Construction method for flexible paper-based sensor used for detecting meat products, and use of flexible paper-based sensor

Abstract

The present invention belongs to the technical field of antibiotic detection. Disclosed are a preparation method for a flexible paper-based sensor used for detecting tetracycline residues in meat products, and a method for detecting tetracycline residues in meat products by using the flexible paper-based sensor. The flexible paper-based sensor is obtained by mixing a UCNPs-cDNA signal probe and an Apt-MIL-53(Fe)@Cu2+ capture probe to obtain a detection probe; and then adding, in a dropwise manner, the detection probe to the central area of a paper-based carrier. By means of the specific recognition effect of Apt, which is located on the surface of the capture probe, on tetracycline, the constructed flexible paper-based sensor has relatively good specificity and anti-interference performance, and can accurately recognize tetracycline, thereby improving the detection accuracy; and the obtained flexible paper-based sensor is convenient to carry, and can achieve rapid and sensitive on-site detection of tetracycline in meat products.

Description

Flexible paper-based sensor construction method and application for meat product detection

[0001] Cross-reference to related applications

[0002] The present application claims priority to the Chinese patent application No. 202410678226.0 filed on May 29, 2024, and entitled "Flexible paper-based sensor construction method and application for tetracycline residue detection in meat products", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of antibiotic detection, in particular to a flexible paper-based sensor construction method and application for meat product detection. BACKGROUND

[0004] Tetracycline is an antibiotic commonly used to treat fish diseases in aquaculture. Due to the lack of understanding of pathogens and antibiotics among some breeders, tetracycline is misused or abused, resulting in its residues in fish bodies. The tetracycline residues in fish meat accumulate in the human body through the food chain, which can harm human health, cause yellowing of teeth, liver damage, gastrointestinal disorders, and allergic reactions. Traditional tetracycline detection methods include high-performance liquid chromatography, capillary electrophoresis, enzyme-linked immunosorbent assay, liquid chromatography-mass spectrometry, etc. These tetracycline detection methods have the advantages of high detection precision and reliable results, but still have the disadvantages of complex operation and long detection time. Therefore, there is an urgent need to develop a rapid and highly sensitive method for detecting tetracycline in fish meat to meet the demand for on-site rapid detection of tetracycline residues in fish meat. SUMMARY

[0005] The purpose of the present application is to provide a flexible paper-based sensor construction method and application for tetracycline residue detection in meat products to solve the problems existing in the prior art. The flexible paper-based sensor is convenient to carry and can accurately identify tetracycline, realizing rapid and sensitive on-site detection of tetracycline in meat products.

[0006] To achieve the above-mentioned purpose, the present application provides the following solutions:

[0007] The present application provides a flexible paper-based sensor for tetracycline residue detection in meat products, and the preparation method is as follows:

[0008] (1) Dissolve yttrium chloride hexahydrate, ytterbium chloride hexahydrate, and erbium chloride hexahydrate in methanol A, add oleic acid and 1-octadecene, and perform first heating and stirring reaction. After the reaction is completed, cool to obtain a mixed solution A;

[0009] The ammonium fluoride, sodium hydroxide is dissolved in methanol B, mixed with the mixed solution A, and the second heating and stirring reaction is carried out, then nitrogen is introduced, and the third heating and stirring reaction is carried out under a nitrogen atmosphere, and a mixed solution B is obtained by cooling; the mixed solution B is washed, centrifuged and dried to obtain the up-conversion fluorescent nanomaterial;

[0010] The up-conversion fluorescent nanomaterial, chloroform, toluene and polyacrylic acid aqueous solution are mixed and stirred, and then centrifuged and dried to obtain the carboxylated up-conversion nanomaterial;

[0011] (2) The carboxylated up-conversion nanomaterial is added with 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride aqueous solution and N-hydroxysuccinimide aqueous solution, and then incubated by oscillation, followed by adding tetracycline aptamer complementary chain solution and shaking to obtain UCNPs-cDNA signal probe;

