Fluorescent probe for rapidly and sensitively detecting tetracycline antibiotics as well as preparation method and application of fluorescent probe

Abstract

The invention discloses a fluorescent probe for rapidly and sensitively detecting tetracycline antibiotics and a preparation method and application thereof.The preparation method comprises the steps that citric acid is dissolved in ultrapure water, polyethyleneimine is added under vigorous stirring till a reagent is completely dissolved, then a mixed solution is transferred into a high-pressure kettle for a hydrothermal reaction, and after natural cooling is conducted to the room temperature, the fluorescent probe is obtained; dialyzing the obtained solution through a dialysis bag to obtain a BCDs solution; europium chloride hexahydrate and trimellitic acid are ultrasonically dissolved in N, N-dimethylformamide, then the prepared BCDs solution is added and stirred, the stirred liquid is transferred into a high-pressure kettle for a solvothermal reaction, after the liquid is naturally cooled to the room temperature, a product is washed with absolute ethyl alcohol and then dried in a vacuum drying oven, and the BCDs / Eu-MOF probe is obtained. The method is suitable for detecting TCs in water and food such as milk and honey, and a simple, rapid and sensitive strategy is provided for visual field quantitative detection of TCs.

Description

Technical Field

[0001] The invention relates to a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics and a preparation method and application thereof, belonging to the technical field of initial detection of antibiotics. Background Art

[0002] Tetracycline antibiotics (TCs) are a broad-spectrum antibiotic with the advantages of low cost, low toxicity, and easy oral absorption. They include tetracycline (TC), demeclocycline (DMC), doxycycline (DOC), metacycline (MTC), chlortetracycline (CTC), oxytetracycline (OTC), etc., and are widely used in medicine, animal husbandry and other fields. However, the excessive use of TCs will cause a large amount of antibiotics to be discharged into the environment, which will not only kill microorganisms in the water and destroy the aquatic ecosystem, but also cause antibiotics to accumulate in animal products such as milk, eggs and meat, and enter the human body through the food chain, thereby causing drug resistance in the human body and endangering human health.

[0003] At present, many conventional technologies can measure TCs, such as electrochemical aptasensors, high performance liquid chromatography, flow injection analysis and enzyme-linked immunosorbent assay. Although these detection methods have high sensitivity and strong anti-interference ability, they also have certain limitations, such as complex sample pretreatment process, expensive instruments, long detection time, etc., and cannot achieve rapid on-site detection. In the past few decades, fluorescence sensing technology has attracted widespread attention due to its advantages such as simple operation, fast response speed, low cost and high sensitivity. For example, Narasimhappa et al. synthesized blue fluorescent CdS quantum dots by culturing Citrobacter fumigatus bacteria. In the presence of TC, the fluorescence at 400nm is continuously quenched with the increase of TC concentration, and its detection limit is 23nM. However, monochromatic fluorescence sensors are easily affected by factors such as probe photobleaching and sample light scattering, and the human eye is not sensitive to changes in monochromatic fluorescence intensity. Summary of the invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics, and a preparation method and application thereof. The fluorescent probe is prepared by combining blue carbon dots (BCDs) with metal organic frameworks (Eu-MOF), which can sensitively and accurately detect TCs without complicated pretreatment.

[0005] In order to achieve the above object, the present invention adopts a method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics, comprising the following steps:

[0006] (1) Synthesis of BCDs: Dissolve citric acid in ultrapure water, add polyethyleneimine under vigorous stirring until the reagent is completely dissolved, and then transfer the mixed solution to an autoclave for hydrothermal reaction. After cooling naturally to room temperature, dialyze the resulting solution through a dialysis bag to obtain a BCDs solution, which is stored in a refrigerator for later use;

[0007] (2) Synthesis of BCDs / Eu-MOF probe: Europium chloride hexahydrate and trimellitic acid were ultrasonically dissolved in N,N-dimethylformamide, and then the BCDs solution prepared above was added and stirred. The stirred liquid was transferred to an autoclave for solvothermal reaction. After naturally cooling to room temperature, the product was washed with anhydrous ethanol and dried in a vacuum oven to obtain a BCDs / Eu-MOF probe, which was stored in a refrigerator for later use.

