Test strip for identifying gram-negative bacteria in peritoneal dialysis solution and preparation method thereof

Abstract

The invention provides a test strip for identifying gram-negative bacteria in a peritoneal dialysis solution and a preparation method, and relates to the technical field of test strips. The test strip comprises a bottom plate as well as a sample pad, a combination pad, a coating pad and a water absorption pad which are sequentially arranged on the bottom plate, wherein a polydopamine coated colloidal gold coupled antibiotic probe is sprayed on the combination pad; a detection line is arranged on the coating pad, and the detection line is formed by hydrogel coated with antibiotics. According to the non-antibody-dependent immunochromatography test paper for detecting the gram-negative bacteria in the peritoneal dialysis solution, provided by the invention, a marker is simple and convenient to prepare, the use of paired antibodies is avoided, and the cost of the test paper is further reduced; moreover, time is gained for clinical diagnosis of microbial pathogens in dialysate, and correspondingly, antibiotic treatment is carried out on a patient in time. Each detection process can be completed within 10 min, the detection result is accurate, and the gram-negative bacteria in a peritoneal dialysis solution sample can be rapidly detected.

Description

Technical Field

[0001] The present application relates to the technical field of test strips, and in particular to a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid and a preparation method thereof. Background Art

[0002] In peritoneal dialysis (PD) patients, repeated episodes of peritonitis can cause peritoneal fibrosis and vascular hyperplasia, leading to a gradual decline in the peritoneal ultrafiltration function until ultrafiltration failure, and even developing into encapsulated peritoneal sclerosis, increasing the risk of death. Foreign studies have shown that peritoneal dialysis-associated peritonitis (PDAP) is the direct or main cause of death in more than 15% of PD patients. Domestic scholars have also found that peritonitis is positively correlated with all-cause mortality or cardiovascular mortality in peritoneal dialysis patients. Timely and accurate diagnosis and treatment of PDAP is the key to improving the dialysis quality and survival rate of PD patients.

[0003] At present, pathogen culture is still the main detection method for PDAP in clinical practice, and it is also the gold standard for diagnosing PDAP. However, the concentration of pathogens in the peritoneal dialysis fluid of PDAP patients is low. The traditional blood culture bottle method is time-consuming, low in sensitivity, and is affected by multiple factors such as the number of effective inoculated bacteria, culture temperature, pH value, oxygen content, culture medium, etc., resulting in an unsatisfactory culture positive rate (60%-70% in many centers. According to the recommendation of ISPD, for professional PD centers, the proportion of culture-negative peritonitis should be less than 10%), which is a limiting factor for the diagnosis of PDAP. The development of molecular diagnostic technology also provides effective means for the diagnosis of pathogens in PDAP. For example, real-time fluorescence quantitative PCR technology has become the preferred method for detecting specific microbial DNA or RNA sequences with its efficient nucleic acid amplification ability and high sensitivity. This technology has significant advantages in improving detection speed and accuracy, but its high equipment investment and maintenance costs and high requirements for professional operating skills have, to a certain extent, limited its popularity in laboratories or clinical environments with limited resources.

[0004] Lateral flow immunoassay (LFI) is a rapid diagnostic technology based on the principle of antigen-antibody specific binding. Since its introduction in the 1980s, the technology has been widely used in many fields such as clinical diagnosis, food safety testing, environmental monitoring, and home self-testing due to its advantages of simple operation, intuitive results, and rapid response. The core advantage of LFI lies in its ease of operation. No professional equipment or technicians are required. Just drop the sample on the designated area and the results can be observed by the naked eye within a few minutes. This intuitive operation makes LFI an ideal on-site rapid detection tool, especially in remote areas or emergency situations where professional laboratory facilities are lacking. It can provide timely test results, which is of great significance for the rapid diagnosis of pathogens. In addition, LFI has a very wide range of applications. It can handle various types of samples, including blood, urine, PD fluid, etc. This flexibility greatly enhances the applicability of LFI in different detection scenarios. However, the design principle of most lateral flow immunochromatography test strips is based on antigen-antibody immune recognition, which leads to a single detection target and obvious antibody dependence. Summary of the invention

[0005] The purpose of the present application is to provide a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid, which is antibody-independent and can be specifically used to monitor Gram-negative bacteria in peritoneal dialysis fluid. This test strip is not only exquisitely designed and easy to operate, but also can achieve accurate identification of Gram-negative bacteria in peritoneal dialysis fluid within 10 minutes by optimizing multiple conditions during the preparation process.

