Synthesis method and application of hg-pd-pdo heterojunction with high peroxidase-like activity

Abstract

The application discloses a synthesis method of Hg-Pd-PdO heterojunction with high peroxidase activity and application thereof. 2+ The PdNS aqueous solution is mixed with Hg 2+ After centrifugal separation, the solid is washed to obtain a series of Hg-Pd-PdO heterojunction PHOs. The application uses a simple proportion control method in water to mix palladium nanosheets with Hg 2+ to obtain a series of heterojunction PHOs, which have strong peroxidase activity, and the affinity for substrates is 21.7 times and 123.6 times that of PdNS and natural peroxidase respectively. By using the super-high peroxidase activity and strong antibody binding capacity of PHO2, the detection of carcinoembryonic antigen based on colorimetric immunoassay can be realized. The application prepares a lateral immunochromatographic CEA detection test paper taking PHOs as core catalytic materials, and the CEA self-detection can be realized in a portable and easy-to-operate manner, and the lateral immunochromatographic CEA detection test paper is expected to be used for early screening detection and rehabilitation monitoring of cancer.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of tumor marker detection and innovative material research and development, and relates to a synthesis method of Hg-Pd-PdO heterojunction with high peroxidase-like activity and application thereof in detection of carcinoembryonic antigen. BACKGROUND

[0002] Due to the complex surface and unique interface of the heterojunction, the preparation of the heterojunction is an effective strategy to improve the catalytic activity. Ru, Rh, Ir, Pd, Pt and other noble metals are excellent catalysts for various catalytic reactions, including enzyme-like active catalysis, electrocatalytic gas oxidation and reduction, organic catalytic oxidation, etc. In order to improve the catalytic activity of noble metals, researchers often introduce their alloys and oxides as the building blocks of the heterojunction. For example, as a peroxidase mimetic nano-enzyme, the catalytic constant of Ni-Pt nanalloy is about 46 times that of Pt nanoparticles. Similarly, the introduction of their oxides also greatly improves the performance of noble metals. Related studies have confirmed that the modification of PdO changes the electronic state of Pd, reducing the energy barrier of hydrogen diffusion. Another report proves that PdOx plays a key role in determining the oxidation activity of Pd, rather than the electronic properties. However, the preparation of oxides on the surface of noble metals always involves harsh experimental conditions, such as high temperature. And the degree of oxidation cannot be controlled. Therefore, it is necessary to find a simple, mild and controllable strategy for the oxidation of noble metals to develop new catalysts with satisfactory activity.

[0003] Carcinoembryonic antigen (CEA) is a 200 kDa glycoprotein that is normally produced during fetal development, but its production ends before birth. It is mainly used as a tumor marker for monitoring the treatment of colorectal cancer or other cancers, identifying recurrence and staging has been extensively studied as a broad-spectrum tumor marker for clinical diagnosis. At the same time, CEA has important clinical value in differential diagnosis, disease monitoring and efficacy evaluation. Immunological methods based on the specific recognition of antigens and antibodies have become the main analytical methods for quantitative detection of CEA. Radioimmunoassay, chemiluminescent immunoassay and enzyme-linked immunoassay are commonly used methods for CEA quantification. However, these methods are mainly based on expensive equipment and time-consuming procedures, and require skilled personnel, which hinders their widespread application in patient monitoring, especially in point-of-care and resource-limited environments. Therefore, there is still a great demand for the development of easy-to-use, rapid, affordable, but effective cancer diagnosis methods without the need for complex, expensive, cumbersome equipment and skilled technicians. Enzyme-linked immunosorbent assay (ELISA) can be represented by color change, and the results can be easily observed with the naked eye without the need for complex instruments.

