Hydrogel sensor, manufacturing method therefor, and use thereof in detection of tetracycline

Abstract

The present application relates to the technical field of sensors, and discloses a hydrogel sensor, a manufacturing method therefor, and a use thereof in detection of tetracycline (TC). The hydrogel sensor comprises a composite hydrogel matrix and an Eu3+ luminescent center; the composite hydrogel matrix is a double-crosslinked aggregation network formed by polymerizing polyacrylamide and sodium alginate (SA); the SA and Eu3+ are chelated to form the Eu3+ luminescent center; the hydrogel contains a large number of hydroxyl groups and deprotonated carboxyl groups. In the present application, due to excellent adhesion performance of the EU / SA hydrogel, the EU / SA hydrogel can be accurately adhered to the surfaces of various animals, and non-invasive and specific site fluorescence intensity measurement is carried out on TC on the surfaces, so that the content of the TC is accurately measured, and the concentration of the TC can be visually distinguished by means of a change in color. The method is an economical, convenient and sensitive rapid detection method when used in detection of the TC, and the method improves the accuracy of biomedicine and drug analysis, and is conducive to targeted therapy and personalized medical treatment.

Description

A hydrogel sensor, a preparation method thereof, and its application in detecting tetracycline Technical Field

[0001] The present application relates to a hydrogel sensor, a preparation method thereof, and application in detecting tetracycline, belonging to the field of sensor technology. Background Art

[0002] Tetracycline is one of the most concerning antibiotics, playing a significant role in the overall spread of antimicrobial resistance among all animal species, including humans. In recent years, antibiotic contamination of environmental water bodies has become an increasingly serious problem. Antibiotic residues can enter the human body through dietary sources such as meat, milk, and eggs. Ingestion of antibiotics can lead to the development of drug resistance, weaken immunity, and thus affect human health. Tetracycline (TC) is a widely used broad-spectrum antibiotic characterized by low cost, strong antimicrobial activity, minimal side effects, and excellent therapeutic efficacy. It is widely used in medicine, animal husbandry, and aquaculture. However, TC is difficult to degrade naturally. To date, detection of TC has primarily relied on high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and liquid chromatography-tandem mass spectrometry (LC-MS / MS). While these instrumental analytical methods are highly sensitive, they are time-consuming, labor-intensive, and require specialized personnel. Immunoassays, including gold immunochromatography (GICA), enzyme-linked immunosorbent assay (ELISA), and fluorescence immunoassay (FIA), offer a simple and cost-effective alternative. However, these methods involve complex processing steps and are subject to strict detection conditions. Therefore, it is crucial to develop a convenient, rapid, and sensitive detection method to monitor the risk of tetracycline contamination.

[0003] Summary of the Invention

[0004] To address the challenges of prior art tetracycline contamination detection, which struggle to achieve both convenience, speed, and sensitivity, this application provides a hydrogel sensor (Eu-H) by introducing a lanthanide metal element (Eu) into a sodium alginate (SA) / polyacrylamide (PAAm) hydrogel. Eu-H, acting as a probe for tetracycline (TC), emits fluorescence ranging from red to yellow when exposed to TC solutions of varying concentrations.

[0005] A hydrogel sensor, comprising a composite hydrogel matrix, Eu 3+ Luminous Center;

[0006] The composite hydrogel matrix is ​​a double cross-linked polymer network formed by polymerization of polyacrylamide and sodium alginate;

[0007] The sodium alginate and Eu 3+ Chelation to form Eu 3+ Luminous Center;

[0008] The hydrogel contains a large number of hydroxyl groups and deprotonated carboxyl groups.

[0009] Optionally, the Eu in the hydrogel sensor 3+ The content of Eu is 0.1-0.5wt% of the weight of sodium alginate. 3+ The content is calculated relative to the weight of the sodium alginate part in the composite hydrogel matrix.

[0010] Optionally, the hydrogel sensor exhibits pink fluorescence under 365nm ultraviolet irradiation.

[0011] Optionally, the water content of the hydrogel sensor is greater than or equal to 80%.

[0012] Optionally, the equilibrium expansion rate of the hydrogel sensor is 400-600%.

[0013] Optionally, the conductivity of the hydrogel sensor is 6.1-8.3 S / m.