[0012] (3) 2-Aminoterephthalic acid and Fe(NO3)3·9H2O are dissolved in N,N-dimethylformamide, and then stirred and dispersed uniformly, and then placed in a high-pressure reaction kettle for reaction, after the reaction is completed, centrifuged, washed and dried to obtain NH2-MIL-53(Fe);

[0013] NH2-MIL-53(Fe) and CuCl2 are dissolved in deionized water and stirred to obtain NH2-MIL-53(Fe)@Cu 2+ ;

[0014] NH2-MIL-53(Fe)@Cu 2+ is added with glutaraldehyde solution and PBS buffer, and then oscillated in the dark, and then centrifuged to obtain the Apt-MIL-53(Fe)@Cu 2 + capture probe;

[0015] (4) The UCNPs-cDNA signal probe is mixed with the Apt-MIL-53(Fe)@Cu 2+ capture probe to obtain a detection probe;

[0016] (5) The detection probe is added dropwise to the center area of the paper-based carrier to obtain the flexible paper-based sensor.

[0017] Further, in step (1), the amount ratio of yttrium chloride hexahydrate, ytterbium chloride hexahydrate, erbium chloride hexahydrate, methanol A, oleic acid and 1-octadecene is (220-250) mg:(70-80) mg:(5-10) mg:(6-10) mL:(6-10) mL:(15-20) mL; the amount ratio of ammonium fluoride, sodium hydroxide and methanol B is (0.1-0.2) g:(0.1-0.15) g:10 mL; the amount ratio of the upconversion fluorescent nanomaterial, chloroform, toluene and polyacrylic acid aqueous solution is 25 mg:2 mL:3 mL:10 mL;

[0018] The temperature of the first heating stirring reaction is 160-170℃, the stirring time is 25-40 min; the temperature of the second heating stirring reaction is 50-70℃, the time is 70-100 min; the temperature of the third heating stirring reaction is 290-300℃, the time is 60-90 min; the stirring rate of the three heating stirring reactions is 300-500 rpm.

[0019] Further, in step (2), the amount ratio of the carboxylated upconversion nanomaterial, 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride aqueous solution, N-hydroxysuccinimide aqueous solution and tetracycline aptamer complementary chain solution is 20 mg:1 mL:1 mL:60 μL; the sequence of the tetracycline aptamer complementary chain is 5'-GCATGCCTTAAGCGATCGGGGGGCCGTCCGGTGCCGAACCCAACCAGGGTGACGCGCACCTAGGCTCGAGGTGCAC-C6-NH2-3'.

[0020] Further, in step (3), the amount ratio of 2-amino terephthalic acid, Fe(NO3)3·9H2O and N,N-dimethylformamide is (0.9-1.0) g:(2.0-2.1) g:50 mL; the amount ratio of NH2-MIL-53(Fe), CuCl2 and deionized water is 50 mg:1 g:10 mL; the amount ratio of NH2-MIL-53(Fe)@Cu 2+ , glutaraldehyde solution, PBS buffer and tetracycline aptamer is 10 mg:1.25 mL:5 mL:30 μL; the sequence of the tetracycline aptamer is 5'NH2C6-CGTACGGAATTCGCTAGCCCCCCGGCAGGCCACGGCTTGGGTTGGTCCCACTGCGCGTGGATCCGAGCTCCACGTG-3';

[0021] The reaction condition of being placed in a high-pressure reaction kettle is 150-160 DEG C for 7-9 hours, and the stirring reaction time is 10-12 hours.

[0022] Further, in step (4), the UCNPs-cDNA signal probe is combined with Apt-MIL-53(Fe)@Cu 2+ The volume ratio of the mixed capture probe is 1:1, the concentration of the UCNPs-cDNA signal probe is 2 mg / mL, the concentration of the Apt-MIL-53(Fe)@Cu 2+ The concentration of the capture probe is 1.2 mg / mL, and the mixing time is 15 min.

