Fluorescent bimetallic MOFs membrane sensor and method capable of sensitively detecting ciprofloxacin

Abstract

The invention discloses a fluorescent bimetal MOFs (Metal-Organic Frameworks) membrane sensor and a method capable of sensitively detecting ciprofloxacin. The fluorescent bimetal MOFs membrane sensor comprises a substrate and a fluorescent bimetal MOFs material, wherein the fluorescent bimetal MOFs material is mainly formed by mixing a bimetal ion A solution and an organic ligand B solution; the bimetallic ion A solution comprises metal ions A1 and metal ions A2, the metal ions A1 are europium ions, the metal ions A2 are terbium ions, the organic ligand B solution comprises an organic ligand B, and the organic ligand B is 5 '-adenylic acid. The fluorescent bimetallic MOFs membrane sensor disclosed by the invention can be used for carrying out direct fluorescent quantitative detection on ciprofloxacin in a crude extraction solution of a real sample, so that the integration of pretreatment and detection is realized, and a simple, convenient and efficient means is provided for rapid and sensitive detection of antibiotics.

Description

Technical Field

[0001] The invention belongs to the field of new material preparation and food quality detection, and specifically relates to a fluorescent bimetallic MOFs film sensor and a method for sensitively detecting ciprofloxacin. Background Art

[0002] Ciprofloxacin (Ciprofloxacin, CIP) is a synthetic third-generation quinolone antibacterial drug. Due to its broad-spectrum antibacterial activity, bactericidal efficacy and low cost, it is widely used in the prevention and control of widespread infections in humans and animals. However, ciprofloxacin has low conversion efficiency in the body and is easily left in livestock and poultry and the human body through the food chain, leading to the occurrence of various diseases and threatening human health. In addition, since ciprofloxacin is difficult to degrade and remains active in the environment, low doses of ciprofloxacin can also cause great harm. Therefore, it is urgent to develop a highly sensitive and simple rapid detection technology to detect ciprofloxacin.

[0003] At present, a variety of methods for detecting ciprofloxacin have been developed and used, including high performance liquid chromatography-mass spectrometry, electrochemical methods, spectrophotometry, etc. Among the above methods, high performance liquid chromatography-mass spectrometry requires very expensive instruments and professionals to operate, electrochemical methods have inevitable environmental interference, which greatly limits their sensitivity, and spectrophotometry detection instruments are relatively large and have some limitations in terms of detection range; in addition, these methods still require complex pre-treatment operations, which are cumbersome and time-consuming, and are not conducive to rapid on-site detection.

[0004] Metal-Organic Frameworks (MOFs) are an emerging probe composed of metal cations or metal clusters and organic ligands. They have the advantages of high surface area, adjustable metal ion types and diverse functional sites. They have strong interactions with guest molecules and have become excellent carriers for selective identification of agricultural chemical pests such as antibiotics and mycotoxins. Some MOFs also have fluorescent properties. Compared with organic fluorophores, fluorescent probes based on MOFs have high stability, simple synthesis, and predictable nanostructures, and can be widely used in the analysis and detection of antibiotics. Conventional MOFs usually exist in powder form, have poor dispersibility, and are difficult to integrate into sensor devices, which limits their application in portable on-site detection.

[0005] Commercial filter membranes are low-cost thin film materials composed of high-molecular polymer materials, and have the advantages of high throughput and low cost. However, single filter membranes and other materials only have supporting, screening and adsorption capabilities, and cannot achieve direct detection of target molecules, and there are still limitations in the field of analytical detection. Summary of the invention

[0006] In order to solve the problems in the background, the present invention proposes a fluorescent bimetallic MOFs film sensor and method for sensitively detecting ciprofloxacin. The present invention utilizes the surface fluorescence image change of the fluorescent bimetallic MOFs film sensor to achieve rapid and sensitive detection of trace ciprofloxacin in agricultural products.

[0007] The technical solution adopted by the present invention is as follows:

[0008] 1. A fluorescent bimetallic MOFs film sensor for sensitive detection of ciprofloxacin

[0009] The fluorescent bimetallic MOFs film sensor comprises a substrate and a fluorescent bimetallic MOFs material loaded on the surface of the substrate. The substrate is used to load the fluorescent bimetallic MOFs material. The fluorescent bimetallic MOFs material is used to produce a fluorescent signal change in response to ciprofloxacin and can be stably fixed on the film substrate.