[0014] Lanthanide metals (Ln) are fluorescent materials with long phosphorescence lifetimes. When coordinated with a ligand, the ligand acts like an "antenna" to absorb energy and then transfer it to the lanthanide ion, generating the unique fluorescence characteristic of lanthanides. Doping with lanthanides can alter the optical and electrical properties of a material by increasing or decreasing the electron transfer rate of the conductor. The successful preparation of lanthanide hydrogels has been demonstrated.

[0015] Sodium alginate (SA) is a polyanionic polysaccharide carbohydrate mainly derived from brown algae, which can be rapidly cross-linked with multivalent cations to form a hydrogel. SA hydrogel has the advantages of good biocompatibility, low immunogenicity, and low price, so it is widely used in interventional therapy, wound dressing, drug delivery and 3D printing. The SA hydrogel network contains a large number of hydroxyl groups and deprotonated carboxyl groups. 3+ and Tb 3+ Lanthanide metal ions such as TC can be functionalized as metal crosslinkers by strongly chelating with the naturally charged, deprotonated carboxyl groups in SA, thereby enhancing the mechanical properties of the hydrogel network. Furthermore, they can serve as luminescent centers introduced into SA hydrogels. The β-diketone structure in TC can bind to Eu to form a complex. Therefore, a fluorescence analysis method using Eu as a probe can be developed to detect TC.

[0016] According to another aspect of the present application, a method for preparing the above-mentioned hydrogel sensor is provided, comprising the following steps:

[0017] S1. Add Eu to the aqueous solution of acrylamide 3+ source, adding an initiator aqueous solution and a cross-linking agent aqueous solution respectively to form solution A;

[0018] S2. Adding a sodium alginate aqueous solution to solution A, and then adding a catalyst to obtain a mixed solution, injecting the mixed solution into a mold, and photocuring and cross-linking the hydrogel sensor.

[0019] Optionally, in step S1, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate;

[0020] Optionally, in step S2, the catalyst is selected from at least one of N,N,N',N'-tetramethylethylenediamine, sodium sulfite, sodium bisulfite and sodium thiosulfate;

[0021] Optionally, in step S1, the cross-linking agent is selected from at least one of N,N-methylenebisacrylamide and ethylene glycol dimethacrylate;

[0022] Optionally, in step S1, the Eu 3+ The source is selected from the nitrate or hydrochloride of europium;

[0023] Optionally, in step S1, Eu 3+ The amount of source is based on the Eu in the hydrogel sensor. 3+ The content is calculated as 0.1 to 0.5 wt% of the weight of sodium alginate;

[0024] Optionally, based on a concentration of 4.8 wt% sodium alginate aqueous solution, 19 wt% acrylamide aqueous solution, 0.2 M initiator aqueous solution, and 2 wt‰ cross-linker aqueous solution, the volume ratio of sodium alginate aqueous solution to acrylamide aqueous solution, initiator aqueous solution, cross-linker aqueous solution, and catalyst is 1: (0.8-1.8): (0.025-0.045): (0.05-0.30): (0.001-0.009).

[0025] According to another aspect of the present application, there is also provided the use of the above-mentioned hydrogel sensor and the hydrogel sensor prepared according to the above-mentioned preparation method in detecting tetracycline.

[0026] Optionally, the detection limit of the hydrogel sensor for tetracycline is ≤0.9 nmol / L;

[0027] Optionally, the hydrogel sensor shows a linear relationship for the detection of tetracycline with a concentration of 10-100 μg / L, and the linear equation is: y=-88.13499x+10689.39805, and the correlation coefficient R 2 =0.9997;

[0028] Optionally, the application includes collecting images of the hydrogel sensor when monitoring tetracycline, converting the color of the hydrogel sensor into corresponding feature values, training the feature data to obtain a detection model, and using the detection model to obtain the concentration value of tetracycline through the color of the hydrogel sensor.

[0029] Optionally, the method of acquiring the image of the hydrogel sensor when monitoring tetracycline includes acquiring the image using a smart mobile device, such as a smart phone.

[0030] Smartphones can capture different colors. By integrating machine learning algorithms and image processing techniques, we established a relationship between color and concentration. This method was applied to real-world samples and comprehensively investigated the performance of fluorescence sensing in detecting TC on animal surfaces. It provides a fast, convenient, and reliable detection method.