[0023] Further, in step (5), the dropwise amount of the detection probe is 3.5 μL, and the preparation method of the paper-based carrier is as follows:

[0024] Ethanol, ammonia and tetraethoxysilane are ultrasonically mixed, cleaned filter paper is added, a first shaking is performed on a shaking table, 3-aminopropyltrimethoxysilane is added, a second shaking is performed, after the reaction, the filter paper is cleaned and dried to obtain a silica-modified filter paper, then the silica-modified filter paper is subjected to hydrophobization treatment to obtain the paper-based carrier.

[0025] The application further provides a method for detecting tetracycline residues in meat products, wherein the sample to be detected is added into the flexible paper-based sensor, the fluorescence intensity signal characteristic value of the sample to be detected is detected, and the content of tetracycline in the sample to be detected is calculated according to a tetracycline detection standard curve.

[0026] Further, the linear regression equation of the tetracycline detection standard curve is y=1873.01x-425.34.

[0027] The application further provides application of the flexible paper-based sensor in preparation of a product for detecting tetracycline residues in meat products.

[0028] Further, the meat product comprises fish meat.

[0029] The application discloses the following technical effects:

[0030] (1) The application discloses a flexible paper-based sensor for detecting tetracycline residues in meat products. The application uses filter paper as a carrier, so that the constructed sensor is convenient to carry. The application modifies silica microspheres on the surface of the filter paper, increases the specific surface area, is favorable for loading more detection probes, and can improve the detection sensitivity.

[0031] (2) The synthesized Apt-MIL-53(Fe)@Cu 2+It is an effective quencher that can effectively quench the fluorescence of UCNPs-cDNA through fluorescence resonance energy transfer, thereby improving detection efficiency by quenching UCNPs-cDNA fluorescence in a short time. Apt-MIL-53(Fe)@Cu was used. 2+ As a capture probe, the flexible paper-based sensor constructed by capturing the specific recognition of tetracycline by Apt on the probe surface has good specificity and anti-interference ability, can accurately identify tetracycline, and improve the accuracy of detection.

[0032] (3) This invention utilizes Cu 2+ The ability to form stable tetracycline-Cu complexes by binding with tetracycline improves detection sensitivity. When tetracycline is present, it captures Cu on the probe surface. 2+ When tetracycline binds to the capture probe, since the capture probe, signal probe, and tetracycline all carry negative potentials, after the tetracycline binds to the capture probe, Apt-MIL-53(Fe)@Cu 2+ The negative charge is further increased, which means that the capture probe and signal probe cannot be connected by electrostatic adsorption after separation, effectively improving the sensitivity and accuracy of the sensor.

[0033] (4) The Apt-MIL-53(Fe)@Cu prepared in this invention 2+ Combined with UCNPs-cDNA detection of tetracycline in actual samples, the concentration of 1.2 mg / mL LAPt-MIL-53(Fe)@Cu was precisely controlled. 2+ The detection probe is prepared by mixing the solution with 2 mg / mL UCNPs-cDNA solution at a volume ratio of 1:1, which can improve the sensitivity and reliability of detection. The detection method proposed in this invention is simple to operate and enables rapid and sensitive on-site detection of tetracycline in meat products. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 is a flowchart of the fabrication process of the flexible paper-based sensor;

[0036] Figure 2 shows a transmission electron microscope image of the upconversion fluorescent nanomaterial;

[0037] Figure 3 shows the fluorescence spectrum of UCNPs-cDNA;

[0038] Figure 4 shows a transmission electron microscope image of NH2-MIL-53(Fe);

[0039] Figure 5 is a fluorescence standard curve of different concentrations of tetracycline;

[0040] Figure 6 is a detection result chart of complex reaction of tetracycline (TC) and Cu 2+ Figure 7 is a potential result chart of tetracycline (TC), signal probe and capture probe.

[0041] Figure 7 is a potential result chart of tetracycline (TC), signal probe and capture probe. DETAILED DESCRIPTION

[0042] The various illustrative embodiments of the present application will now be described in detail in connection with the accompanying drawings. This description is made for the purpose of demonstrating certain aspects of the present application and is not intended to limit the present application in any manner. Those skilled in the art will recognize that there are numerous variations of the illustrative embodiments described herein that have been omitted in order to not obscure the inventive nature of the present application.