[0006] Another object of the present application is to provide a method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid, which preparation method is simple and convenient.

[0007] In order to solve the above technical problems, the technical solution adopted in this application is: On the one hand, the present application provides a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid, comprising a base plate and a sample pad, a conjugation pad, a coating pad and a water-absorbing pad arranged in sequence on the base plate, wherein the conjugation pad is sprayed with a polydopamine-coated colloidal gold-coupled antibiotic probe; the coating pad is provided with a detection line, which is formed by a hydrogel coated with an antibiotic.

[0008] On the other hand, the present application provides a method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid, comprising the following steps: S1. Adding potassium carbonate solution to the polydopamine-coated colloidal gold solution, and then adding antibiotic small molecules and stirring for labeling to obtain a polydopamine-coated colloidal gold-coupled antibiotic probe; S2, spraying the polydopamine-coated colloidal gold-coupled antibiotic probe onto a glass fiber membrane, and drying to obtain a probe binding pad; S3, preparing a carboxymethyl chitosan solution, an oxidized dextran solution and an antibiotic solution, spraying them on the nitrocellulose membrane in sequence to form a detection line, and obtaining a coated pad after drying; S4. The sample pad, the probe binding pad, the coating pad and the absorbent pad are sequentially attached to the bottom plate along the length direction, and a test strip for detecting Gram-negative bacteria in peritoneal dialysis fluid is obtained after cutting.

[0009] Compared with the prior art, the embodiments of the present application have at least the following advantages or beneficial effects: The non-antibody-dependent immunochromatographic test strips for detecting Gram-negative bacteria in peritoneal dialysis fluid provided in this application are simple to prepare markers and avoid the use of paired antibodies, further reducing the cost of test strips and the complex steps required for paired experiments; and they buy time for clinical diagnosis of microbial pathogens in dialysis fluid, and accordingly, timely antibiotic treatment of patients. Each detection process can be completed within 10 minutes, and the test results are accurate, with a sensitivity 1-2 orders of magnitude higher than that of traditional colloidal gold test strips, and can quickly detect Gram-negative bacteria in peritoneal dialysis fluid samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0011] Figure 1 is a TEM image, where Figure 1 (a) is the TEM image of Au@PDA nanoparticles. Figure 1 (b) is the TEM image of Au@PDA-PMB reporter probe; Figure 2 Example 2 of the present application is an antibody-independent hydrogel lateral flow chromatography test paper for G + and G - Selective results graph for pathogenic bacteria; Figure 3 This is a photograph of a lateral flow chromatography test strip of E. coli of different concentrations under natural light in Example 2 of the present application. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The colloidal gold (20 nm), dopamine hydrochloride (DA·HCl), hydrogen peroxide, ammonia solution (NH4OH, 28-30%), NC membrane, PVC base plate and marking pad used in the following embodiments were all purchased from McLean Biochemical Co., Ltd. (Shanghai, China). The reagents or instruments used without indicating the manufacturer are all conventional products that can be purchased commercially.

[0013] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to specific embodiments.

[0014] A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid comprises a base plate and a sample pad, a conjugation pad, a coating pad and a water-absorbing pad which are sequentially arranged on the base plate, wherein a polydopamine-coated colloidal gold-coupled antibiotic probe is sprayed on the conjugation pad; and a detection line is arranged on the coating pad, and the detection line is formed by a hydrogel coated with an antibiotic.

