of target VP can be established.

[0025] Compared with the prior art, the advantages of the present invention are: the present method places the biorecognition reaction process in the gun tip, simplifies the operation steps, reduces the inevitable operation errors in the process of multiple sample transfers, and can easily achieve high-throughput biorecognition. In addition, the use of the phase transition of the light-controlled hydrogel as the signal output is not only separated from the biorecognition process, but also successfully avoids the heterogeneous problem caused by the use of magnetic materials that are prone to self-aggregation in conventional MRS methods, effectively improving the precision of the detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the principle of the magnetic relaxation switch biosensor of the present invention for detecting foodborne pathogens;

[0027] Figure 2 This is an electron microscope image of the gel state of the present invention;

[0028] Figure 3 It is an electron microscope image of the sol state of the present invention;

[0029] Figure 4 This is the linear relationship diagram of the magnetic relaxation switch biosensor detecting different Vibrio parahaemolyticus concentrations;

[0030] Figure 5Plot of sensor selectivity and specificity for the magnetic relaxation switch biosensor detecting different bacterial species at the same concentration. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings. 1. Specific embodiments

[0033] Preparation method and application of magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel, this method is not for diagnosis or treatment purposes, such as Figure 1 As shown, the following steps are included:

[0034] (1) Preparation of signal unit LAP-MXene@AuNPs-ssDNA

[0035] a. Slowly add 65 μL of 0.1 mol / L HAuCl4 solution into 5 mL of 1 mg / mL MXene dispersion, stir in the dark for 40 min, centrifuge at 5629 × g, and redisperse in 5 mL of water to obtain MXene@AuNPs dispersion.

[0036] b. Add 5 mg of phenyl (2,4,6-trimethylbenzoyl) lithium phosphate LAP to the MXene@AuNPs dispersion and shake it at room temperature for 4 h. LAP is bound to MXene by electrostatic adsorption to obtain LAP-MXene@AuNPs. Wash it by centrifugation several times and redisperse it in 5 mL of water.

[0037] c. Continue to add 1mL 1OD ssDNA dispersion and stir at room temperature for 5h. The ssDNA is bound to LAP-MXene@AuNPs through Au-S bonds. After centrifugation and washing several times, it is dispersed in 5mL of water to obtain the signal unit LAP-MXene@AuNPs-ssDNA dispersion.

[0038] (2) Preparation of the gun tip sensing interface

[0039] a. Use a pipette tip to absorb the grafting solution, place it under a UV lamp for irradiation, and obtain a pipette tip with a carboxylated inner surface. The specific process is as follows: Add 182 mg of benzophenone BP and 4.8 mL of acrylic acid AA to 5.2 mL of water, and shake well to obtain a grafting solution. Use a polypropylene pipette tip to absorb 0.5 mL of the grafting solution, wipe off the residual liquid on the outer surface, and place it under a UV lamp (365 nm, 20 W) for irradiation for 30 minutes. Then drain the solution, absorb enough methanol, and then ultrasonically wash it for 30 minutes to remove excess substances. Dry at 60°C to obtain a pipette tip with a carboxylated inner surface.

[0040] b. Activate the carboxyl group in the pipette tip and modify the aptamer Apt, and then connect LAP-MXene@AuNPs-ssDNA to prepare the tip sensing interface. The specific process is as follows: Dissolve 12mg 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride EDC and 7mg N-hydroxysuccinimide NHS in 5mL water, and adjust pH to 5.0 with 0.01mol / L hydrochloric acid HCl. Use a carboxylated tip to absorb 0.5mL of the above solution and incubate at room temperature for 2h to activate the carboxyl group. Then drain the liquid and wash with water, inhale 0.5mL 0.5μM aptamer Apt, and incubate at room temperature for 2h to allow the 5′ terminal amino group of Apt and the activated carboxyl group on the inner surface of the tip to undergo a coupling reaction. Drain the liquid, inhale 0.5mL 2wt% bovine serum albumin BSA solution at 37°C to block nonspecific binding sites for 1h, and wash with water three times. Finally, 0.5 mL of LAP-MXene@AuNPs-ssDNA dispersion was inhaled and reacted at room temperature for 2 h. Apt and ssDNA fixed the signal unit on the inner surface of the gun tip through hybridization to obtain the gun tip sensing interface.

[0041] (3) Preparation of test solution

[0042] Add 0.5 mL of 1 wt% four-arm thiol-terminated polyethylene glycol 4ARM-PEG-SH solution, 0.01 mL of 0.5 mol / L hydrogen peroxide H2O2 solution and 0.01 mL of 1 mol / L sodium iodide NaI solution into a 1.5 mL sample bottle and react at room temperature for 35 min to obtain a test solution.

[0043] (4) Detection of foodborne pathogens

[0044] a. Pipette 0.5 mL of the sample to be tested into the functionalized pipette tip and incubate at room temperature for 30 min to allow Apt to fully capture the target. Inject the solution in the pipette tip into the test solution, react under ultraviolet light for 10 min, and then measure T2.

