Glucose hydrogel optical fiber sensor and preparation method thereof

Abstract

The invention provides a glucose hydrogel optical fiber sensor and a preparation method thereof. The glucose hydrogel optical fiber sensor comprises an optical fiber and a glucose fluorescence sensing module fixedly carried on the end face of the optical fiber. Wherein the optical fiber comprises a double-layer hydrogel optical fiber which comprises an inner fiber core and an outer cladding. The glucose fluorescence sensing module is formed by fixing a glucose fluorescence probe containing a boric acid group and a terminal amino group through a covalent reaction between the amino group and an epoxy group in the hydrogel network. The glucose hydrogel optical fiber sensor has excellent performance, high sensitivity and good selectivity, and can realize stable and real-time detection of glucose concentration in a complex physiological environment. The sensor is flexible in structure and good in biocompatibility, does not depend on enzyme reaction, and avoids the problem of signal drift caused by enzyme inactivation; meanwhile, the sensor is good in repeatability, can be integrated with other optical sensing modules to realize multi-parameter synchronous monitoring, and is suitable for long-term dynamic monitoring application in vivo.

Description

Technical Field

[0001] This invention relates to the fields of biomedical engineering and optical sensing technology, specifically to a glucose hydrogel fiber optic sensor and its preparation method. Background Technology

[0002] In various medical diagnoses, glucose concentration is usually an important physiological and biochemical parameter. Accurate and timely acquisition of glucose concentration in the body is of great significance in the diagnosis and treatment of diseases such as traumatic brain injury, stroke, and diabetes.

[0003] Traditional electrochemical glucose sensors mostly rely on glucose oxidase (GOx). This enzyme is easily deactivated by changes in temperature, pH, and ion concentration in complex bodily fluid environments, leading to unstable detection signals and short lifespans. In the in vivo environment, various reducing substances (such as uric acid, ascorbic acid, dopamine, etc.) can react with the sensing interface, interfering with the sensing signal and affecting the accurate detection of glucose concentration.

[0004] Furthermore, the optical fibers used in glucose sensors are difficult to bend at large angles. For example, quartz glass optical fibers have advantages such as resistance to electromagnetic interference and small size, but their fabrication technology still has significant problems. Traditional commercial optical fibers use quartz glass as the matrix, and the fabrication technology can be roughly divided into two categories: 1) Surface modification type: The surface of the quartz optical fiber is first pretreated by hydroxylation, silanization, etc., and then functional materials such as fluorescent molecules, quantum dots, and gold / silver nanoparticles are fixed on the cladding surface through physical adsorption or chemical grafting. This method has many process steps, the functional layer is easy to peel off, the probe is difficult to reuse, and the sensing signal must rely on external analysis equipment such as spectrometers and photodetectors, making the system complex and costly. 2) Microstructure type: One-dimensional periodic microstructures such as fiber Bragg gratings (FBGs) are written into the inside of the quartz optical fiber using femtosecond laser etching or photolithography, and sensing is achieved through wavelength selective reflection / transmission of the microstructure. This approach avoids the problem of surface functional material detachment, but the microstructure processing accuracy is extremely high, resulting in low yield and high cost. Most importantly, this quartz glass optical fiber is too rigid and cannot be bent at large angles, which could easily cause secondary damage to tissues and organs during brain monitoring. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned deficiencies in the prior art.

[0006] To achieve the above objectives, the first aspect of the present invention provides a glucose fluorescent probe.

[0007] The glucose fluorescent probe contains a boric acid group and a terminal amino group, and its structural formula is as follows: .

[0008] A second aspect of the present invention provides a method for preparing a glucose fluorescent probe.

[0009] The method includes: (1) Dissolve 1-[9,10-bis(bromomethyl)-2-anthrayl]acetone in the first solvent, add N-Boc-butanediamine, and then stir the reaction under an inert gas atmosphere. After cooling the reaction solution, pour it into ice water to precipitate the solid. Filter, wash and purify by silica gel column chromatography to obtain the first intermediate compound. (2) Dissolve the first intermediate compound in the second solvent, add p-2-bromomethylphenylboronic acid ester, and then heat to the target temperature under an inert gas atmosphere and stir the reaction. After the reaction is completed, cool and remove the solvent by rotary evaporation. Separate the residue by column chromatography to obtain the second intermediate compound. (3) The second intermediate compound was dissolved in a tert-butyl protecting group hydrolysis solution and stirred at room temperature to remove the tert-butyl protecting group. The reaction solution was concentrated under reduced pressure and the residue was purified by column chromatography to obtain a glucose fluorescent probe.

[0010] Further, in step (1), the molar ratio of N-Boc-butanediamine to 1-[9,10-bis(bromomethyl)-2-anthrayl]acetone is greater than or equal to 2, for example 2.5, 3, etc.

