Preparation method and application of core-sheath structure wet-slippery hydrogel optical fiber

Abstract

This invention discloses a method for preparing and applying a core-sheath structured wet-slip hydrogel optical fiber. The method includes: injecting a core layer hydrogel precursor solution into a mold and curing and crosslinking it under ultraviolet light to obtain a crosslinked and cured hydrogel optical fiber core layer; immersing the crosslinked and cured hydrogel optical fiber core layer in a ferrous ion solution to obtain ferrous ion-loaded core fiber; and immersing the core fiber in a sheath layer hydrogel precursor solution to grow a hydrogel sheath layer. This invention solves the problems of existing core-sheath bilayer structure hydrogel optical fiber materials being limited to a single system and methods restricted to rapid ionic crosslinking of alginate. The preparation method of this invention is not limited to specific reactions of specific materials, is universal for free radical polymerization reaction systems, has no specific requirements for the state of the precursor (it can be in solution), and the obtained bilayer structured hydrogel optical fiber exhibits good optical conductivity and high stability in bodily fluid environments.

Description

Technical Field

[0001] This invention relates to a method for preparing hydrogel optical fibers, specifically to a method for preparing and applying a core-sheath structure wet-slip hydrogel optical fiber. Background Technology

[0002] In recent years, photomedicine, as an emerging medical approach, has received widespread attention due to its good therapeutic effects and reliable safety. Currently, photomedicine mainly includes photodynamic therapy, photothermal therapy, and optogenetics, all of which require a light source to penetrate deep into the tissue to stimulate photosensitive agents or specific nerves to achieve therapeutic goals. However, due to tissue absorption and light scattering, the penetration depth of light in the near-infrared region is limited to a few millimeters, and even less in shorter wavelength regions, which cannot meet the needs of practical medical treatment. Therefore, it is necessary to implant light-guiding materials within the body to conduct external light sources deep into the tissue to achieve photomedicine treatment. Traditional implantable light-guiding materials mainly include silicon-based glass optical fibers and polymer optical fibers. Both of these materials have high hardness, with Young's modulus between 1.0 × 10⁻⁶. 3 ~1.0×10 5 MPa, which is far above the biomechanical range of biological soft tissue, this mismatch in mechanical properties will cause damage to the biological soft tissue after implantation, thus causing secondary damage to the organism.

[0003] In contrast, hydrogel-based polymer fibers have been developed to replace traditional rigid implantable optical fibers due to their excellent flexibility, stretchability, and biocompatibility. Furthermore, hydrogels can be molecularly designed to possess mechanical properties and environmental stimuli responsiveness (temperature, pH, magnetism, electricity) adapted to biological soft tissues, thus achieving specific functions while simultaneously conducting light. Therefore, polyethylene glycol diacrylate (PEGDA), polyacrylamide (PAAm), agarose, and gelatin have been extensively studied for use in hydrogel optical fibers in recent years. To improve the optical conductivity of fibers, hydrogel fibers with a core-sheath bilayer structure are the best choice for clinical applications, as they not only possess excellent optical conductivity but also integrate the functional characteristics and structural advantages of bilayer hydrogels. Bilayer hydrogel fibers can further expand their functionality based on monolayer hydrogel fibers, for example, enabling more sophisticated wearable electronics and multi-drug controlled release. However, the slippery properties of hydrogels limit the fabrication technology of compatible bilayer hydrogel fibers, further restricting the practical application of hydrogel optical fibers. Currently, the fabrication techniques for bilayer hydrogel optical fibers mainly involve processing a single-layer structure, primarily including coaxial wet spinning and impregnation-based surface coating techniques. While the former allows for continuous large-scale fabrication, it requires high precision in the state of the hydrogel precursor and must meet specific conditions for successful fabrication. The latter involves coating a single-layer fiber surface with a hydrogel coating to create a bilayer structure. In current research, alginate gels are frequently used to construct the gel sheath due to their rapid ionic crosslinking properties. Currently, the material systems for fabricating core-sheath bilayer hydrogel optical fibers are relatively limited, and the methods are mainly confined to the rapid ionic crosslinking of alginate. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a core-sheath structure wet-slip hydrogel optical fiber, which solves the problem that the existing core-sheath double-layer structure hydrogel optical fiber material system is singular and the method is limited to rapid ionic crosslinking of alginate.