[0008] As an improvement, the mass ratio of citric acid to polyethyleneimine is 2:(1-3).

[0009] As an improvement, the temperature of the hydrothermal reaction is 150-260°C, and the reaction time is 4-8h; the molecular weight cutoff of the dialysis bag is 800-1200Da.

[0010] As an improvement, the mass ratio of europium chloride hexahydrate to trimellitic acid is 2:(1-3).

[0011] As an improvement, the amount of N,N-dimethylformamide used is 50-100 ml, and the mass ratio of N,N-dimethylformamide to europium chloride hexahydrate is (100-200):1; the amount of BCDs solution used in step (2) is 0.5-3 ml, and the mass ratio of N,N-dimethylformamide to europium chloride hexahydrate is (10-80):1.

[0012] As an improvement, the temperature of the solvent thermal reaction is 100-150°C, and the reaction time is 20-40h.

[0013] As an improvement, the autoclave is provided with a polytetrafluoroethylene lining; the drying temperature of the vacuum oven is 50-80°C.

[0014] The second aspect of the present invention provides a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics, which is prepared by the preparation method. The fluorescent probe exhibits blue fluorescence in the absence of TCs and exhibits red fluorescence after contacting TCs.

[0015] The third aspect of the present invention provides an application of the fluorescent probe for rapid and sensitive detection of tetracycline antibiotics, which is used to detect whether a substance contains tetracycline antibiotics and to detect the content of tetracycline antibiotics.

[0016] The fourth aspect of the present invention provides a portable detection device for rapid and sensitive detection of tetracycline antibiotics, comprising a portable capillary detection box and a smart phone; the portable capillary detection box comprises a detection box body, a capillary encapsulating the fluorescent probe, a capillary storage rack, a mobile phone holder and a compact ultraviolet lamp.

[0017] The ratiometric fluorescence system sensing mechanism of the fluorescent probe of the present invention is combined with Fig.12 As shown, specifically:

[0018] Stage 1: The fluorescence intensity of carbon dots can be effectively enhanced by N doping, so that BCDs show strong blue fluorescence at 454nm under the excitation of 350nm ultraviolet light, while Eu 3+ The fluorescence emission is very weak due to the blockade of ff transition, so BCDs / Eu-MOF shows strong blue fluorescence when TCs are not added.

[0019] Stage 2: After contacting TCs, the fluorescence excitation spectrum of BCDs overlaps with the UV-visible spectrum of TCs. Therefore, the blue fluorescence of BCDs is well quenched by TCs based on the inner filter effect. The β-diketone structure in TCs can react with Eu 3+ Formation of rare earth organic complexes (Eu 3+ -TCs), so that the energy absorbed by TCs is transferred to Eu via non-radiative transition 3+ , thereby effectively sensitizing Eu 3+ And it produces strong red "on" fluorescence at 616nm. Therefore, self-calibration is achieved through ratiometric fluorescence, blue fluorescence is "off", and red fluorescence is "on", successfully realizing a dual-emission ratiometric fluorescence sensing system, which can detect TCs intuitively and sensitively.

[0020] Compared with the prior art, the present invention utilizes the special optical properties between TCs and BCDs / Eu-MOF to prepare a dual-emission fluorescent probe. In the presence of TCs, the fluorescence of BCDs is “turned off” and the formed Eu 3+ The fluorescence emission of the -TCs complex is significantly enhanced, thereby achieving self-calibration through ratiometric fluorescence, and its detection limit is as low as 1.370nM, which is far lower than the maximum residue limit in animal-derived foods specified by the World Health Organization. It is therefore suitable for the detection of TCs in water bodies and foods such as milk and honey, providing a simple and sensitive strategy for the visual on-site quantitative detection of TCs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1(a) XRD image of Eu-MOF, (b) XPS Eu 3d image of Eu-MOF, (c) nitrogen adsorption-desorption isotherm and pore size distribution diagram of Eu-MOF (inset), (d) and (e) SEM images of Eu-MOF, (f) TEM image of Eu-MOF, (g) UV-visible absorption spectra of Eu-MOF, TCs and Eu-MOF+TCs, (h) FT-IR spectra of BCDs and BCDs+TCs, (i) fluorescence spectra of BCDs / Eu-MOF at different excitation wavelengths;