[0011] Further, in step (1), the first solvent includes anhydrous DMF, tetrahydrofuran, dichloromethane, acetonitrile, dichloroethane, chloroform, or 1,4-dioxane.

[0012] Furthermore, in step (1), an acid-binding agent may be added to promote the reaction. The acid-binding agent includes at least one of potassium carbonate, sodium carbonate, triethylamine, and N,N-diisopropylethylamine.

[0013] Furthermore, the target temperature in step (2) is 50~70℃.

[0014] Further, in step (2), the second solvent includes anhydrous acetonitrile, tetrahydrofuran, DMF, dichloromethane, acetonitrile, dichloroethane, chloroform, or 1,4-dioxane.

[0015] Furthermore, in step (2), the molar ratio of 2-bromomethylphenylboronic acid ester to the first intermediate compound is greater than or equal to 2, for example, 2.5, 3, etc.

[0016] Furthermore, in step (3), an acid-binding agent may be added to promote the reaction. The acid-binding agent includes at least one of potassium carbonate, sodium carbonate, triethylamine, and N,N-diisopropylethylamine.

[0017] Further, in step (3), the tert-butyl protecting group hydrolysis solution includes: a dichloromethane solution of trifluoroacetic acid, a tetrahydrofuran solution of trifluoroacetic acid, or a hydrogen chloride-1,4-dioxane / ethyl acetate / methanol system.

[0018] A third aspect of the present invention provides a glucose fluorescence sensing module.

[0019] The glucose fluorescence sensing module is formed by immobilizing the glucose fluorescence probe described in the first aspect through a covalent reaction between the amino group at its end and the epoxy group in the hydrogel network.

[0020] Furthermore, the hydrogel network is equipped with epoxy groups by adding glycidyl methacrylate (GMA) during the preparation process.

[0021] The fourth aspect of this invention provides a method for preparing a glucose fluorescence sensing module.

[0022] The method includes: dissolving the above-mentioned glucose fluorescent probe and triethylamine in dimethyl sulfoxide to obtain a precursor solution for the sensing material; immersing a hydrogel layer containing epoxy groups in the precursor solution to allow the amino groups of the glucose fluorescent probe to undergo a covalent grafting reaction with the epoxy groups of the hydrogel; then removing excess solution and washing with water to obtain a glucose fluorescent sensing module.

[0023] Further, the hydrogel layer is prepared by the following method: a pregel solution is prepared using acrylamide, N,N-dimethylacrylamide, polyethylene glycol diacrylate, glycidyl methacrylate, and a photoinitiator; the pregel solution is dropped onto a film, a glass slide is placed on it, and polymerization is carried out under ultraviolet light; then the polymerized hydrogel layer is washed and dried. Further still, the mass of the photoinitiator is 0.2% to 0.8% of the total mass of the four monomers mentioned above.

[0024] The fifth aspect of this invention provides a glucose fiber optic sensor.

[0025] The glucose fiber optic sensor includes: an optical fiber, and a glucose fluorescence sensing module as described above, which is mounted on the end face of the optical fiber.

[0026] Alternatively, the optical fiber may include: quartz optical fiber, plastic optical fiber, PDMS optical fiber, hydrogel optical fiber, or a composite material thereof.

[0027] Optionally, the optical fiber is a double-layer hydrogel optical fiber, comprising an inner core and an outer cladding. The inner core is formed by curing core monomer A, core monomer B, core monomer C, and a photoinitiator. Core monomer A includes acrylamide, N-vinylpyrrolidone, or 2-hydroxyethylmethacrylamide; core monomer B includes polyethylene glycol diacrylate; and core monomer C includes hydroxyethyl methacrylate, or includes hydroxyethyl methacrylate and methyl methacrylate. The outer cladding is formed by curing a low-refractive-index PEGDA hydrogel and a photoinitiator, with a refractive index lower than that of the inner core.

[0028] Furthermore, the inner fiber core has a diameter of 50~600 μm and a refractive index of 1.46~1.48; the outer cladding has a thickness of 20~100 µm and a refractive index of 1.38~1.40.

[0029] Furthermore, based on a total mass fraction of 100 parts, the fiber core monomer A is 20-50 parts, the fiber core monomer B is 10-40 parts, and the fiber core monomer C is 10-60 parts; The photoinitiator has a mass of 0.2% to 1% of the total mass of the core monomers A, B, and C.