[0005] To achieve the above objectives, the present invention provides a method for preparing a core-sheath structured slippery hydrogel optical fiber, the method comprising:

[0006] (1) The core layer hydrogel precursor solution is injected into the mold and cured and crosslinked under ultraviolet light to obtain a crosslinked and cured hydrogel fiber core layer. The diameter of the hydrogel fiber core layer is consistent with the inner diameter of the mold. The core layer hydrogel precursor solution is prepared by uniformly mixing polyethylene glycol diacrylate aqueous solution and water-soluble photoinitiator.

[0007] (2) The cross-linked and cured hydrogel fiber core is immersed in a ferrous ion solution to obtain a ferrous ion-loaded core fiber; the ferrous ion solution is prepared by uniformly mixing an aqueous ferrous ion solution and citric acid; the concentration of ferrous ions in the aqueous ferrous ion solution is 0.1-0.2 mol / L; the immersion time is 1-10 min.

[0008] (3) The core fiber is immersed in a hydrogel precursor solution to grow a hydrogel sheath, thereby obtaining the core-sheath structure wet-slip hydrogel optical fiber; the growth time of the hydrogel sheath is 10-60 s; the hydrogel precursor solution is prepared by uniformly mixing an unsaturated monomer aqueous solution, a water-soluble photoinitiator, and a thermal initiator; the unsaturated monomer aqueous solution is any one or more of acrylamide, N-acryloylglycine amide (NAGA), and N,N-dimethylacrylamide.

[0009] Preferably, in step (1), the molecular weight of the polyethylene glycol diacrylate (PEGDA) is 700 to 20,000; and the mass fraction of the polyethylene glycol diacrylate in the core layer hydrogel precursor solution is 15 to 45 wt%.

[0010] Preferably, in step (1), the inner diameter of the mold is 300-3000 μm; the curing and crosslinking time is 5-15 min.

[0011] Preferably, in step (2), the ferrous ion aqueous solution is any one or more of ferrous sulfate, ferrous chloride, and ferrous carbonate; the amount of citric acid added to the ferrous ion solution is 0.1 to 0.3 mol / L.

[0012] Preferably, in step (3), the mass fraction of the unsaturated monomer aqueous solution is 15-50 wt%.

[0013] Preferably, in steps (1) and (3), the water-soluble photoinitiator is any one or more of the following: lithium phenyl-2,4,6-trimethylbenzoyl phosphate, azobisisobutyramidine hydrochloride (V-50), sodium phenyl bis-2,4,6-trimethylbenzoyl phosphate, lithium phenyl bis-2,4,6-trimethylbenzoyl phosphate, and polyethylene glycol / phenyl bis-2,4,6-trimethylbenzoylphosphine oxide.

[0014] Preferably, in step (3), the thermal initiator is any one of ammonium persulfate, potassium persulfate, and sodium persulfate; the mass of the thermal initiator is 0.3 to 1 wt% of the mass of unsaturated acrylamide monomer in the sheath hydrogel precursor solution.

[0015] Preferably, in step (3), the growth time of the hydrogel sheath is 10 to 60 seconds; the mass of the water-soluble photoinitiator is 0.2 to 1 wt% of the mass of the unsaturated acrylamide monomer in the hydrogel sheath precursor solution.

[0016] A core-sheath structured wet-slip hydrogel optical fiber prepared by the method described above.

[0017] Application of a core-sheath structured wet-slip hydrogel fiber optic as described above in the fields of bio-optical fiber materials and biomedical devices.