[0004] ELISA has been widely used in bioanalysis since it was first established by Van Weemen and Schuurs in 1971. In this context, lateral flow immunoassays (LFIA) are simple and easy-to-use immunochromatographic test strip devices that exploit the specific binding of antigens to antibodies and are widely used in clinical analysis, food safety control, environmental monitoring and drug abuse assessment, to some extent meeting the standards of the World Health Organization. Interestingly, the integration of smartphone technology with LFIA by meeting real-time connectivity can effectively facilitate its further potential applications. Thanks to simplicity and portability, a large number of smartphone-based (bio)sensing platforms have been reported for the detection of various analytes. It is necessary to achieve a portable, easy-to-use CEA self-test, which is of great significance for further achieving early screening of cancer. SUMMARY

[0005] The application provides a preparation method of Hg-Pd-PdO heterojunction with high peroxidase-like activity, improves the catalytic activity of noble metal, provides a simple, mild and controllable noble metal oxidation strategy, and effectively solves the harsh experimental conditions involved in the preparation of oxides on the surface of noble metal.

[0006] The application also provides the prepared Hg-Pd-PdO heterojunction and application thereof.

[0007] Technical scheme: In order to achieve the above-mentioned purpose, the synthesis method of the Hg-Pd-PdO heterojunction with high peroxidase-like activity comprises the following steps:

[0008] Hg is added to the PdNS aqueous solution 2+ The product is centrifuged and separated, and then the solid is washed to obtain a series of Hg-Pd-PdO heterojunction PHOs.

[0009] The PdNS is synthesized by adding palladium acetylacetonate, PVP and NaI into a mixed solvent of DMF and ultrapure water, uniformly mixing, high-pressure heating reaction, centrifuging and separating the product, and then washing to obtain the PdNS.

[0010] The concentration of the PdNS aqueous solution is 1-10 μg / mL -1 .

[0011] Preferably, the concentration of the PdNS aqueous solution is 5 μg / mL -1 .

[0012] Different concentrations of Hg are added to the PdNS aqueous solution 2+, Hg 2+ The final concentration in the system is 50-500nM.

[0013] As preferred, Hg 2+ , Hg 2+ The final concentration in the system is 50, 200 or 500nM, and the molar ratio of Pd, Hg and PdO in the system is 0.748:0.018:0.234, 0.532:0.067:0.411 and 0.182:0.114:0.804 respectively.

[0014] As preferred, Hg 2+ Shaking at room temperature for 30-200min.

[0015] The Hg-Pd-PdO heterojunction synthesized by the synthesis method of the Hg-Pd-PdO heterojunction with high peroxidase-like activity.

[0016] The application of the Hg-Pd-PdO heterojunction in qualitative and quantitative CEA detection.

[0017] As preferred, the application of the Hg-Pd-PdO heterojunction in preparing qualitative and quantitative CEA detection reagents or materials

[0018] The application of the Hg-Pd-PdO heterojunction in preparing early screening detection and rehabilitation monitoring reagents or tools for cancer.

[0019] A lateral immunochromatography test paper based on the Hg-Pd-PdO heterojunction.

[0020] The present application realizes the oxidation of Pd in different degrees by controlling the amount of Hgde, and a series of Pd x Hg y (PdO) z (Hg-Pd-PdO heterojunction, PHOs), including PHO1, PHO2 and PHO3, and the molar ratio of Pd, Hg and PdO in them is 0.748:0.018:0.234, 0.532:0.067:0.411 and 0.182:0.114:0.804 respectively.