[0010] Specifically, the fluorescent bimetallic MOFs material is mainly prepared by mixing a bimetallic ion A solution and an organic ligand B solution; the components of the bimetallic ion A solution include metal ions A1 and metal ions A2, and the metal ions A1 are europium ions Eu 3+ , the metal ion A2 is terbium ion Tb 3+ , the components of the organic ligand B solution include organic ligand B, and the organic ligand B is 5'-adenylic acid.

[0011] Specifically, the ratio of the sum of the amounts of metal ions A1 and A2 in the metal ion A solution to the amount of organic ligand B in the organic ligand B solution is 0.5 to 10:1. The ratio of the amount of metal ions A1 to the amount of metal ions A2 is 0.2 to 5:1.

[0012] Specifically, the fluorescent bimetallic MOFs material responds to ciprofloxacin to produce a fluorescent signal change as follows: under an excitation wavelength of 365 nm, the fluorescence intensity value of the fluorescent bimetallic MOFs material at a characteristic wavelength is positively correlated with the logarithm of the concentration of ciprofloxacin; the characteristic wavelength is selected from 615 to 625 nm, and the characteristic wavelength is preferably 620 nm.

[0013] 2. A method for preparing a fluorescent bimetallic MOFs film sensor capable of sensitively detecting ciprofloxacin. The preparation method comprises the following steps:

[0014] 1) mixing the bimetallic ion A solution and the organic ligand B solution at 20-30° C. (preferably 25° C.) for a certain period of time, taking the precipitate after the reaction, washing and drying the precipitate to prepare a fluorescent bimetallic MOFs material;

[0015] In the step 1), the bimetallic ion A solution is prepared by mixing a metal ion A1 solution having a concentration of 0.01 mol / L to 1 mol / L and a metal ion A2 solution having a concentration of 0.01 mol / L to 1 mol / L in a volume ratio of 1:1. The concentration of the organic ligand B solution is 0.05 mol / L to 1 mol / L.

[0016] In the step 1), the bimetallic ion A solution and the organic ligand B solution are mixed in a volume ratio of 11:7.5.

[0017] In the step 1), the drying temperature is 50-70°C, preferably 60°C;

[0018] 2) Obtaining a substrate material, cleaning the substrate material, and drying it for later use to obtain a substrate. Specifically, obtaining a substrate material, and then ultrasonically cleaning the substrate material three times with deionized water, ethanol, and deionized water, respectively, and then drying it for no less than 10 minutes to obtain a substrate.

[0019] In the step 2), the substrate material is a nylon membrane, a polyethersulfone membrane, a polytetrafluoroethylene membrane, a cellulose acetate membrane or a filter paper.

[0020] 3) Fixing the fluorescent bimetallic MOFs material obtained in step 1) on the substrate obtained in step 2) by a secondary growth method, and obtaining the fluorescent bimetallic MOFs film sensor after cleaning and drying.

[0021] In the step 3), the secondary growth method is coating, filtration, chemical cross-linking or electrostatic spinning. The drying temperature is 50-70°C, preferably 60°C.

[0022] In the step 3), the mass of the fluorescent bimetallic MOFs material is: the loading area of ​​the fluorescent bimetallic MOFs material on the substrate is 100-800 μg: 132.7 mm 2 .

[0023] Preferably, in step 3), the secondary growth method is a suction filtration method, and the specific process is: the filter membrane is washed and dried to obtain a filter membrane base; then the filter membrane base is placed in a vacuum filtration device, and 200 μL of a fluorescent bimetallic MOFs solution (Eu / Tb-MOFs solution) with a concentration of 500 to 4000 μg / mL is filtered to the filter membrane base (with a loading area of ​​132.7 mm 2 ), and then the filter membrane substrate after filtration is placed in a washing liquid for cleaning, which can clean and remove particles that are easy to fall off, and finally the washed filter membrane substrate is placed in an oven and dried at 60° C. for 2 hours to obtain a film with uniform and stable loading of fluorescent bimetallic MOFs material as a fluorescent bimetallic MOFs membrane sensor. The washing liquid is an ethanol aqueous solution.