[0018] The present invention discloses a method for preparing and applying a core-sheath structured wet-slip hydrogel optical fiber, which solves the problems of existing core-sheath double-layer structured hydrogel optical fibers having a single material system and methods limited to rapid ionic crosslinking of alginate, and has the following advantages:

[0019] 1. The method for preparing a hydrogel fiber core-sheath bilayer structure of the present invention is proposed for the first time. The concentration of the core layer hydrogel precursor, the concentration of the sheath layer hydrogel precursor, the immersion time of the core fiber in ferrous ions, the concentration of ferrous ions, and the growth time of the sheath layer have a significant impact on the preparation of the hydrogel fiber. The concentration of the core layer hydrogel precursor determines the optical transmission efficiency of the core fiber; the concentrations of the core and sheath layer hydrogel precursors determine whether a total internal reflection interface between the core and sheath layers can be effectively constructed; the immersion time of the core fiber in ferrous ions and the concentration of ferrous ions determine the ferrous ion loading, and changes in the ferrous ion loading affect the growth efficiency of the sheath layer; the growth time of the sheath layer and the ferrous ion loading together determine the thickness of the sheath layer.

[0020] 2. The preparation method of the present invention is not limited to specific reactions of specific materials, and is universal for free radical polymerization reaction systems. There are no specific requirements for the state of the precursor, which can be in solution state. Monolayer fibers are prepared by template molding, and then a hydrogel sheath structure is in situ grown on the core hydrogel substrate by loading metal ion catalysts on the surface of the monolayer fibers and using an interfacial autocatalytic polymerization method based on the redox reaction mechanism.

[0021] 3. This invention enables the production of bilayer hydrogel optical fibers with varying diameters (300–3000 μm) and sheath thicknesses (0–500 μm, and not zero) through a simple impregnation growth method. These hydrogel optical fibers exhibit excellent light transmission capabilities, enabling effective optical conduction within tissues and application in targeted photothermal therapy and controlled drug release in vivo. They also demonstrate high stability in bodily fluid environments and possess a modulus similar to that of human tissue (Young's modulus 1.0 × 10⁻⁶). 3 ~1.0×10 5With its excellent bio-lubricating properties (average coefficient of friction ~0.065), it has great application potential in implantable photomedical devices. Attached Figure Description

[0022] Figure 1 Adding Fe to this invention 2+ A photograph of the rapid gelation of the hydrogel precursor in the sheath layer after catalytic solution.

[0023] Figure 2 This is a schematic diagram of the process for preparing a core-sheath bilayer hydrogel optical fiber according to Embodiment 1 of the present invention;

[0024] Figure 3 This is a schematic diagram of the total internal reflection effect of the macroscopic optical fiber structure of the present invention;

[0025] Figure 4 This is a graph showing the transmittance and refractive index of the core layer material and sheath material of different concentrations in this invention.

[0026] Figure 5 Optical microscope cross-sectional views of the double-layer optical fibers with different core diameters according to the present invention;

[0027] Figure 6 This is a diagram illustrating the mechanical properties of the optical fiber of this invention.

[0028] Figure 7 This is a graph showing the thickness variation trend of the hydrogel optical fiber sheath under different catalytic solution concentrations according to the present invention.

[0029] Figure 8 This is a graph showing the thickness variation trend of the optical fiber sheath layer after immersion in ferrous ions for different times according to the present invention.

[0030] Figure 9 This is a diagram illustrating the growth process of the optical fiber sheath under different catalytic solution concentrations according to the present invention.

[0031] Figure 10 This is a diagram illustrating the optical transmission performance of the double-layer optical fiber prepared in Example 5 of the present invention;

[0032] Figure 11 The graph shows the changes in sheath thickness and diameter of the double-layer optical fiber for different hydrogel sheaths in PBS solution according to the present invention.

[0033] Figure 12 This is a photograph of the hydrogel optical fiber prepared using alginate gel as the sheath layer in Comparative Example 3 of the present invention in PBS solution.

[0034] Figure 13 This is a photograph of the hydrogel optical fiber prepared using the sheath of PNAGA in Example 5 of the present invention in PBS solution.

[0035] Figure 14 This is a schematic diagram of the optical fiber material modulus test, a schematic diagram of the material modulus, a friction diagram, and a friction curve obtained in Embodiment 5 of the present invention;

[0036] Figure 15 This is a simulation test diagram of photothermal therapy under biological tissue with the core-sheath structure hydrogel fiber of the present invention.