[0015] Among them: the sample pad is used to place the sample to be tested. It can maintain the balance of the sample to avoid contamination or affect the test results; the binding pad fits tightly with the sample pad to effectively fix the biological detection probe and provide the necessary stability; the coating pad: as the carrier of the test line (T line), it plays a key role in transferring the antigen to the antibody or other recognition elements. It has good conductivity and mechanical strength, ensuring effective contact between the pathogen and the T line biological molecules; the absorbent pad is placed after the T line to absorb excess water to prevent erroneous results during the test.

[0016] In some embodiments of the present application, the above-mentioned antibiotic is polymyxin B. The present application also introduces polydopamine-coated colloidal gold (Au@PDA) with better light absorption performance as a labeling probe. PDA can not only stabilize colloidal gold, but also provide abundant functional groups for subsequent functional modification. Au@PDA is coupled to antibiotic small molecules (polymyxin B, PMB) to replace traditional antibody coupling. The Au@PDA-PMB reporter probe is established by utilizing the specific recognition effect of PMB on negatively charged lipid A on the outer membrane lipopolysaccharide of Gram-negative bacteria.

[0017] In some embodiments of the present application, the particle size of the polydopamine-coated colloidal gold is 25-40 nm; the conjugated amount of the antibiotic in the probe is 1-4 mg / mL. Preferably, the particle size of the polydopamine-coated colloidal gold is 30 nm; the conjugated amount of the antibiotic in the probe is 1.5 mg / mL.

[0018] In some embodiments of the present application, in a test strip of conventional width, the spraying amount of the polydopamine-coated colloidal gold-coupled antibiotic probe on the conjugate pad is 1 μL / cm.

[0019] In some embodiments of the present application, the hydrogel is formed by the reaction of carboxymethyl chitosan and oxidized dextran. The content of carboxymethyl chitosan in the hydrogel is 0.5-3%, and the content of oxidized dextran is 2-5%; the concentration of antibiotics coated in the hydrogel is 0.5-2 mg / mL. Preferably, the content of carboxymethyl chitosan in the hydrogel is 1.5%, and the content of oxidized dextran is 3%; the concentration of antibiotics coated in the hydrogel is 1 mg / mL. The content of carboxymethyl chitosan and oxidized dextran is determined according to the mass fraction of the two polymers required to prepare the final hydrogel, and the content of antibiotics is based on the final mass concentration (based on the hydrogel). The present application utilizes the water-retaining properties of the hydrogel to immobilize PMB in the T zone. When the test object flows to the T zone, the hydrogel slows down the flow rate of the sample, allowing the sample to fully react with the exposed PMB, which is G - The capture of bacteria provides sufficient reaction time. - The "sandwich" complex of "bacteria + PMB" retains the bacteria in the T zone and continuously enriches them, making the color of the area darker and positively correlated with the content of the target.

[0020] In some embodiments of the present application, the total coating amount of the hydrogel+PMB in the above-mentioned coating pad is 1.2 μL / cm.

[0021] A method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid comprises the following steps: S1. Adding potassium carbonate solution to the polydopamine-coated colloidal gold solution, and then adding antibiotic small molecules and stirring for labeling to obtain a polydopamine-coated colloidal gold-coupled antibiotic probe; S2, spraying the polydopamine-coated colloidal gold-coupled antibiotic probe onto a glass fiber membrane, and drying to obtain a probe binding pad; S3, preparing a carboxymethyl chitosan solution, an oxidized dextran solution and an antibiotic solution, spraying them on the nitrocellulose membrane in sequence, and obtaining a coated pad after drying; S4. The sample pad, the probe binding pad, the coating pad and the absorbent pad are sequentially attached to the bottom plate along the length direction, and a test strip for detecting Gram-negative bacteria in peritoneal dialysis fluid is obtained after cutting.

[0022] In some embodiments of the present application, the pH of the polydopamine-coated colloidal gold solution is adjusted by the potassium carbonate solution in step S1 to 7.0-10.0, preferably 8.5.