[0031] The beneficial effects of this application include:

[0032] The hydrogel sensor and its preparation method provided by this application are prepared by successfully preparing Eu / SA hydrogel and adding TC to Eu 3+ Fluorescence quenching was performed and a ratiometric fluorescence analysis method was established. Utilizing the excellent adhesion properties of Eu / SA hydrogel, it can accurately adhere to the surfaces of various animals and perform non-invasive and site-specific fluorescence intensity measurement of tetracycline (TC) on the surface, thereby accurately detecting the content of TC. The concentration of TC can be intuitively distinguished by color changes. In the application of tetracycline detection, this method is an economical, convenient, sensitive and rapid detection method. This method improves the accuracy of biomedical and drug analysis, contributes to targeted therapy and personalized medicine, and overcomes the problems of traditional detection methods that require complex pretreatment, separation and detection, and are difficult to solve the spatial variation and intricate distribution pattern of the analyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a schematic diagram of (A) SA / PAAm and Eu-H under 365nm ultraviolet light (scale bar 20μm), (B) different concentrations of Eu added to the Eu-H system 3+ The change of fluorescence intensity after (C)Eu-H system and Eu 3+ Comparison of fluorescence intensity of the system, (D) SEM image of SA / PAAm hydrogel (scale bar 2μm), (E) SEM image of Eu-H (scale bar 2μm), (F) EDS elemental analysis of Eu-H: (G) Different Eu 3+ Concentration: Water content of hydrogel, (H) swelling behavior of Eu-H in deionized water over time, (I) Effect of reaction time on the fluorescence intensity of Eu-H system.

[0034] Figure 2 is a schematic diagram of the adhesion of Eu-H on different biological tissues in this application: (A) Schematic diagram of the adhesion of Eu-H on different substrates; (B) Adhesion strength of Eu-H on different substrates; (C) Adhesion strength of Eu-H on different substrates 3+ Stress-strain curves at different concentrations; (D) Sensitivity of Eu-H; (E) Resistance change of Eu-H after 250 cycles of cyclic stretching at 50% strain; (Fluorescence spectra of Eu-H at different TC concentrations (C TC for a~k:0μgL -1 , 10μgL -1 , 20μgL -1 , 30μgL -1 40μgL -1 , 50μgL -1 , 60μgL - 1 , 70μgL -1 , 80μgL -1 , 90μgL -1 , 100μgL -1 ), and the corresponding linear relationship of (G), (H)Eu-H anti-interference test.

[0035] Figure 3 shows: (A) machine learning flowchart; (B) feature data analysis; (C) accuracy of the training model; and (D) detection results of regional concentrations in actual samples in this application.

[0036] Figure 4 shows the optimal excitation and emission wavelengths of the lanthanide element Eu.

[0037] Figure 5 shows the fluorescence intensity of Eu at different excitation wavelengths.

[0038] Figure 6 shows the effect of different concentrations of Eu3+ on fluorescence intensity.

[0039] Figure 7 shows the relationship between TC and Eu 3+ The fluorescence quenching reaction (C TC : 100PPM, solvent: methanol, C Eu3+ :300mmol / L).

[0040] Figure 8 shows Eu of different volumes 3+ Effect on the fluorescence intensity of the system.

[0041] Figure 9 shows Eu 3+ Comparison of solution (left) and Eu / TC solution (right) under 365nm ultraviolet light (scale bar 34μm, CEu 3+ : 1mol / L, CTC: 100PPM).

[0042] Figure 10 is a schematic diagram of the gelation mechanism of Eu-H.

[0043] Figure 11 shows the excitation wavelength of Eu-H.

[0044] FIG12 shows the fluorescence quantum yield.

[0045] Figure 13 shows the equilibrium expansion ratio of Eu-H.

[0046] Figure 14 is a physical image of the adhesion test.

[0047] FIG15 is a fluorescence spectrum of Eu-H detecting TC and showing fluorescence quenching.

[0048] Figure 16 shows that Eu-H can be made into various shapes.

[0049] Figure 17 shows Eu-H sensors of different shapes pasted on pig skin for real-time monitoring of local tetracycline. DETAILED DESCRIPTION

[0050] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0051] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0052] Unless otherwise specified, conventional methods were used for testing, and instrument settings were those recommended by the manufacturer.

