A Raman sensing analysis method for enterotoxin C based on Au-Ag Janus@Au NPs

Abstract

The present invention provides an enterotoxin C Raman sensing analysis method based on Au-Ag Janus@Au NPs, belonging to the technical field of Raman spectroscopy analysis. The present invention first synthesizes Au-Ag Janus NPs by guiding the directional growth of Ag islands on Au cores through 2-mercaptobenzimidazole-5-carboxylic acid (MBIA), and the ligand MBIA also acts as a Raman beacon molecule. By regulating the pH, an Au layer is grown on the surface of Au-Ag Janus NPs to obtain Au-Ag Janus@Au NPs, which have a stronger and more stable SERS signal. With MBIA 1278cm ‑1 Using the SERS signal at the site as the detection signal, a Raman sensor for detecting enterotoxin C was designed. The Raman sensor has the advantages of good sensitivity, high accuracy, strong stability and strong anti-interference ability.

Description

Technical Field

[0001] The invention belongs to the technical field of Raman spectroscopy analysis, and in particular refers to an enterotoxin C Raman sensing analysis method based on Au-Ag Janus@AuNPs. Background Art

[0002] Enterotoxin C is the full name of Staphylococcus aureus enterotoxin C. It is a highly toxic foodborne pathogen that can still maintain a certain activity under high temperature and acid-base environment. It is widely present in common foods such as meat products and dairy products, causing food poisoning and seriously threatening human health. Therefore, it is of great significance to establish an accurate and sensitive detection method for enterotoxin C.

[0003] Traditional methods for detecting enterotoxin C include liquid chromatography, fluorescent immunoassay, polymerase chain reaction, electrochemical analysis, etc. However, these detection methods have certain limitations, such as expensive instruments, complex operations, high detection costs, long detection time, and high pretreatment requirements. Surface-enhanced Raman scattering technology has the advantages of high detection sensitivity, strong selectivity, and simple operation. Therefore, it is particularly important to construct an enterotoxin C detection method based on surface-enhanced Raman scattering. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an enterotoxin C Raman sensing analysis method based on Au-Ag Janus@AuNPs.

[0005] The object of the present invention is to provide an enterotoxin C Raman sensing analysis method based on Au-Ag Janus@AuNPs, comprising the following steps:

[0006] (1) After incubating Au-Ag Janus@AuNPs with the enterotoxin C aptamer SEC-Apt for 10-13 h, the solid-liquid separation was performed to obtain the solid phase and the solid phase was redispersed in water to obtain the Au-Ag Janus@Au NPs / SEC-Apt solution;

[0007] (2) incubating the Au-Ag Janus@Au NPs / SEC-Apt solution obtained in step (1) with NiCo-MOF / Fe3O4 NSs for 10-13 h to obtain Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4 NSs assembly;

[0008] (3) The Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4 NSs assembly obtained in step (2) is mixed with an enterotoxin C standard solution in a Tris-HCl solution, and after the reaction, the SERS signal is detected by magnetic separation to achieve qualitative or quantitative analysis of enterotoxin C.

[0009] In one embodiment of the present invention, the preparation method of Au-Ag Janus@Au NPs in step (1) is as follows:

[0010] S1, after incubating the AuNPs solution with 2-mercaptobenzimidazole-5-carboxylic acid at 50-70°C, 10 mM hydroquinone and 1 mM silver nitrate solution were added in sequence, and the reaction was allowed to stand for 2-6 h to obtain Au-Ag Janus NPs;

[0011] S2, the Au-Ag Janus NPs obtained in S1 are mixed with 1-3% (w / v) PVP aqueous solution and 0.1-0.3M ascorbic acid solution, the pH is adjusted to 8-10, HAuCl4·4H2O solution is added, the solid-liquid separation is performed after the reaction to obtain the solid phase, and the solid phase is redispersed in water to obtain Au-Ag Janus@AuNPs.

[0012] In one embodiment of the present invention, the concentration of HAuCl4·4H2O in S2 is 0.1-1.0 mM.

[0013] In one embodiment of the present invention, the SEC-Apt sequence of the aptamer SEC of enterotoxin C in step (1) is SH-(CH2)6-AGC-AGC-ACA-GAG-GTC-AGA-TGT-ATA-CTT-CTA-AAA-TTT-GTT-TGT-ATC-TAC-GAT-GTT-CTT-CGT-CCT-ATG-CGT-GCT-ACC-GTG-AA.