[0024] 3. A method for detecting ciprofloxacin using fluorescent bimetallic MOFs film sensor

[0025] The specific process of the detection method is: using a fluorescence measuring instrument to detect the original fluorescence signal of the fluorescent bimetallic MOFs film sensor, then mixing the fluorescent bimetallic MOFs film sensor with the liquid to be detected for 3 to 30 minutes, taking out the fluorescent bimetallic MOFs film sensor after the reaction, using a fluorescence measuring instrument to detect the post-reaction fluorescence signal of the post-reaction fluorescent bimetallic MOFs film sensor, obtaining a fluorescence signal change value based on the post-reaction fluorescence signal and the original fluorescence signal, substituting the fluorescence signal change value into a pre-established standard curve to obtain the concentration of ciprofloxacin in the liquid to be detected.

[0026] Specifically, the fluorescence signal is fluorescence intensity or fluorescence image color.

[0027] When the fluorescent signal is the fluorescence intensity, the process of obtaining the fluorescence signal change value according to the post-reaction fluorescence signal and the original fluorescence signal is specifically as follows: obtaining the difference between the post-reaction fluorescence intensity F and the original fluorescence intensity F0 by calculation, and then obtaining the ratio (F-F0) / F0 of the difference and the original fluorescence intensity F0 by calculation, and using the ratio (F-F0) / F0 as the fluorescence signal change value;

[0028] When the fluorescence signal is the color of a fluorescence image, the process of obtaining the fluorescence signal change value based on the post-reaction fluorescence signal and the original fluorescence signal is specifically as follows: the Euclidean distance (ED) between the post-reaction fluorescence image color and the original fluorescence image color is obtained by calculation, and the Euclidean distance is used as the fluorescence signal change value.

[0029] The mixing method of the fluorescent bimetallic MOFs sensor and the liquid to be detected includes but is not limited to immersion and filtration. The process of mixing the fluorescent bimetallic MOFs film sensor with the liquid to be detected is specifically as follows:

[0030] Immersing the fluorescent bimetallic MOFs film sensor in the liquid to be detected;

[0031] Alternatively, the fluorescent bimetallic MOFs membrane sensor is placed in a filter tank of a filtration device, and then a vacuum pump in the filtration device is started, and the negative pressure difference generated by the vacuum pump is used to push the liquid to be detected through the fluorescent bimetallic MOFs membrane sensor. During the filtration process, the fluorescent bimetallic MOFs membrane sensor reacts with the liquid to be detected, and the reaction time can be controlled between 3 and 30 minutes by controlling the filtration speed.

[0032] The liquid to be tested is commercially available skimmed milk powder or chicken breast extract.

[0033] The process of establishing the standard curve is specifically as follows: preparing a ciprofloxacin standard solution containing a gradient concentration, using a fluorescence measuring instrument to detect the original fluorescence signal of the fluorescent bimetallic MOFs film sensor, mixing each portion of the ciprofloxacin standard solution and the fluorescent bimetallic MOFs film sensor evenly, reacting for 3 to 30 minutes, taking out the post-reaction fluorescent bimetallic MOFs film sensor, using a fluorescence measuring instrument to detect the post-reaction fluorescence signal of the post-reaction fluorescent bimetallic MOFs film sensor, calculating the change value between the post-reaction fluorescence signal and the original fluorescence signal, fitting the change value corresponding to each ciprofloxacin standard solution with their respective actual concentrations, and obtaining the standard curve.

[0034] The present invention utilizes the characteristics that the fluorescent bimetallic MOFs material can adsorb ciprofloxacin and induce changes in the fluorescent signal. Since the energy transfer frequency and efficiency in the fluorescent bimetallic MOFs material are higher, the fluorescence response ability of the sensor to ciprofloxacin is improved. The fluorescent bimetallic MOFs material is prepared into a film with good enrichment performance and stability, which can meet the needs of actual detection, broaden the application of metal organic framework materials in colorimetric sensing, and provide a certain reference for on-site portable detection.

[0035] Beneficial effects of the present invention:

[0036] 1. The present invention prepares fluorescent bimetallic MOFs materials, realizes visual detection, and utilizes the higher energy transfer times and more efficient energy transfer effect in the bimetallic MOFs materials to improve the detection effect of the sensor on ciprofloxacin.

[0037] 2. The fluorescent bimetallic MOFs film sensor of the present invention has strong stability by virtue of the coordination effect between metal ions and organic ligands, and can directly detect ciprofloxacin in organic reagents.

