Preparation of ZGC / ZIF-8-NH2 / chitosan hydrogel and its application in dopamine detection

Abstract

The present invention discloses an amino-modified ZIF-8 / ZGC nanocomposite material, which is mainly obtained by compounding PLNPs with a modified hierarchical porous zeolite imidazole framework ZIF-8-NH2. The ZGC / NH2-ZIF-8 chitosan hydrogel provided by the present invention can realize rapid visual detection of DA in human blood, and can perform sensitive and accurate detection without complicated sample pretreatment. The hydrogel sensor in the present invention has good luminescence performance, high sensitivity and rapid response of visual detection, and the detection limit of DA is as low as 1.0mM. The present invention combines the ZGC / NH2-ZIF-8 composite fluorescent probe with an intelligent wearable device to perform visual quantitative detection of DA in human blood samples, and compares the test results with other detection methods, and proposes an effective quantitative monitoring strategy for DA in biological samples, thereby protecting human health.

Description

Technical Field

[0001] The present invention relates to the preparation of a ZGC / ZIF-8-NH2 / chitosan hydrogel and its application in dopamine detection, belonging to the fields of material synthesis technology, fluorescence visualization detection technology, and human health (dopamine) monitoring technology. Background Art

[0002] Dopamine (DA), also known as 3,4-dihydroxyphenylethylamine, is the most abundant catecholamine neurotransmitter in the brain and plays a key role in the central nervous system and immune system. It has attracted significant attention due to its effects on various physiological functions of the central nervous system. Dysregulation of the dopamine system has been linked to the pathogenesis of Parkinson's disease, schizophrenia, and other disorders. Therefore, DA levels have been used as an indicative marker for these neurological disorders, and highly sensitive and selective DA detection is essential for clinical diagnosis and subsequent treatment. Numerous methods have been developed for DA detection, including fluorescence analysis, electrochemical methods, and high-performance liquid chromatography. Fluorescence analysis, in particular, has garnered increasing attention and has been widely used for DA analysis due to its high sensitivity, selectivity, simplicity, rapidity, and stability. DA oxidation products are widely used for DA detection because they exhibit excellent fluorescence quenching ability for monochromatic fluorophores, primarily through photoinduced electron transfer (PET) or Forster resonance energy transfer (FRET) mechanisms. However, for the detection of DA in biological matrices, due to the presence of impurities such as proteins and other biological chromophores, fluorescence analysis is inevitably interfered and affected by autofluorescence or light scattering, which affects the interaction of autofluorescence or light scattering, thereby affecting the signal-to-noise ratio (SNR) and detection sensitivity. In this regard, there is an urgent need to develop alternative non-autoluminescent optical sensing strategies for the detection of DA in biological samples.

[0003] Persistent luminescence is a phenomenon that persists for seconds, hours, or even days after the excitation stops, which has attracted widespread interest in the past few years. Given that the autofluorescence of biological tissues decays rapidly after the in situ excitation is removed, the long-lasting afterglow properties of PLNPs make them considered as promising luminescent probes. In particular, in the past few years, a large number of long-lasting nanomaterials have been rapidly developed, the most typical representative of which is Cr 3+ Doped zinc gallate nanomaterials (ZnGa2O4:Cr 3 +ZGC PLNPs (ZGC PLNPs) exhibit persistent near-infrared (NIR, 650-750nm) luminescence and have been used as non-excitation optical nanoprobes in various sensors for sensory determination of various targets. Furthermore, to our knowledge, no studies on DA detection using ZGC PLNPs have been reported to date. Furthermore, integrating optical nanoprobes with other functional nanomaterials as carriers can further enhance sensing performance. Specifically, ideal nanocarriers should possess a strong loading capacity for optical nanoprobes or exhibit special interactions with luminophores.

[0004] Metal-organic frameworks (MOFs) are crystalline porous materials with a network structure, formed by the self-assembly of transition metal ions and organic ligands. They have achieved significant applications in sensing, catalysis, and gas storage. Due to their advantages—high porosity, low density, large surface area, tunable pore size, diverse topologies, and modifiable properties—highly porous MOFs have been exploited as unique hosts for various functional nanomaterials, such as fluorescent nanoclusters, fluorescent nanoclusters, upconversion nanoparticles, and metal nanoparticles, bringing new functionalities to various applications. Importantly, MOFs offer unique advantages when applied to sensing platforms: First, the abundant pores within MOFs exhibit excellent molecular adsorption capacity, acting as natural enrichment sites for target molecules. This allows MOFs to pre-concentrate target analytes within the porous matrix, enhancing overall sensitivity. Second, the unique microenvironment within the frameworks, such as Lewis acidic or basic sites on the ligands and open metal sites, can induce interactions between the MOFs and analytes, thereby improving detectable changes related to analyte concentration. Therefore, the present invention studies and designs an amino-modified ZIF-8 / ZGC nanocomposite material, and uses it to construct a hydrogel fluorescence sensing platform for ultrasensitive DA detection. Summary of the Invention

