Preparation method and application of dry chemical reagent for measuring urea stored at normal temperature

Abstract

The invention discloses a preparation method of a dry chemical reagent for measuring urea stored at normal temperature. The preparation method comprises the following steps: S1, preparing a buffer reagent and a protective component; s2, dissolving the biological enzyme and the chromophoric substrate to form a dissolving reagent; s3, coating by using a biological film-forming material to form a coating reagent; s4, coating and printing the coating reagent in the pore channels of the specified bottom plate base material manually or by equipment in a volume quantification manner; the equipment comprises a single-channel type pipettor, a multi-channel type pipettor, a continuous multi-gear distributor or automatic dot printing equipment. S5, placing the specified bottom plate base material printed with the coating reagent in forced air drying equipment or drying equipment with the same efficiency; and S6, measuring the moisture content after drying and film forming, and judging whether substances containing biologically active enzymes and substrates in the reagent are completely locked to the position of the net-shaped cavernous body structure of the biological film forming material or not based on the moisture content. The invention also discloses application of the dry chemical reagent for measuring urea stored at normal temperature, and the dry chemical reagent is applied to samples formed by urine, serum or tissues.

Description

Technical Field

[0001] The invention relates to the technical field of dry chemical reagents and urea determination, and in particular to a preparation method of a dry chemical reagent for urea determination stored at room temperature and application thereof. Background Art

[0002] Urea is the end product of human protein metabolism, with a molecular weight of 60. The determination of urea content in human blood and urine is currently one of the main detection indicators for kidney disease. Amino acids in the human body are decomposed into α-keto acids and NH3 by deamination. NH3 undergoes urea cycle in liver cells and reacts with CO2 to produce urea. The synthesized urea is secreted into the bloodstream and then collected by the kidneys and excreted from the urine. The amount of urea produced mainly depends on the amount of dietary protein intake, the catabolism of tissue protein and the function of the liver. The urea cycle is a detoxification mechanism for the human body, which can synthesize urea that is harmless to the human body from the NH3 produced by metabolism, and then excrete it. Once the urea cycle is obstructed, it will cause a series of diseases, such as damage to the nervous system and liver caused by hyperammonemia.

[0003] Today, laboratory medicine has a polarized development trend. On the one hand, there are various large-scale automated and efficient instruments and equipment. This type of equipment usually uses liquid reagents, and its advantages are low price and high measurement accuracy. Disadvantages: It requires supporting large-scale equipment, and has high requirements for equipment price, floor space, and personnel training. On the other hand, there is a POCT testing model with miniaturized and handheld laboratories, simple operations, and timely test result reports. The POCT model not only meets the rescue and treatment needs of critically ill patients on the medical side, but also meets the needs of primary diagnosis and treatment institutions and outpatient clinics with small sample sizes and immediate testing. With the advancement of science, the rise of the Internet and the need for patient privacy, POCT timely testing products are gradually entering families. For single indicators or complex joint inspection indicators with obvious clinical indicators, projects that require continuous monitoring to realize value have entered a new pattern of family self-diagnosis.

[0004] The method of quantitative determination of urea by dry chemistry can be traced back to the late 1970s, when the dry multi-layer composite film dry chemical reagent developed by Kodak pioneered the dry chemical quantitative detection technology. Following Kodak, FUJI, BM, and Arkray have successively developed similar products. On the one hand, at present, the detection principles of urea dry chemical reagents on the market include direct method and indirect method. Johnson & Johnson and Fuji's dry chemical reagents are all determined by the indirect method, while Kyoto urea dry chemical reagents use the direct method. And there are only a few companies in the world that can produce dry chemical reagents for urea detection. The reagents for dry chemical quantitative detection of urea are imported, which makes them expensive. As a result, small hospitals or community clinics cannot afford the cost. It is even more impossible to achieve the purpose of home self-testing and continuous monitoring.