[0037] Figure 16 This is a diagram illustrating the application of the hydrogel optical fiber prepared in Example 5 of this invention for controlled drug release. Detailed Implementation

[0038] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Example 1

[0040] A method for fabricating a core-sheath structured slippery hydrogel optical fiber, such as... Figure 2 The process shown illustrates the fabrication of a core-sheath bilayer hydrogel optical fiber. This method includes:

[0041] (1) Prepare 50 mL of 0.1 mol / L ferrous ion solution (using ferrous chloride or other ferrous ion solutions as an example), and add citric acid at a concentration of 0.1 mol / L; dissolve 4 g of polyethylene glycol diacrylate (molecular weight 700) and 0.012 g of water-soluble photoinitiator LAP in 6 mL of deionized water (40 wt%) to prepare a core layer hydrogel precursor solution; dissolve 10 g of N-acryloylglycine amide, 0.03 g of water-soluble photoinitiator LAP, and 0.1 g of thermal initiator ammonium persulfate in 40 mL of deionized water (20 wt%) to prepare a sheath layer hydrogel precursor solution;

[0042] (2) The core layer hydrogel precursor solution was injected into a silicone rubber tube mold with a diameter of 300 μm and cured and crosslinked under a UV lamp to obtain a crosslinked and cured hydrogel fiber core layer. The UV lamp had a light source wavelength of 365 nm, a light source intensity of 400 mW, and a crosslinking time of 5 minutes.

[0043] (3) The cross-linked and cured hydrogel fiber core was immersed in a ferrous ion solution for 5 minutes to obtain the core fiber; see [link to relevant documentation]. Figure 2 After the core fiber is loaded with ferrous ions, the sheath gel monomers are rapidly polymerized and grown on the core fiber.

[0044] (4) The core fiber is immersed in the hydrogel precursor solution to grow the hydrogel sheath. The growth time is 10 to 60 seconds.

[0045] Example 2

[0046] The preparation method of a core-sheath structure wet-slip hydrogel optical fiber is basically the same as that in Example 1, except that:

[0047] In step (1), a 0.15 mol / L ferrous ion solution is prepared;

[0048] In step (2), the core layer hydrogel precursor solution is injected into a silicone rubber tube mold with a diameter of 500 μm.

[0049] Example 3

[0050] The preparation method of a core-sheath structure wet-slip hydrogel optical fiber is basically the same as that in Example 1, except that:

[0051] In step (1), a 0.2 mol / L ferrous ion solution was prepared, and citric acid was added at a concentration of 0.1 mol / L. 4.5 g of polyethylene glycol diacrylate (molecular weight 700) and 0.014 g of water-soluble photoinitiator LAP were dissolved in 5.5 mL of deionized water (45 wt%) to prepare a core layer hydrogel precursor solution. 10 g of N-acryloylglycine amide, 0.02 g of water-soluble photoinitiator LAP, and 0.03 g of thermal initiator ammonium persulfate were dissolved in 40 mL of deionized water (20 wt%) to prepare a sheath hydrogel precursor solution.

[0052] In step (2), the core layer hydrogel precursor solution is injected into a silicone rubber tube mold with a diameter of 800 μm.

[0053] Example 4

[0054] The preparation method of a core-sheath structure wet-slip hydrogel optical fiber is basically the same as that in Example 3, except that:

[0055] In step (1), a 0.15 mol / L ferrous ion solution is prepared, and citric acid is added at a concentration of 0.2 mol / L.

[0056] In step (2), the core layer hydrogel precursor solution is injected into a silicone rubber tube mold with a diameter of 1000 μm.

[0057] Example 5

[0058] The preparation method of a core-sheath structure wet-slip hydrogel optical fiber is basically the same as that in Example 3, except that:

[0059] In step (2), the core layer hydrogel precursor solution is injected into a silicone rubber tube mold with a diameter of 3000 μm.

[0060] Example 6

[0061] The preparation method of a core-sheath structure wet-slip hydrogel optical fiber is basically the same as that in Example 1, except that:

[0062] In step (1), the molecular weight of polyethylene glycol diacrylate is 15,000 or 20,000.