[0005] The present invention aims to provide an amino-modified ZIF-8 / ZGC chitosan hydrogel and its preparation, and to apply it to dopamine detection and wearable devices. The ZGC / ZIF-8-NH2 chitosan hydrogel provided by the present invention can achieve rapid visual detection of DA in human blood. Specifically, the present application adopts the following technical solutions to achieve this:

[0006] A ZGC / ZIF-8-NH2 nanocomposite material mainly composed of Cr-doped 3+The researchers synthesized zinc gallate persistent luminescent nanoparticles (ZGC PLNPs) composited with an amino-modified hierarchical porous zeolite imidazole framework (ZIF-8-NH2). The PLNPs exhibit inherent fluorescence properties, specifically red fluorescence at 450 and 700 nm under 254 nm ultraviolet excitation.

[0007] The preparation method of the ZGC / ZIF-8-NH2 nanocomposite material can be to prepare ZGCPLNPs by a hydrothermal method, and then add ZIF-8-NH2 powder to prepare the amino-modified ZIF-8 / ZGC nanocomposite material by a coprecipitation method.

[0008] In the above-described preparation method, preferably, the hydrothermal method for preparing ZGC PLNPs is to use water-soluble zinc salt, water-soluble gallium salt, and water-soluble chromium salt as raw materials, hydrothermally react at 180-300°C for 6-20 hours, and then post-treat them. Specifically, the hydrothermal method for preparing ZGC PLNPs is to mix 2-4 mmol Zn(NO3)2·6H2O, 2-4 mmol Ga(NO3)3·xH2O, and 0.001-0.005 mmol Cr(NO3)3·xH2O, add ultrapure water, adjust the total volume to 15-30 mL, and stir vigorously. Then, 25-30% ammonia solution is quickly added to adjust the pH to 9-10, and a white precipitate is immediately observed. After stirring for 0.5-1 hour, the mixture is transferred to a polytetrafluoroethylene-lined autoclave (50-75 ml) and sealed. The mixture is reacted at 200-250°C for 10-12 hours. After cooling to room temperature, the white precipitate was collected by centrifugation and washed with 0.01-0.05M HCl to remove possible zinc oxide impurities. It was then mixed with isopropanol and centrifuged. Finally, the ZGC PLNPs were dispersed in ultrapure water and stored at a concentration of about 1-5 mg / mL. The inventors found that the optimal pH for synthesizing ZGC PLNPs was 9-10, especially 9.5. When the pH was less than 9, no white precipitate could be formed and the yield of ZGC PLNPs was low. When the pH was greater than 10, a higher molar content of Zn 2+ and Ga 3+ Rapid reaction polymerization to form polymers, unable to make the Cr content less 3+ Reaction polymerization.

[0009] In the aforementioned preparation methods, preferably, the co-precipitation method for preparing ZGC / ZIF-8-NH2 comprises redispersing the ZGC PLNPs in ultrapure water, adding 100-200 mg of ZIF-8-NH2 powder, and stirring for 2-4 hours to obtain a ZGC / ZIF-8-NH2 composite material. The molar ratio of ZGC PLNPs to ZIF-8-NH2 is preferably 0.2-0.5:1, more preferably 0.4:1. The inventors found that when the molar ratio is lower than 0.2:1, the ZGC PLNPs content is low, resulting in low luminescence efficiency of ZGC / ZIF-8-NH2; when the molar ratio is higher than 0.5:1, the porosity and pore size of ZIF-8-NH2 are limited. Due to the high content of ZGC PLNPs in the system, the ZGCPLNPs will block the pores of ZIF-8-NH2 after compounding with ZIF-8-NH2, which will, on the one hand, cause a slight decrease in the luminescence efficiency of ZGC / ZIF-8-NH2, and on the other hand, affect the output of the fluorescence signal in the sensing of DA.

[0010] The preparation method of ZIF-8-NH2 is as follows: 1.0-3.0g Zn(NO3)2·6H2O is mixed with 10-15mL ultrapure water, 3.3-4.3g 2-methylimidazole is mixed with 4.5-5.5mL ultrapure water, and then 3.0-5.0mL triethylamine is added (the role of triethylamine here is to facilitate the reaction of 2-methylimidazole and Zn 2+ The ZIF-8 structure formed after polymerization is uniform), and Zn 2+ The solution is slowly poured into the mixture, mixed thoroughly, and stirred for 30-60 minutes. After repeated centrifugation 3-5 times with ultrapure water, the mixture is dried at 60°C for 12 hours to obtain ZIF-8. Take 1-2g of the dried ZIF-8 powder, add 20-30mL of 25% ammonia solution, sonicate for 1-2 hours, vigorously stir at room temperature for 24 hours, and then centrifuge. After repeated washing with ultrapure water, the mixture is dried at 60°C for 24-48 hours to obtain ZIF-8-NH2.