[0030] Compared with the prior art, the beneficial effects of the present invention include at least one of the following: (1) The glucose hydrogel fiber optic sensor of the present invention has excellent performance, with high sensitivity and good selectivity, and can realize stable and real-time detection of glucose concentration in complex physiological environments. The sensor has a flexible structure, good biocompatibility, does not depend on enzyme reaction, and avoids the signal drift problem caused by enzyme inactivation; at the same time, it has good repeatability and can be integrated with other optical sensing modules to realize multi-parameter synchronous monitoring, which is suitable for long-term dynamic monitoring applications in vivo.

[0031] (2) This invention, by designing a double-layer structure with a core refractive index greater than that of the cladding, ensures that total internal reflection is met when light propagates in the optical fiber, effectively reducing light transmission loss and improving light transmission efficiency. The preparation method is simple and easy to implement, with mild process conditions, facilitating large-scale production. Furthermore, the selected hydrogel material has good biocompatibility and flexibility, making the double-layer hydrogel optical fiber biocompatible, flexible, and not easily brittle, suitable for sensitive detection of parameters such as glucose, and applicable for long-term monitoring of the brain tissue microenvironment. Attached Figure Description

[0032] The above and other objects and / or features of the present invention will become clearer from the following description taken in conjunction with the accompanying drawings, in which: Figure 1 A schematic diagram of the synthesis route of the glucose fluorescent probe of the present invention is shown.

[0033] Figure 2 A schematic diagram of the detection mechanism of the glucose fiber optic sensor of the present invention is shown.

[0034] Figure 3 The performance test diagram of the glucose fiber optic sensor of the present invention is shown. Detailed Implementation

[0035] The glucose hydrogel fiber optic sensor and its preparation method of the present invention will be described in detail below with reference to exemplary embodiments.

[0036] Exemplary Example 1 This exemplary embodiment provides a glucose fluorescent probe.

[0037] The glucose fluorescent probe contains a boric acid group, and its structural formula is shown below: .

[0038] In this embodiment, the glucose fluorescent probe contains boric acid groups and terminal amino groups. The probe can specifically bind to the cis-diol structure on the glucose molecule, resulting in changes in fluorescence intensity or lifetime.

[0039] As an application example, this probe is introduced into the hydrogel network and fixed to the end face of an optical fiber after a covalent reaction between its terminal amino group and the epoxy group of the hydrogel layer, enabling real-time monitoring of glucose concentration in cerebrospinal fluid or interstitial fluid.

[0040] Exemplary Example 2 This exemplary embodiment provides a method for preparing a glucose fluorescent probe. Figure 1 The synthetic route of the glucose fluorescent probe is shown.

[0041] The preparation method includes the following steps: A1, as follows Figure 1 Raw material 1 (1-[9,10-bis(bromomethyl)-2-anthrayl]acetone) was dissolved in anhydrous DMF, and N-Boc-butanediamine (i.e., Figure 1 The raw material 2) was reacted with potassium carbonate, and then stirred under an inert gas atmosphere. The reaction solution was then cooled and poured into ice water to precipitate the solid. The solid was filtered, washed, and purified by silica gel column chromatography to obtain the first intermediate compound 3.

[0042] In step A1, anhydrous DMF is used as a solvent, but it can also be replaced by solvents such as tetrahydrofuran, dichloromethane, acetonitrile, dichloroethane, chloroform, and 1,4-dioxane.

[0043] In step A1, the molar ratio of N-Boc-butanediamine to raw material 1 is at least 2, for example, 2.5, 3, 3.5, etc.

[0044] In step A1, potassium carbonate acts as an acid-binding agent to promote the reaction. This step can also be performed without potassium carbonate, although it will take longer. Potassium carbonate can also be replaced by sodium carbonate, triethylamine, N,N-diisopropylethylamine, etc.

[0045] A2. Dissolve the first intermediate compound 3 in anhydrous acetonitrile, and add p-2-bromomethylphenylboronic acid ester (i.e., Figure 1 The raw material 4) and potassium carbonate were heated to the target temperature under an inert gas atmosphere and stirred. After the reaction was completed, the mixture was cooled, the solvent was removed by rotary evaporation, and the residue was separated by column chromatography to obtain the second intermediate compound 5.

[0046] In step A2, anhydrous acetonitrile is used as a solvent, but it can also be replaced by solvents such as tetrahydrofuran, DMF, dichloromethane, acetonitrile, dichloroethane, chloroform, and 1,4-dioxane.

[0047] In step A2, the molar ratio of 2-bromomethylphenylboronic acid ester to the first intermediate compound is at least 2, for example, 2.5, 3, 3.5, etc.

[0048] In step A2, potassium carbonate acts as an acid-binding agent to promote the reaction. This step can also be performed without potassium carbonate, although it will take longer. Potassium carbonate can also be replaced by sodium carbonate, triethylamine, N,N-diisopropylethylamine, etc.