[0022] Figure 2 XPS spectrum of Eu-MOF;

[0023] Figure 3 is the XPS spectrum of BCDs;

[0024] Figure 4 is the EDS data of Eu-MOF;

[0025] Figure 5 DLS data of (a) Eu-MOF, (b) Eu-MOF+TCs, (c) BCDs, and (d) BCDs+TCs;

[0026] Figure 6 For (1) BCDs, (2) BCDs+TCs, (3) Eu-MOF, (4) Eu-MOF+TCs, (5)

[0027] Zeta potential data of BCDs / Eu-MOF, (6) BCDs / EU-MOF+TCs, and (7) TCs;

[0028] Figure 7 Fluorescence spectra of BCDs / Eu-MOF prepared by adding different amounts of BCDs: (a) 0.5 ml, (b) 1 ml, (c) 1.5 ml;

[0029] Figure 8 The fluorescence spectra of BCDs / Eu-MOF probes when different amounts of (a) DOC, (b) DMC, (c) MTC, (d) CTC, (e) TC, and (f) OTC were added. The inset shows the fluorescence color photographs under 350 nm UV light when the corresponding concentrations of TCs were added.

[0030] Fig. 9 I of BCDs / Eu-MOF with different amounts of (a) DOC, (b) DMC, (c) MTC, (d) CTC, (e) TC, and (f) OTC 616 / I 454 Linear fitting graph of fluorescence intensity ratio and TCs concentration;

[0031] Fig.10 (a) Fluorescence spectra of the BCDs / Eu-MOF probe after adding 2.2 μM of various interfering substances. The inset shows the corresponding fluorescence color photograph under 350 nm UV irradiation. (b) Selectivity and interference test of BCDs / Eu-MOF.

[0032] Fig.11 (a) The structure of the portable capillary detection box, (b) the schematic diagram of the RGB color recognition software for smartphones, and (c) the linear fitting diagram of TCs and R / B at different concentrations;

[0033] Fig.12 Diagram of the detection mechanism of TCs by fluorescent probe. DETAILED DESCRIPTION

[0034] The following embodiments are further descriptions of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0035] Example 1

[0036] A method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics comprises the following steps:

[0037] (1) Synthesis of BCDs: 1 g of citric acid was dissolved in 30 mL of ultrapure water, and then 0.5 g of polyethyleneimine was added under vigorous stirring until the reagent was completely dissolved. The mixed solution was then transferred to an autoclave lined with polytetrafluoroethylene and reacted at 200 °C for 6 h. After naturally cooling to room temperature, the resulting solution was dialyzed through a 1000 Da molecular weight dialysis bag to obtain a BCDs solution, which was stored in a refrigerator at 4 °C for future use;

[0038] (2) Synthesis of BCDs / Eu-MOF probe: 0.0366 g EuCl3·6H2O (europium chloride hexahydrate) and 0.0210 g trimellitic acid were ultrasonically dissolved in 50 ml DMF, and then 1 ml of the BCDs solution prepared in step (1) was added and stirred for 30 min. The stirred liquid was transferred to an autoclave lined with polytetrafluoroethylene and reacted at 120°C for 24 h. After naturally cooling to room temperature, the reaction product was washed three times with anhydrous ethanol and dried in a vacuum oven at 60°C to obtain a BCDs / Eu-MOF probe, which was stored in a refrigerator at 4°C for future use.

[0039] The BCDs / Eu-MOF probe prepared in Example 1 was structurally characterized:

[0040] Considering that the detection sensitivity of the probe to the analyte is related to its own properties, the structural characteristics of BCDs and BCDs / Eu-MOF probes were studied using FT-IR, UV-vis, XPS, Zeta potential and DLS particle size distribution, and their spectral characteristics were also studied to find the optimal emission.