[0045] b. T2 was measured at 35°C with the following parameters: main frequency 19.00MHz, sampling frequency 100kHz, RF delay 0.5ms, waiting time 5000ms, echo time 1.0ms, number of echoes 18000, accumulation times 2, digital gain 3, analog gain 15.0dB. The value of ΔT2 is calculated by the following formula: ΔT2=T2(positive)–T2(negative). Among them, T2(positive) is the average T2 without VP, and T2(positive) is the average T2 with VP.

[0046] The above-mentioned foodborne pathogenic bacteria are selected from Vibrio parahaemolyticus, Vibrio vulnificus, Staphylococcus aureus, Escherichia coli and Salmonella.

[0047] 2. Experimental Results Analysis

[0048] 1. Gel system analysis

[0049] The LF-NMR test solution is in a gel state without the target object to be detected. Figure 2 As shown in Figure 2, in the gel state, the three-dimensional network structure of the hydrogel can be observed on the surface of the precursor. When the dispersion output from the tip sensing interface after VP incubation is added to the LF-NMR test solution, the gel is transformed into a sol state, as shown in Figure 2. Figure 3 As shown, this indicates that LAP-MXene@AuNPs-ssDNA as the signal unit can effectively cleave the hydrogel under light, thereby directly affecting the T2 of the system and achieving effective sensing.

[0050] 2. Sensitivity analysis

[0051] The detection performance of the magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel prepared in Example 1 for VP was shown in Table 1. As the VP concentration increased from 1.0×10 2 to 1.0×10 8 As CFU / mL increases, the lateral relaxation decay rate slows down and T2(positive) increases. Therefore, when T2(negative) remains unchanged, ΔT2 increases with the increase of VP concentration, such as Figure 4 As shown, at 1.0×10 2 CFU / mL~1.0×10 8 In the CFU / mL range, the logarithm of ΔT2(y,ms) and VP concentration (x,CFU / mL) showed a good linear relationship, and the linear regression equation was y=-70.1+90.4lgx, R 2 = 0.997. Considering that the noise is 15 ms and the VP concentration is 1.0×10 1 The ΔT2 of the sample with CFU / mL was 39 ms. Based on the signal-to-noise ratio S / N=3, the detection limit (LOD) can be estimated to be 1.0×10 1 CFU / mL has good sensitivity.

[0052] 3. Selectivity analysis

[0053] 1.0×10 4 CFU / mL of VP, LM, SA, VV, EC, SM standard solutions, blank samples, and mixed samples (containing 1.0×10 4 CFU / mL of SA, EC, VV, LM, SM and VP) were used to investigate the selectivity of the sensor. The results are shown in Figure 5 1.0×10 4The ΔT2 of LM, SA, VV, EC, and SM samples with CFU / mL was similar to that of blank samples, while that of mixed samples with 1.0×10 4 The ΔT2 generated by the CFU / mL VP standard solution was almost the same, indicating that the sensor had good selectivity and specificity, which was attributed to the specific recognition ability of Apt on the signal unit for VP.

[0054] 4. Accuracy analysis

[0055] The spiked recovery test was performed on seawater samples and oyster samples. As shown in Table 1, the recovery rate of seawater samples was 97.4% to 105.8%, and the RSD was 3.3% to 4.8%. The recovery rate of oyster samples was 98.3% to 101.3%, and the RSD was 2.9% to 5.6%. The inter-group t test was performed with the plate count test results. The t values ​​of seawater and oyster samples were 0.68 and 0.55, respectively, which were less than t 0.05,4 =2.78, which indicates that there is no significant difference between the two methods. In summary, this method has good precision and accuracy and can be used to reliably detect actual samples.

[0056] Table 1 Detection of VP in seawater and oyster samples ( n=5)

[0057]

[0058] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by a person skilled in the art within the spirit and scope of the present invention shall also fall within the protection scope of the present invention.