[0038] 3. The fluorescent bimetallic MOFs film sensor of the present invention can be used as a simple on-site detection device to directly perform fluorescent quantitative detection of ciprofloxacin in the crude extract solution, realize the integration of pretreatment and detection, and provide a simple and efficient means for the rapid and simultaneous detection of antibiotics.

[0039] 4. The detection range of the fluorescent bimetallic MOFs film sensor of the present invention is 0.001-10 μg / mL, and the detection limit is 1.7 ng / mL. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic diagram of the fluorescent bimetallic MOFs film sensor of the present invention;

[0041] Figure 2 It is a scanning electron microscope and element distribution diagram of the fluorescent bimetallic MOFs prepared in Example 1 of the present invention and the film sensor prepared in Example 2;

[0042] Figure 3 This is a performance diagram of the fluorescent bimetallic MOFs prepared in Example 1 of the present invention for detecting ciprofloxacin;

[0043] Figure 4 This is a performance diagram of the fluorescent bimetallic MOFs film sensor prepared in Example 2 of the present invention for detecting ciprofloxacin;

[0044] Figure 5 It is a performance diagram of two fluorescent bimetallic MOFs prepared in the comparative example of the present invention for detecting ciprofloxacin. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0046] The fluorescent bimetallic MOFs film sensor of the present invention can use the change of fluorescence signal to quickly detect ciprofloxacin; the fluorescent bimetallic MOFs film sensor can perform direct fluorescence quantitative detection of ciprofloxacin in the crude extraction solution of real samples, realize the integration of pretreatment and detection, and provide a simple and efficient means for the rapid and sensitive detection of antibiotics.

[0047] like Figure 1 As shown, the fluorescent bimetallic MOFs film sensor includes a substrate and a fluorescent bimetallic MOFs material loaded on the surface of the substrate; the fluorescent bimetallic MOFs material is mainly prepared by mixing a metal ion A solution and an organic ligand B solution, and sensitive detection of ciprofloxacin is achieved through changes in fluorescence signals.

[0048] The amount of metal ion A1 in the metal ion A solution: the amount of metal ion A2 is 0.2:1 to 5:1.

[0049] The total amount of metal ion A1 and metal ion A2 in the metal ion A solution: the amount of organic ligand B in the organic ligand B solution is 0.5:1 to 10:1.

[0050] Specifically, in the metal ion A solution, metal ions A1 and A2 are Eu 3+ , Tb 3+ ; The organic compound B in the organic ligand B solution is 5'-adenylic acid.

[0051] The double metal ion A solution is mainly composed of a metal ion A1 solution with a concentration of 0.01 mol / L to 1 mol / L and a metal ion A2 solution with a concentration of 0.01 mol / L to 1 mol / L in a volume ratio of 1:1. The concentration of the organic ligand B solution is 0.05 mol / L to 1 mol / L.

[0052] In a specific implementation, the fluorescent bimetallic MOFs material is directly prepared by mixing the above-mentioned metal ion A solution and the organic ligand B solution in a volume ratio of 11:7.5; the preparation methods of the fluorescent bimetallic MOFs material include but are not limited to solvothermal method, microwave method, electrochemical method and ultrasonic method.

[0053] The principle of the fluorescent bimetallic MOFs film sensor for quantitative detection of ciprofloxacin is as follows: Eu in the fluorescent bimetallic Eu / Tb-MOFs 3+ and Tb 3+ The coordination is unsaturated, and part of the empty orbital is occupied by water molecules, resulting in almost no fluorescence in the fluorescent bimetallic Eu / Tb-MOFs. This is mainly due to the high-frequency OH bond vibration of water molecules, which quenches the luminescence of Eu / Tb-MOFs. When ciprofloxacin is present, ciprofloxacin acts as a bridging molecule to replace the coordinated water molecules and acts as an antenna molecule to transfer energy to Tb 3+ and Eu 3+ , and Tb 3+ It will also be passed to Eu 3+ , causing the fluorescent bimetallic Eu / Tb-MOFs to emit red fluorescence under 365nm ultraviolet light. The higher the concentration of ciprofloxacin, the higher the intensity of the red fluorescence.