[0021] The present application mixes Hg 2+A series of Hg-Pd-PdO heterojunctions (PHOs) are prepared from PdNS, a controllable preparation method of the Hg-Pd-PdO heterojunctions, an enzyme-linked immunosorbent assay (ELISA) for detecting CEA, and application of lateral flow immunochromatography test paper in carcinoembryonic antigen are disclosed. 2+ The ratio of Pd, Hg and PdO in the heterojunctions can be easily controlled by adjusting the ratio of PdNS and Pd nanomaterials, so as to regulate the peroxidase activity of the Pd, Hg and PdO. The PHOs have strong peroxidase activity, and the affinity of PHO2 to the substrate is 21.7 times and 123.6 times that of PdNS and natural peroxidase (HRP) respectively. Compared with PHO1 and PHO3, PHO2 has high peroxidase activity and strong antibody binding capacity, so PHO2 is used for colorimetric immunoassay of carcinoembryonic antigen, and it is found that PHO2 has an ultra-low detection limit (1.33 pg mL -1 ), which is 8.6 times and 282 times lower than that of PdNS and natural HRP. Based on the above results, lateral flow immunochromatography (LFIA) test paper is prepared, a simple, rapid, quantitative and accurate CEA detection method is obtained, the test paper detection result of a clinical sample is consistent with that of a clinical method (chemiluminescence detection), and portable and simple CEA self-detection is realized, which is expected to be used for early screening and detection of cancer and rehabilitation monitoring.

[0022] The application discloses a simple method for obtaining high peroxidase activity nanomaterials PHOs, wherein the ultra-high peroxidase activity and strong antibody binding capacity of PHO2 are used to realize carcinoembryonic antigen (CEA) detection based on a colorimetric immunoassay method, and PHO2 is used as a core catalytic component to prepare a CEA detection test paper, so as to realize portable, simple and easy-to-operate CEA self-detection, and the CEA detection test paper is expected to be used for early screening and detection of cancer and rehabilitation monitoring.

[0023] Advantages: Compared with the prior art, the application has the following advantages:

[0024] 1. The material preparation method disclosed by the application is simple, and Pd nanosheets and Hg 2+ are mixed by using a simple ratio control method, so that a series of Hg-Pd-PdO heterojunctions (PHOs) are obtained.

[0025] 2. The PHOs have ultra-high peroxidase activity, and the affinity of PHO2 to the substrate is 21.7 times and 123.6 times that of PdNS and natural peroxidase (HRP) respectively; the affinity of PHO3 to the substrate is 21.7 times and 123.6 times that of PdNS and natural peroxidase (HRP) respectively.

[0026] 3. PHO2 is used as a core catalytic material for colorimetric immunoassay of carcinoembryonic antigen, and it is found that PHO2 has an ultra-low detection limit (1.33 pg mL -1), 8.6 times and 282 times lower than PdNS and natural HRP, which can be effectively applied to qualitative and quantitative CEA detection.

[0027] 4, PHO2 as the core catalytic material of lateral flow immunochromatography test paper, realizes simple, rapid, quantitative and accurate CEA detection method, and the test paper detection result of clinical sample is consistent with the clinical method (chemiluminescence detection), realizes portable and simple CEA self-test, which is expected to be used for early screening and detection of cancer and rehabilitation monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 TEM and XPS of A1, B1 and C1 as Pd, A2, B2 and C2 as PHO1, A3, B3 and C3 as PHO2 and A4, B4 and C4 as PHO3;

[0029] Figure 2 PHO1, PHO2 and PHO3 binding antibody ability comparison chart;

[0030] Figure 3 ELISA detection of different concentrations of CEA corresponding absorbance is made into a first function image to determine the detection limit of PHO2;

[0031] Figure 4 LFIAT structure chart;

[0032] Figure 5 Flowchart of qualitative and quantitative detection of CEA by lateral flow immunochromatography test paper;

[0033] Figure 6 Application of lateral flow immunochromatography test paper in CEA concentration detection in serum;

[0034] Figure 7 Comparison of lateral flow immunochromatography test paper and chemiluminescence method for detecting CEA concentration in serum;

[0035] Figure 8 Application of lateral flow immunochromatography test paper in CEA concentration detection in serum. DETAILED DESCRIPTION

[0036] The present application can be better understood according to the following examples. Those skilled in the art will readily understand that the contents described in the examples are only used to illustrate the present application, and should not and will not limit the present application described in detail in the claims. The materials, reagents and the like used in the following examples, if not specially specified, can be obtained from commercial channels. The experimental methods not specified in the examples are usually carried out according to the conventional conditions, or according to the conditions recommended by the manufacturer.