[0063] Example 7

[0064] The preparation method of a core-sheath structure wet-slip hydrogel optical fiber is basically the same as that in Example 1, except that:

[0065] In step (1), N-acrylylglycine amide is adjusted to N,N-dimethylacrylamide or acrylamide, while the mass remains unchanged.

[0066] Comparative Example 1

[0067] A method for preparing an in-situ self-grown core-sheath bilayer hydrogel optical fiber, which is basically the same as that in Example 1, except that:

[0068] In step (1), no ferrous ion solution is prepared.

[0069] There is no step (3).

[0070] Comparative Example 2

[0071] A method for preparing an in-situ self-grown core-sheath bilayer hydrogel optical fiber, which is basically the same as that in Example 1, except that:

[0072] In step (1), no initiator ammonium persulfate was added to the sheath hydrogel precursor solution.

[0073] Comparative Example 3

[0074] The preparation method of a traditional hydrogel optical fiber with an alginate sheath is basically the same as that in Example 1, except that:

[0075] In step (1), a sodium alginate aqueous solution with a mass fraction of 2 wt% and a calcium chloride aqueous solution with a mass fraction of 4 wt% are prepared (the ferrous ion solution and the sheath hydrogel precursor solution are not prepared).

[0076] In step (3), the cross-linked and cured hydrogel fiber core is immersed in calcium chloride solution to obtain core fiber, wherein the immersion time is 5-10 minutes;

[0077] In step (4), the core fiber is immersed in sodium alginate solution to prepare the sheath layer for 1-5 minutes to obtain the core-sheath fiber. The obtained core-sheath fiber is then soaked in calcium chloride solution and cured for 15 minutes.

[0078] Experiment 1: Fabrication of optical fibers and investigation under different conditions

[0079] 1. Gel formation rate

[0080] This invention explores the addition of Fe to Comparative Example 1 and Examples 1-6. 2+ The rate of gelation of the hydrogel precursor in the sheath layer after catalysis solution.

[0081] like Figure 1 As shown, the present invention adds Fe 2+ A photograph showing the rapid gelation of the sheath hydrogel precursor after catalytic solution preparation. One drop of Fe was added to the prepared sheath precursor solution. 2+ After catalytic solution, observe the state of the sheath precursor, from Figure 1 It can be seen that the sheath hydrogel precursor rapidly gels within 5 seconds under the catalysis of ferrous ions, proving that the sheath hydrogel precursor is catalyzed by Fe... 2+ The catalysis enables a rapid gelation reaction, ensuring the rapid growth of the sheath hydrogel. In contrast, in Comparative Example 1, without Fe... 2+ In this case, the sheath hydrogel precursor cannot grow on the core fiber.

[0082] 2. Optical microscopy characterization of optical fibers

[0083] The optical fibers obtained in Examples 1-4 were characterized by optical microscopy.

[0084] like Figure 5 The figures shown are optical microscope cross-sectional views of double-layer optical fibers with different core diameters according to the present invention, where A is the optical fiber obtained in Example 1; B is the optical fiber obtained in Example 2; C is the optical fiber obtained in Example 3; and D is the optical fiber obtained in Example 4. Figure 5 It can be seen that hydrogel optical fibers with different core diameters can be obtained by using tube molds of different diameters. At the same time, the hydrogel optical fibers prepared in Examples 1 to 4 have a clear core-sheath double-layer structure and different sheath thicknesses.

[0085] 3. Optical fibers fabricated with different sheath layers

[0086] The stability of core-sheath bilayer optical fibers with different hydrogel sheaths prepared using different materials in Comparative Example 3 and Example 5 was investigated in PBS. The results are detailed in [link to relevant documentation]. Figures 12 to 13 .

[0087] like Figure 12 The image shown is a photograph of the hydrogel optical fiber prepared using alginate gel as the sheath layer in PBS solution, as presented in Comparative Example 3 of this invention. Figure 12 It can be seen that the alginate gel sheath layer dissolves and peels off rapidly in PBS solution, losing its coating effect on the core layer.