[0053] Reagents: Sodium alginate (SA, 99% purity), N,N,N',N'-tetramethylethylenediamine (TEMED), acrylamide (AAm, ≥99%), N,N'-methylenebisacrylamide (Bis, 99%), and ammonium persulfate (APS, ≥98%) were purchased from Sigma-Aldrich. Tetracycline (TC, 90% purity), sulfadiazine (99% purity), sulfabenzamide (99% purity), sulfapyridine (99% purity), and trimethoprim (99% purity) were purchased from Shanghai Yuanye Biotechnology Co., Ltd. Europium nitrate hexahydrate (Eu(NO3)3-6H2O, 99.9% purity) was purchased from Shanghai Anjin Chemical Co., Ltd. Methanol (chromatographic grade) was purchased from Fisher Chemical Company.

[0054] Experimental instruments: ZEISS Sigma500 field emission scanning electron microscope (Zeiss, Germany); XFlash 6130EDS (Bruker, Germany); ZQ-990L universal tensile testing machine (Zhiqu Instrument, Dongguan); PS-20A ultrasonic cleaner (Jiekang, Shenzhen); E4980 ALLCR meter (Keysight, China); RF-6000 fluorescence spectrophotometer (Shimadzu); UV analyzer (Qiwei, China); X0-18S vacuum freeze dryer (Xian'ou, Nanjing); P60 Huawei smartphone (Huawei, China).

[0055] The test methods used in this application are:

[0056] Scanning electron microscopy morphological characterization: The hydrogel samples to be tested were pre-frozen in a -20°C freezer for 2 hours and then completely dried in a vacuum freeze dryer for 48 hours. The samples were freeze-fractured in liquid nitrogen to reveal cross-sections, which were then spread onto a flat silicon wafer and gold-sputtered to visualize the internal microstructure. Mapping images of the materials were obtained using energy-dispersive X-ray spectroscopy (EDS) scanning.

[0057] Swelling test of hydrogel: The swelling rate was calculated based on the change in weight over time. The mass of the blank hydrogel was measured and then immersed in deionized water at room temperature. The sample was taken out every 30 minutes, the excess solution was wiped off, and then weighed until the weight of the hydrogel reached equilibrium. Swelling rate (W s ) is calculated as W s =(W t -W0) / W0, where W t is the weight of the hydrogel after absorbing water, and W0 is the weight of the blank;

[0058] Tensile testing: The mechanical tensile properties of the hydrogels were measured using a mechanical testing machine (ZQ-990L, Zhiqu, China). The tests were conducted at room temperature using rectangular hydrogel specimens measuring 40 × 10 × 2 mm. The tensile speed was maintained at 100 mm / min.

[0059] Electrical performance test: conductivity of hydrogel (σ, Sm -1 ) was obtained by an LCR digital bridge tester (E4980AL, Keysight). The conductivity was calculated as σ = L / (R × S), where L (m) is the distance between the test electrodes, R (Ω) is the resistance of the hydrogel, and S (m 2 ) is the cross-sectional area of ​​the hydrogel. The sensitivity (GF) of the hydrogel was calculated using the formula: GF = (ΔR / R0) / ε, where ΔR is the change in resistance, R0 is the initial resistance, and ε is the strain of the hydrogel;

[0060] Image capture and feature extraction: The hydrogel was placed flat on a table and the UV light source was adjusted to ensure that the hydrogel was fully illuminated. Images were captured using a Huawei P60 smartphone. Throughout the image capture process, all shots were taken using the camera's automatic mode without any image enhancement. -1500 images were captured from different angles at 50 TC concentrations within a range of 1000 nm to serve as a training dataset. Subsequently, all images were transferred to the MATLAB computing and visualization environment (version 2016b, Mathworks, Natick, MA, USA) for processing and feature extraction. For each image, we extracted and masked regions of interest (ROIs) covering meaningful and important areas in each image to extract color and texture features for machine learning. First, the RGB values ​​of the images were converted to grayscale, HSV, and Lab* to analyze the impact of color space on concentration levels. Then, texture features based on intensity and color transformations, including contrast, correlation, and uniformity, were extracted to improve the accuracy of the model. Finally, 15 features were extracted from each masked image, including average RGB, average grayscale, H, S, V, L*, a*, B*, entropy, contrast, correlation, uniformity, and STD. All data were transferred to Excel to generate the final training dataset;