[0023] In some embodiments of the present application, the drying temperature in the above step S3 is 30-40°C, preferably 35°C.

[0024] In some embodiments of the present application, the cutting width of the test strip in step S4 is 0.3-0.4 cm.

[0025] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0026] Example 1 This embodiment provides a method for preparing and using a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid.

[0027] There are many factors that affect the quality of antibody-independent immunochromatographic test strips, such as the particle size of polydopamine-coated colloidal gold (Au@PDA), the concentration of coated antibiotics (polymyxin B, PMB), the type of nitrocellulose (NC) membrane and glass fiber membrane, the preparation of buffer, etc. Due to factors such as steric hindrance, different markers require different Au@PDA particle sizes. Au@PDA size, ionic strength, loading concentration, etc. all affect its binding performance with bacteria. The present invention has obtained more suitable Au@PDA particle size, ionic strength, etc. through a large number of experimental verifications.

[0028] Step 1. In the lateral flow chromatography rapid detection, the NC membrane is used as the solid phase support for carrying the T line. The type of the membrane is very important. It is necessary to screen comprehensively from the aspects of chromatography speed, sensitivity and non-specific binding, and select an NC membrane that can load the marker and the sample to be detected well and is not adsorbed. After a large number of experiments, the Sartorius-100 NC membrane was selected, which has the best effect.

[0029] Step 2: Au@PDA was prepared by in-situ oxidation of dopamine on the surface of colloidal gold. The specific operation method is as follows: 4 mL of colloidal gold solution (1 mg / mL) was placed in a 25 mL reaction bottle, NaOH (0.1 mol / L) was used to adjust the pH to 7.0, and then 20 µL of hydrogen peroxide (3%) was added. After 5 minutes, 100 µL of dopamine (5 mg / mL) was added and stirred at room temperature for 12 hours. Centrifugal separation (10,000 rpm, 10 minutes), the precipitate was washed with water twice, and Au@PDA nanoparticles with an average particle size of 30 nm were obtained. The TEM image is shown in the figure. Figure 1 As shown in (a).

[0030] Step 3: Preparation of polydopamine-coated colloidal gold-conjugated antibiotic (Au@PDA-PMB) reporter probe 1) Determination of the optimal PMB modification amount The effect of PMB on the stability of PDA was determined by the test tube observation method, and then the optimal amount of PMB modification was determined. The specific operation method is as follows: Take 8 centrifuge tubes, add 1.0 mL of the Au@PDA solution (particle size 30 nm) prepared in step 2 to each tube, add 3, 5, 7, 9, 11, 13, 15 or 17 μL of 0.2 M K2CO3 and 1, 1.5, 2, 2.5, 3, 3.5 or 4 mg of 200 μL of PMB to each tube, mix and stir for 20 min, and observe its color. When the Au@PDA solution does not aggregate and precipitate, and the color does not change or changes slightly, the amount of PMB used at this time is the optimal labeling amount.

[0031] 2) Preparation of Au@PDA-PMB probe with optimal PMB modification amount Take 2 mL of the Au@PDA solution obtained in step 2 and place it in a 10 mL reaction bottle. Add 20 μL of 0.2 M K2CO3 dropwise to make the pH reach 8.5. Then add 0.5 mL of PMB (2 mg / mL) and stir overnight. Centrifuge at 1000 rpm / min for 15 min, discard the supernatant, and retain the concentrated PMB-labeled Au@PDA particles. Make up to 6 mL with pure water, mix well, and store at 4°C for later use. After PMB coupling, the particle size of Au@PDA-PMB does not change much. Its TEM image is shown in the figure below. Figure 1 As shown in (b), the morphology and size remain uniform.