[0088] like Figure 13 The image shown is a physical photograph of the hydrogel optical fiber fabricated using the sheath of PNAGA in Example 5 of this invention, in PBS solution. Figure 13 It can be seen that the PNAGA sheath has high stability in the PBS simulated body fluid environment, and the sheath has not changed significantly throughout the test period.

[0089] 4. Growth process under different growth times and different catalytic solution concentrations

[0090] The thickness variation of the hydrogel fiber sheath under different catalytic solution concentrations and growth times was investigated. Core fibers with a core diameter of 3000 μm prepared in Example 5 were immersed in 0.1 mol / L, 0.15 mol / L, and 0.2 mol / L ferrous chloride solutions for 5 min, respectively. The ferrous ion-loaded hydrogel core fibers were then immersed in a sheath precursor (PNAGA) solution to grow the sheath layer. Cross-sections were taken every 10 s, and the sheath thickness was measured under a microscope.

[0091] like Figure 7 As shown in the figure, the sheath thickness variation trend of the present invention under different catalytic solution concentrations is shown in the figure, where the horizontal axis is time and the vertical axis is thickness.

[0092] like Figure 9 The diagram shows the growth process of the optical fiber sheath under different catalytic solution concentrations according to the present invention. The first row shows the growth process of the hydrogel optical fiber sheath in Example 5 with a ferrous ion concentration of 0.1 M; the second row shows the growth process of the hydrogel optical fiber sheath in Example 5 with a ferrous ion concentration of 0.15 M; and the third row shows the growth process of the hydrogel optical fiber sheath in Example 5 with a ferrous ion concentration of 0.2 M. Figure 9 It can be seen that the hydrogel fiber sheath grows gradually under the catalysis of different ferrous ions and exhibits different sheath growth rates. The concentration of the catalyst determines the growth rate; the higher the concentration, the faster the growth rate. The catalyst content is determined by the amount of ferrous ions.

[0093] 5. Effect of core fiber soaking time in ferrous ions on sheath growth

[0094] To investigate the effect of immersion time in ferrous ions on sheath growth, the core fibers prepared in Example 5 were immersed in a 0.1 mol / L ferrous ion solution for 1 min, 3 min, and 5 min. The ferrous-loaded core fibers were then immersed in a sheath precursor solution to grow a sheath layer. Cross-sections were taken every 10 s, and the sheath thickness was measured under an optical microscope.

[0095] like Figure 8 The figure shows the thickness variation trend of the optical fiber sheath layer after immersion in ferrous ions for different times. Figure 8It can be seen that when soaked in ferrous ion solution for different times, the thickness of the sheath layer shows different growth rates and sheath layer thicknesses depending on the soaking time.

[0096] Experiment Example 2 Performance Test

[0097] 1. Reflection effect

[0098] To demonstrate the total internal reflection effect caused by the refractive index difference between the core and sheath materials, macroscopic sandwich structures were prepared using the two materials (PEGDA and PNAGA) mentioned in Examples 1-5 as raw materials to verify the total internal reflection phenomenon caused by the refractive index difference. Experimental results show that the material combinations used in Examples 1-5 can form a total internal reflection phenomenon. The purpose of preparing the macroscopic sandwich structures is to facilitate direct observation of this phenomenon.

[0099] like Figure 3 As shown, this invention presents a schematic diagram of the total internal reflection effect of a macroscopic optical fiber structure. A 532nm wavelength light source is focused onto the middle layer (PEGDA layer) of the sandwich structure to observe the changes in the propagation path of the optical fiber within the sandwich structure under different incident light angles. A represents the propagation of light along a straight line in the macroscopic optical fiber; B represents the total internal reflection phenomenon when light propagates at a certain angle (45°) in the macroscopic optical fiber, where reflection at the core-sheath interface is clearly observed, confining the light propagation within the core layer; C represents the propagation effect in the macroscopic optical fiber when the incident angle is greater than the critical angle (90°). Figure 3 It can be seen that the significant difference in refractive index between the core material and the sheath material can effectively construct a total internal reflection interface at the core-sheath interface.