[0054] When the fluorescent bimetallic MOFs film sensor of the present invention is used, the dried fluorescent MOFs film sensor is immersed in a solution containing ciprofloxacin and kept for a period of time to adsorb the ciprofloxacin in the solution, and then the fluorescent bimetallic MOFs film sensor adsorbing ciprofloxacin is taken out, cleaned, and measured, and the performance results of the fluorescent bimetallic MOFs film sensor are obtained using information acquisition technology. Information acquisition technology refers to the technology of measuring fluorescence spectra and color changes, and the tools used include but are not limited to electronic scanning microscopes, fluorescence measurement instruments, and image processing software.

[0055] Among them, the fluorescence measuring instrument includes but is not limited to an enzyme reader, a fluorescence spectrophotometer or a color recognition device. The enzyme reader and the fluorescence spectrophotometer can be used to directly measure the fluorescence intensity change of the fluorescent bimetallic MOFs film sensor. The color recognition device includes an image capture device such as a mobile phone and a camera. The image capture device can capture the image information of the fluorescent MOFs material before and after the reaction, and then use the image processing software such as Image J software to accurately identify the captured image, and obtain the color change of the fluorescent MOFs material according to the Euclidean distance of the image before and after the reaction.

[0056] In the specific implementation, the solution containing ciprofloxacin refers to the sample solution to be tested. The sample solution to be tested is mainly the extract of commercially available agricultural products such as skimmed milk powder or chicken breast. The extract includes a crude extract solution. The crude extract solution refers to a pre-extracted solution that is initially extracted from skimmed milk powder or chicken breast by physical or chemical methods but has not yet been further separated and purified.

[0057] The specific embodiments of the present invention are as follows:

[0058] Example 1

[0059] In this example, a fluorescent bimetallic MOFs material Eu / Tb-MOFs that can sensitively detect ciprofloxacin (CIP) was prepared, and Eu / Tb-MOFs was used to quantitatively detect ciprofloxacin. The specific process is as follows:

[0060] 1) 0.125mmol Tb(NO3)3·6H2O and 0.125mmol Eu(NO3)3·6H2O were uniformly dispersed in 11mL ultrapure water to form a uniform suspension. Secondly, 7.5mL of Tris buffer (0.1mol / L, pH=7.4) containing 0.5mmol 5'-AMP was added to the suspension at a certain stirring speed, and the reaction was stirred at room temperature for 2h. The precipitate was taken and washed with methanol, ethanol and water at a speed of 10000rpm for 10min respectively, and finally dried at 60℃ overnight to obtain the fluorescent bimetallic MOFs material Eu / Tb-MOFs and collected for later use.

[0061] 2) Eu / Tb-MOFs were ultrasonically prepared into a Eu / Tb-MOFs solution with a concentration of 4 mg / mL using ethanol. 200 μL of the Eu / Tb-MOFs solution was reacted with 500 μL of ciprofloxacin solution of different concentrations (prepared in acetonitrile and water) for 10 min. Ciprofloxacin was quantitatively detected based on the change in fluorescence intensity of Eu / Tb-MOFs at the emission peak of 620 nm before and after the reaction.

[0062] The scanning electron microscope (upper left) and element distribution diagram (upper right) of the fluorescent bimetallic MOFs material Eu / Tb-MOFs obtained in this example are shown in Figure 2 .

[0063] Figure 3It is a performance diagram of the fluorescent bimetallic MOFs prepared in Example 1 of the present invention for detecting ciprofloxacin. It can be seen that after adding ciprofloxacin, the fluorescence intensity of Eu / Tb-MOFs continues to increase, and the fluorescence color changes from red to orange and then to green. The main reason is that the blue fluorescence of high-concentration ciprofloxacin is mixed with red MOFs. The fluorescence enhancement rate increases significantly with the increase of ciprofloxacin concentration. Image J is used to collect data on the fluorescence intensity of the picture, and the fluorescence change rate ((F-F0) / F0, y) is analyzed. When the concentration of ciprofloxacin (c) is between 0.005 and 0.25 μg / mL, y and the logarithm of the concentration of ciprofloxacin (lgc) satisfy the linear relationship y=9.10lgc+21.92(r 2 =0.847); when the concentration of ciprofloxacin (c) is between 0.25 μg / mL≤c≤10 μg / mL, y and the logarithm of the concentration of ciprofloxacin (lgc) satisfy the linear relationship y=71.08lgc+61.02(r 2 =0.996), and the detection limit (LOD) was 3.9 ng / mL (signal-to-noise ratio S / N=3), which is lower than most other reported fluorescent MOFs detection effects and can be used for stable detection in acetonitrile water organic reagents, demonstrating that fluorescent bimetallic Eu / Tb-MOFs can be used for sensitive and rapid detection of ciprofloxacin.