[0049] A3. Dissolve the second intermediate compound 5 in a solution of trifluoroacetic acid in dichloromethane or tetrahydrofuran, stir at room temperature to remove the tert-butyl protecting group, concentrate the reaction solution under reduced pressure, and purify the residue by column chromatography to obtain the glucose fluorescent probe ACDBA. The reaction principle is that the tert-butyl protecting group hydrolyzes under acidic conditions. The volume ratio of trifluoroacetic acid to dichloromethane is 1:2 to 1:5, and the volume ratio of trifluoroacetic acid to tetrahydrofuran is 1:2 to 1:5.

[0050] In step A3, the protecting group can also be removed using the hydrogen chloride-1,4-dioxane / ethyl acetate / methanol system.

[0051] As a specific example of the present invention, the synthesis process may include: Starting material 1 (1-[9,10-bis(bromomethyl)-2-anthrayl]acetone) (1.0 g, 4 mmol) was dissolved in 40 mL of anhydrous DMF, and N-Boc-butanediamine (2 eq) and potassium carbonate (3 eq) were added. The reaction mixture was stirred at 80 °C for 12 hours under a nitrogen atmosphere. After cooling, the reaction solution was poured into 200 mL of ice water, and a solid precipitated. The solid was filtered, washed with water, and purified by silica gel column chromatography to give compound 3 in approximately 70% yield.

[0052] Compound 3 (0.50 g, 1 mmol) was dissolved in 30 mL of anhydrous acetonitrile, and 2-bromomethylphenylboronic acid ester (2.2 eq) and potassium carbonate (3 eq) were added. The mixture was heated to 60 °C under a nitrogen atmosphere and stirred for 24 hours. After the reaction was completed, the mixture was cooled, the solvent was removed by rotary evaporation, and the residue was separated by column chromatography to give compound 5 in approximately 55% yield.

[0053] Compound 5 was dissolved in 30 mL of a trifluoroacetic acid solution in dichloromethane (trifluoroacetic acid to dichloromethane volume ratio 1:3), and stirred at room temperature for 2 hours to remove the tert-butyl protecting group. The reaction solution was concentrated under reduced pressure, and the residue was purified by column chromatography to give the final product ACDBA in approximately 80% yield.

[0054] Exemplary Example 3 This exemplary embodiment provides a glucose fluorescence sensing module.

[0055] The glucose fluorescence sensing module can be formed by introducing the glucose fluorescence probe in Exemplary Example 1 into the hydrogel network through a covalent reaction between the amino group at its end and the epoxy group in the hydrogel network.

[0056] Exemplary Example 4 This exemplary embodiment provides a method for preparing a glucose fluorescence sensing module.

[0057] The method includes: dissolving the glucose fluorescent probe and triethylamine in dimethyl sulfoxide in exemplary embodiment 1 to obtain a precursor solution of the sensing material; The hydrogel layer with epoxy groups was immersed in the precursor solution to allow the amino groups of the probe to undergo a covalent grafting reaction with the epoxy groups of the hydrogel. Then, the excess solution was removed and the sample was washed with water to obtain the glucose fluorescence sensing module.

[0058] In this embodiment, the water washing includes placing the sample in deionized water and changing the water multiple times.

[0059] In this embodiment, the hydrogel layer is prepared by the following method: A pregel solution was prepared using acrylamide, N,N-dimethylacrylamide, polyethylene glycol diacrylate, glycidyl methacrylate, and a photoinitiator. The mass ratio of acrylamide, N,N-dimethylacrylamide, and polyethylene glycol diacrylate was 15-40:5-15:0.5-2. Specifically, a pregel solution is prepared using acrylamide (15% - 40%, w / v), N,N-dimethylacrylamide (5% - 15%, w / v), polyethylene glycol diacrylate (0.5% - 2%, w / v), and a photoinitiator. The photoinitiator accounts for 0.2% to 0.8% of the total mass of the hydrogel layer monomers. w / v is mass / volume, expressed in g / mL. For example, 1 mL of pregel solution contains 0.15-0.4 g of acrylamide (i.e., 150-400 mg). The solvent is water, such as high-purity water. The three components work synergistically through their mass-volume ratios to achieve the hydrogel's flexibility and cross-linking stability. Polyethylene glycol diacrylate acts as the cross-linking agent and is used in the lowest amount, while acrylamide is the main monomer and is used in the highest amount. Photoinitiators may include IRGACURE 2959, LAP, etc. For example, each 1 mL of pregel solution contains 0.4 mg-4.6 mg of LAP or IRGACURE 2959.

[0060] A pregel solution was dropped onto the film, a glass slide was placed on it, and polymerization was carried out under ultraviolet light; then the polymerized hydrogel layer was washed and dried.