[0061] Model development using machine learning algorithms: The training dataset was uploaded to MATLAB R2016b and Rapid Miner Studio 9.9 software for model development. Based on the training data, a model was built using an artificial neural network (ANN) approach. An artificial neural network consists of interconnected nodes (called artificial neurons) that mimic the synaptic connections (called edges) in the brain. Each connection has a weight. The network consists of an input layer, an output layer, and one or more hidden layers. The neurons in each layer use the outputs of all the nodes in the previous layer as input, forming interconnected neurons throughout the layer. During the training process, the assigned weights are adjusted to change the signal strength of each neuron in each layer to develop the best neural network for the training data;

[0062] To evaluate the actual TC content in the samples, the hydrogel was attached to giant salamanders and pig skin, and standard TC was added to a concentration ranging from 9 to 1.8 × 10 6 μgL -1 A smartphone camera was used to capture images under UV illumination. Image data was extracted using the previously mentioned method and used for dataset development. This dataset and the best model from the training dataset were used to estimate TC concentration on the surface of skin samples.

[0063] Example 1 Preparation of Eu / SA hydrogel

[0064] Take 2.75mL acrylamide (19wt.%), add europium nitrate hexahydrate (Eu(NO3)3-6H2O) powder and mix thoroughly, then add 70μL ammonium persulfate (APS, 0.2molL -1) and 300 μL N,N-methylenebisacrylamide (BIS, 2 wt.‰) to form solution A. 2 mL of sodium alginate solution (SA, 4.8 wt.%) was mixed with solution A. Finally, 10 μL of N,N,N',N'-tetramethylethylenediamine (TEMED) was added. After thorough mixing, the mixture was injected into a mold and cross-linked under ultraviolet light (365 nm, 1 h). After gelation, the mixture was demolded to obtain the Eu / SA hydrogel, designated Eu-H.

[0065] The amount of europium nitrate hexahydrate added is expressed as Eu 3+ Calculated relative to the amount of SA (2 mL), different weight fractions of Eu were weighed. 3+ (0.1wt.%, 0.2wt.%, 0.3wt.%, 0.4wt.%, 0.5wt.%) corresponding europium nitrate hexahydrate was used as raw material to obtain Eu / SA hydrogels with different Eu contents.

[0066] Example 2 Detection of tetracycline

[0067] A 1000 PPM tetracycline (TC) stock solution was prepared in methanol and diluted to different concentrations (10 μg L -1 , 20 μg L -1 , 30 μg L -1 , 40 μg L -1 , 50 μg L -1 , 60 μg L -1 , 70μgL -1 , 80 μg L -1 , 90 μg L -1 , 100 μg L -1 100 μL of TC at different concentrations was added to Eu-H for fluorescence testing (parameters are as follows: excitation wavelength 380 nm, slit width 10 nm, fluorescence emission spectra collected in the range of 400-750 nm). Under the same conditions, tetracycline was replaced with other antibiotics such as sulfadiazine, sulfabenzamide, sulfapyridine, and trimethoprim to conduct selectivity experiments. The anti-interference performance was also studied by adding other ingredients.

[0068] Test Example 1 Fluorescence and swelling test of Eu-H hydrogel

[0069] The optimal excitation wavelength for europium (Eu) is 395 nm, corresponding to an emission wavelength of 615 nm (the fluorescence excitation and emission spectra are shown in Figure 4). Within the excitation wavelength range of 385-405 nm, a clear trend can be observed: the emission intensity first increases and then decreases. As shown in Figure 5, when the excitation wavelength is 395 nm, the fluorescence emission intensity reaches its maximum, thus determining the optimal excitation wavelength. As shown in Figure 6, the fluorescence intensity of the Eu(NO3)3-6H2O solution gradually increases as the concentration increases from 100 mM to 300 mM, reaching a maximum at 300 mM. Therefore, 300 mM was selected for solution-phase testing.

[0070] Tetracycline (TC) itself does not have fluorescent properties. 3+ When mixed with TC, as shown in Figure 7, Eu 3+ The fluorescence intensity of TC decreased, indicating that TC 3+ In order to study the effect of Eu 3+ The effect of solution volume on the fluorescence intensity of Eu-H system was studied. The fluorescence spectrum was scanned and the results showed that as Eu 3+ As the volume of the solution increases, F0 / F decreases. When the volume of the Eu solution is 1 mL, the fluorescence intensity F0 / F of the system reaches its maximum value. However, when the volume exceeds 1 mL, F0 / F decreases significantly (Figure 8). Therefore, 1 mL of Eu was added to a 5 mL quartz cuvette. 3+ solution for further experiments.