[0014] In one embodiment of the present invention, the molar ratio of Au-Ag Janus@Au NPs to the aptamer SEC-Apt in step (1) is 1:50-1:150.

[0015] In one embodiment of the present invention, the preparation method of NiCo-MOF / Fe3O4 NSs in step (2) is as follows:

[0016] Add cobalt salt, nickel salt and terephthalic acid to the mixed solvent, and quickly add triethylamine or triethanolamine after all are dissolved, stir, and wash with ethanol and water for several times after ultrasonic treatment for 4-8 hours to obtain NiCo-MOF NSs. Add iron salt and ferrous salt to the NiCo-MOF NSs solution, stir at 70-90°C, inject 25wt% ammonia water, and continue stirring to obtain NiCo-MOF / Fe3O4 NSs.

[0017] In one embodiment of the present invention, the mixed solvent includes ethanol, deionized water and N,N-dimethylformamide.

[0018] In one embodiment of the present invention, the nickel salt is selected from one or more of nickel chloride, nickel oxalate, nickel sulfate, nickel nitrate and nickel acetate.

[0019] In one embodiment of the present invention, the cobalt salt is selected from one or more of cobalt chloride, cobalt nitrate, cobalt sulfate, cobalt acetate and cobalt oxalate.

[0020] In one embodiment of the present invention, the iron salt is selected from one or more of ferric chloride, ferric nitrate and ferric sulfate.

[0021] In one embodiment of the present invention, the ferrous salt is selected from one or more of ferrous chloride, ferrous nitrate and ferrous sulfate.

[0022] In one embodiment of the present invention, the molar ratio of Au-Ag Janus@Au NPs / SEC-Apt to NiCo-MOF / Fe3O4 NSs in step (2) is 1:1-2:1.

[0023] In one embodiment of the present invention, the method for preparing the standard curve for quantitative analysis in step (3) is as follows:

[0024] The Au-Ag Janus@AuNPs+NiCo-MOF / Fe3O4 NSs assembly was mixed with enterotoxin C solutions of different concentrations. After the reaction, the solid-liquid separation was performed to obtain the solid phase. The SERS signal intensity of the solid phase was detected, with the logarithm of the enterotoxin C concentration as the horizontal axis and the logarithm of 1278 cm -1 The SERS signal intensity at is taken as the ordinate to obtain the standard curve.

[0025] In one embodiment of the present invention, the concentration range of the enterotoxin C solution is 0.1 pg / mL-100 ng / mL.

[0026] In one embodiment of the present invention, 785 nm Ar + The SERS signal intensity is detected by an ion laser source.

[0027] The beneficial technical effects of the present invention are:

[0028] The present invention proposes an enterotoxin C Raman sensing analysis method based on Au-Ag Janus@AuNPs, which has high sensitivity and specificity. The present invention uses a label-free SERS probe Au-Ag Janus@AuNPs, which has a strong and stable SERS signal and strong anti-interference ability. When the target enterotoxin C is present, due to the affinity between the enterotoxin C aptamer and enterotoxin C, Au-Ag Janus@AuNPs falls off from the substrate material NiCo-MOF / Fe3O4 NSs, thereby causing the SERS intensity to weaken, thereby achieving sensitive detection of enterotoxin C. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0030] Figure 1 This is a TEM image of Au-Ag Janus@AuNPs prepared in Example 2 of the present invention.

[0031] Figure 2 It is the Raman spectrum and standard curve of the Raman sensor when there are different concentrations of enterotoxin C in Example 2 of the present invention.

[0032] Figure 3 It is the specific experimental result in the test example of the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0034] Embodiment 1

[0035] 1. Preparation of Au-Ag Janus@AuNPs:

[0036] Au NPs were synthesized by sodium citrate reduction method. 1% (w / v) HAuCl4·4H2O was added to 50 mL of ultrapure water, heated to boiling, and then 0.5 mL of 1% (w / v) sodium citrate was quickly added. After boiling for 15 min, the mixture was cooled to room temperature and redispersed in water by centrifugation to obtain AuNPs. 5 mL of AuNPs solution was added to 45 mL of ultrapure water, and 1 mL of 2-mercaptobenzimidazole-5-carboxylic acid was added. The mixture was incubated at 60 ° C for 1.5 h, and 2.8 mL of 10 mM hydroquinone and 2.8 mL of 1 mM silver nitrate were slowly added in sequence. The mixture was allowed to stand for 2 h, and redispersed in water after centrifugation to obtain Au-Ag Janus NPs.