[0005] On the other hand, conventional reflectance photometry for dry chemical quantitative detection of urea reagents mostly adopts a composite structure, which is divided into three layers in structure, from top to bottom: diffusion layer, reagent layer and transparent support layer. The diffusion layer is generally composed of titanium dioxide, barium sulfate, cellulose acetate and other structures, which can quickly disperse and cover the colored substances in the sample. At the same time, these reflective compounds also play a role in providing a reflective background for the color development layer. It can now be achieved through composite membrane layer structures such as asymmetric polyethersulfone. The reagent layer is divided into multiple functional reagent layers according to actual needs, and can be roughly divided into a reaction zone and a color development zone according to specific functions. The main function of the reaction zone is to convert the analyte into a compound that can be combined with the color development substance through physical, chemical, biochemical reactions and other reactions. The main function of the color development zone is to use a specific indicator system or color developer to make the analyte react to generate a compound that can be measured by reflection; the transparent support layer is located at the bottom layer of the reagent, generally using an optically transparent plastic substrate, allowing the incident light and reflected light to pass through completely, while playing a supporting role. There are the following technical defects: (1) During the test, the light source inside the instrument emits a beam of light, which passes through the transparent support layer. After the light is partially absorbed by the colored compound in the reagent layer, it is reflected on the reflective surface provided by the diffusion layer. The reflected light passes through the filter device and returns to the photometer to be read. The optical density is converted into a voltage reading to form a digital reading. During the reflection process, the colored substance is absorbed, and the analyte concentration is not proportional to the reflected light density; a direct limiting relationship cannot be generated, and conversion must be achieved through a complex functional relationship; (2) In the preparation process of reagent dry films, a process similar to film production is often used. The complex, biological enzyme, and colorimetric substrate are evenly spread on the support layer by scraping or spraying. Through the rapid drying process, the water in the solution is lost, and the viscous film-forming material in the liquid is tightly combined with the support layer. During the preparation process, the dispersion layer contains solids, and a screw flat coating method is required for coating. A large coating machine is required during the production and preparation process. The process requirements are extremely high, and the product structure is relatively complex. It is difficult for domestic equipment to meet the process requirements. Production equipment is mostly imported and relies on large imported equipment. It is difficult to break through the technology and the cost is high. The production and preparation cost is high and cumbersome. Large-scale production is even more difficult, and the equipment cost is high. It is not suitable for small and medium-sized production enterprises and can no longer meet the purpose of enterprises pursuing benefits.

[0006] (3) Dry chemical urea quantitative test strips have complex structures and difficult manufacturing processes. The reagent form is fixed, making it difficult to achieve joint testing of multiple biochemical indicators. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art, to address the problems in the related art, to provide a preparation method and application of a dry chemical reagent for urea determination stored at room temperature, by organically combining the use of biofilm-forming materials with traditional dry chemical determination technology, using biofilm-forming materials to encapsulate the main reaction enzyme, auxiliary tool enzyme, chromogenic substrate, buffer reagent and protective component in the dry chemical reaction process, and then printing the above mixture on the bottom plate of the reaction device. Through drying means, the water in the mixture is completely removed. The main components are firmly locked in the pores of the reaction substrate by physical adsorption, so as to achieve the effect of reagent drying and fixation. The advantage is that the production and preparation process is simple and easy, and the experimental and manufacturing costs are low. While meeting the small-scale manual production, it can also be used in semi-automatic and fully automated production lines. The product is suitable for the single detection of urea indicators, and is also suitable for joint detection with multiple biochemical indicators. It can be realized on both traditional dry chemical technology platforms and microfluidic technology platforms.

[0008] The first aspect of the present invention is to provide a method for preparing a dry chemical reagent for urea determination stored at room temperature, comprising: S1, prepare buffer reagents and protective components; S2, dissolving the biological enzyme and the chromogenic substrate to form a dissolving reagent; S3, using a biofilm-forming material to form a coating agent; S4, applying and printing the coating reagent into the channels of the designated bottom substrate in a volumetric manner manually or with the aid of a device; the device includes a single-channel pipette, a multi-channel pipette, a continuous multi-speed dispenser or an automated dot-printing device; S5, placing the designated base plate substrate printed with the coating reagent in a forced air drying device or a drying device with equivalent efficiency; S6, measuring the moisture content after drying and forming the film, and judging whether the substances containing biologically active enzymes and substrates in the reagent have been completely locked into the mesh sponge structure position of the biological film-forming material based on the moisture content.

[0009] Preferably, the S1 comprises: S11, select a suitable buffer system, including: Tris-HCL, MOPS, HEPES and phosphate buffer based buffer systems; S12, configuring protective components.

[0010] Preferably, the S12 includes: (1) adding a certain concentration of sucrose, trehalose, raffinose, bovine serum albumin, silk protein, casein, bovine serum and amino acids to the basic buffer system; (2) adding a surfactant to the basic buffer system, wherein the surfactant comprises Tween-20, glycerol and PEG; (3) Adding a certain concentration of EDTA, disodium EDTA, tetrasodium EDTA, potassium ferrocyanide, bilirubin oxidase and ascorbic acid oxidase into the basic buffer system.