[0037] CEA, CEA antibody (Ab1), CEA antibody (Ab2) were purchased from Shanghai Lingchao Biotechnology Co., Ltd. Among them: CEA: 1 mg / mL. Affinity purified. L2C01001; Ab1: 1.9 mg / mL. Affinity purified. L1C00205; Ab2: 3.7 mg / mL. Affinity purified. L1C00203.

[0038] Washing buffer: weigh 2.204 g of disodium hydrogen phosphate, 0.6 g of sodium dihydrogen phosphate and 8.766 g of sodium chloride, and make a solution of 1 L with deionized water, and store at 4℃ for standby.

[0039] Blocking buffer: weigh 2.204 g of disodium hydrogen phosphate, 0.6 g of sodium dihydrogen phosphate and 8.766 g of sodium chloride, and make a solution of 1 L with deionized water, and add 2% bovine serum albumin (BSA), and store at 4℃ for standby.

[0040] Example 1

[0041] PdNS synthesis:

[0042] Palladium acetonyl acetonate (50.0 mg), polyvinylpyrrolidone (PVP, MW = 30000, 160.0 mg) and NaI (75.0 mg) were added to a mixed solvent of N,N-dimethylformamide (9 mL) and ultrapure water (3 mL) to obtain a uniform yellow solution, which was transferred to a polytetrafluoroethylene high-pressure reaction kettle. Seal, charge CO to 2.5 bar, heat to 100℃ at room temperature, continue to stir for 2.5 h, and then naturally cool to room temperature to obtain a dark blue solution. Add acetone to form a precipitate, separate by centrifugation, and then wash the solid with an ethanol-acetone mixture (volume ratio of 1:8) three times to obtain PdNS, which is then dispersed in water for use in the synthesis of PHOs in the next step.

[0043] Synthesis of PHOs

[0044] In the presence of 5 μg mL -1 PdNS in water, different concentrations of mercury sulfate (Hg 2+ 50, 200 and 500 nM) were added, and the reaction was stirred at room temperature for half an hour (450 r / min), and an excess of acetone was added to produce a precipitate. After centrifugal separation, the solid was washed with an ethanol-acetone mixture (volume ratio of 1:8) three times to obtain a series of Hg-Pd-PdO heterojunction PHOs, and the solid was then dispersed in ethanol for further use. Among them, Hg 2+PHO1, PHO2, and PHO3 were prepared at final concentrations of 50, 200, and 500 nM, respectively. The molar ratios of Pd, Hg, and PdO in the three materials were 0.748:0.018:0.234, 0.532:0.067:0.411, and 0.182:0.114:0.804, respectively.

[0045] like Figure 1 As shown, transmission electron microscopy (TEM) was used to observe the size and morphology of PHO1, PHO2, and PHO3. The results showed that the PHO1, PHO2, and PHO3 nanoparticles had regular structures and morphologies, indicating that the addition of Hg did not affect the original morphology. X-ray photoelectron spectroscopy (XPS) was used to determine the composition of the material. A1, B1, and C1 are Pd; A2, B2, and C2 are PHO1; A3, B3, and C3 are PHO2; and A4, B4, and C4 are PHO3. (TEM and XPS spectra are shown.)