[0100] The influence of the intrinsic optical properties of the material on the performance of optical fibers was also investigated. High optical transmission performance requires the material to have high transmittance. Transmittance reflects the material's absorption effect on light and the attenuation of light within the material. The higher the transmittance value, the less the light attenuates in the medium, and the better the propagation effect. Simultaneously, the refractive index of the core material must be higher than that of the sheath material to effectively construct a total internal reflection interface between the core and sheath.

[0101] like Figure 4 As shown, this invention presents a graph illustrating the transmittance and refractive index of core and sheath materials at different concentrations. A represents the transmittance of core material (PEGDA) at different concentrations, with the horizontal axis representing wavelength and the vertical axis representing transmittance; B represents the transmittance of sheath material (PNAGA) at different concentrations, with the horizontal axis representing wavelength and the vertical axis representing transmittance; C represents the refractive index of the core and sheath layers in the 400–800 nm range, with the horizontal axis representing wavelength and the vertical axis representing refractive index. Figure 4As shown in A, the concentration of the core layer precursor determines the transmittance of the core fiber; the higher the concentration of the core layer precursor, the higher the transmittance of the core layer material, and the better the propagation effect of the core layer. Figure 4 From B, we know that the concentration of the sheath precursor determines the permeability of the sheath fibers. Figure 4 As can be seen from C, the core layer (45wt%) exhibits a higher refractive index than the sheath layer (20wt%), which meets the material requirements for fiber optic transmission and the construction of total internal reflection.

[0102] This invention uses different materials to construct different hydrogel fiber sheaths, and the intrinsic optical properties of the materials determine the optical transmission efficiency of the core-sheath double-layer fiber. The aforementioned performance tests were also conducted on the materials of Examples 6-7. The experimental results show that the unsaturated monomers mentioned in Examples 1-7 of this invention all have high transmittance and optical properties, and are suitable for constructing hydrogel fibers.

[0103] 2. Mechanical properties

[0104] The optical fiber prepared in Example 4, as an implant, can withstand complex deformations to conform to changes in organ curvature while ensuring optical transmission performance.

[0105] like Figure 6 The diagram shows the mechanical properties of the optical fiber of the present invention (Example 4), where A is a diagram showing the hydrogel optical fiber wound on a cylindrical object; B is a diagram showing the hydrogel optical fiber knotted. Figure 6 It can be seen that the prepared hydrogel optical fiber has good mechanical flexibility and can effectively withstand various complex deformations such as twisting and knotting.

[0106] 3. Light transmission performance

[0107] Light sources with wavelengths of 450 nm, 532 nm, and 660 nm were focused onto the front end of the double-layer optical fiber prepared in Example 5 to test its optical transmission performance.

[0108] like Figure 10 As shown in the figure, the optical transmission performance of the double-layer optical fiber prepared in Example 5 of the present invention is illustrated. A represents the ability of light sources with wavelengths of 450nm, 532nm, and 660nm to propagate in a straight line along the hydrogel fiber; B represents the ability of light sources with wavelengths of 450nm, 532nm, and 660nm to propagate in a curved manner along the hydrogel fiber; C and D represent the ability of light sources with wavelengths of 450nm, 532nm, and 660nm to propagate along a fixed path within biological tissue. Figure 10It can be seen that light sources with wavelengths of 450nm, 532nm and 660nm can propagate along the hydrogel optical fiber in a straight line or a curve. At the same time, light sources with wavelengths of 450nm, 532nm and 660nm can propagate along a fixed path in biological tissue and penetrate the tissue, indicating that the hydrogel optical fiber prepared in Example 5 can effectively conduct light in biological tissue in a straight line or a curve.

[0109] 4. Diameter variation

[0110] The diameter and sheath thickness changes of the optical fibers prepared in Example 5 and Comparative Example 3 were studied. Hydrogel optical fibers with different sheath materials were immersed in PBS solution (main components are Na2HPO4, KH2PO4, NaCl and KCl, pH 7.4) to simulate the body fluid environment. The changes in their overall diameter and sheath thickness were measured using an optical microscope at 1, 3, 5 and 7 days.