[0041] The phase purity of the synthesized Eu-MOF was determined by XRD, as Figure 1 As shown in (a), the synthesized sample is consistent with the pattern of single crystal diffraction data in the literature, indicating high purity. In order to better understand the elemental composition and structure of BCDs and Eu-MOF, the present invention recorded their XPS spectra, such as Figure 2 , Figure 3 The full scan spectrum shows that Eu-MOF contains C, Eu, O and N element peaks, while BCDs are mainly composed of C, O and N elements. Figure 1 (b) shows that the two peaks at 1165.9eV and 1135.1eV in the Eu 3d high-resolution spectrum can be attributed to the double peaks 3d3 / 2 and 3d5 / 2 formed by the spin-orbit coupling of the larger nuclear energy levels of Eu 3d. Figure 2 (b)) shows three peaks at 284.3 eV, 285.2 eV and 288.6 eV, corresponding to CC, OC / NC and OC=O bonds, respectively. Figure 2 (c)), the peaks at 531.2 eV and 532.3 eV correspond to C=O and CO / C=O bonds, respectively. The presence of N1s in the high-resolution spectrum and bonding with N in the C1s spectrum may be due to the presence of N,N-dimethylformamide during the synthesis process.

[0042] EDS further confirmed the elemental composition of Eu-MOF, such as Figure 4 The presence of Eu, C, N, and O in Eu-MOF was demonstrated and their distribution was shown. The specific surface area and pore size of Eu-MOF were obtained by nitrogen adsorption-desorption experiments, such as Figure 1 As shown in (c), the presence of mesopores in the Eu-MOF framework material is revealed, which exhibits a considerable specific surface area. This leads to an enrichment effect, which can effectively capture TCs and improve their detection sensitivity. In addition, the abundant active sites shorten the reaction time (as low as 1s), giving BCDs / Eu-MOF excellent sensitivity and rapid detection capabilities for TCs. Scanning electron microscopy can be used to observe that the synthesized Eu-MOF has a spherical micro-flower structure, such as Figure 1 (d) In addition, the lamellar structure of microflowers Figure 1 It is also obvious in (e), the diameter is about 25 μm. From TEM ( Figure 1 It can also be seen in (f) that the diameter of BCDs is about 1.5 nm.

[0043] In order to study the changes of Eu-MOF before and after adding TCs, the UV-visible absorption spectra of Eu-MOF, Eu-MOF+TCs and TCs were detected. Figure 1 (g)). It can be seen that a new absorption peak appears in the spectrum of Eu-MOF+TCs. Compared with the absorption peak of Eu-MOF, the new absorption peak appears at about 390nm. In addition, it is found that the position of the new absorption peak is red-shifted compared with the absorption peak position of TCs at this position. This phenomenon can be attributed to the formation of rare earth organic complexes (Eu 3+ -TCs), thus shifting the absorption frequency to a lower position.

[0044] At the same time, DLS( Figure 5 ) showed that before adding TCs, the particle sizes of BCDs and Eu-MOF were 186.1nm and 160.6nm, respectively. After adding TCs, the particle size of Eu-MOF increased to 212.2nm, while the particle size of BCDs remained basically unchanged at 185.8nm. This indicates that Eu-MOF interacted with TCs, resulting in an increase in particle size, while BCDs did not undergo this reaction. From the FR-IR of BCDs and BCDs+TCs ( Figure 1 (h)) It can also be seen that there is no obvious change in the spectrum before and after adding TCs. Figure 6 As shown in the figure, there is a positive correlation between the absolute value of the Zeta potential and the stability of the system. After the addition of TCs, the Zeta potential of BCDs, Eu-MOF and BCDs / Eu-MOF all changed significantly, proving that energy transfer occurred between them. These phenomena indicate that TCs interact with Eu-MOF to "turn on" its red fluorescence, while BCDs do not react and quench its blue fluorescence through the inner filter effect. Figure 1 As shown in (i), by adding a certain amount of TCs to the BCDs / Eu-MOF probe and using different wavelengths for excitation, the optimal excitation conditions of BCDs / Eu-MOF can be determined. The results show that the optimal excitation condition for BCDs / Eu-MOF is 350nm, which can produce the most effective Eu-MOF "turn-on" effect. At this time, BCDs also has a good fluorescence effect, so 350nm is used as the excitation condition for the BCDs / Eu-MOF fluorescent probe.