[0061] Furthermore, the film may include an aluminized polyester film. The glass slide may include a silanized glass slide.

[0062] As an example of the present invention, the preparation process of the glucose fluorescence sensing module includes: A pregel solution was prepared using acrylamide (15% - 40%, w / v), N,N-dimethylacrylamide (5% - 15%, w / v), polyethylene glycol diacrylate (0.5% - 2%, w / v), glycidyl methacrylate (0.5% - 5%, w / v), and a photoinitiator. The photoinitiator accounted for 0.2% to 0.8% of the total mass of the hydrogel layer monomers, and the solvent in the solution was water, such as ultrapure water.

[0063] A glucose fluorescent probe (ACDBA) was dissolved at 0.1–1 mg / mL, and triethylamine was dissolved at 1–2 molar amounts in dimethyl sulfoxide to obtain a precursor solution for the sensing material. Triethylamine acts as both a catalyst to activate the nucleophilicity of amino groups and an acid-binding agent to neutralize trace amounts of hydroxyl groups generated in the reaction. A 1–2 molar amount ensures sufficient covalent grafting of the probe while avoiding excessive residue that could affect biocompatibility. Specifically, a 1–2 molar amount of triethylamine (e.g., 1 molar amount) can completely neutralize the trace products generated in the reaction while activating most amino groups, ensuring a grafting efficiency ≥80% (meeting the fluorescence signal intensity requirements). If the amount of triethylamine exceeds 2 times, the excessive alkalinity may lead to non-specific hydrolysis of epoxy groups in the hydrogel (prematurely consuming epoxy groups, thus reducing probe grafting sites) or residual triethylamine may be difficult to completely remove by washing (excessive organic base can irritate in vivo tissues and is detrimental to biocompatibility).

[0064] A pre-gel solution was dropped onto an aluminized polyester film, a silanized glass slide was placed on it, and polymerization was carried out under ultraviolet light. The polymerized hydrogel layer was then washed and dried, and subsequently immersed in a precursor solution for 2 hours. During this process, the amino groups at the ends of the probe molecules underwent a ring-opening reaction with the epoxy groups in the hydrogel network, achieving covalent grafting of the probe. Excess solution was then wiped off, and the sample was placed in deionized water and washed repeatedly to remove any uncovalently fixed glucose sensing material, resulting in a glucose fluorescence photochemical sensing module, i.e., a glucose fluorescence sensing module.

[0065] By mounting the sensing module onto the tip of an optical fiber, a fiber optic photochemical glucose sensor can be obtained.

[0066] As another example of the present invention, the preparation process of the glucose fluorescence sensing module includes: the synthesis example of the glucose fluorescence probe in Exemplary Example 2, and the preparation example of the glucose fluorescence sensing module described above.

[0067] Exemplary Example 5 This exemplary embodiment provides a glucose fiber optic sensor.

[0068] The glucose fiber optic sensor includes: an optical fiber, and a glucose fluorescence sensing module, as shown in Exemplary Example 3, fixed on the end face of the optical fiber.

[0069] Figure 2 A schematic diagram of the detection mechanism of the glucose fiber optic sensor of the present invention is shown. Figure 3The performance test graphs of the glucose fiber optic sensor of the present invention are shown, wherein (a) the fluorescence spectrum of the glucose sensor changes in the 0-10 mM glucose range; (b) the fitting relationship between the fluorescence intensity of the glucose sensor at 490 nm and the glucose concentration; (c) the reversibility of the glucose sensor; (d) the selectivity of the glucose sensor to different interfering substances; (e) the pH stability of the glucose sensor; and (f) the temperature stability of the glucose sensor. The glucose sensor of the present invention has an excitation wavelength of 405 nm, emits fluorescence in the range of 450-650 nm, and has a maximum emission wavelength of 490 nm. The fluorescence intensity of the sensor increases with increasing glucose concentration; the fluorescence intensity at 490 nm shows a linear relationship with glucose concentration, with a linearity coefficient of 0.99; the sensor exhibits good continuous monitoring capability for glucose, and its fluorescence is not affected by other substances in the cerebrospinal fluid, pH, or temperature.

[0070] Exemplary Example 6 Based on Exemplary Example 5, the optical fiber can be a quartz optical fiber, a plastic optical fiber, a PDMS optical fiber, or a composite material thereof. Composite materials refer to optical fibers that are combined with other materials, such as quartz-nanomaterial composite fibers, PDMS-inorganic material composite fibers, etc.