Claims

1. Preparation method and application of magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel, characterized in that The following steps are involved: (1) Preparation of signal unit LAP-MXene@AuNPs-ssDNA a. Slowly add 40-120 μL 0.1 mol / L HAuCl4 solution into 2-12 mL 1 mg / mL MXene dispersion, stir for 40 min in the dark, centrifuge at 5000-6000 × g, and redisperse in 2-12 mL water to obtain MXene@AuNPs dispersion. b. Add 2-8 mg of phenyl (2,4,6-trimethylbenzoyl) lithium phosphate LAP to the MXene@AuNPs dispersion and shake it at room temperature for 4 h. LAP is bound to MXene by electrostatic adsorption to obtain LAP-MXene@AuNPs. Wash it by centrifugation several times and redisperse it in 2-8 mL of water. c. Continue to add 0.5-3 mL of 1OD ssDNA dispersion and stir at room temperature for 5 h. The ssDNA is bound to LAP-MXene@AuNPs through the Au-S bond. After centrifugation and washing several times, it is dispersed in 2-8 mL of water to obtain the signal unit LAP-MXene@AuNPs-ssDNA dispersion. (2) Preparation of the gun tip sensing interface a. Use a pipette tip to absorb the grafting solution and place it under ultraviolet light to obtain a pipette tip with a carboxylated inner surface. b. Activate the carboxyl group in the pipette tip and modify the aptamer Apt, and then connect LAP-MXene@AuNPs-ssDNA to prepare the pipette tip sensing interface. (3) Preparation of test solution Add four-arm thiol-terminated polyethylene glycol 4ARM-PEG-SH solution, hydrogen peroxide H2O2 solution and sodium iodide NaI solution into a 1.5 mL sample bottle and react at room temperature for 35 minutes to obtain a test solution. (4) Detection of foodborne pathogens a. The sample to be tested is sucked into the functionalized pipette tip and incubated at room temperature. Then the solution in the pipette tip is injected into the test solution and T2 is measured after UV irradiation. b. T2 was measured at 35°C with the following parameters: main frequency 19.00MHz, sampling frequency 100kHz, RF delay 0.5ms, waiting time 5000ms, echo time 1.0ms, number of echoes 18000, accumulation times 2, digital gain 3, analog gain 15.0dB. The value of ΔT2 is calculated by the following formula: ΔT2=T2(positive)–T2(negative). Among them, T2(negative) is the average T2 without VP, and T2(positive) is the average T2 with VP.

2. The preparation method and application of the magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel according to claim 1, wherein the method is not for the purpose of diagnosis or treatment, and is characterized in that The specific process of step (2) a is as follows: add 150-250 mg of benzophenone BP and 3-7 mL of acrylic acid AA to 4-8 mL of water, and shake well to obtain a grafting solution. Use a polypropylene pipette tip to absorb 0.5 mL of the grafting solution, wipe off the residual liquid on the outer surface, and place it under a UV lamp (365 nm, 20 W) for 30 minutes. Then drain the solution, absorb enough methanol, and then ultrasonically wash for 30 minutes to remove excess substances. Dry at 60°C to obtain a pipette tip with a carboxylated inner surface.

3. The preparation method and application of the magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel according to claim 1, wherein the method is not for the purpose of diagnosis or treatment, and is characterized in that The specific process of step (2) b is as follows: 6-18 mg 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride EDC and 4-10 mg N-hydroxysuccinimide NHS are dissolved in 5 mL of water, and the pH is adjusted to 5.0 with 0.01 mol / L hydrochloric acid HCl. 0.5 mL of the above solution is sucked using a carboxylated gun tip, and incubated at room temperature for 2-4 hours to activate the carboxyl group. The liquid is then discharged and washed with water, and 0.5 mL of 0.5 μM aptamer Apt is sucked in, and incubated at room temperature for 2 hours to allow the 5′ terminal amino group of Apt and the activated carboxyl group on the inner surface of the gun tip to undergo a coupling reaction. The liquid is discharged, and 0.5 mL of 2 wt% bovine serum albumin BSA solution is sucked in at 37° C. to block nonspecific binding sites for 0.5-2 hours, and washed with water three times. Finally, 0.5 mL of LAP-MXene@AuNPs-ssDNA dispersion was inhaled and reacted at room temperature for 1 to 3 h. Apt and ssDNA fixed the signal unit on the inner surface of the gun tip through hybridization to obtain the gun tip sensing interface.

4. The preparation method and application of the magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel according to claim 1, wherein the method is not for the purpose of diagnosis or treatment, and is characterized in that The specific process of step (3) is as follows: add 0.5 mL of 1 wt% four-arm thiol-terminated polyethylene glycol 4ARM-PEG-SH solution, 0.01 mL of 0.5 mol / L hydrogen peroxide H2O2 solution and 0.01 mL of 1 mol / L sodium iodide NaI solution into a 1.5 mL sample bottle, react at room temperature for 35 min, and obtain a test solution.

5. The preparation method and application of the magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogel according to claim 1, wherein the method is not for the purpose of diagnosis or treatment, and is characterized in that The specific process of step (4) a is as follows: 0.5 mL of the sample to be tested is sucked into the functionalized gun tip, incubated at room temperature for 30 to 60 min to allow Apt to fully capture the target, the solution in the gun tip is injected into the test solution, reacted under ultraviolet light for 10 min, and then T2 measurement is performed.

6. A method for preparing a magnetic relaxation switch biosensor for detecting foodborne pathogens based on photocleavable hydrogels obtained by the preparation method of any one of claims 1 to 5 and its application, wherein the method is not for the purpose of diagnosis or treatment, and is characterized in that: The foodborne pathogenic bacteria are selected from Vibrio parahaemolyticus, Vibrio vulnificus, Staphylococcus aureus, Escherichia coli and Salmonella.

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