[0045] Effect of fluorescent probe ratio:

[0046] The introduction of TCs caused the blue fluorescence generated by BCDs to be replaced by the red fluorescence emitted by Eu-MOF. This transition from blue to purple to red occurred in a gradual and continuous manner. Compared with monochromatic fluorescence changes, ratiometric fluorescence is less susceptible to environmental interference and can therefore more accurately visualize the measurement results. The detection performance of fluorescent probes depends largely on the fluorescence intensity ratio I 616 / I 454 ,like Figure 7 As shown, the most effective and obvious visualization of fluorescence changes was achieved when 1 ml of BCDs was added during the preparation process compared to other addition amounts. This effect was observed over a wider concentration measurement range from bright blue to bright red, which allowed the addition of 1 ml of BCDs to be determined as the optimal condition for naked eye detection.

[0047] Selectivity and anti-interference ability of fluorescent probes:

[0048] For an excellent fluorescent sensing system, it is crucial to have good selectivity for TCs and maintain a selective response to TCs even in the presence of interferents. Therefore, the present invention conducted a series of experiments to explore the selectivity and anti-interference ability of fluorescent probes in detecting TCs. Under the same conditions, pesticides (cypermethrin, glufosinate, tetrachlorvinphos), heavy metals (Fe 2+ Cr 3+ , Cu 2+ ) and some antibiotics (lincomycin, piperacillin, clindamycin, roxithromycin, cefazolin, vancomycin, clarithromycin, pefloxacin, lomefloxacin, gentamicin, amoxicillin, cefaclor) were used to experiment with fluorescent probes. Fig.10 .

[0049] In order to objectively reflect the application advantages of the fluorescent probe of the present invention, it was compared with other methods reported in existing literature, and the results are shown in Table 1.

[0050] Table 1 Performance of fluorescent probes

[0051]

[0052] [1]Chen J,Xu F,Zhang Q,et al.Tetracycline antibiotics and NH(4)(+)detection by Zn-organic framework fluorescent probe[J].Analyst,2021,146(22):6883-92.

[0053] [2]Li Y, Wang Y, Du P, et al. Fabrication of carbon dots@hierarchicalmesoporous ZIF-8 for simultaneous ratiometric fluorescence detection and removal of tetracycline antibiotics[J]. Sensors and Actuators B: Chemical, 2022, 358: 131526.

[0054] [3] Wu J, Chang X, Guo Y, et al. Synthesis of a hybrid nanocomposite: Incorporating MoS2 within a ZIF-8 for fluorescence-based detection and adsorption of tetracyclines antibiotics[J]. Dyes and Pigments, 2024, 226: 112137.

[0055] [4]Wang C, Sun Q, Yang M, et al. Preparation of highly luminescentnitrogen-doped carbon quantum dots and their detection of tetracyclineantibiotics[J]. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2022, 653: 129982.

[0056] Table 1 can clearly demonstrate that, compared with previous probes, the probe of the present invention has an ultra-short response time, as low as 1 s, and a lower detection limit, as low as 1.51 nM. The ultra-fast response speed can provide inspiration for the strategy of designing fast and sensitive portable detection devices in a wider range of applications.

[0057] Detection method of TCs content:

[0058] Draw a standard curve: In a 3 ml clean cuvette, dissolve the fluorescent probe of the present invention in 2 ml distilled water, add different amounts of TCs solution to the probe solution so that the final TCs concentration range is 0-2.6 μM, as shown in FIG. Figure 8As shown, the fluorescence intensity of the fluorescent probe was measured before and after the addition of the TCs standard solution, and its fluorescence photos were taken under the condition of 350nm ultraviolet light irradiation. A linear formula was established based on the change in the fluorescence intensity at the emission peak of the system before and after the addition of TCs and the concentration of TCs, and a standard curve was drawn. A linear formula was established, such as Fig. 9 shown.