[0043] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, the use of the term "about" in relation to a value or a range of values is intended to include each individual intermediate value and each smaller range that falls within the range of values. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned in this specification are herein incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference in this specification is not intended as an admission that the reference is prior art to this application.

[0045] Many modifications and variations of this application can be made in the light of the above teachings without departing from the spirit and scope thereof. Other implementations of this application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The examples in the specification including examples of the application solely for illustrative purposes.

[0046] It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0047] Example 1

[0048] To further verify the detection effect of the flexible paper-based sensor (Figure 1 is a preparation flow chart of the flexible paper-based sensor) and the detection method prepared by the present application on tetracycline in meat products, the present application takes the detection of tetracycline in fish meat as an example, and the specific operation steps are as follows:

[0049] (1) Preparation of carboxylated upconversion nanomaterials: 236.6 mg yttrium chloride hexahydrate, 77.5 mg ytterbium chloride hexahydrate, 7.6 mg erbium chloride hexahydrate were dissolved in 6 mL of methanol, 6 mL of oleic acid, 15 mL of 1-octadecene were added, nitrogen was bubbled, and heated to 160°C under nitrogen atmosphere for 30 min with a stirring rate of 400 rpm. After the reaction was completed, it was cooled to room temperature to obtain a mixed solution A. 0.1482 g of ammonium fluoride and 0.1 g of sodium hydroxide were dissolved in 10 mL of methanol, mixed with the mixed solution A, heated to 70°C and continuously stirred for 90 min, then nitrogen was bubbled, and heated to 300°C under nitrogen atmosphere for 80 min. After cooling to room temperature, a mixed solution B was obtained. The mixed solution B was washed with a mixture of ethanol and cyclohexane, centrifuged and dried to obtain upconversion fluorescent nanomaterials (Figure 2). The prepared upconversion fluorescent nanomaterials were uniformly dispersed and had a consistent size of about 50 nm.

[0050] 50.0 mg of upconversion fluorescent nanomaterials were added to a round-bottom flask containing 6.0 mL of toluene and 4.0 mL of chloroform, and were ultrasonically dissolved. Then, the above mixture was added to 20.0 mL of a 15 mg / mL aqueous polyacrylic acid solution, and was stirred vigorously under light shielding conditions for 48 h. Finally, the excess polyacrylic acid was removed by centrifugation and washing to obtain carboxylated upconversion nanomaterials.

[0051] (2) Preparation of signal probe: 10 mg of carboxylated upconversion nanomaterials were dissolved in 10 mL of MES buffer. 0.5 mL of 1 mg / mL N-hydroxysuccinimide aqueous solution and 0.5 mL of 2 mg / mL 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride aqueous solution were added, and were shaken and incubated for 2 h. Then, 30 μL of 100 μM aptamer complementary chain solution (the tetracycline aptamer and its complementary chain were purchased from GenScript Biotech Corporation (Shanghai, China), and the base sequence was: 5' NH2C6-CGTACGGAATTCGCTAGCCCCCCGGCAGGCCACGGCTTGGGTTGGTCCCACTGCGCGTGGATCCGAGCTCCACGTG-3' (tetracycline aptamer), 5'-GCATGCCTTAAGCGATCGGGGGGCCGTCCGGTGCCGAACCCAACCAGGGTGACGCGCACCTAGGCTCGAGGTGCAC-C6-NH2-3' (aptamer complementary chain)), and were shaken for 12 h. After centrifugation and washing to remove surface impurities, the UCNPs-cDNA signal probe was resuspended in 5 mL of PBS buffer, and had good luminescence performance, could avoid the interference of background fluorescence, and was conducive to improving the accuracy of detection (Figure 3).