[0011] The present invention also provides a ZGC / ZIF-8-NH2 / chitosan hydrogel, which is obtained by cross-linking and polymerizing the ZGC / ZIF-8-NH2 nanocomposite material and chitosan hydrogel (CTs gel).

[0012] As a preferred solution, the method for preparing the hydrogel is to add the ZGC / ZIF-8-NH2 nanocomposite material to an aqueous solution of chitosan, stir to form a uniform mixture, freeze and store, thaw at room temperature and then continue to freeze, repeat the freezing and thawing steps 3 to 5 times, and then store in a refrigerator. The inventors found that multiple freezing and thawing are conducive to the uniform mixing of the ZGC / ZIF-8-NH2 nanocomposite material and the chitosan aqueous solution and sufficient polymerization to form a hydrogel. The chitosan aqueous solution is obtained by a common acid swelling method, specifically, 1 to 3 g of chitosan powder can be dissolved in 1 L of water, and then glacial acetic acid is added to adjust the pH, the acetic acid concentration is 0.1 to 0.5 mol / L, and then heated at 80 to 85 ° C for 2 to 4 hours to allow the chitosan to swell and dissolve.

[0013] More preferably, the hydrogel preparation method comprises adding 100-500 mg of the ZGC / ZIF-8-NH2 nanocomposite to 10-50 mL of a 1-3 g / L chitosan aqueous solution, slowly adding 1-2 mL of anhydrous ethanol, and continuously stirring until the hydrogel system forms a uniform mixture. The mixture is then poured into a specific glass cuvette, cooled to room temperature, and stored frozen at -18°C for 12-24 hours. After thawing at room temperature, the mixture is further frozen at -18°C for 4-8 hours, repeated 3-5 times, and then stored in a refrigerator at 4°C. Of course, the hot alcohol solution also facilitates the formation of an aqueous solution of chitosan and further molecular cross-linking to form a gel. Since chitosan is basically insoluble in water and slightly soluble in hot water, acetic acid is used in the present invention to adjust the pH of the solution to acidic (because there is a -NH2 group in the chitosan structural unit, therefore, chitosan can be dissolved in dilute inorganic acid or organic acid under weak acid conditions) and continuously stirred. After it is completely dissolved, the ZGC / ZIF-8-NH2 composite material is added, and a certain amount of ethanol solution is slowly added. Continuous stirring can form a uniform mixed liquid of the hydrogel system.

[0014] The ZGC / ZIF-8-NH2 / chitosan hydrogel of the present invention can be used for dopamine detection. A preferred solution is to use the ZGC / ZIF-8-NH2 / chitosan hydrogel as a visual fluorescent probe for dopamine detection. As another feasible solution, the ZGC / ZIF-8-NH2 / chitosan hydrogel is integrated into a wearable device as a fluorescent sensing material or fluorescent sensor. The ZGC / ZIF-8-NH2 / chitosan hydrogel in a wearable device can be used as a detection reagent module during the dopamine detection process.

[0015] Dopamine (DA) detection methods require complex sample pretreatment, expensive instrumentation, and cumbersome instrumental procedures. Therefore, it is necessary to develop simple, rapid, and low-cost detection methods and testing technologies. Hydrogels are generally considered to be highly hydrated, cross-linked, three-dimensional (3D) networks that can be endowed with various functionalities by adjusting their composition and structure. Hydrogels are primarily prepared by adding MOFs to a polymer precursor solution. Chemical crosslinking of the polymer components surrounding the MOFs can be achieved through free radical polymerization. The introduction of hydrogels improves the dispersion of MOFs and prevents MOF instability, thereby enhancing the mechanical strength, water absorption, and total pore volume of the hydrogel matrix and providing functional tunability. Persistent luminescent nanoparticles (PLNPs) are materials that continue to emit light for seconds, hours, or even days after excitation ceases. The fabrication of near-infrared ZGC PLNPs requires solid-state annealing at extremely high temperatures and complex physical methods to convert the synthesized bulk crystals into nanosized particles. The ZGC nanoparticles synthesized by the hydrothermal method can effectively eliminate the interference of spontaneous fluorescence, greatly improve the sensitivity and signal-to-noise ratio of biosensors, and have the advantages of stable chemical properties and low cytotoxicity. On this basis, the present invention designs a highly sensitive and selective ZGC / MOF-CTS probe composed of persistent luminescent nanoparticles, amino-modified ZIF-8, namely ZIF-8-NH2, and natural hydrogel chitosan to detect DA. In the system of ZIF-8-NH2 and ZGC / ZIF-8-NH2, the final oxide polydopamine covers the surface of ZIF-8-NH2 to form a black layer. As the concentration of DA increases, the sensitivity of polydopamine to Zn 2+ The capture ability of Zn 2+ The -2-MI coordination bond is broken, and the released Zn 2+ At the same time, it is chelated by PDA, resulting in the destruction of the ZIF-8-NH2 structure. At the same time, electrons are transferred from the photoexcited ZGC / NH2-ZIF-8 to the oxidation product polydopamine, resulting in the fluorescence quenching of ZGC / NH2-ZIF-8.