[0059] In order to evaluate the feasibility and reproducibility in practical applications, the BCDs / Eu-MOF probe was used to detect TCs in actual samples by the standard addition method. Taking lake water, milk and honey as examples, the lake water came from the Dongpu Reservoir near the laboratory, and the milk and honey were purchased from local supermarkets;

[0060] Pretreatment: dilute the honey with water first, then centrifuge at 10000rpm for 3 minutes, collect the supernatant for later use; accurately weigh 15 grams of milk, then add 35 ml of anhydrous ethanol, mix thoroughly and let stand for two minutes, collect the supernatant for later use.

[0061] Before testing, lake water, honey supernatant and milk supernatant were filtered separately with a 0.22 μm microporous filter to remove impurities.

[0062] Then TCs were added to three water samples (lake water, milk and honey) to form TCs solutions with concentrations of 0.1 μM, 0.5 μM and 1 μM, respectively, as shown in Table 2 below, and tested.

[0063] Table 2 Determination of TCs spike recovery in actual samples

[0064]

[0065] As shown in Table 2, good recoveries of 0.1 μM, 0.5 μM and 1 μM TCs spiked in real samples were in the range of 97.20-107.08%, and the relative standard deviations (RSDs) ranged from 0.99% to 3.34%, indicating good accuracy and reliability. The results showed that the probe of the present invention is suitable for practical applications in water, milk and honey.

[0066] When applied: the liquid to be tested is added to the BCDs / Eu-MOF and then irradiated with a 350nm UV lamp so that the color change of the probe can be observed with the naked eye. This method is not as accurate as the instrument method and does not allow quantitative detection. In addition, fluorescence sensing requires the use of a handheld UV lamp and is carried out in a dark environment, which makes the procedure more complicated and does not allow for rapid real-time monitoring.

[0067] Therefore, the present invention also designs a portable detection device, which includes a portable capillary detection box based on 3D printing and a smart phone. Fig.11As shown, the portable capillary detection box mainly includes a detection box body, a capillary encapsulating the BCDs / Eu-MOF probe, a capillary storage rack, a mobile phone holder and a compact ultraviolet lamp. Initially, a specific amount of BCDs / Eu-MOF is encapsulated in a capillary (liquid level one) and the capillary is stored in a capillary storage rack, which is installed in the detection box body. When in use, a specified volume of the liquid to be tested (reaching liquid level two) is sucked out with the capillary encapsulating the BCDs / Eu-MOF probe, and then placed in the sample slot of the detection box body, the lid of the detection box is covered to provide a dark environment, and after incubation for 5 minutes, the compact ultraviolet lamp is turned on. As shown Fig.11 As shown in (b), the color photo of the fluorescence is then quickly captured and converted into RGB values ​​by color recognition software on the smartphone. The concentration of TCs is then estimated by calculating the ratio of the red channel to the blue channel. Fig.11 As shown in (c), the ratio of the red channel to the blue channel (R / G) has a strong linear correlation with the concentration of TCs, R 2 The detection limit was 1.902 nM, which indicated that the constructed simple and portable real-time monitoring platform was capable of sensitive TCs detection, providing a promising strategy for public safety and food safety monitoring.

[0068] Example 2

[0069] A method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics comprises the following steps:

[0070] (1) Synthesis of BCDs: 1 g of citric acid was dissolved in 40 mL of ultrapure water, and then 1 g of polyethyleneimine was added under vigorous stirring until the reagent was completely dissolved. The mixed solution was then transferred to an autoclave lined with polytetrafluoroethylene and reacted at 150 °C for 8 h. After naturally cooling to room temperature, the resulting solution was dialyzed through an 800 Da molecular weight dialysis bag to obtain a BCDs solution, which was stored in a refrigerator at 4 °C for future use;

[0071] (2) Synthesis of BCDs / Eu-MOF probe: 0.0521 g EuCl3·6H2O and 0.0321 g trimellitic acid were ultrasonically dissolved in 60 ml DMF, followed by adding 0.5 ml of the BCDs solution prepared in step (1) and stirring for 40 min. The stirred liquid was transferred to an autoclave lined with polytetrafluoroethylene and reacted at 100°C for 40 h. After naturally cooling to room temperature, the reaction product was washed three times with anhydrous ethanol and dried in a vacuum oven at 50°C to obtain a BCDs / Eu-MOF probe, which was stored in a refrigerator at 4°C for future use.