[0052] (3) Preparation of the capture probe: 0.905 g of 2-amino terephthalic acid and 2.02 g of Fe(NO3)3·9H2O were dissolved in 50 mL of N,N-dimethylformamide, and stirred for 10 min to disperse uniformly. Subsequently, the solution was placed in a high-pressure reaction kettle, heated at 150°C for 8 h. When the temperature dropped to room temperature, the material in the reaction kettle was taken out, centrifuged at a speed of 6000 r / min for 5 min, and the precipitate was washed with N,N-dimethylformamide and anhydrous ethanol, and finally dried at 60°C for 12 h to obtain a brown product NH2-MIL-53(Fe) (Fig. 4). The synthesized NH2-MIL-53(Fe) has an olive-type structure, the nanoparticle surface is smooth and the morphology is complete, the size is uniform, the average particle size length is about 410 nm, and it has a large pore volume and a high specific surface area, which is beneficial to the adsorption of Cu 2+ . 100 mg of NH2-MIL-53(Fe) was taken, 2 g of CuCl2 was added, dissolved in 20 mL of water, stirred for 10 h, centrifuged and washed to obtain NH2-MIL-53(Fe)@Cu 2+ . Subsequently, 10 mg of NH2-MIL-53(Fe)@Cu 2+ was weighed, 1.25 mL of glutaraldehyde solution and 5 mL of PBS buffer were added, and the solution was oscillated in the dark at 25°C for 2 h. Subsequently, the solution was centrifuged, the obtained precipitate was washed three times, and 5 mL of PBS solution was added. Then, 30 μL of 100 μM tetracycline aptamer was added, and the solution was slowly oscillated at 37°C overnight. Finally, the above solution was centrifuged, the obtained precipitate was washed with PBS buffer and resuspended in PBS buffer to obtain Apt-MIL-53(Fe)@Cu 2+ solution as a capture probe;

[0053] (4) Preparation of the detection probe: 2 mg / mL of UCNPs-cDNA and 1.2 mg / mL of Apt-MIL-53(Fe)@Cu 2+ were mixed at a volume ratio of 1:1, and incubated at 37°C to obtain a detection probe;

[0054] (5) Preparation of the paper-based carrier: Whatman No. 1 qualitative filter paper was cut into equal size shapes, soaked in 0.1 mol / L HCl for 30 min, then washed with deionized water and dried in a 50°C drying oven to obtain clean filter paper. Then 20 mL of 80% ethanol, 500 μL of ammonia water and 300 μL of TEOS (tetraethoxysilane) were ultrasonically mixed, and the clean filter paper was added and shaken in a 40°C water bath shaker for 8 h. Then 300 μL of APTES (3-aminopropyltrimethoxysilane) was added and shaken for another 2 h. After the reaction, the filter paper was washed with deionized water and anhydrous ethanol for 3 times, respectively, and dried at 50°C for 1 h to obtain the silica-modified filter paper. Then, the edges of the silica-modified filter paper were subjected to hydrophobic treatment. The pattern was drawn on the computer and then printed on the silica-modified filter paper using an inkjet printer. The printed filter paper was placed in a 200°C oven for 6 h to allow the carbon powder to penetrate into the filter paper fibers, forming a hydrophobic region on the surface of the filter paper. After natural cooling, the obtained paper-based carrier was stored in a dry environment for standby;

[0055] (6) Preparation of the flexible paper-based sensor: 3.5 μL of the detection probe was dropped on the central region of the paper-based carrier to obtain the flexible paper-based sensor; the sensor has a small volume, is easy to carry, and is simple to detect, and can adapt to the needs of on-site detection;

[0056] (7) Establishment of the fluorescence standard curve for tetracycline content detection: different concentrations of tetracycline standard solution were prepared, different concentrations of tetracycline standard solution (20, 50, 100, 500, 1000, 5000, 10000 μg / L) were added to the flexible paper-based sensor, the fluorescence intensity of the flexible paper-based sensor was detected, and the standard curve of tetracycline concentration was drawn according to the fluorescence intensity corresponding to different concentrations of tetracycline standard solution (Fig. 5), with the logarithmic value of the tetracycline standard solution concentration as the abscissa and the fluorescence intensity signal characteristic value as the ordinate; the detection limit of this method is 1.18 μg / L, and the detection range is 20-10000 μg / L; tetracycline can not only specifically bind to the tetracycline aptamer APT on the surface of the capture probe, but also complex with Cu 2+ to improve the electronegativity of the capture probe (Fig. 7), further separate the capture probe from the signal probe, and improve the accuracy and sensitivity of the detection.