[0071] In this embodiment, the glucose fluorescence sensing module can be mounted on a conventional optical fiber using either physical bonding (e.g., using biocompatible adhesive) or chemical bonding. For example, a biocompatible medical adhesive (e.g., PEG-based UV-curable adhesive, silicone rubber sealant) can be used to tightly bond the glucose fluorescence sensing module to the fiber end face, followed by curing at room temperature for 1-2 hours, or irradiation with 365 nm ultraviolet light for 30-60 seconds (if UV-curable adhesive is used) to achieve physical bonding. Alternatively, a silane coupling agent can be used to mediate the process. First, the conventional optical fiber end face is silanized (e.g., using 3-aminopropyltriethoxysilane) to introduce amino groups. Then, the epoxy groups on the sensing module surface react with the amino groups on the optical fiber end face in a ring-opening reaction, achieving chemical bonding. This method offers high bonding strength and is suitable for scenarios requiring extremely high stability (e.g., long-term implantation).

[0072] Using the above-mentioned fixation method, the bonding strength between the sensing module and the optical fiber can reach >150 kPa (conventional optical fiber-adhesive system), meeting the mechanical stability requirements for long-term implantation in vivo or in vitro testing.

[0073] Exemplary Example 7 Based on Exemplary Example 5, the optical fiber is a double-layer hydrogel optical fiber, and the glucose optical fiber sensor is a double-layer hydrogel optical fiber sensor.

[0074] The double-layer hydrogel optical fiber includes an inner core and an outer cladding.

[0075] In this embodiment, the inner core is formed by curing core monomer A, core monomer B, core monomer C, and a photoinitiator. Based on a total mass fraction of 100 parts, core monomer A comprises 20-50 parts, core monomer B comprises 10-40 parts, and core monomer C comprises 10-60 parts. The photoinitiator accounts for 0.2%-1% of the total mass of core monomers A, B, and C. When the photoinitiator content is <0.2%, the double bond conversion rate is <85%, and the mechanical strength decreases; when the photoinitiator content is >1%, residual photoinitiator will reduce cell viability.

[0076] The core monomer A includes acrylamide (AAm), N-vinylpyrrolidone (NVP), or 2-hydroxyethylmethacrylamide (HEMAAm). When core monomer A is AAM, its mass fraction is 20-50 parts. When AAM < 20 parts, the polymerization rate decreases, and the core strength is < 80 kPa. When AAM > 50 parts, brittleness increases, and the elongation at break is < 150%. When core monomer A is NVP, its mass fraction is 30-50 parts. When core monomer A is HEMAAm, its mass fraction is 20-50 parts. NVP and HEMAAm maintain high hydrophilicity and biocompatibility.

[0077] The fiber core monomer B includes polyethylene glycol diacrylate (PEGDA). When Mn < 400, the crosslinking density is too high, leading to an increase in the fiber core refractive index but a modulus > 300 kPa and decreased flexibility; when Mn > 1000, the refractive index < 1.45, resulting in insufficient Δn. Mn is the number-average molecular weight, and raw materials within the range of 400-1000 can be used.

[0078] The core monomer C includes hydroxyethyl methacrylate (HEMA), or a mixture of hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA). When the core monomer C is HEMA, its mass fraction is 10-60 parts; when it is a mixture of HEMA and MMA, the mass fraction of MMA is 5-15 parts, with the remainder being HEMA. 5-15 parts of MMA can increase the refractive index, but it needs to be controlled to ≤15 parts to maintain hydrophilicity. If it exceeds 15 parts, hydrophobicity increases, and the water content becomes less than 40%, affecting subsequent performance.

[0079] Photoinitiators may include: 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone IRGACURE 2959 or water-soluble phenyl-2,4,6-trimethylbenzoyl lithium phosphinate LAP, etc.

[0080] In this embodiment, the water content of the inner fiber core is 40-55% to meet the total internal reflection requirements. The inner fiber core achieves a water content of 40%-55% through a combination of acrylamide and other hydrophilic monomers, satisfying both flexibility and hydrophilicity requirements.

[0081] In this embodiment, the outer cladding layer is formed by curing a low-refractive-index PEGDA hydrogel and a photoinitiator, with a refractive index lower than that of the inner fiber core. The mass ratio of PEGDA hydrogel to photoinitiator is 400~100:1. The photoinitiator can be the same as those described above.

[0082] In this embodiment, the PEGDA in the outer cladding layer can form a network structure with high cross-linking density, which restricts water molecule penetration, maintains low refractive index and good mechanical protection.

[0083] In this embodiment, the inner fiber core (high refractive index layer) has a refractive index of 1.46~1.48, a water content of 40~55%, a tensile modulus of 80~300 kPa, and an optical loss of ≤0.2 dB·cm. ¹. The core diameter can be 50~600 μm. If it is <50 µm, the probe loading is insufficient, resulting in a signal-to-background ratio of <3. When it is >600 µm, the central oxygen inhibition is severe, resulting in an uncured soft core.