[0037] 100 μL of 200 mM ascorbic acid and 200 μL of synthesized Au-AgJanus NPs were added to 1 mL of 2% (w / v) PVP aqueous solution, and the pH of the mixed solution was adjusted to 8.0 with NaOH, stirred for 5 min, and 500 μL of 0.2 mM HAuCl4 solution was slowly added dropwise, reacted for 1 h, and then centrifuged and washed and redispersed in 200 μL of ultrapure water to obtain Au-Ag Janus@AuNPs.

[0038] 2. Preparation of NiCo-MOF / Fe3O4NSs:

[0039] 0.10g CoCl2·6H2O, 0.05g NiCl2·6H2O and 0.12g terephthalic acid were added to a mixed solution of 2mL ethanol, 2mL deionized water and 30mL N,N-dimethylformamide in sequence. After all dissolved, 0.8mL triethylamine was quickly added, stirred for 5min, and ultrasonicated for 5h before washing with ethanol and water several times to obtain NiCo-MOF NSs. 0.010g FeCl3·6H2O and 0.010g FeSO4·7H2O were added to 20mL NiCo-MOF NSs solution, stirred at 90℃ for 30min, and then 80μL 25 wt% ammonia water was quickly injected and stirred for 30min. After cooling to room temperature, NiCo-MOF / Fe3O4NSs were obtained by washing several times using magnetic adsorption separation.

[0040] 3. Establishment of Raman sensor for enterotoxin C:

[0041] The Au-Ag Janus@AuNPs with SERS signals were incubated with the enterotoxin C aptamer SEC-Apt in a 1×TBE solution containing 50 mM NaCl for 10 h with a mixing molar ratio of 1:50 to obtain an Au-Ag Janus@AuNPs / SEC-Apt solution.

[0042] The sequence of the aptamer SEC-Apt for enterotoxin C is:

[0043] SH-(CH2)6-AGC-AGC-ACA-GAG-GTC-AGA-TGT-ATA-CTT-CTA-AAA-TTT-GTT-TGT-ATC-TAC-GAT-GTT-CTT-CGT-CCT-ATG-CGT-GCT-ACC-GTG-AA.

[0044] The Au-Ag Janus@AuNPs / SEC-Apt solution was incubated with NiCo-MOF / Fe3O4 NSs at room temperature for 10 h with a mixing molar ratio of 1:1 to obtain the Au-Ag Janus@AuNPs+NiCo-MOF / Fe3O4NSs assembly.

[0045] 4. Establish a standard curve for the detection of enterotoxin C:

[0046] The Au-Ag Janus@AuNPs+NiCo-MOF / Fe3O4NSs assembly was mixed with different concentrations of enterotoxin C (0, 0.1 pg / mL, 1.0 pg / mL, 10.0 pg / mL, 100.0 pg / mL, 1.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 50.0 ng / mL, 100.0 ng / mL) in Tris-HCl solution. After the reaction, the solid-liquid separation was carried out to obtain the solid phase. The solid phase was obtained by using 785 nm Ar + The SERS intensity of the assembly was detected by an ion laser source, with the logarithm of the enterotoxin C concentration as the horizontal axis and the logarithm of the concentration at 1278 cm -1 The SERS signal intensity at the position is taken as the ordinate, and the detection standard curve of enterotoxin C is obtained.

[0047] Embodiment 2

[0048] 1. Preparation of Au-Ag Janus@AuNPs:

[0049] Au NPs were synthesized by sodium citrate reduction method. 1% (w / v) HAuCl4·4H2O was added to 80 mL of ultrapure water, heated to boiling, and then 0.8 mL of 1% (w / v) sodium citrate was quickly added. After boiling for 15 min, it was cooled to room temperature and redispersed in water by centrifugation to obtain AuNPs. 3 mL of AuNPs solution was added to 27 mL of ultrapure water, and 0.6 mL of 2-mercaptobenzimidazole-5-carboxylic acid was added. The mixture was incubated at 60 ° C for 2.5 h, and 1.8 mL of 10 mM hydroquinone and 1.8 mL of 1 mM silver nitrate were slowly added in sequence. The mixture was allowed to stand for 2 h, and redispersed in water after centrifugation to obtain Au-Ag Janus NPs.