[0011] Preferably, S2 includes: S21, selecting a certain concentration of urease to be dissolved in the basic buffer system; S22, dissolving a certain concentration of o-phenolphthalein complexing agent with an organic reagent, and adding the solution to the basic buffer system; wherein the dissolved reagent formed after dissolving the biological enzyme and the chromogenic substrate is a precipitation-free homogeneous reagent.

[0012] Preferably, S3 includes: S31, selecting a biofilm-forming material suitable for the urea determination methodology, and preparing the biofilm-forming material into a film-forming base liquid of a certain concentration; S32, after the film-forming base liquid is cooled to room temperature, the dissolving reagent is added to the film-forming base liquid at room temperature, and the mixture is thoroughly mixed.

[0013] Preferably, the biofilm-forming material includes one or more of chitin, polysaccharides, agarose and PVA.

[0014] Preferably, S4 includes: S41, clean and passivate the surface of the designated baseboard substrate before use; S42, manually or with the aid of equipment, apply and print the coating reagent into the pores of the designated bottom plate substrate in a volumetrically quantitative manner.

[0015] Preferably, S5 includes: S51, setting the wind speed, temperature and drying time of the blast drying equipment or a drying equipment with equal efficiency; S52, placing the designated base substrate after printing the coating reagent in a blast drying device or a drying device with equivalent efficiency, and drying the coating reagent printed in the pores of the designated base substrate through the air duct and the drying device; S53, determining whether the film formation after drying meets the film formation standard; the film formation standard includes: the film layer surface is smooth, without cracks, peeling and separation from the base material.

[0016] Preferably, the determining of the moisture content after drying and forming the film comprises determining the moisture content after drying and forming the film by gravimetric method or Karl Fischer method.

[0017] The second aspect of the present invention provides an application of a dry chemical reagent for urea determination stored at room temperature prepared by the preparation method of the first aspect, which is applied to samples formed by urine, serum or tissue, comprising: S1', diluting the sample based on a diluent to obtain a diluted sample; the diluent is prepared based on 50umol / L-50mmol / L Tris-HCL and phosphate buffer prepared with purified water, and a preservative component is added at a concentration of 1 / 10,000 to 1 / 1000; S2', adding sample and reacting; including: adding the diluted sample to the reaction well of the corresponding reagent at a sample volume of 15-35uL per reaction system, and completing the biochemical reaction within 3-10 minutes; the biochemical reaction can be carried out at room temperature and 37°C, and the sample color changes from colorless to purple; S3', according to the color change of the sample from colorless to purple after the reaction, the color change is observed by naked eyes, and the color scale card established by the standard concentration sample is compared to achieve semi-quantitative detection; and / or a standard curve is established using the standard concentration sample, corresponding to the CCD, CMOS and sample color sensing equipment, and the color weight analysis is performed and then matched with the standard curve to achieve quantitative detection.

[0018] The preparation method of the present invention and the beneficial effects of its application: With the help of biofilm-forming materials, the original biochemical reagents or multi-layer dry chemical reagents are improved, and a one-time film-forming preparation process is adopted to realize a rapid preparation method for urea quantitative dry chemical reagents. Innovations have been made in the implementation plan of the one-time film-forming preparation process, the selection and use concentration of biofilm-forming materials, the components for removing interfering substances in the reagent system, the preparation plan of the diluent, and the treatment method of the substrate material. The production and preparation process is simple and easy, and the experimental and manufacturing costs are low. While meeting the needs of small-scale manual production, it can also be used in semi-automatic and fully automated production lines. The product is suitable for the separate detection of urea indicators, and is also suitable for joint detection with multiple biochemical indicators. It can be achieved on both traditional dry chemical technology platforms and microfluidic technology platforms. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the related technologies, the drawings required for use in the specific embodiments or the related technical descriptions will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A flow chart of a method for preparing a dry chemical reagent for urea determination stored at room temperature according to an embodiment of the present invention; Figure 2 This is a flow chart of step S1 of a method for preparing a dry chemical reagent for urea determination stored at room temperature according to an embodiment of the present invention; Figure 3This is a flow chart of step S2 of a method for preparing a dry chemical reagent for urea determination stored at room temperature according to an embodiment of the present invention; Figure 4 This is a flow chart of step S3 of a method for preparing a dry chemical reagent for urea determination stored at room temperature according to an embodiment of the present invention; Figure 5 This is a flow chart of step S4 of a method for preparing a dry chemical reagent for urea determination stored at room temperature according to an embodiment of the present invention; Figure 6 This is a flow chart of step S5 of a method for preparing a dry chemical reagent for urea determination stored at room temperature according to an embodiment of the present invention; Figure 7 A flow chart of an application method for storing a dry chemical reagent for urea determination at room temperature according to an embodiment of the present invention; Figure 8 A schematic diagram of the color gradient of the standard curve system provided according to an embodiment of the present invention; Fig. 9 A linear schematic diagram of product labeling provided according to an embodiment of the present invention; Fig.10 A schematic diagram of a limiting range provided according to an embodiment of the present invention; Fig.11 A schematic diagram of the long-term stability of a product corresponding to 2-8°C provided according to an embodiment of the present invention; Fig.12 A schematic diagram of the long-term stability of a product at 30°C provided according to an embodiment of the present invention; Fig.13 A schematic diagram of clinical sample comparison provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Embodiment 1