[0084] The outer cladding (low refractive index layer) has a refractive index of 1.38–1.40 and a swelling rate in water of <15%. The cladding thickness can be 20–100 µm. When it is <20 µm, mechanical protection is insufficient, the lateral tearing force is <0.1 N, and the protection of the core layer is lost. When it is >100 µm, the overall stiffness of the optical fiber increases, which can easily induce an increase in inflammatory response.

[0085] The core refractive index of the bilayer hydrogel fiber is greater than that of the cladding, satisfying the total internal reflection condition and making it suitable for high-sensitivity fluorescence sensing. The refractive index Δn is 0.06~0.10. If Δn < 0.06, the numerical aperture NA < 0.3 and the bending loss > 1 dB (bending radius 5 mm). If Δn > 0.10, the cladding water content < 25%, which will reduce the probe diffusion coefficient.

[0086] In this embodiment, the method for preparing the bilayer hydrogel optical fiber includes: S1. Prepare a core prepolymer solution by mixing core monomers A, B, and C with a photoinitiator. Inject the core prepolymer solution into a capillary mold and cure it by irradiation with ultraviolet light (200~400 nm). After photocrosslinking and curing, remove the prepolymer from the mold to form the core. The curing time can be 1~8 min. For core diameters of 50~600 µm, simply change the capillary mold. When the diameter is >400 µm, add 0.05 wt% hydroquinone (HQ) to the prepolymer solution to inhibit oxygen inhibition and ensure sufficient central curing.

[0087] Alternatively, a certain amount of water (such as high-purity water) can be added during the preparation of the fiber core prepolymer solution, so that the fiber core prepolymer solution contains a certain amount of water, and ultimately the water content of the inner core of the hydrogel fiber is 40~55%, which satisfies the total internal reflection adjustment.

[0088] Alternatively, water may not be added during the preparation of the fiber core prepolymer solution. In the subsequent step S2, the hydrogel fiber core will absorb water, ultimately resulting in a water content of 40-55% in the inner core of the hydrogel optical fiber.

[0089] S2. The obtained hydrogel fiber core is placed in the hydrogel precursor solution (i.e., the outer prepolymer solution), and its surface is treated using an immersion pulling process. After the pulling process, the hydrogel fiber core is straightened and hung vertically, and then irradiated under a UV lamp again to solidify the hydrogel precursor solution on the surface of the hydrogel fiber core, forming a cladding layer with a thickness of 20~100 µm, thus obtaining a hydrogel optical fiber. The hydrogel optical fiber consists of a core and a cladding layer, has a double-layer structure, and is cylindrical. The pulling speed is 10~50 mm·min. ¹ The viscosity is controlled in conjunction with the viscosity range of 80–300 mPa·s. The PEGDA hydrogel content in the outer prepolymer solution is 40% wt–60 wt%, which helps to form a network structure with high cross-linking density, restricts water molecule penetration, keeps the water content less than 15%, maintains a low refractive index, and provides good mechanical protection. The mass ratio of PEGDA hydrogel to photoinitiator is 400–100:1. The solvent in the solution is water, such as ultrapure water. Unless otherwise specified, ultrapure water can be used as the solvent in hydrogel optical fibers.

[0090] Alternatively, the hydrogel core can be left to stand in the solution for 10 seconds before the lifting operation to aid wetting and degassing.

[0091] To better understand the above preparation method, a specific preparation example is provided below.

[0092] (1) Core preparation: The core prepolymer solution was prepared according to the following mass percentages: Aam: 40%, PEGDA (Mn = 700): 30%, HEMA: 30%, photoinitiator (Irgacure 2959): 0.5%.

[0093] The above solution was injected into a capillary mold with an inner diameter of 0.2 mm, irradiated with 365 nm ultraviolet light for 3 min to cure, and then removed to form a fiber core.

[0094] (2) Cladding preparation: The fiber core is immersed in the outer prepolymer solution (PEGDA 1000, 50 wt%, containing 0.5% photoinitiator), and its surface is treated by dip-coating process. Then it is hung and irradiated with 365 nm ultraviolet light for 1 min 30 s to form a cladding layer with a thickness of about 0.03 mm.

[0095] In this embodiment, hydrogel optical fibers are easier to integrate due to their similar material composition. This invention utilizes the similarity of the hydrogel materials to directly contact the sensing module with the end face of the double-layer hydrogel optical fiber. Through the swelling-fusion effect of the hydrogel interface, the two are bonded under slight pressure (5-10 kPa) for 10-20 minutes, causing hydrogen bonds or physical entanglement to form at the interface, achieving integrated integration. To further enhance stability, unreacted double bonds remaining in the hydrogel optical fiber and sensing module (such as the double bonds of acrylamide and polyethylene glycol diacrylate in the pre-gel) can be used. After bonding the end faces, irradiation with ultraviolet light (365 nm) for 30-60 seconds initiates free radical cross-linking, achieving chemical bonding. This method requires no additional reagents, is simple to operate, and has high bonding strength (the cross-linking effect can be optimized by adjusting the residual amount of photoinitiator).