[0016] ZGC PLNPs modified on the ZIF-8-NH2 surface exhibit persistent fluorescence and serve as a signaling element. The hierarchically porous ZIF-8-NH2 metal-organic framework (MOF) acts as an analyte concentrator, pre-enriching dopamine (DA) around the ZGC PLNPs. Furthermore, the alkaline microenvironment provided by the imidazole ligands of ZIF-8-NH2 favors the oxidative polymerization of the enriched DA, producing polydopamine (PDA). This DA ultimately suppresses the luminescence of the ZGC / ZIF-8-NH2 structure via a photoinduced electron transfer (PET) mechanism. Based on this response mechanism, the composite material is cross-linked with chitosan molecules to form a hydrogel. This hydrogel is then cut into a suitable shape and integrated into a smart chip sensor with a microneedle structure. When the microneedles of the chip penetrate the human skin, blood in the capillaries is gradually adsorbed by the hydrogel patch, where DA is enriched. Under ultraviolet light, the red color of the hydrogel patch gradually fades, turning black under natural light. The color of its color-changing hydrogel probe changes continuously from red to colorless, and the DA content in human blood is detected by the degree of color change in the hydrogel sensor fluorescence system.

[0017] The ZGC / ZIF-8-NH2 or ZGC / ZIF-8-NH2 / chitosan hydrogels can be used for dopamine detection. Specifically, the ZGC / NH2-ZIF-8 composite (1-5 mg, white powder) was first dispersed in a Tris-HCl buffer solution (0.5-1.0 mL, 2.5-3.0 mM, pH 7.4). Various amounts of DA were added to adjust the final volume to 1-2 mL, with a final DA concentration ranging from 0.0025 to 75 μM. Subsequently, 1-3 mL of the probe solution was mixed with the DA analytical solution, diluted with deionized water, and thoroughly mixed. The mixture was then transferred to a quartz cuvette for fluorescence detection under UV light. After incubation at 37°C for 1-4 hours, a continuous luminescence spectrum was recorded without in situ excitation. Images of the fluorescence color change were captured using a camera in a dark environment. To ensure the reliability of the experimental results, each sample was measured at least three times, and the average was taken before proceeding to the next step. To evaluate the specificity of ZGC / ZIF-8-NH2 for DA, several amino acids and neurotransmitters were added to the ZGC / ZIF-8-NH2 solution in Tris-HCl buffer following the aforementioned experimental procedures. Software was used to capture the red-green-blue (RGB) values ​​corresponding to the fluorescence image, and dopamine was quantitatively detected by analyzing the RGB values. To ensure data accuracy, the experiment was repeated three times, and the average R / B ratio (R / B), which represents the ratio of red to blue information, was calculated.

[0018] Furthermore, the pH of the detection system is preferably 7.4, which is closer to the pH of human blood.

[0019] Under ultraviolet excitation at 254 nm, the ZGC / NH2-ZIF-8 of the present invention exhibits dual red fluorescence at 450 nm and 700 nm. The addition of DA further enriches the polydopamine (PDA), which ultimately inhibits the luminescence of ZGC / ZIF-8-NH2 through a photoinduced electron transfer (PET) mechanism, resulting in a gradual decrease in emission at 450 nm and 700 nm, resulting in a significant color change from red to colorless under ultraviolet light.

[0020] The ZGC / ZIF-8-NH2 nanocomposite designed in this paper quenches DA-induced luminescence, achieving ultrahigh sensitivity for DA determination. As the core of the sensing system, PDA-polydopamine acts as a quencher in the ZGC / ZIF-8-NH2-based sensing platform. PDA production can be further verified by UV-vis and FT-IR spectroscopy. The quenching effect is likely caused by a photoinduced electron transfer mechanism, in which the excited photoelectrons of ZGC are immediately captured by PDA as a favorable electron acceptor. The ultrahigh sensitivity of the proposed sensor, in addition to the persistent luminescence of the ZGC element without excitation, is largely due to the involvement of ZIF-8-NH2. The rough surface of ZIF-8-NH2 provides numerous anchoring sites for ZGC, enabling the enrichment of optical elements within the ZIF-8-NH2 support matrix. Furthermore, due to its high surface area, hierarchical microporous and mesoporous structure, and excellent molecular adsorption capacity, ZIF-8-NH2 can serve as a preconcentrator to effectively enrich DA within the porous MOF matrix. This means that a large number of DA molecules can approach ZGC, greatly improving sensitivity. Furthermore, the chitosan hydrogel's gel properties and excellent biocompatibility make it highly feasible for wearable devices such as wearable sensors. This allows for the detection of DA in human blood samples, providing a theoretical basis for the construction of a reliable and convenient real-time visual detection platform, and has enormous potential for application in chemical and analytical sensing.