[0050] 50 μL of 100 mM ascorbic acid and 200 μL of synthesized Au-AgJanus NPs were added to 1 mL of 1% (w / v) PVP aqueous solution, and the pH of the mixed solution was adjusted to 9.0 with NaOH. After stirring for 5 min, 500 μL of 0.4 mM HAuCl4 solution was slowly added dropwise and reacted for 3 h. After centrifugal washing, the mixture was redispersed in 200 μL of ultrapure water to obtain Au-Ag Janus@Au NPs. The TEM characterization results of the Au-AgJanus@Au NPs are shown in Figure 2. Figure 1 shown.

[0051] 2. Preparation of NiCo-MOF / Fe3O4NSs:

[0052] 0.10g CoCl2·6H2O, 0.05g NiCl2·6H2O and 0.12g terephthalic acid were added to a mixed solution of 2mL ethanol, 2mL deionized water and 30mL N,N-dimethylformamide in sequence. After all dissolved, 0.8mL triethylamine was quickly added, stirred for 5min, and ultrasonicated for 6h, and then washed with ethanol and water several times to obtain NiCo-MOF NSs. 0.012g FeCl3·6H2O and 0.012g FeSO4·7H2O were added to 24mL NiCo-MOF NSs solution, stirred at 80℃ for 30min, and then 100μL 25 wt% ammonia water was quickly injected and stirred for 30min. After cooling to room temperature, NiCo-MOF / Fe3O4NSs were obtained by washing several times using magnetic adsorption separation.

[0053] 3. Establishment of Raman sensor for enterotoxin C:

[0054] The Au-Ag Janus@AuNPs with SERS signals were incubated with the enterotoxin C aptamer SEC-Apt in a 1×TBE solution containing 50 mM NaCl for 12 h with a mixing molar ratio of 1:100 to obtain an Au-Ag Janus@AuNPs / SEC-Apt solution.

[0055] The sequence of the aptamer SEC-Apt for enterotoxin C is:

[0056] SH-(CH2)6-AGC-AGC-ACA-GAG-GTC-AGA-TGT-ATA-CTT-CTA-AAA-TTT-GTT-TGT-ATC-TAC-GAT-GTT-CTT-CGT-CCT-ATG-CGT-GCT-ACC-GTG-AA.

[0057] The Au-Ag Janus@AuNPs / SEC-Apt solution was incubated with NiCo-MOF / Fe3O4 NSs at room temperature for 12 h with a mixing molar ratio of 2:1 to obtain the Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4NSs assembly.

[0058] 4. Establish a standard curve for the detection of enterotoxin C:

[0059] The Au-Ag Janus@AuNPs+NiCo-MOF / Fe3O4 NSs assembly was mixed with different concentrations of enterotoxin C (0, 0.1 pg / mL, 1.0 pg / mL, 10.0 pg / mL, 100.0 pg / mL, 1.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 50.0 ng / mL, 100.0 ng / mL) in Tris-HCl solution. After the reaction, the solid-liquid separation was carried out to obtain the solid phase. The solid phase was obtained by using 785 nm Ar + The SERS intensity of the assembly was detected by an ion laser source, with the logarithm of the enterotoxin C concentration as the horizontal axis and the logarithm of the concentration at 1278 cm -1 The SERS intensity at the position is taken as the ordinate, and the detection standard curve of enterotoxin C is obtained. Figure 2 As shown in Figure 2, with the increase of enterotoxin C concentration, the -1 The SERS intensity at 1278 cm gradually weakened, and in the range of 1.0 pg / mL-10.0 ng / mL, the logarithm of the enterotoxin C concentration was significantly different from that at 1278 cm -1 There is a good linear relationship between the SERS intensity at 1278 =-1168.95Log C SEC +7761.90).