[0071] As shown in Figure 9, under ultraviolet light, Eu 3+ The solution itself emits a strong pink fluorescence (left), but after adding TC solution, the fluorescence almost disappears (right). Due to the inconvenience and complexity of solution phase experiments, we applied to use Eu 3+ Introduced into SA / PAAm to form Eu-H. As shown in Figure 10, SA / PAAm hydrogel contains a large number of hydroxyl groups and deprotonated carboxyl groups (Figure 10a). AAm self-polymerizes through crosslinking agents to form PAAm chains (Figure 10b), while Eu 3+ It can act as a functional metal cross-linker to strongly chelate the deprotonated carboxyl groups in SA (Figure 10c), which not only enhances the mechanical properties of the hydrogel network, but also introduces luminescent groups into the SA / PAAm hydrogel. Under 365nm ultraviolet irradiation, the SA / PAAm hydrogel is colorless and non-fluorescent (upper figure of Figure 1A), while the Eu-H hydrogel exhibits pink fluorescence (lower figure of Figure 1A). As shown in Figure 11, the optimal excitation wavelength of Eu-H is 395nm. When a concentration of 0.1wt.% to 0.5wt.% Eu is introduced into the hydrogel 3+, the fluorescence intensity of the hydrogel gradually increased (Figure 1B), and the fluorescence signal value also increased significantly (Table 1).

[0072] Table 1. Fluorescence intensity of Eu-H at different mass fractions.

[0073] SA, as a polysaccharide compound, can effectively form complexes with lanthanide elements. Therefore, under the same conditions, the fluorescence intensity of the Eu-H system is approximately Eu 3+ Seven times that of the monomer (Figure 1C). The quantum yield of Eu-H is also higher than that of Eu 3+ The internal microstructures of SA / PAAm and Eu-H were observed by scanning electron microscopy. As shown in Figure 1D and Figure 1E, the freeze-dried hydrogel showed many microporous structures. The internal network of Eu-H was more dense, which was mainly due to the interaction between SA as a ligand and Eu. 3+ The metal coordination reaction occurred, forming a double network hydrogel with smaller pore size. SEM images show that at the same scale, the introduction of Eu 3+ The pores of the hydrogel are smaller than those of the SA / PAAm hydrogel. As shown in Figure 1F, the EDS characterization of Eu-H shows that the Eu element is evenly distributed in the hydrogel, further confirming the successful synthesis of Eu-H. The water content of the prepared hydrogel was tested. As shown in Figure 1G, the water content of the prepared hydrogel with different mass fractions of Eu 3+ The water content of the hydrogel was obviously always kept above 80%, which indicated that the hydrogel had good water retention properties. 3+ The swelling rate of Eu-H under different concentrations. Swelling is a basic property of hydrogels, which reflects the ability of hydrogels to absorb solvents and increase volume. Figure 1H describes the swelling rate of each hydrogel over time. The swelling rate increases rapidly within 200 minutes and reaches equilibrium at around 250 minutes. The order of equilibrium swelling rate is as follows: 0.1>0.2>0.3>0.4>0.5wt.% (Figure 13). At room temperature, the effect of reaction time on the fluorescence intensity of the Eu-H system was studied. The results in Figure 1I show that the reaction rate of TC with Eu-H is very fast (less than 1 minute), and the system remains stable within 20 minutes, indicating that it has a fast reaction rate and good stability. The main reason is that with the development of the microstructure of the hydrogel, the pores become smaller and smaller, the density becomes higher and higher, and less and less water enters.

[0074] Test Example 2 Adhesion, Mechanical Properties, and Selectivity Tests of Eu-H Hydrogel

[0075] As shown in Figure 14, the hydrogel's adhesion properties were evaluated by measuring shear strength using a lap shear test. A schematic diagram of the hydrogel's adhesion to pigskin, shells, and fish skin is shown in Figure 2A. The abundant hydrogen bonds impart excellent flexibility to the hydrogel, enabling strong adhesion to biological tissue surfaces such as pigskin and shells. Four representative substrates were selected for the adhesion experiments: pigskin, polyethylene terephthalate (PET), glass, and polyimide (PI). The highest lap shear strengths achieved by the hydrogel were 44.90 kPa for pigskin, 11.70 kPa for PET, 17.22 kPa for glass, 17.22 kPa for polyimide, and 12.77 kPa for PI (Figure 2B). This excellent adhesion is attributed to the amino groups in PAAm, allowing the hydrogel to adhere firmly to the fish's surface without falling off during movement.