[0021] The present invention provides an application of ZGC / ZIF-8-NH2 chitosan hydrogel in dopamine detection and wearable devices. The designed ZGC / ZIF-8-NH2 chitosan hydrogel wearable device has the characteristics of high sensitivity, good selectivity, and sustainable monitoring of target objects.

[0022] The hydrogel sensor in this invention exhibits excellent luminescence properties, high sensitivity, and rapid response to visual detection, with a detection limit of 1.0 mM for DA. This study combines a ZGC / ZIF-8-NH2 composite fluorescent probe with a smart wearable device for visually quantifying DA in human blood samples. The results are compared with other detection methods, proposing an effective strategy for quantitatively monitoring DA in biological samples, thereby safeguarding human health. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the design steps of ZGC / ZIF-8-NH2 chitosan hydrogel as a wearable patch for human skin.

[0024] Figure 2 Schematic diagram of the color change mechanism of ZGC / ZIF-8-NH2 chitosan hydrogel.

[0025] Figure 3 (a) FT-IR spectrum of ZGC at pH 9.0-10.0, (b) FT-IR spectrum of ZGC / ZIF-8-NH2 at n[ZGC] / n[ZIF-8-NH2]. (c) Powder X-ray diffraction pattern of ZGC at pH 9.0-10.0, (d) Powder X-ray diffraction pattern of ZGC / ZIF-8-NH2 at n[ZGC] / n[ZIF-8-NH2]. Fourier transform infrared spectroscopy (FT-IR) confirmed the formation of ZGC / ZIF-8-NH2. Figure 3 As shown in the comparison between (a) and 3(b), Zn-N and CN at 422 cm-1 are clearly present in the spectrum of ZGC / ZIF-8-NH2. -1 and 1100-1400cm -1 The characteristic absorption peaks at these locations belong to ZIF-8-NH2. Figure 3 Comparison between (c) and 3(d) shows that the ZGC / ZIF-8-NH2 sample also has 585cm-1, which represents the bending vibration characteristics of Zn-O and Ga-O (only present in ZGC). -1 and 450cm -1 In addition, ZGC / ZIF-8-NH 2 The XRD pattern of Figure 3 (d) includes two groups of diffraction peaks belonging to ZnGa2O4 cubic spinel crystals and ZIF-8 framework, respectively, indicating that ZGC / ZIF-8-NH 2 The preparation of nanomaterials was successful.

[0026] Figure 4 (a) Photoluminescence spectra of ZGC at pH 9.0-10.0 and (b) photoluminescence spectra of ZGC / ZIF-8-NH2 at different molar ratios of n[ZGC] / n[ZIF-8-NH2]. The persistent luminescence quenching performance of ZGC and ZGC / ZIF-8-NH2 on DA. (c) Persistent luminescence spectra of ZGC in the presence of DA at a concentration of 0-25 μM, (d) Persistent luminescence spectra of ZGC / ZIF-8-NH2 in the presence of DA at a concentration of 0-25 μM. Figure 4As shown in (a) and (b), we compared the fluorescence spectra of ZGC with different pH values ​​and ZGC / ZIF-8-NH2 with different molar ratios under the same experimental operation with 254 nm excitation. At the same time, we compared the quenching reaction of ZGC and ZGC / ZIF-8-NH2 to DA in aqueous solution. Figure 4 As shown in (c) and (d), under the same experimental procedures, the addition of a 25 μM DA solution significantly decreased the photoluminescence intensity of ZGC and ZGC / ZIF-8-NH2, with quenching efficiencies reaching nearly 29% and 72%, respectively. This indicates that ZIF-8-NH2 plays a significant role in accelerating the quenching of ZGC luminescence by DA. Therefore, the ZGC / ZIF-8-NH2 nanomaterial has been demonstrated to be a promising probe for DA detection.

[0027] Figure 5 (a) Selectivity of the ZGC / ZIF-8-NH2-based sensing platform. (b) Anti-interference experiment. In Tris-HCl buffer (2.5 mM, pH 7.4), the concentrations of DA and interfering substances were 10 μM and 50 μM, respectively. The corresponding fluorescence images were captured under 365 nm UV light. DETAILED DESCRIPTION

[0028] The following embodiments are further descriptions of the present invention to illustrate 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.

[0029] Example 1:

[0030] Preparation of ZGC / ZIF-8-NH2 chitosan hydrogel

[0031] (1) ZGC PLNPs were synthesized by a one-pot hydrothermal method. 2 mmol Zn(NO3)2·6H2O, 2 mmol Ga(NO3)3·xH2O, and 0.002 mmol Cr(NO3)3·xH2O were mixed and stirred vigorously. The total volume was adjusted to 20 mL by adding ultrapure water. Then, 28% ammonia solution was quickly added to adjust the pH to 9.5, and a white precipitate was immediately observed. After stirring for 0.5 to 1 h, the mixture was transferred into a polytetrafluoroethylene-lined autoclave and sealed. The mixture was reacted at 220°C for 10 to 12 h. After cooling to room temperature, the white precipitate was collected by centrifugation and washed with 0.01 to 0.05 M HCl to remove possible zinc oxide impurities. It was then mixed with isopropanol and centrifuged to obtain ZGC PLNPs. Finally, the ZGC PLNPs were dispersed in ultrapure water for storage, and the concentration of ZGC PLNPs was approximately 1 to 5 mg / mL.