[0057] (8) Detection of tetracycline in fish meat: 5 g of fish meat sample is taken, different concentrations of tetracycline standard solution are added, then it is mixed with 20 mL of EDTA·2Na-Mcllvaine buffer, vortexed for 10 min, 5 mL of 18.5% H2SO4 solution and 5 mL of 70 mg / mL sodium tungstate solution are added, vortexed for 1 min, after centrifugation, the supernatant is collected, the obtained precipitate is extracted with EDTA·2Na-Mcllvaine buffer for two times respectively, the supernatants are combined, large particle impurities are filtered with filter paper, then 0.22 μm microporous filter membrane is used for filtering, to obtain sample liquid; 3.5 μL of sample liquid is taken and added into a flexible paper-based sensor, the fluorescence intensity signal characteristic value of the sample liquid is determined, according to the tetracycline detection standard curve, the content of tetracycline in the fish meat sample is calculated;

[0058] For 3 fish meat samples, the content of tetracycline in fish meat is determined by using the method and steps described in the embodiment 1 of the present application, and the national standard method is used for verification, and the determination results are shown in Table 1, it can be seen that the method of the present application has good accuracy in actual samples, and has good application prospect.

[0059] Table 1: Results of detecting the content of tetracycline in fish meat sample by the method of the present application and high performance liquid chromatography method

[0060] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application, under the premise of not departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art should fall within the protection scope determined by the claims of the present application.

Claims

1. A flexible paper-based sensor for detecting tetracycline residues in meat products, characterized in that, Its preparation method is as follows: (1) Dissolve yttrium chloride hexahydrate, ytterbium chloride hexahydrate and erbium chloride hexahydrate in methanol A, add oleic acid and 1-octadecene, and carry out the first heating and stirring reaction. After the reaction is completed, cool to obtain mixed solution A; Ammonium fluoride and sodium hydroxide were dissolved in methanol B and mixed with mixed solution A. A second heating and stirring reaction was carried out. Then, nitrogen gas was introduced, and a third heating and stirring reaction was carried out under a nitrogen atmosphere. After cooling, mixed solution B was obtained. Mixed solution B was washed, centrifuged, and dried to obtain upconversion fluorescent nanomaterials. Upconversion fluorescent nanomaterials, chloroform, toluene, and an aqueous solution of polyacrylic acid were mixed, stirred, centrifuged, and dried to obtain carboxylated upconversion nanomaterials. (2) Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride aqueous solution and N-hydroxythiosuccinimide aqueous solution to carboxylated upconversion nanomaterials, shake and incubate, then add tetracycline aptamer complementary strand solution and shake to obtain UCNPs-cDNA signal probe. (3) 2-Aminoterephthalic acid and Fe(NO3)3·9H2O were dissolved in N,N-dimethylformamide, stirred and dispersed evenly, and then placed in a high-pressure reactor for reaction. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain NH2-MIL-53(Fe); NH2-MIL-53(Fe) and CuCl2 are dissolved in deionized water and reacted with stirring to obtain NH2-MIL-53(Fe)@Cu 2+ ; NH2-MIL-53(Fe)@Cu 2+ Add glutaraldehyde solution and PBS buffer, shake in the dark, centrifuge to collect the precipitate, add tetracycline aptamer to the precipitate, shake overnight, and centrifuge to obtain Apt-MIL-53(Fe)@Cu 2+ Capture probe; (4) The UCNPs-cDNA signal probe was combined with Apt-MIL-53(Fe)@Cu 2+ The capture probes are mixed to obtain the detection probes; (5) The detection probe is dropped onto the central region of the paper-based carrier to obtain the flexible paper-based sensor. In step (1), the ratio of the amounts of yttrium chloride hexahydrate, ytterbium chloride hexahydrate, erbium chloride hexahydrate, methanol A, oleic acid and 1-octadecene is (220-250) mg: (70-80) mg: (5-10) mg: (6-10) mL: (6-10) mL: (15-20) mL; the ratio of the amounts of ammonium fluoride, sodium hydroxide and methanol B is (0.1-0.2) g: (0.1-0.15) g: 10 mL; the ratio of the amounts of upconversion fluorescent nanomaterial, chloroform, toluene and polyacrylic acid aqueous solution is 25 mg: 2 mL: 3 mL: 10 mL. The temperature of the first heating and stirring reaction is 160-170℃, and the stirring time is 25-40 min; the temperature of the second heating and stirring reaction is 50-70℃, and the time is 70-100 min; the temperature of the third heating and stirring reaction is 290-300℃, and the time is 60-90 min; the stirring rate of the three heating and stirring reactions is 300-500 rpm.