[0076] The hydrogel not only has adhesive properties but also has excellent mechanical properties. 3+ The mechanical properties of the hydrogels with different contents were different, and tensile strain tests were carried out using a tensile testing machine. As shown in Figure 2C, the maximum strain can reach 1200%. In the small strain stretching range of 0 to 100%, the sensitivity (GF) is 2.702, and in the large strain stretching range of 0 to 700%, the sensitivity (GF) increases to 5.898 (Figure 2D). The hydrogels were evenly cut into rectangles (length 4.0 cm, width 1.0 cm, thickness 0.01 cm), and the resistance was tested using an LCR meter. As shown in Table 2, with the increase of Eu 3+ With the increase of content, the conductivity gradually increases, reaching a maximum of 8.3S m -1 .

[0077] Table 2. Electrical conductivity of Eu-H at different mass fractions.

[0078] In addition, after 250 cycles of stretching at 50% strain, the resistance change remained stable, showing good fatigue resistance (Figure 2E). SA itself does not emit light, but it can interact with Eu 3+ After binding, a strong fluorescence signal is generated. When 100 PPM of TC is introduced, fluorescence quenching occurs (Figure 15). Under optimal conditions, TC is detected using a ratio fluorescence system. The results in Figure 2F show that as the TC concentration increases, the fluorescence intensity at 615 nm gradually decreases. Under normal circumstances, the TC concentration in wastewater from livestock and poultry farms and surrounding water bodies is higher than 10 μg / L. -1 As shown in Figure 2G, the TC concentration ranged from 10 to 100 μg / L -1The linear relationship was good within the range, and the linear equation was: y = -88.13499x + 10689.39805, with a correlation coefficient R2 = 0.9997. According to the formula LOD = 3σ / k, the detection limit (LOD) was determined to be 0.9nmolL -1 (3σ=1.4142,k=88.13499). 3+ It has a strong enrichment capacity and reacts with the β-diketone group in TC, resulting in fluorescence quenching. As shown in Figure 2H, under the same conditions, the Eu / SA system showed little reaction to sulfadiazine, sulfabenzamide, sulfapyridine, and trimethoprim. This demonstrates that the detection system has excellent selectivity for tetracycline antibiotics and avoids interference with the detection results from other antibiotics.

[0079] Test Example 3 Application Test of Eu-H Hydrogel

[0080] As shown in Figure 3A, the machine learning workflow diagram. Images are captured using a smartphone and the colors are converted into corresponding feature values ​​(Table 3). In Figure 3B, the feature data are trained and the optimal model is finally obtained. The accuracy of the model reaches 90.8% (Figure 3C). Depending on different practical application scenarios, Eu-H hydrogel can be processed into various shapes, such as pentagrams, petals, rectangles, and strips (Figure 16). As shown in Figures 3D and 17, Eu-H is attached to the surface of giant salamanders and pigskin. By extracting the color of the hydrogel, the specific concentration of tetracycline contamination in different areas (such as the back, head, etc.) can be obtained.

[0081] Table 3 Parameter values ​​for mobile phone image conversion

[0082] The meaning of each parameter is as follows:

[0083] RGB (Red, Green, Blue): This is a color representation in which the color is represented by a combination of three channels: red, green, and blue.

[0084] Average Grayscale: The average grayscale value of an image, which represents the average grayscale value of all pixels in the image.

[0085] H, S, V (Hue, Saturation, Value): This is a color representation method, where hue (Hue) represents the type of color, saturation (Saturation) represents the depth of the color, and value (Value) represents the brightness of the color.

[0086] L, a, b* (CIELAB color space): **This is a color space in which L represents lightness, a represents the range from red to green, and b* represents the range from yellow to blue.

[0087] Entropy: A measure of the uncertainty or disorder of the grayscale distribution in an image. A high entropy indicates that there are many different grayscale levels in the image.

[0088] Contrast: A measure of the difference in grayscale levels between different regions in an image. High contrast indicates significant brightness changes in the image.

[0089] Correlation: A measure of the linear relationship between gray levels in an image. A high correlation indicates that the gray levels in the image have a certain linear relationship.