[0032] (2) Synthesize ZGC / ZIF-8-NH2 composite material by coprecipitation method: add ZIF-8-NH2 powder to the aqueous dispersion of ZGC PLNPs produced in step (1) and stir for 2-4 hours, n[ZGC] / n[ZIF-8-NH2]=0.4:1, centrifuge after reaction to obtain ZGC / ZIF-8-NH2 composite material, wash with ultrapure water and dry. The preparation method of ZIF-8-NH2 powder is as follows: take 2.0g Zn(NO3)2·6H2O and mix it with 12mL ultrapure water, mix 4g 2-methylimidazole with 5mL ultrapure water, add 4mL triethylamine, and Zn 2+ The solution is slowly poured into the mixture, mixed thoroughly, and stirred for 30-60 minutes. The mixture is then centrifuged 3-5 times with ultrapure water and dried at 60°C for 12 hours to obtain ZIF-8. 1g of dried ZIF-8 powder is added to 25mL of 25% ammonia solution, sonicated for 1-2 hours, and vigorously stirred at room temperature for 24 hours before centrifugation. After repeated washing with ultrapure water, the mixture is dried at 60°C for 36 hours to obtain ZIF-8-NH2.

[0033] (3) Preparation of ZGC / ZIF-8-NH2 chitosan hydrogel: Chitosan powder was dissolved in hot ultrapure water, and the pH of the solution was adjusted to acidic with acetic acid and stirred continuously. After it was completely dissolved, 20-30 mL of chitosan aqueous solution with a concentration of 2 g / L was obtained. Then 200-300 mg of ZGC / ZIF-8-NH2 composite material was added, and 1-2 mL of anhydrous ethanol was slowly added. The mixture was stirred continuously to form a uniform mixture of the hydrogel system. The mixture was then poured into a glass cuvette and cooled to room temperature. The mixture was placed in a -18°C refrigerator and stored for 20 h. After thawing at room temperature, the mixture was placed in a -18°C refrigerator and frozen for 6 h. This was repeated 3-5 times and then stored in a 4°C refrigerator to obtain a light yellow, slightly transparent, sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel.

[0034] Example 2:

[0035] The difference is that in step (1), the pH is adjusted to 9.0. The other processes are the same as those in Example 1, and a light yellow, slightly transparent, sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel is obtained.

[0036] Example 3:

[0037] The difference is that in step (1), the pH is adjusted to 9.2. The other processes are the same as those in Example 1, and a light yellow, slightly transparent, sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel is obtained.

[0038] Example 4:

[0039] The difference is that in step (1), the pH is adjusted to 9.7. The other processes are the same as those in Example 1, and a light yellow, slightly transparent, sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel is obtained.

[0040] Example 5:

[0041] The difference is that in step (1), the pH is adjusted to 10.0. The other processes are the same as those in Example 1, and a light yellow, slightly transparent, sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel is obtained.

[0042] Example 6:

[0043] The difference is that in step (2), n[ZGC] / n[ZIF-8-NH2]=0.2:1, and the other processes are the same as in Example 1, obtaining a light yellow and slightly transparent sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel.

[0044] Example 7:

[0045] The difference is that in step (2), n[ZGC] / n[ZIF-8-NH2]=0.5:1, and the other processes are the same as in Example 1, obtaining a light yellow, slightly transparent, sheet-like ZGC / ZIF-8-NH2 chitosan hydrogel.

[0046] Example 8:

[0047] Fluorescence detection of dopamine

[0048] 1. Detection was performed using fluorescence spectrophotometry with an excitation wavelength of 240–280 nm. The excitation and emission slit widths were set to 5–20 nm. Fluorescence spectra were recorded within the 300–800 nm range. A white powder of the ZGC / ZIF-8-NH2 composite (1–3 mg) was first dispersed in a Tris-HCl buffer solution (0.5–1.0 mL, 2.5–3.5 mM, pH 7.4). Various amounts of DA were added to adjust the final volume to 1–2 mL, with a final DA concentration range of 0–25 μM. Subsequently, 1–3 mL of the probe solution was mixed with the DA analytical solution, diluted with deionized water, and thoroughly mixed. The mixture was then transferred to a quartz cuvette for fluorescence detection under UV light. After incubation at 37°C for 1–4 h, continuous luminescence spectra were recorded without in situ excitation. Images of the fluorescence color change were captured using a camera in a dark environment. To ensure the reliability of the experimental results, at least three measurements were taken for each sample, and the average was calculated before proceeding to the next step.