[0046] Example 2

[0047] Peroxidase activity and substrate affinity determination of PHOs

[0048] PHOs exhibited typical Michaelis-Menten catalytic behavior for both TMB and H2O2. At 25 °C, in an acetate-sodium acetate buffer solution (pH = 4.5), with a fixed H2O2 concentration of 0.125 mM and a TMB concentration ranging from 0 to 0.25 mM, and with a fixed TMB concentration of 0.25 mM and an H2O2 concentration ranging from 0 to 12.5 mM, the reaction time was 15 min. The concentration of PdNS or PHOs was 0.5 μg / mL. -1 ), and compared with PdNS and natural HRP (Z.Xi, KCWei, QXWang, MJKim and SHSun, J.Am.Chem.Soc, 2021, 143, 7.). The Lineweaver-Burk equation 1 / v=(k m / v max (1 / [S]+1 / v) max (In the formula, v is the initial velocity, v max For the maximum reaction rate, k m The Michaelis-Menten constant (km) was used to determine key enzyme kinetic parameters, where [S] is the substrate concentration. m As is well known, k m k is generally considered an indicator of enzyme affinity for its substrate. mThe lower, the higher the enzyme affinity, and vice versa. The results show that PHOl, PHO2 and PHO3 have peroxidase-like activity; PHO2 and PHO3 have stronger peroxidase-like activity and substrate affinity than PHOl (Table 1).

[0049] Table 1 Comparison of PHOl, PHO2, PHO3 and HRP with substrate affinity

[0050]

[0051]

[0052] Example 3

[0053] Bioconjugation of PHO with CEA antibody (Ab2)

[0054] First, the ability of PHOs to conjugate Ab2 was detected by protein quantification BCA method, and the antibody binding capacity was determined by protein quantification method, i.e. standard protein samples (0.5 mg mL -1 ) were added to the protein standard wells of the 96-well plate at 0, 2, 4, 6, 8, 12, 16, 20 μL, and the standard sample diluent was added to make up to 20 μL. At the same time, the appropriate volume of sample was added to the sample wells of the 96-well plate, and the standard sample diluent was added to make up to 20 μL. 200 μL of protein working solution was added to each well, the liquid was mixed, and then it was placed at 37°C for 30-60 min. The liquid was cooled to room temperature, and the absorbance value was measured on the enzyme marker instrument. Finally, the concentration of protein was calculated according to the standard curve for protein quantification of the sample. The comparison of experimental results showed that, compared with PHOl and PHO3, PHO2 had both high peroxidase-like activity and stronger antibody binding capacity Figure 2 ). Therefore, PHO2 was used as the corresponding detection material in the subsequent experiments. The bioconjugation process of PHO2 and Ab2 was as follows: PHO2 (final concentration 5 μg mL -1 ), Ab2 (final concentration 0.5 μg mL -1 ) were added to the phosphate buffer solution (PBS, pH 7.4) containing 1% BSA, 0.25% Tween 20 and 1% sucrose, and shaken at room temperature for 1 hour. Then, it was centrifuged at 4°C for 10 minutes (14000 r min -1 ), the supernatant was discarded, and the precipitate was collected to obtain Ab2-PHO2. Then, it was washed with deionized water twice, and dispersed in 10 mM phosphate buffered saline (PBS, pH 7.4) buffer. It was stored at 4°C.

[0055] Example 4

[0056] Detection of CEA by Ab2-PHO2

[0057] 96-well polyethylene plates were coated with 5 μg mL -1 Ab1 (100 μL per well in Na2CO3-NaHCO3 buffer at pH 9.6) was incubated overnight at 4°C. The 96-well polyethylene plates were washed with washing buffer and shaken for three times. Then, the plates were blocked with blocking buffer (200 μL per well) for 1 hour at room temperature with gentle shaking. After washing with washing buffer for three times, CEA standards were diluted to a series of concentrations ([CEA] = 1000, 500, 250, 125, 62.5, 31.25, 15.63, 7.86, 3.93 and 1.96 pg mL -1 ) with dilution buffer and added to the wells. After 2 hours of incubation at room temperature, the plates were washed with washing buffer for three times. Then, Ab2-PHO2 (100 μL, directly using Ab2-PHO2 dispersed in PBS as described in Example 3) was added to each well of the plates. The plates were incubated for another hour at room temperature and washed with washing buffer for three times. Freshly prepared 100 μL substrate solution (0.125 mM TMB and 50 mM H2O2 in acetic acid-sodium acetate buffer at pH 4.0) was added to each well of the plates. After 20 minutes, the reaction was stopped by adding 50 μL of 2.0 M H2SO4 to each well. The plates were shaken well and the absorbance values at 450 nm were measured using a microplate reader and the color change of the solution was recorded by taking a photograph. The different concentrations of CEA were detected by Ab2-PHO2 with a very low detection limit of 1.33 pg mL Figure 3 as shown in Figure 6. The absorbance values at 450 nm were fitted to a linear equation y = 0.01291x + 0.0623 (R 2 = 0.9995) and the slope of the equation and the standard deviation of 11 blank experiments were used to determine the detection limit (3θ / k) Figure 3 ) of 1.33 pg mL -1 .