[0032] Step 4: Determination of the optimal detection line (T line) concentration Carboxymethyl chitosan was diluted to 4 concentrations of 0.5%, 1%, 2%, and 3% in sequence, oxidized dextran was diluted to 4 concentrations of 2%, 3%, 4%, and 5% in sequence, and PMB coating concentration was diluted to 3 concentrations of 0.5, 1, and 2 mg / mL in sequence; the NC membrane was attached to the bottom plate, and then the diluted carboxymethyl chitosan, oxidized dextran, and PMB were sprayed on the NC membrane using a film scribing instrument to prepare a T line and dried at 37°C. The optimal concentration of the T line was determined based on the T line and the color depth. The optimal coating amounts of carboxymethyl chitosan, oxidized dextran, and PMB for the test line were 1.5%, 3%, and 1 mg / mL, respectively.

[0033] Step 5: Assembly of non-antibody dependent lateral flow chromatography test strips The Au@PDA-PMB solution labeled in step 3 was sprayed on the glass fiber membrane using a film sprayer. The spraying amount on the binding pad was 1 μL / cm, and the PDA binding pad was obtained by constant temperature drying at 37°C. 1% carboxymethyl chitosan, 3% oxidized dextran, and 1 mg / mL PMB were fixed on the carrier of the T line, i.e., the NC membrane, as the detection line (T line) using a film scribing instrument. The coating amount was 1.2 μL / cm, and it was placed in a vacuum constant temperature drying oven at 37°C and dried for more than 2 h. The sample pad (2 cm long), PDA binding pad (5 mm long), coating pad, and absorbent pad (2 cm long) were successively attached to the bottom PVC plate along the length direction, and then cut into strips with a width of 0.4 cm, i.e., immunochromatographic test strips for detecting Gram-negative bacteria in peritoneal dialysis fluid. The prepared test strips were placed in an aluminum foil bag, sealed with a desiccant, and stored at 4°C.

[0034] Step 6: Detection method and judgment criteria for antibody-independent lateral flow chromatography test strips Add 50 μL of peritoneal dialysis fluid to be tested into the sample well, take the test paper prepared in step 5, immerse one end of the sample pad into the sample well, and observe the results within 10 minutes. If a dark red band appears at the test line of the test paper, it indicates that the sample is positive and contains Gram-negative bacteria; if no band appears on the test paper, it indicates that the sample is negative and does not contain Gram-negative bacteria.

[0035] Example 2 This example provides a performance test of the immunochromatographic test paper for Gram-negative bacteria in peritoneal dialysis fluid.

[0036] 1. Test strip specificity experiment The test strips prepared in step 5 of Example 1 were used to simultaneously detect several G - Bacteria such as P. mirabilis, E. coli, and P. aeruginosa. Prepare the sample at a concentration of 10 5 cfu / mL solution, take 40 μL sample and 10 μL Au@PDA@PMB reporter probe solution in a 96-well plate and incubate for 5 min, then take out all the liquid to titrate the test strip. Wait for 10 min, read the T line value through the mobile phone software to obtain the selective experimental results. The experimental results are as follows Figure 2 As shown, Figure 2 The technique is clearly demonstrated in differentiating the above G - and G + The specific performance on bacteria (such as Staphylococcus aureus (S. Aureus) and Bacillus subtilis (B. Subtilis)) indicates that the antibody-free lateral flow chromatography test paper prepared by the present invention has no cross-reaction and has good specificity.

[0037] 2. Test strip sensitivity test Dilute the bacteria with 0.01 M PBS buffer and add 40 μL of 10 0 , 10 1 , 10 2 , 10 3 , 10 4 , 10 5 , 10 6 , 10 7 , 10 8 cfu / mL of E. coli solution was added to a 96-well plate and incubated with 10 μL of Au@PDA-PMB reporter probe solution for 5 min. All the liquid was then taken out and dripped onto the sample pad of the test strip. After waiting for 10 min, the qualitative results were read with the naked eye after the reaction stabilized, confirming that the hydrogel lateral flow chromatography test strip could detect G - The sensitivity of the hydrogel test strip in qualitative mode is obtained by observing the color of the T line with the naked eye. Figure 3 The results show that the dilution concentration of E. coli is 10 2 cfu / mL, the detection line is still visible, indicating that the sensitivity of the test strip is relatively excellent. As the concentration of E. coli increases, the color of the T line becomes darker (from 10 2 cfu / mL to 10 6 cfu / mL); however, when the bacterial concentration exceeded 10 8 cfu / mL, the color of the T line weakened due to the hook effect.