[0049] 2. Hydrogel sensing mechanism, optimization of detection conditions, and response to DA

[0050] 2a. Fluorescence sensing mechanism of ZGC / ZIF-8-NH2 hydrogel system

[0051] The sensing performance of the sensor proposed in the present invention is due to the unique morphological and structural characteristics of ZIF-8-NH2, as well as the ultra-small size and background-free continuous luminescence of ZGC PLNPs. Due to the large specific surface area, the ultra-small ZGCPLNPs can be more electrostatically adsorbed on the surface of ZIF-8-NH2. DA can be enriched by ZIF-8-NH2, and due to the alkaline environment provided by 2-methylimidazole, DA is more easily oxidized to PDA around ZGC / ZIF-8-NH2 rather than in the solution. Therefore, the luminescence of ZGC can be effectively quenched by the adjacent PDA through the PET mechanism. With the increase of DA concentration, due to the Zn 2+ The synergistic effect of ZIF-8-NH2 and PDA disrupts the ZIF-8-NH2 structure, which may lead to different linear correlations at low and high DA concentrations. The proposed ZGC / ZIF-8-NH2 hydrogel system easily displays fluorescence color changes under ultraviolet light, enabling wearable devices to further enable accurate and rapid visual detection of DA.

[0052] 2b. Response of ZGC / ZIF-8-NH2 hydrogel fluorescence system to DA

[0053] Because the detection of analytes by fluorescent probes is dependent on their fluorescence intensity, a chitosan hydrogel fluorescent probe was prepared by appropriately mixing the probes. This probe emits strong red fluorescence under ultraviolet light. Since the eye is very sensitive to red, after the addition of DA, the red fluorescence of the fluorescent probe gradually weakens to colorless under ultraviolet light at 254nm excitation, resulting in a more obvious visual color change. Furthermore, fluorescence spectroscopy has also been used to study the stability of color-changing hydrogel fluorescent probes. The ZGC / ZIF-8-NH2 chitosan hydrogel of the present invention showed excellent stability over 14 days, indicating that the designed ZGC / ZIF-8-NH2 chitosan hydrogel is feasible for the detection of DA.

[0054] 2c. Effects of temperature and pH on fluorescent probes

[0055] The present invention conducted a series of experiments to optimize the detection reaction time, temperature, and pH of the buffer solution, and studied the time course of fluorescence quenching caused by DA. Fluorescence intensity did not decrease significantly after a 60-minute reaction with 45 μM DA. Therefore, the present invention selected an incubation time of 1 hour for further experiments. Temperature is another important factor affecting DA quenching of fluorescence activity. The quenching efficiency increases with increasing temperature (from 30°C to 45°C), likely due to the higher efficiency of intermolecular interactions at higher temperatures. To best simulate the physiological environment, the present invention selected 37°C for subsequent sensing responses. Furthermore, the present invention attempted to vary the pH of the Tris-HCl buffer (4.0, 5.0, 6.0, 6.8, 7.4, and 8.5). It was found that varying the pH within this range had no significant effect on the quenching efficiency. Therefore, Tris-HCl buffer (2.5 mM, pH = 7.4) was used as the final reaction solution in the present invention. pH = 7.4 can also be considered the optimal pH for simulating the internal environment of the human body.

[0056] Selectivity of 2D color-changing hydrogel fluorescence system

[0057] For an excellent fluorescent sensing system, it is important to have good selectivity for DA and maintain a selective response to DA even in the presence of interferents. Therefore, a series of experiments were carried out to explore the selectivity of the color-changing hydrogel sensing system in detecting DA. Under the same conditions, glutathione (GSH), ascorbic acid (AA), glucose (G), uric acid (UA), levodopa (L-Dopa), epinephrine (E), glutamic acid (Glu), lysine (Lys), phenylalanine (Phe), histidine (His), valine (Val), alanine (Ala), proline (Pro), glycine (Gly), cysteine ​​(Cys) and arginine (Arg) were selected to evaluate the selectivity of the color-changing hydrogel fluorescent sensing system for DA. Figure 5 Due to the complexity of human blood, in addition to the sensitivity of the sensing platform, high specificity also needs to be considered. Therefore, we studied several common amino acids in the human body and neurotransmitters with similar chemical structures to DA. Figure 5As shown in (a), ZGC / ZIF-8-NH2 can be quenched only when DA is added. The other sixteen interfering substances including histidine (His), valine (Val), alanine (Ala), glutamic acid (Glu), proline (Pro), phenylalanine (Phe), glycine (Gly), leucine (Leu), cysteine ​​(Cys), arginine (Arg), glutathione (GSH), ascorbic acid (AA), glucose (G), uric acid (UA), levodopa (L-Dopa) and epinephrine (E) have little effect on the quenching efficiency, even if their concentration is five times that of DA. In particular, Figure 5 As shown in (b), when 10 μM DA was added to the above interfering substances, the sustained luminescence intensity was only 7% of the original, indicating that ZGC / ZIF-8-NH2 also has good anti-interference properties.