[0024] like Figure 1 As shown, this embodiment provides a method for preparing a dry chemical reagent for urea determination stored at room temperature, comprising: S1, prepare buffer reagents and protective components; like Figure 2 As shown, as a preferred embodiment, the S1 includes: S11, selecting a suitable buffer system, including: a buffer system based on Tris-HCL, MOPS, HEPES and phosphate buffers, in order to maintain the stability of the pH value of the buffer system and ensure the biological activity of the main raw materials such as urease; S12, configure protection components, including: (1) adding a certain concentration of sucrose, trehalose, raffinose, bovine serum albumin, silk protein, casein, bovine serum and amino acids to the basic buffer system to reduce the possibility of active enzymes being oxidized and losing their effectiveness; (2) adding a certain proportion of surfactants such as Tween-20, glycerol and PEG to the basic buffer system to make the contents in the buffer system evenly dispersed; (3) A certain concentration of EDTA, disodium EDTA, tetrasodium EDTA, potassium ferrocyanide, bilirubin oxidase and ascorbic acid oxidase are added to the basic buffer system to remove interfering substances in the sample.

[0025] S2, dissolving the biological enzyme and the chromogenic substrate to form a dissolving reagent; like Figure 3 As shown, as a preferred embodiment, the S2 includes: S21, selecting a suitable concentration of urease and dissolving it in the basic buffer system; S22, dissolving an o-phenolphthalein complexing agent of suitable concentration with an organic reagent, and adding the solution to the basic buffer system; wherein the dissolved reagent formed after dissolving the biological enzyme and the chromogenic substrate should be a homogeneous reagent as a whole without precipitation.

[0026] S3, using a biofilm-forming material to form a coating agent; like Figure 4 As shown, as a preferred implementation, S3 includes: S31, selecting a biofilm-forming material suitable for the urea determination methodology, preferably chitin, polysaccharide, agarose, PVA, etc.; and preparing the biofilm-forming material into a film-forming base liquid of a certain concentration. Generally, the biofilm-forming material is a high molecular weight substance, and the dissolution process is relatively difficult, requiring high temperature or other methods to assist dissolution; S32, after the film-forming base liquid is cooled to room temperature, the dissolving reagent is added to the film-forming base liquid at room temperature, and the mixture is thoroughly mixed.

[0027] S4, applying and printing the coating reagent into the channels of the designated bottom substrate in a volumetric manner manually or with the aid of a device; the device includes a single-channel pipette, a multi-channel pipette, a continuous multi-speed dispenser or an automated dot-printing device; like Figure 5 As shown, as a preferred embodiment, the S4 includes: S41, in order to ensure the cleanliness, flatness and surface water purity of the designated base plate substrate, the designated base plate substrate is cleaned and surface passivated before use, the purpose of which is to remove impurities and burrs of the base plate substrate and improve the hydrophilicity, which is conducive to the adhesion of the film-forming material; S42, manually or with the aid of equipment, apply and print the coating reagent into the pores of the designated bottom plate substrate in a volumetrically quantitative manner.