[0060] Embodiment 3

[0061] 1. Preparation of Au-Ag Janus@AuNPs:

[0062] Au NPs were synthesized by sodium citrate reduction method. 1% (w / v) HAuCl4·4H2O was added to 100 mL of ultrapure water, heated to boiling, and then 1.0 mL of 1% (w / v) sodium citrate was quickly added. After boiling for 15 min, the mixture was cooled to room temperature and redispersed in water by centrifugation to obtain AuNPs. 4 mL of AuNPs solution was added to 36 mL of ultrapure water, and 0.8 mL of 2-mercaptobenzimidazole-5-carboxylic acid was added. The mixture was incubated at 70 ° C for 2 h, and 2.4 mL of 10 mM hydroquinone and 2.4 mL of 1 mM silver nitrate were slowly added in sequence. The mixture was allowed to stand for 6 h, and redispersed in water after centrifugation to obtain Au-Ag Janus NPs.

[0063] 100 μL of 200 mM ascorbic acid and 200 μL of synthesized Au-AgJanus NPs were added to 1 mL of 3% (w / v) PVP aqueous solution, and the pH of the mixed solution was adjusted to 10.0 with NaOH, stirred for 5 min, and 500 μL of 0.8 mM HAuCl4 solution was slowly added dropwise, and reacted for 2 h. After centrifugation and washing, the mixture was redispersed in 200 μL of ultrapure water to obtain Au-Ag Janus@AuNPs.

[0064] 2. Preparation of NiCo-MOF / Fe3O4 NSs:

[0065] 0.10g CoCl2·6H2O, 0.05g NiCl2·6H2O and 0.12g terephthalic acid were added to a mixed solution of 2mL ethanol, 2mL deionized water and 30mL N,N-dimethylformamide in sequence. After all dissolved, 0.8mL triethylamine was quickly added, stirred for 5min, and ultrasonicated for 6h, and then washed with ethanol and water several times to obtain NiCo-MOF NSs. 0.010g FeCl3·6H2O and 0.010g FeSO4·7H2O were added to 20mL NiCo-MOF NSs solution, stirred at 80℃ for 30min, and then 100μL 25wt% ammonia water was quickly injected and stirred for 30min. After cooling to room temperature, NiCo-MOF / Fe3O4 NSs were obtained by washing several times using magnetic adsorption separation.

[0066] 3. Establishment of Raman sensor for enterotoxin C:

[0067] The Au-Ag Janus@AuNPs with SERS signals were incubated with the enterotoxin C aptamer SEC-Apt in a 1×TBE solution containing 50 mM NaCl for 11 h with a mixing molar ratio of 1:150 to obtain an Au-Ag Janus@AuNPs / SEC-Apt solution.

[0068] The sequence of the aptamer SEC-Apt for enterotoxin C is:

[0069] SH-(CH2)6-AGC-AGC-ACA-GAG-GTC-AGA-TGT-ATA-CTT-CTA-AAA-TTT-GTT-TGT-ATC-TAC-GAT-GTT-CTT-CGT-CCT-ATG-CGT-GCT-ACC-GTG-AA.

[0070] The Au-Ag Janus@AuNPs / SEC-Apt solution was incubated with NiCo-MOF / Fe3O4 NSs at room temperature for 11 h with a mixing molar ratio of 2:1 to obtain the Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4NSs assembly.

[0071] 4. Establish a standard curve for the detection of enterotoxin C:

[0072] The Au-Ag Janus@AuNPs+NiCo-MOF / Fe3O4 NSs assembly was mixed with different concentrations of enterotoxin C (0, 0.1 pg / mL, 1.0 pg / mL, 10.0 pg / mL, 100.0 pg / mL, 1.0 ng / mL, 5.0 ng / mL, 10.0 ng / mL, 50.0 ng / mL, 100.0 ng / mL) in Tris-HCl solution. After the reaction, the solid-liquid separation was carried out to obtain the solid phase. The solid phase was obtained by using 785 nm Ar + The SERS intensity of the assembly was detected by an ion laser source, with the logarithm of the enterotoxin C concentration as the horizontal axis and the logarithm of the concentration at 1278 cm -1 The SERS intensity at the position is taken as the ordinate, and the detection standard curve of enterotoxin C is obtained.