[0058] 3. Detection of DA using smart wearable devices and their sensing platforms

[0059] A ZGC / ZIF-8-NH2 hydrogel fluorescence sensing system was designed using smart wearable device manufacturing technology. By interconnecting data between a portable smartphone and a wearable device, the system can further continuously monitor changes in dopamine in human blood. The color information corresponding to the red-green-blue (RGB) values ​​of the fluorescence photograph can be obtained using a smartphone color recognition application (APP). Therefore, dopamine is quantitatively detected by analyzing the RGB values. To ensure data accuracy, the experiment was repeated three times to obtain the average value of R / B, which represents the ratio of red to blue information.

[0060] 4. Analysis of DA in human blood samples using color-changing hydrogel

[0061] To evaluate the feasibility of the ZGC / NH2-ZIF-8 complex for detecting DA in real samples, serum was collected from healthy volunteers and diluted 100-fold with Tris-HCl buffer (pH 7.4, 2.5 mM). DA standard solutions of varying concentrations were then added to the diluted serum to prepare spiked samples. These samples were then mixed with ZGC / ZIF-8-NH2. After incubation at 37°C for 1–4 hours, the continuous luminescence intensity was monitored at 700 nm for quantitative analysis.

[0062] It should be noted that the technical contents of the present invention described above are only for the purpose of explaining and illustrating the technical essence of the present invention to enable those skilled in the art to understand the technical essence of the present invention. Therefore, the technical contents described above are not intended to limit the substantial protection scope of the present invention. The substantial protection scope of the present invention shall be based on the claims. Those skilled in the art should be aware that any modifications, equivalent substitutions, and improvements based on the substantial spirit of the present invention shall fall within the substantial protection scope of the present invention.

Claims

1. A ZGC / ZIF-8-NH2 nanocomposite material, mainly composed of Cr-doped 3+ The zinc gallate persistent luminescent nanoparticles ZGC PLNPs are composited with a modified hierarchical porous zeolite imidazole framework ZIF-8-NH2; the preparation method of the ZGC / ZIF-8-NH2 nanocomposite material is as follows: first, ZGC PLNPs are prepared by a hydrothermal method; then, ZIF-8-NH2 powder is added and ZGC / ZIF-8-NH2 is prepared by a co-precipitation method; the co-precipitation method for preparing ZGC / ZIF-8-NH2 is to disperse ZGC PLNPs in ultrapure water to obtain a dispersion with a concentration of 1-5 mg / mL, and then 100-200 mg of ZIF-8-NH2 powder is added and stirred for 2-4 h, and the molar ratio of ZGCPLNPs to ZIF-8-NH2 is 0.4:

1.

2. The ZGC / ZIF-8-NH2 nanocomposite material according to claim 1, wherein The hydrothermal method for preparing ZGCPLNPs involves mixing 2-4 mmol Zn(NO3)2·6H2O, 2-4 mmol Ga(NO3)3·xH2O, and 0.001-0.005 mmol Cr(NO3)3·xH2O, stirring vigorously, and adding ultrapure water to adjust the total volume to 15-30 mL. Subsequently, a 25-30% ammonia solution is quickly added to adjust the pH to 9-10. A white precipitate is observed. After stirring for 0.5-1 h, the mixture is placed in a polytetrafluoroethylene-lined autoclave and reacted at 200-250°C for 10-12 h. After cooling to room temperature, the white precipitate is collected by centrifugation, washed with 0.01-0.05 M HCl to remove impurities, mixed with isopropanol, centrifuged, and dispersed in ultrapure water for storage.

3. Use of the ZGC / ZIF-8-NH2 nanocomposite material according to claim 1 or 2 in dopamine detection.

4. A ZGC / ZIF-8-NH2 / chitosan hydrogel, characterized in that: The ZGC / ZIF-8-NH2 nanocomposite material according to claim 1 or 2 is cross-linked and polymerized with chitosan hydrogel.

5. The method for preparing the ZGC / ZIF-8-NH2 / chitosan hydrogel according to claim 4, characterized in that: The method comprises adding 100-500 mg of ZGC / ZIF-8-NH2 nanocomposite material to 10-50 mL of an aqueous chitosan solution with a concentration of 1-3 g / L, stirring to form a uniform mixture, freezing the mixture, thawing the mixture at room temperature, and then freezing the mixture again. The freezing and thawing steps are repeated 3-5 times and the mixture is stored in a refrigerator.

6. Use of the ZGC / ZIF-8-NH2 / chitosan hydrogel according to claim 4 or obtained by the preparation method according to claim 5 in dopamine detection.

7. The use according to claim 6, characterized in that Application of ZGC / ZIF-8-NH2 / chitosan hydrogel as a visual fluorescent probe in dopamine detection.

8. The use according to claim 6, characterized in that The ZGC / ZIF-8-NH2 / chitosan hydrogel is used as a wearable patch for human skin.

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