2. The flexible paper-based sensor according to claim 1, characterized in that, In step (2), the ratio of carboxylated upconversion nanomaterial, aqueous solution of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, aqueous solution of N-hydroxythiosuccinimide, and tetracycline aptamer complementary chain solution is 20 mg: 1 mL: 1 mL: 60 μL; the sequence of the tetracycline aptamer complementary chain is 5′-GCATGCCTTAAGCGATCGGGGGGCCGTCCGGTGCCGAACCCAACCAGGGTGACGCGCACCTAGGCTCGAGGTGCAC-C6-NH2-3′.

3. The flexible paper-based sensor as described in claim 1, characterized in that, In step (3), the ratio of 2-aminoterephthalic acid, Fe(NO3)3·9H2O and N,N-dimethylformamide is (0.9-1.0)g:(2.0-2.1)g:50mL; the ratio of NH2-MIL-53(Fe), CuCl2 and deionized water is 50mg:1g:10mL; the ratio of NH2-MIL-53(Fe)@Cu 2+ The ratio of glutaraldehyde solution, PBS buffer, and tetracycline aptamer was 10 mg: 1.25 mL: 5 mL: 30 μL; the sequence of the tetracycline aptamer was 5'NH2C6-CGTACGGAATTCGCTAGCCCCCCGGCAGGCCACGGCTTGGGTTGGTCCCACTGCGCGTGGATCCGAGCTCCACGTG-3'; the reaction conditions in the high-pressure reactor were 150–160 °C for 7–9 h; the stirring time was 10–12 h.

4. The flexible paper-based sensor according to claim 1, characterized in that, In step (4), the UCNPs-cDNA signal probe and Apt-MIL-53(Fe)@Cu 2+ The capture probe was mixed in a 1:1 volume ratio; the concentration of the UCNPs-cDNA signal probe was 2 mg / mL; and the Apt-MIL-53(Fe)@Cu 2+ The concentration of the capture probe was 1.2 mg / mL; the mixing time was 15 min.

5. The flexible paper-based sensor according to claim 1, characterized in that, In step (5), the amount of the detection probe added is 3.5 μL; the preparation method of the paper-based carrier is as follows: Ethanol, ammonia, and tetraethoxysilane were ultrasonically mixed until homogeneous. Cleaned filter paper was added, and the mixture was shaken for the first time on a shaker. Then, 3-aminopropyltrimethoxysilane was added, and the mixture was shaken for the second time. After the reaction was completed, the filter paper was washed and dried to obtain silica-modified filter paper. Subsequently, the silica-modified filter paper was subjected to hydrophobic treatment to obtain the paper-based carrier.

6. A method for detecting tetracycline residues in meat products, characterized in that, The sample to be tested is added to the flexible paper-based sensor according to any one of claims 1-5, the fluorescence intensity signal characteristic value of the sample to be tested is detected, and the content of tetracycline in the sample to be tested is calculated according to the tetracycline detection standard curve.

7. The method according to claim 6, characterized in that, The linear regression equation for the tetracycline detection standard curve is: y = 1873.01x - 425.34.

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