[0073] Test Case

[0074] Specificity experiment: In order to further evaluate the selectivity of the Raman sensor for detecting enterotoxin C constructed in Example 2, the assembly was mixed and incubated with 1.0 ng / mL of ochratoxin A (OTA), bisphenol A (BPA), bovine serum albumin (BSA), microcystin-LR (MC-LR) and enterotoxin C (SEC), and the solid-liquid separation was performed after the reaction to test the SERS intensity of the solid phase. The specificity results are shown in Figure 2. Figure 3 As shown, due to the affinity between the enterotoxin C aptamer and enterotoxin C, the SERS intensity corresponding to enterotoxin C is significantly reduced, while other nonspecific molecules have almost no effect on the SERS signal, which further confirms that the Raman sensor constructed by the present invention has good specificity.

[0075] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A Raman sensing analysis method for enterotoxin C based on Au-Ag Janus@Au NPs, characterized in that: The following steps are involved: (1) Incubate Au-Ag Janus@Au NPs with the enterotoxin C aptamer SEC-Apt for 10-13 h, then separate the solid phase from the liquid phase and disperse the solid phase in a solvent to obtain an Au-Ag Janus@Au NPs / SEC-Apt solution; (2) incubating the Au-Ag Janus@Au NPs / SEC-Apt solution obtained in step (1) with NiCo-MOF / Fe3O4 NSs for 10-13 h to obtain Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4 NSs assembly; (3) mixing the Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4 NSs assembly obtained in step (2) with the solution to be detected in a buffer solution, magnetically separating the solid phase after the reaction, and detecting the SERS signal intensity of the solid phase to achieve qualitative or quantitative analysis of enterotoxin C; The sequence of the enterotoxin C aptamer SEC-Apt in step (1) is SH-(CH2)6-AGC-AGC-ACA-GAG-GTC-AGA-TGT-ATA-CTT-CTA-AAA-TTT-GTT-TGT-ATC-TAC-GAT-GTT-CTT-CGT-CCT-ATG-CGT-GCT-ACC-GTG-AA; The molar ratio of Au-Ag Janus@Au NPs to aptamer SEC-Apt in step (1) is 1:50-1:150; The preparation method of NiCo-MOF / Fe3O4 NSs in step (2) is as follows: Add cobalt salt, nickel salt and terephthalic acid to the mixed solvent, add triethylamine or triethanolamine after all are dissolved, stir and react to obtain NiCo-MOF NSs, add iron salt solution and ferrous salt solution, stir and react, inject ammonia water, continue to stir and react to obtain the NiCo-MOF / Fe3O4 NSs; The molar ratio of Au-Ag Janus@Au NPs / SEC-Apt to NiCo-MOF / Fe3O4 NSs in step (2) is 1:1-2:

1.

2. The enterotoxin C Raman sensing analysis method according to claim 1, characterized in that: The preparation method of Au-Ag Janus@Au NPs in step (1) is as follows: S1, the Au NPs solution was mixed and incubated with 2-mercaptobenzimidazole-5-carboxylic acid at 50-70 °C, and hydroquinone and silver salt solution were added, and the reaction was allowed to stand for 2-6 h to obtain Au-Ag Janus NPs; S2, mixing the Au-Ag Janus NPs obtained in S1 with the PVP aqueous solution and the ascorbic acid solution, adjusting the pH to 8-10, adding the HAuCl4·4H2O solution for mixing and reaction, and obtaining the Au-Ag Janus@Au NPs.

3. The enterotoxin C Raman sensing analysis method according to claim 2, characterized in that: The concentration of HAuCl4·4H2O in S2 is 0.1-1.0 mM.

4. The enterotoxin C Raman sensing analysis method according to claim 1, characterized in that: The method for preparing the standard curve for quantitative analysis in step (3) is as follows: The Au-Ag Janus@Au NPs+NiCo-MOF / Fe3O4 NSs assembly was mixed with enterotoxin C solutions of different concentrations. After the reaction, the solid-liquid separation was performed to obtain the solid phase. The SERS signal intensity of the solid phase was detected, with the logarithm of the enterotoxin C concentration as the horizontal axis and the logarithm of 1278 cm -1 The SERS signal intensity at is taken as the ordinate to obtain the standard curve.

5. The enterotoxin C Raman sensing analysis method according to claim 4, characterized in that: The concentration range of enterotoxin C solution is 0.1 pg / mL-100 ng / mL.

6. The enterotoxin C Raman sensing analysis method according to claim 4, characterized in that: Using 785 nm Ar + The SERS signal intensity is detected by an ion laser source.

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