[0064] Example 2

[0065] In this example, a fluorescent bimetallic MOFs film sensor Nylon@Eu / Tb-MOFs capable of sensitively detecting ciprofloxacin was prepared. The specific process is as follows:

[0066] 1) 0.125mmol Tb(NO3)3·6H2O and 0.125mmol Eu(NO3)3·6H2O were uniformly dispersed in 11mL ultrapure water to form a uniform suspension. Next, 7.5mL of Tris buffer (0.1mol / L, pH=7.4) containing 0.5mmol 5'-AMP was added to the suspension at a certain stirring speed, and the reaction was stirred at room temperature for 2h. The precipitate was washed with methanol, ethanol and water at a speed of 10000rpm for 10min respectively, and finally dried at 60℃ overnight and collected for use.

[0067] 2) Obtain a nylon filter membrane through commercial means, and wash and dry the nylon filter membrane for later use;

[0068] 3) Place the dried nylon filter membrane obtained in step 2) in a vacuum filtration device, and filter 200 μL of the 4 mg / mL fluorescent bimetallic MOFs solution onto the nylon membrane by pressure to obtain a filtered nylon membrane, soak the filtered nylon membrane in ethanol water for cleaning and place it in an oven at 60°C for 2 hours to obtain a film uniformly and stably loaded with fluorescent bimetallic MOFs as a fluorescent bimetallic MOFs membrane sensor Nylon@Eu / Tb-MOFs. The loading area of ​​the fluorescent bimetallic MOFs on the nylon filter membrane is 132.7 mm 2 .

[0069] 4) The fluorescent bimetallic MOFs film sensor was mixed evenly with the test solution containing different concentrations of ciprofloxacin prepared with acetonitrile aqueous solution, and the solution was taken out after reacting for 10 minutes. The fluorescence images of the fluorescent bimetallic MOFs film sensor before and after the reaction after excitation with 365nm ultraviolet light were photographed with a mobile phone, and a response relationship model between the Euclidean distance (ED) between the fluorescence images before and after the reaction and different ciprofloxacin concentrations was established.

[0070] The scanning electron microscope (lower left) and element distribution diagram (lower right) of the fluorescent bimetallic MOFs film sensor Nylon@Eu / Tb-MOFs obtained in this example are shown in Figure 2 .

[0071] Figure 4 This is a performance diagram of the fluorescent bimetallic MOFs film sensor prepared in this example for detecting the concentration of ciprofloxacin. Figure 4 In the fluorescence images of the Nylon@Eu / Tb-MOFs film sensor before and after the reaction, the ED(y) value increases with the increase of ciprofloxacin concentration (c). When the concentration of ciprofloxacin is in the range of 0.001 to 0.1 μg / mL, the linear relationship y=16.86lgc+53.49(r 2 =0.931); when c is between 0.1 and 5 μg / mL, the linear relationship is y=70.62lgc+104.48(r 2 =0.984), the detection limit (LOD) was 1.4ng / mL (S / N=3), and the LOD of the fluorescent bimetallic MOFs film sensor Nylon@Eu / Tb-MOFs was reduced by 1 / 2.79 compared with the powder Eu / Tb-MOFs. The fluorescent bimetallic MOFs film sensor has excellent detection performance in organic reagents such as acetonitrile water. The above results all show that the fluorescent bimetallic MOFs film sensor can be used for on-site sensitive and rapid detection of ciprofloxacin.

[0072] Example 3

[0073] This example uses the fluorescent bimetallic MOFs membrane sensor prepared in Example 2 to detect the ciprofloxacin content in skim milk powder and chicken breast. The following table shows the spiked recovery effect of the fluorescent bimetallic MOFs membrane sensor prepared in Example 3 for detecting ciprofloxacin in skim milk powder and chicken breast:

[0074]

[0075] In this embodiment, the recoveries of 0.1, 0.5 and 2 μg / mL ciprofloxacin in skimmed milk powder detected by Nylon@Eu / Tb-MOFs membrane sensor were 94.2%±7.85%, 90.4%±11.4% and 120.4%±12.9%, respectively; the recoveries of 0.1, 0.5 and 2 μg / mL ciprofloxacin in chicken samples detected by Nylon@Eu / Tb-MOFs membrane sensor were 94.5%±8.6%, 93.5%±7.2% and 92.1%±10.7%, respectively, both demonstrating the ability of Nylon@Eu / Tb-MOFs membrane sensor to detect ciprofloxacin in agricultural products.