[0038] 3. Clinical sample verification The test strips prepared in Example 1 of the same batch were used to test 10 Gram-negative bacteria and 5 Gram-positive bacteria infected peritoneal dialysis fluid samples, and the results were recorded after 10 minutes. Results: Among the 15 sample dialysis fluids, the test strips prepared in Example 1 showed positive results for 10 samples and negative results for 5 samples, and the accurate compliance rate of the test strips prepared in Example 1 was 100%.

[0039] In summary, the test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid and the preparation method thereof according to the embodiment of the present application have the following advantages: the non-antibody-dependent immunochromatographic test strip for detecting Gram-negative bacteria in peritoneal dialysis fluid provided by the present application is simple to prepare the marker, avoids the use of paired antibodies, and further reduces the cost of the test strip; and saves time for clinical diagnosis of microbial pathogens in dialysis fluid, and accordingly timely provides antibiotic treatment to patients. Each detection process can be completed within 10 minutes, and the test results are accurate, with a sensitivity 1-2 orders of magnitude higher than that of traditional colloidal gold test strips, and can quickly detect Gram-negative bacteria in peritoneal dialysis fluid samples.

[0040] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present application.

Claims

1. A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid, comprising a base plate and a sample pad, a binding pad, a coating pad and a water-absorbing pad sequentially arranged on the base plate, characterized in that: The conjugation pad is sprayed with a polydopamine-coated colloidal gold-coupled antibiotic probe; the coated pad is provided with a detection line, which is formed by a hydrogel coated with antibiotics.

2. A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 1, characterized in that: The antibiotic is polymyxin B.

3. A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 2, characterized in that: The particle size of the polydopamine-coated colloidal gold is 25-40 nm; the coupling amount of the antibiotic in the probe is 1-4 mg / mL.

4. A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 3, characterized in that: The spraying amount of the polydopamine-coated colloidal gold-coupled antibiotic probe on the conjugate pad is 1 μL / cm.

5. A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 1, characterized in that: The content of carboxymethyl chitosan in the hydrogel is 0.5-3%, and the content of oxidized dextran is 2-5%; the concentration of antibiotics coated in the hydrogel is 0.5-2 mg / mL.

6. A test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 5, characterized in that: The coating volume of the coating pad was 1.2 μL / cm.

7. A method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Adding potassium carbonate solution to the polydopamine-coated colloidal gold solution, and then adding antibiotic small molecules and stirring for labeling to obtain a polydopamine-coated colloidal gold-coupled antibiotic probe; S2, spraying the polydopamine-coated colloidal gold-coupled antibiotic probe onto a glass fiber membrane, and drying to obtain a probe binding pad; S3, preparing a carboxymethyl chitosan solution, an oxidized dextran solution and an antibiotic solution, spraying them on the nitrocellulose membrane in sequence to form a detection line, and obtaining a coated pad after drying; S4. The sample pad, the probe binding pad, the coating pad and the absorbent pad are sequentially attached to the bottom plate along the length direction, and a test strip for detecting Gram-negative bacteria in peritoneal dialysis fluid is obtained after cutting.

8. The method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 7, characterized in that: In step S1, the potassium carbonate solution is used to adjust the pH of the polydopamine-coated colloidal gold solution to 7.0-10.

0.

9. The method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 7, characterized in that: The drying temperature in step S3 is 30-40°C.

10. The method for preparing a test strip for identifying Gram-negative bacteria in peritoneal dialysis fluid according to claim 7, characterized in that: The cutting width of the test strip in step S4 is 0.3-0.4 cm.

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