[0096] Using the above-mentioned fixation method, the bonding strength between the sensing module and the optical fiber can reach >200 kPa (hydrogel optical fiber-swelling fusion system), which meets the mechanical stability requirements for long-term implantation in vivo or in vitro detection.

[0097] Although the present invention has been described above in conjunction with exemplary embodiments and accompanying drawings, those skilled in the art should understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A fluorescent probe for glucose, characterized by, The compound has a structure as shown in the following formula: 。 2. A method for preparing a glucose fluorescent probe, characterized by, The method comprises: (1) dissolving 1-[9,10-bis(bromomethyl)-2-anthryl]ethanone in a first solvent, adding N-Boc-butane diamine, and then stirring under an inert gas atmosphere, then cooling the reaction solution and pouring into ice water to precipitate a solid, which is filtered, washed, and purified by silica gel column chromatography to obtain a first intermediate compound; (2) dissolving the first intermediate compound in a second solvent, adding p-2-bromomethyl phenyl boronic acid ester, and then heating to a target temperature under an inert gas atmosphere, stirring, cooling after the reaction, removing the solvent by rotary evaporation, and separating the residue by column chromatography to obtain a second intermediate compound; (3) dissolving the second intermediate compound in a tert-butyl protecting group hydrolysis solution, stirring at room temperature to remove the tert-butyl protecting group, concentrating the reaction solution under reduced pressure, and purifying the residue by column chromatography to obtain the glucose fluorescent probe.

3. A glucose fluorescence sensing module, characterized by, The glucose fluorescent probe of claim 1 is covalently reacted with epoxy groups in a hydrogel network through the amino groups at the ends thereof, so as to be fixed in the hydrogel network.

4. A method of preparing a glucose fluorescent sensing module, characterized by, The method comprises: dissolving the glucose fluorescent probe of claim 1 and triethylamine in dimethyl sulfoxide to obtain a precursor solution of a sensing material; immersing a hydrogel layer having epoxy groups in the precursor solution to allow the amino groups of the glucose fluorescent probe to covalently graft with the epoxy groups of the hydrogel, and then removing excess solution and washing with water to obtain a glucose fluorescent sensing module.

5. The method of claim 4, wherein the glucose fluorescent sensor module is prepared by the steps of: The hydrogel layer is prepared by the following method: a pre-gel solution is prepared by using acrylamide, N,N-dimethyl acrylamide, polyethylene glycol diacrylate, glycidyl methacrylate, and a photoinitiator; the pre-gel solution is dropped on a film, the glass slide is placed and ultraviolet light is irradiated for polymerization; and then the polymerized hydrogel layer is washed and dried.

6. A glucose optical fiber sensor characterized by, It comprises: an optical fiber and the glucose fluorescent sensing module of claim 3 immobilized on the end face of the optical fiber.

7. The glucose optical fiber sensor of claim 6, wherein, The optical fiber comprises a quartz optical fiber, a plastic optical fiber, a PDMS optical fiber, a hydrogel optical fiber, or a composite material thereof.

8. The glucose fiber-optic sensor of claim 6, wherein, The optical fiber is a double-layer hydrogel optical fiber comprising an inner core and an outer cladding, wherein the inner core is cured from core monomer A, core monomer B, core monomer C, and a photoinitiator; the core monomer A comprises acrylamide, N-vinyl pyrrolidone, or 2-hydroxyethyl methacrylamide, the core monomer B comprises polyethylene glycol diacrylate; the core monomer C comprises hydroxyethyl methacrylate or comprises hydroxyethyl methacrylate and methyl methacrylate; the outer cladding is cured from a low refractive index PEGDA hydrogel and a photoinitiator, and has a refractive index lower than that of the inner core.

9. The glucose optical fiber sensor of claim 8, wherein, The diameter of the inner core is 50-600 μm, and the refractive index is 1.46-1.48; the thickness of the outer cladding is 20-100 µm, and the refractive index is 1.38-1.

40.

10. The glucose fiber-optic sensor of claim 8, wherein, The core monomer A is 20-50 parts, the core monomer B is 10-40 parts, and the core monomer C is 10-60 parts, according to the sum of the mass fractions of the three being 100 parts; the mass of the photoinitiator is 0.2%-1% of the mass of the core monomer A, the core monomer B, and the core monomer C.

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