[0028] S5, placing the designated base plate substrate printed with the coating reagent in a forced air drying device or a drying device with equivalent efficiency; like Figure 6 As shown, as a preferred implementation, the S5 includes: S51, setting the wind speed, temperature and drying time of the blast drying equipment or drying equipment of equal efficiency to ensure that the reagent is completely dried; S52, placing the designated base substrate after printing the coating reagent in a blast drying device or a drying device with equivalent efficiency, and drying the coating reagent printed in the pores of the designated base substrate through the air duct and the drying device; S53, determining whether the film formation after drying meets the film formation standard; the film formation standard includes: the film layer surface is smooth, and there should be no cracking, peeling, separation from the base material, etc.

[0029] S6, determine the moisture content after drying and film formation by weighing method or Karl Fischer method, and judge whether the substances containing biologically active enzymes and substrates in the reagent have been completely locked into the mesh sponge structure of the biofilm-forming material based on the moisture content. The biofilm-forming material uses a three-dimensional structure similar to the sponge pores to lock the substances containing biologically active enzymes, substrates, etc. in the reagent into the mesh sponge structure of the biofilm-forming material, and can keep the reagent stable at room temperature, so as to achieve the purpose of not interfering with each other and not causing biochemical reactions. Embodiment 2

[0030] like Figure 7 As shown, this embodiment provides an application of a dry chemical reagent for urea determination stored at room temperature prepared by the preparation method of Example 1, which is applied to samples formed by urine, serum or tissue, including: S1', diluting the sample based on a diluent to obtain a diluted sample; the diluent is prepared based on 50umol / L-50mmol / L Tris-HCL and phosphate buffer prepared with purified water, and a preservative component is added at a concentration of 1 / 10,000 to 1 / 1000.

[0031] This embodiment takes urine samples as an example: the dilution ratio is between 1:14 and 1:29.

[0032] S2', adding sample and reacting; including: adding the diluted sample to the reaction well of the corresponding reagent at a sample volume of 15-35uL per reaction system, and completing the biochemical reaction within 3-10 minutes; the biochemical reaction can be carried out at room temperature and 37°C, and the sample color changes from colorless to purple. In this reaction system, the urease content and the o-phenolphthalein complexing agent content are both excessive, so the reaction will not be terminated before the urea in the sample is completely consumed; S3', according to the color change of the sample from colorless to purple after the reaction, semi-quantitative detection can be achieved by observing the color change with the naked eye and comparing it with the color scale card established with the standard concentration sample; a standard curve is established using the standard concentration sample, corresponding to the CCD, CMOS and sample color sensing equipment, and the color weight analysis is performed and then matched with the standard curve to achieve quantitative detection.

[0033] Analysis of test results of embodiment: 1. Actual data display and analysis: A. Standard curve system color gradient, such as Figure 8 As shown, the standard concentrations are: 0 (purified water), 100mmol / L, 200mmol / L, 400mmol / L, 600mmol / L, 800mmol / L, 1000mmol / L, 1200mmol / L, the dilution ratio is 1:29.

[0034] B. Product standard linearity is shown in Table 1 and Fig. 9 As shown; Table 1

[0035] C. Blank limit and detection limit are shown in Table 2 and Table 3: Table 2

[0036] Table 3

[0037] D. The limiting range is shown in Table 4 and Fig.10 As shown: Table 4

[0038] Fig.10 Medium requirement: R 2 >0.975.

[0039] E. Repeatability and accuracy are shown in Tables 5, 6 and 7, corresponding to different target concentrations.

[0040] Table 5

[0041] Table 6

[0042] Table 7

[0043] Require: (1) Repeatability: Variation dilution CV <15%; (2) Accuracy: Relative deviation from target value <15%.

[0044] F. The batch-to-batch variability of the products is shown in Table 8.

[0045] Table 8

[0046] Batch difference: relative range ≤±15% G. Product stability The long-term stability diagram of the product at 2-8°C and 30°C is as follows Fig.11 and Fig.12 As shown (the curves from top to bottom in the icon correspond to sample concentrations of 200, 400 and 800mmol / L); this product can achieve a storage period of 12 months under 2~30℃ conditions.

[0047] H. Schematic diagram of clinical sample comparison Fig.13 After comparison with Mindray S-400 biochemical analyzer and its matching biochemical kit, 58 blind urine samples showed a correlation R 2 >0.90.