[0090] Uniformity: A measure of how evenly the gray levels are distributed in an image. A high uniformity indicates that the gray levels are more evenly distributed in the image.

[0091] STD (Standard Deviation): Measures the dispersion of grayscale levels in an image. A high standard deviation indicates a large variation in grayscale levels in the image.

[0092] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A hydrogel sensor, characterized in that: The hydrogel sensor includes a composite hydrogel matrix, Eu 3+ Luminous Center; The composite hydrogel matrix is ​​a double cross-linked polymer network formed by polymerization of polyacrylamide and sodium alginate; The sodium alginate and Eu 3+ Chelation to form Eu 3+ Luminous Center; The hydrogel contains a large number of hydroxyl groups and deprotonated carboxyl groups.

2. The hydrogel sensor according to claim 1, characterized in that Eu in the hydrogel sensor 3+ The content is 0.1 to 0.5 wt% of the weight of sodium alginate.

3. The hydrogel sensor according to any one of claims 1 or 2, characterized in that The hydrogel sensor exhibits pink fluorescence under 365 nm ultraviolet irradiation.

4. The hydrogel sensor according to any one of claims 1 to 3, characterized in that The water content of the hydrogel sensor is greater than or equal to 80%.

5. The hydrogel sensor according to any one of claims 1 to 4, characterized in that The equilibrium expansion rate of the hydrogel sensor is 400-600%.

6. The hydrogel sensor according to any one of claims 1 to 5, characterized in that: The conductivity of the hydrogel sensor is 6.1-8.3 S / m.

7. The method for preparing the hydrogel sensor according to any one of claims 1 to 6, characterized in that: The steps include: S1. Add Eu to the aqueous solution of acrylamide 3+ source, adding an initiator aqueous solution and a cross-linking agent aqueous solution respectively to form solution A; S2. Adding a sodium alginate aqueous solution to solution A, and then adding a catalyst to obtain a mixed solution, injecting the mixed solution into a mold, and photocuring and cross-linking the hydrogel sensor.

8. The preparation method according to claim 7, characterized in that In step S1, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

9. The preparation method according to claim 7 or 8, characterized in that In step S2, the catalyst is selected from at least one of N,N,N',N'-tetramethylethylenediamine, sodium sulfite, sodium bisulfite and sodium thiosulfate.

10. The preparation method according to any one of claims 7 to 9, characterized in that: In step S1, the cross-linking agent is selected from at least one of N,N-methylenebisacrylamide and ethylene glycol dimethacrylate.

11. The preparation method according to any one of claims 7 to 10, characterized in that: In step S1, the Eu 3+ The source is selected from the nitrate or hydrochloride of europium.

12. The preparation method according to any one of claims 7 to 11, characterized in that: In step S1, Eu 3+ The amount of source is based on the Eu in the hydrogel sensor. 3+ The content is calculated as 0.1 to 0.5 wt% of the weight of sodium alginate.

13. The preparation method according to any one of claims 7 to 12, characterized in that: Based on the concentration of the sodium alginate aqueous solution being 4.8 wt%, the concentration of the acrylamide aqueous solution being 19 wt%, the concentration of the initiator aqueous solution being 0.2 M, and the concentration of the cross-linking agent aqueous solution being 2 wt‰, the volume ratio of the sodium alginate aqueous solution to the acrylamide aqueous solution, the initiator aqueous solution, the cross-linking agent aqueous solution, and the catalyst is 1:(0.8-1.8):(0.025-0.045):(0.05-0.30):(0.001-0.009).

14. Use of the hydrogel sensor according to any one of claims 1 to 6 or the hydrogel sensor prepared according to the preparation method according to any one of claims 7 to 13 in detecting tetracycline.

15. The use according to claim 14, characterized in that The detection limit of the hydrogel sensor for tetracycline is ≤0.9 nmol / L.

16. The use according to claim 14 or 15, characterized in that The hydrogel sensor showed a linear relationship in the detection of tetracycline at concentrations of 10 to 100 μg / L.

17. The use according to any one of claims 14 to 16, characterized in that The application includes collecting images of the hydrogel sensor when monitoring tetracycline, converting the color of the hydrogel sensor into corresponding characteristic values, training the characteristic data to obtain a detection model, and using the detection model to obtain the concentration value of tetracycline through the color of the hydrogel sensor.

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