[0072] Example 3

[0073] A method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics comprises the following steps:

[0074] (1) Synthesis of BCDs: 1 g of citric acid was dissolved in 50 mL of ultrapure water, and then 1.5 g of polyethyleneimine was added under vigorous stirring until the reagent was completely dissolved. The mixed solution was then transferred to an autoclave lined with polytetrafluoroethylene and reacted at 250 °C for 4 h. After naturally cooling to room temperature, the resulting solution was dialyzed through a 1200 Da molecular weight dialysis bag to obtain a BCDs solution, which was stored in a refrigerator at 4 °C for future use;

[0075] (2) Synthesis of BCDs / Eu-MOF probe: 0.0666 g EuCl3·6H2O and 0.0421 g trimellitic acid were ultrasonically dissolved in 60 ml DMF, and then 1.5 ml of the BCDs solution prepared in step (1) was added and stirred for 30 min. The stirred liquid was transferred to an autoclave lined with polytetrafluoroethylene and reacted at 150°C for 20 h. After naturally cooling to room temperature, the reaction product was washed three times with anhydrous ethanol and dried in a vacuum oven at 80°C to obtain a BCDs / Eu-MOF probe, which was stored in a refrigerator at 4°C for future use.

[0076] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics, characterized in that: The following steps are involved: (1) Synthesis of BCDs: Dissolve citric acid in ultrapure water, add polyethyleneimine under vigorous stirring until the reagent is completely dissolved, and then transfer the mixed solution to an autoclave for hydrothermal reaction. After cooling naturally to room temperature, dialyze the resulting solution through a dialysis bag to obtain a BCDs solution, which is stored in a refrigerator for later use; (2) Synthesis of BCDs / Eu-MOF probe: Europium chloride hexahydrate and trimellitic acid were ultrasonically dissolved in N,N-dimethylformamide, and then the BCDs solution prepared above was added and stirred. The stirred liquid was transferred to an autoclave for solvothermal reaction. After naturally cooling to room temperature, the product was washed with anhydrous ethanol and dried in a vacuum oven to obtain a BCDs / Eu-MOF probe, which was stored in a refrigerator for later use.

2. The method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics according to claim 1, characterized in that: The mass ratio of the citric acid to the polyethyleneimine is 2:(1-3).

3. The method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 150-260° C., and the reaction time is 4-8 hours; the molecular weight cutoff of the dialysis bag is 800-1200 Da.

4. The method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics according to claim 1, characterized in that: The mass ratio of the europium chloride hexahydrate to trimellitic acid is 2:(1-3).

5. The method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics according to claim 4, characterized in that: The amount of N,N-dimethylformamide used is 50-100 ml, and the mass ratio of N,N-dimethylformamide to europium chloride hexahydrate is (100-200):1; the amount of BCDs solution used in step (2) is 0.5-3 ml, and the mass ratio of N,N-dimethylformamide to europium chloride hexahydrate is (10-80):

1.

6. The method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics according to claim 1, characterized in that: The temperature of the solvent thermal reaction is 100-150° C., and the reaction time is 20-40 hours.

7. The method for preparing a fluorescent probe for rapid and sensitive detection of tetracycline antibiotics according to claim 1, characterized in that: The autoclave is provided with a polytetrafluoroethylene lining; the drying temperature of the vacuum oven is 50-80°C.

8. A fluorescent probe for rapid and sensitive detection of tetracycline antibiotics, characterized in that: The fluorescent probe is prepared by the preparation method according to any one of claims 1 to 7, and exhibits blue fluorescence in the absence of TCs and exhibits red fluorescence after contacting TCs.

9. An application of the fluorescent probe for rapid and sensitive detection of tetracycline antibiotics as claimed in claim 8, characterized in that: Used to detect whether a substance contains tetracycline antibiotics, and to detect the content of tetracycline antibiotics.

10. A portable detection device for rapid and sensitive detection of tetracycline antibiotics, characterized in that: It comprises a portable capillary detection box and a smart phone; the portable capillary detection box comprises a detection box body, a capillary encapsulating the fluorescent probe according to claim 8, a capillary storage rack, a mobile phone holder and a compact ultraviolet lamp.

Images