[0058] Example 5

[0059] Preparation of lateral flow immunochromatographic test strip

[0060] The two antigenic determinants on CEA bind to the PHO2-labeled antibody Ab2 on the conjugate pad and the capture antibody Ab1 on the test line, forming Ab2-PHO2-Ab1. PHO2 has strong peroxidase activity and reacts with the substrate solution to generate blue substances. The unbound Ab2-PHO2 is intercepted on the control line and reacts with the substrate solution to generate blue substances. The treated sample pad, conjugate pad, nitrocellulose membrane (NC membrane), and absorbent pad are assembled, and after the antibody incubation on the test line and control line is completed, the matched card shell is loaded.

[0061] The specific process is as follows:

[0062] (1) Conjugate pad treatment: add PdNS (final concentration 100 μg / mL -1 ), Hg 2+ (final concentration 200 nM), and Ab2 (final concentration 5 μg / mL -1 ) in a phosphate buffer solution (PBS, pH 7.4) containing 1% BSA, 0.25% Tween 20, and 1% sucrose, and shake at room temperature for 1 hour. Then add 2% BSA, shake thoroughly for 1 hour, and centrifuge at 4°C for 20 minutes (10000 r / min -1 ). Discard the supernatant and collect the particles to obtain (Ab2-PHO2). Wash with deionized water twice, and then disperse in a phosphate buffer solution (PBS, pH 7.4) containing 1% BSA, 0.25% Tween 20, and 1% sucrose. Soak the conjugate pad in the above buffer solution at room temperature for 24 hours, and dry at room temperature;

[0063] (2) Sample pad treatment: soak the conjugate pad in a phosphate buffer solution (PBS, pH 7.4) containing 1% BSA and 0.25% Tween 20 for 24 hours, and dry at room temperature;

[0064] (3) NC membrane treatment: use a spot printer to print Ab1 (test line) on the NC membrane 0.5 cm away from the conjugate pad, and use a spot printer to print lgG (control line) on the NC membrane 0.8 cm away from the conjugate pad.

[0065] (4) Assemble the sample pad, conjugate pad, NC membrane, and absorbent pad on the base plate in sequence, and load the matched card shell after the antibody incubation on the test line and control line is completed and the liquid marks on the test line and control line dry and disappear. Figure 4

[0066] Example 6

[0067] Lateral immunochromatographic test strip for detecting CEA concentration in serum

[0068] Use the test strip prepared in Example 5 above to detect serum samples containing different concentrations of CEA, and the detection process is as shown in Figure 5 .​

[0069] 50 μL of fluid containing CEA ([CEA] = final concentrations of 0, 2.5, 5, 10, 15, and 20 pg / mL) was prepared. -1 Serum samples were added to the sample pad. When the sample solution was about to reach the test line, 2 μL of substrate solution (acetic acid-sodium acetate buffer solution of 0.125 mM TMB and 125 mM H2O2, pH 4) was added. When the sample solution reached the control line, another 2 μL of substrate solution was added. Figure 6 As shown, the phone captures and records color changes. Simultaneously, the phone's Color Assist app is used to read the corresponding RGB values ​​(R represents red, G represents green, and B represents blue), and a linear equation is derived between the RGB values ​​and the CEA concentration: y = 0.02815x + 0.9284(R). 2 =0.9963).