[0048] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above embodiments can be implemented by software, or by means of software plus necessary general hardware platforms. Based on such understanding, the technical solutions of the above embodiments can be embodied in the form of software products, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), including several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a dry chemical reagent for urea determination stored at room temperature, characterized in that: include: S1, prepare buffer reagents and protective components; S2, dissolving the biological enzyme and the chromogenic substrate to form a dissolving reagent; S3, using a biofilm-forming material to form a coating agent; S4, applying and printing the coating reagent into the channels of the designated bottom substrate in a volumetric manner manually or with the aid of a device; the device includes a single-channel pipette, a multi-channel pipette, a continuous multi-speed dispenser or an automated dot-printing device; S5, placing the designated base plate substrate printed with the coating reagent in a forced air drying device or a drying device with equivalent efficiency; S6, measuring the moisture content after drying and forming the film, and judging whether the substances containing biologically active enzymes and substrates in the reagent have been completely locked into the mesh sponge structure position of the biological film-forming material based on the moisture content.

2. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 1, characterized in that: The S1 includes: S11, select a suitable buffer system, including: Tris-HCL, MOPS, HEPES and phosphate buffer based buffer systems; S12, configuring protective components.

3. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 2, characterized in that: The S12 includes: (1) adding a certain concentration of sucrose, trehalose, raffinose, bovine serum albumin, silk protein, casein, bovine serum and amino acids to the basic buffer system; (2) adding a surfactant to the basic buffer system, wherein the surfactant comprises Tween-20, glycerol and PEG; (3) Adding a certain concentration of EDTA, disodium EDTA, tetrasodium EDTA, potassium ferrocyanide, bilirubin oxidase and ascorbic acid oxidase into the basic buffer system.

4. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 3, characterized in that: The S2 includes: S21, selecting a certain concentration of urease to be dissolved in the basic buffer system; S22, dissolving a certain concentration of o-phenolphthalein complexing agent with an organic reagent, and adding the solution to the basic buffer system; wherein the dissolving reagent formed after dissolving the biological enzyme and the chromogenic substrate is a precipitation-free homogeneous reagent.

5. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 4, characterized in that: The S3 includes: S31, selecting a biofilm-forming material suitable for the urea determination methodology, and preparing the biofilm-forming material into a film-forming base liquid of a certain concentration; S32, after the film-forming base liquid is cooled to room temperature, the dissolving reagent is added to the film-forming base liquid at room temperature, and the mixture is thoroughly mixed.

6. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 5, characterized in that: The biofilm-forming material includes one or more of chitin, polysaccharide, agarose and PVA.

7. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 6, characterized in that: The S4 includes: S41, clean and passivate the surface of the designated baseboard substrate before use; S42, manually or with the aid of equipment, apply and print the coating reagent into the pores of the designated bottom plate substrate in a volumetrically quantitative manner.

8. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 7, characterized in that: The S5 includes: S51, setting the wind speed, temperature and drying time of the blast drying equipment or a drying equipment with equal efficiency; S52, placing the designated base substrate after printing the coating reagent in a blast drying device or a drying device with equivalent efficiency, and drying the coating reagent printed in the pores of the designated base substrate through the air duct and the drying device; S53, determining whether the film formation after drying meets the film formation standard; the film formation standard includes: the film layer surface is smooth, without cracks, peeling and separation from the base material.

9. The method for preparing a dry chemical reagent for urea determination stored at room temperature according to claim 8, characterized in that: The determining of the moisture content after drying and forming the film comprises determining the moisture content after drying and forming the film by gravimetric method or Karl Fischer method.

10. Use of a dry chemical reagent for urea determination stored at room temperature prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Applicable to samples of urine, serum or tissue, including: S1', diluting the sample based on a diluent to obtain a diluted sample; the diluent is prepared based on 50umol / L-50mmol / L Tris-HCL and phosphate buffer prepared with purified water, and a preservative component is added at a concentration of 1 / 10,000 to 1 / 1000; S2', adding sample and reacting; including: adding the diluted sample to the reaction well of the corresponding reagent at a sample volume of 15-35uL per reaction system, and completing the biochemical reaction within 3-10 minutes; the biochemical reaction can be carried out at room temperature and 37°C, and the sample color changes from colorless to purple; S3', according to the color change of the sample from colorless to purple after the reaction, the color change is observed by naked eyes, and the color scale card established by the standard concentration sample is compared to achieve semi-quantitative detection; and / or a standard curve is established using the standard concentration sample, corresponding to the CCD, CMOS and sample color sensing equipment, and the color weight analysis is performed and then matched with the standard curve to achieve quantitative detection.

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