[0076] Comparative Example

[0077] In this comparative example, two fluorescent single metal MOFs materials, Eu-MOFs and Tb-MOFs, were prepared and used to detect the content of ciprofloxacin. The preparation process of the fluorescent single metal MOFs material capable of detecting ciprofloxacin is as follows:

[0078] 1) 0.25mmol Eu(NO3)3·6H2O was evenly dispersed in 11mL ultrapure water to form a uniform suspension. Secondly, 7.5mL of Tris buffer (0.1M, pH=7.4) containing 0.5mmol 5'-AMP was added to the suspension at a certain stirring speed, and the reaction was stirred at room temperature for 2h. The precipitate was washed with methanol, ethanol and water at a speed of 10000rpm for 10min respectively, and finally dried at 60℃ overnight to obtain the fluorescent single metal MOFs material Eu-MOFs and collected for later use.

[0079] 2) 0.25mmol Tb(NO3)3·6H2O was evenly dispersed in 11mL ultrapure water to form a uniform suspension. Secondly, 7.5mL of Tris buffer (0.1M, pH=7.4) containing 0.5mmol 5'-AMP was added to the suspension at a certain stirring speed, and the reaction was stirred at room temperature for 2h. The precipitate was washed with methanol, ethanol and water at a speed of 10000rpm for 10min respectively, and finally dried at 60℃ overnight to obtain the fluorescent single metal MOFs material Tb-MOFs and collected for later use.

[0080] 3) The Eu-MOFs obtained in step 1) and the Tb-MOFs obtained in step 2) were ultrasonically dispersed in ethanol and prepared into solutions with a concentration of 4 mg / mL. 200 μL of the Eu-MOFs and Tb-MOFs solutions were reacted with 500 μL of ciprofloxacin solutions of different concentrations for 10 min, respectively. Ciprofloxacin was quantitatively detected based on the changes in the fluorescence intensity of Eu-MOFs and Tb-MOFs at the emission peaks of 548 nm and 620 nm before and after the reaction, respectively, and the detection effect was compared with that of Eu / Tb-MOFs.

[0081] Figure 5 It is a performance diagram of two fluorescent bimetallic MOFs prepared in the comparative example of the present invention for detecting ciprofloxacin. Figure 5 (Left) The actual picture shows that the red fluorescence intensity of Eu-MOFs gradually increases with the increase of ciprofloxacin concentration until the blue fluorescence of high-concentration ciprofloxacin itself appears; Figure 5 (Right) shows that the green fluorescence of Tb-MOFs becomes increasingly obvious as the concentration of ciprofloxacin increases, and the fluorescence spectrum also shows the same trend. Judging from the fluorescence spectrum and the fluorescence changes of the actual object, the minimum detection limit of Eu-MOFs is 0.5μg / mL, and the fluorescence intensity at 620nm does not change significantly; the minimum detection limit of Tb-MOFs is 0.1μg / mL, and the fluorescence change is not obvious at low concentrations (<0.5μg / mL). The minimum detection limit of the fluorescent bimetallic Eu / Tb-MOFs in Example 1 is 0.025μg / mL, which is 20 times lower than the detection limit of Eu-MOFs and 4 times lower than the detection limit of Tb-MOFs. Both reflect that the fluorescent bimetallic Eu / Tb-MOFs improve the fluorescence detection performance of ciprofloxacin due to the one-step energy transfer process inside MOFs, and the detection limit is lower, which also shows the good potential of fluorescent bimetallic Eu / Tb-MOFs in low-concentration ciprofloxacin detection.

[0082] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the method of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fluorescent bimetallic MOFs film sensor for sensitive detection of ciprofloxacin, characterized in that: The fluorescent bimetallic MOFs film sensor includes a substrate and a fluorescent bimetallic MOFs material, wherein the substrate is used to load the fluorescent bimetallic MOFs material, and the fluorescent bimetallic MOFs material is used to respond to ciprofloxacin; the fluorescent bimetallic MOFs material is mainly formed by mixing a bimetallic ion A solution and an organic ligand B solution; the components of the bimetallic ion A solution include metal ions A1 and metal ions A2, wherein the metal ions A1 are europium ions, and the metal ions A2 are terbium ions; the components of the organic ligand B solution include organic ligand B, and the organic ligand B is 5'-adenylic acid.