[0070] After establishing the standard curve, the specific steps for serum sample testing are as follows: After the blood clots naturally at room temperature, centrifuge at 1000 rpm for 20 minutes at 4°C. Collect the supernatant for testing. The sample volume is 50 μL, added to the sample pad. When the sample solution is about to reach the test line, add 2 μL of substrate solution (acetic acid-sodium acetate buffer solution of 0.125 mM TMB and 125 mM H2O2, pH 4). When the sample solution reaches the control line, add another 2 μL of substrate solution. Record the color change by taking a picture with your phone. Use the Color Assist software on your phone to read the corresponding RGB values. Determine the CEA concentration in the serum according to the standard curve. Compare the calculated values ​​with clinical data (chemiluminescence method). The results are consistent, indicating accurate data. Figure 7 The above results demonstrate that the design and preparation of CEA-based lateral immunochromatographic test strips can achieve portable, simple, sensitive, and accurate CEA self-testing.

[0071] Example 7

[0072] Lateral immunochromatographic test strips detect CEA in blood samples

[0073] 50 μL of fluid containing CEA ([CEA] = final concentrations of 0, 2.5, 5, 10, 15, and 20 pg / mL) was prepared. -1 A blood sample was dropped onto a sample pad. When the sample solution was about to reach the test line, 2 μL of substrate solution (acetic acid-sodium acetate buffer solution of 0.125 mM TMB and 125 mM H2O2, pH 4) was added. When the sample solution reached the control line, another 2 μL of substrate solution was added. The color change was recorded by taking a picture with a mobile phone. The corresponding RGB values ​​were read using the phone's Color Assist software, and the linear equation between the RGB values ​​and the CEA concentration was calculated: y = 0.09122x + 0.9470 (R²). 2 =0.995)(Figure 8 ).

[0074] After establishing the standard curve, the specific steps for testing blood samples are as follows: Add 50 μL of CEA ([CEA] = 5 pg / mL) -1 A blood sample is dropped onto the sample pad. When the sample solution is about to reach the test line, 2 μL of substrate solution (acetic acid-sodium acetate buffer solution of 0.125 mM TMB and 125 mM H2O2, pH 4) is added. When the sample solution reaches the control line, another 2 μL of substrate solution is added. The color change is recorded by taking a picture with a mobile phone and then inputting the RGB values ​​into the equation. This test strip can also be used to detect CEA in blood samples.

Claims

1. A method of synthesis of Hg-Pd-PdO heterojunction with high peroxidase-like activity, characterized in that, It comprises the following steps: PdNS aqueous solution was added with Hg 2+ The product was centrifuged and the solid was washed to obtain a series of Hg-Pd-PdO heterojunction PHOs; The PdNS is synthesized by adding palladium acetylacetonate, PVP and NaI into a mixed solvent of DMF and ultrapure water, uniformly mixing, high-pressure heating reaction, centrifugal separation of the product, and cleaning to obtain PdNS. The concentration of the PdNS aqueous solution is 1-10 μg mL -1 ; The PdNS aqueous solution is added with different concentrations of Hg 2+ , Hg 2+ The final concentration in the system is 50-500 nM; The molar ratio of Pd, Hg and PdO is 0.532:0.067:0.

411.

2. The method of synthesis of Hg-Pd-PdO heterojunction with high peroxidase-like activity according to claim 1, characterized in that, The PdNS aqueous solution is added with Hg 2+ Shaking at room temperature for 30-200 min. 3.A Hg-Pd-PdO heterojunction synthesized by the synthesis method of the Hg-Pd-PdO heterojunction with high peroxidase-like activity according to claim 1. 4.The use of the Hg-Pd-PdO heterojunction according to claim 3 in the preparation of a reagent or tool for qualitative and quantitative detection of carcinoembryonic antigen (CEA). 5.A lateral immunochromatographic test paper comprising the Hg-Pd-PdO heterojunction according to claim 3.

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