2. The fluorescent bimetallic MOFs film sensor capable of sensitively detecting ciprofloxacin according to claim 1, characterized in that: The ratio of the sum of the amounts of metal ions A1 and A2 in the metal ion A solution to the amount of organic ligand B in the organic ligand B solution is 0.5 to 10:

1.

3. The fluorescent bimetallic MOFs film sensor capable of sensitively detecting ciprofloxacin according to claim 2, characterized in that: The ratio of the amount of metal ion A1 to the amount of metal ion A2 is 0.2 to 5:

1.

4. The fluorescent bimetallic MOFs film sensor capable of sensitively detecting ciprofloxacin according to claim 1, characterized in that: The fluorescent bimetallic MOFs material responds to ciprofloxacin specifically as follows: under an excitation wavelength of 365 nm, the fluorescence intensity value of the fluorescent bimetallic MOFs material at a characteristic wavelength is positively correlated with the logarithm of the concentration of ciprofloxacin; and the characteristic wavelength is selected from 615 to 625 nm.

5. A method for preparing a fluorescent bimetallic MOFs film sensor as claimed in any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: 1) mixing a bimetallic ion A solution and an organic ligand B solution at 20 to 30° C. to prepare a fluorescent bimetallic MOFs material; 2) washing the substrate material and drying it to obtain a substrate; 3) Fixing the fluorescent bimetallic MOFs material obtained in step 1) on the substrate obtained in step 2) by a secondary growth method, and obtaining the fluorescent bimetallic MOFs film sensor after cleaning and drying.

6. The preparation method according to claim 5, characterized in that: In the step 2), the substrate material is a nylon membrane, a polyethersulfone membrane, a polytetrafluoroethylene membrane, a cellulose acetate membrane or a filter paper.

7. A method for detecting ciprofloxacin using the fluorescent bimetallic MOFs film sensor according to any one of claims 1 to 4 or the fluorescent bimetallic MOFs film sensor prepared by the preparation method according to claim 5 or 6, characterized in that: The specific process of the detection method is: using a fluorescence measuring instrument to detect the original fluorescence signal of the fluorescent bimetallic MOFs film sensor, then mixing the fluorescent bimetallic MOFs film sensor with the liquid to be detected for 3 to 30 minutes, taking out the fluorescent bimetallic MOFs film sensor after the reaction, using a fluorescence measuring instrument to detect the post-reaction fluorescence signal of the post-reaction fluorescent bimetallic MOFs film sensor, obtaining a fluorescence signal change value based on the post-reaction fluorescence signal and the original fluorescence signal, substituting the fluorescence signal change value into a pre-established standard curve to obtain the concentration of ciprofloxacin in the liquid to be detected.

8. The ciprofloxacin detection method according to claim 7, characterized in that: The fluorescent signal is the fluorescence intensity or the color of the fluorescent image; when the fluorescent signal is the fluorescence intensity, the process of obtaining the fluorescence signal change value according to the post-reaction fluorescence signal and the original fluorescence signal is specifically as follows: the difference between the post-reaction fluorescence intensity F and the original fluorescence intensity F0 is obtained by calculation, and then the ratio (F-F0) / F0 of the difference and the original fluorescence intensity F0 is obtained by calculation, and the ratio (F-F0) / F0 is used as the fluorescence signal change value; When the fluorescence signal is the color of a fluorescence image, the process of obtaining the fluorescence signal change value according to the post-reaction fluorescence signal and the original fluorescence signal is specifically as follows: the Euclidean distance between the post-reaction fluorescence image color and the original fluorescence image color is obtained by calculation, and the Euclidean distance is used as the fluorescence signal change value.

9. The ciprofloxacin detection method according to claim 7, characterized in that: The process of mixing the fluorescent bimetallic MOFs film sensor with the liquid to be detected is: immersing the fluorescent bimetallic MOFs film sensor in the liquid to be detected; or placing the fluorescent bimetallic MOFs film sensor in a filter tank, and then starting a vacuum pump to push the liquid to be detected through the fluorescent bimetallic MOFs film sensor.

10. The ciprofloxacin detection method according to claim 7, characterized in that: The liquid to be tested is skimmed milk powder or chicken breast extract.

Images