[0111] like Figure 11 The figure shows the changes in sheath thickness and diameter of the bilayer optical fiber in PBS solution for different hydrogel sheaths of the present invention. SA is the sheath of Comparative Example 3, PNAGA is the sheath of Example 5, PEGDA@SA is the optical fiber prepared in Comparative Example 3, and PEGDA@PNAGA is the optical fiber prepared in Example 5. A represents the thickness change of different sheaths, with time on the horizontal axis and thickness on the vertical axis. B represents the diameter change of hydrogel optical fibers with different sheath materials, with time on the horizontal axis and diameter on the vertical axis.

[0112] like Figure 12 The image shown is a physical picture of the hydrogel optical fiber prepared by Comparative Example 3 of the present invention using alginate gel as the sheath layer in PBS solution.

[0113] like Figure 13 The image shown is a physical picture of the hydrogel optical fiber prepared using the sheath of PNAGA in Example 5 of the present invention in PBS solution.

[0114] Depend on Figures 11 to 13 It can be seen that, compared with the traditional alginate sheath prepared in Comparative Example 3, the PNAGA sheath prepared in Example 5 exhibits higher stability in the body fluid environment, and the sheath thickness and optical fiber diameter do not change significantly throughout the test period.

[0115] 5. Friction properties

[0116] The optical fiber prepared in Example 5, as an implant, needs to have mechanical properties similar to those of tissue and good lubrication characteristics to provide good interfacial contact with biological tissue. Rotational rheological tests were performed on the core and sheath materials to observe their mechanical properties.

[0117] like Figure 14As shown, schematic diagrams of the modulus test, material modulus, friction diagram, and friction curve of the optical fiber material prepared in Example 5 of the present invention are presented. A is a schematic diagram of the modulus test of the hydrogel optical fiber material; B is the modulus test of PEGDA (hydrogel optical fiber core material), with shear stress on the horizontal axis and modulus on the vertical axis; C is the modulus test of PNAGA (hydrogel optical fiber sheath material), with shear stress on the horizontal axis and modulus on the vertical axis. The test parameters are: shear frequency 0.1–100 rad / s, stress range 0.1–1500 Pa. The lubrication performance of the material was studied using a ball-and-disc sliding contact friction testing machine. D is a schematic diagram of the friction test of the hydrogel optical fiber; E is the friction curve of the hydrogel optical fiber. The test parameters are: load 1 N, frequency 1 Hz, and the friction pair is a glass ball. Figure 14 It can be seen that hydrogel optical fibers have good tissue-like modulus (Young's modulus 1.0 × 10⁻⁶). 3 ~1.0×10 5 With good bio-lubricating properties (average coefficient of friction ~0.065), it can provide a good contact interface for biological tissues.

[0118] 6. Photothermal therapy

[0119] The optical fiber prepared in Example 5 was subjected to photothermal therapy testing to verify the photothermal therapy and drug release capabilities of the prepared core-sheath structure hydrogel optical fiber. Specifically, the photothermal therapy test involved embedding the optical fiber prepared in Example 5 entirely within porcine subcutaneous tissue. An 808nm near-infrared light source was focused onto one end of the fiber, with a pre-prepared photothermal reagent (gelatin-coated nano-ferric oxide) placed at the fiber's end. A control group was prepared by directly irradiating a predetermined location with an infrared light source without hydrogel optical fiber mediation.

[0120] like Figure 15 The image shows a simulated photothermal therapy test of the core-sheath structure hydrogel optical fiber of the present invention under biological tissue. The first row ("No optical fiber") represents test images without optical fiber at 0 min, 10 min, and 20 min. The second row ("With optical fiber") represents test images with optical fiber at 0 min, 10 min, and 20 min. Figure 15As can be seen, without fiber optic mediation, the light source cannot reach deep into the tissue due to scattering and absorption. Infrared imaging reveals localized temperature changes; only the tissue near the light source shows slight temperature changes during the 20-minute irradiation period, indicating that the pre-embedded photothermal reagent was not triggered. Conversely, with fiber optic mediation, compared to the group without fiber optics, a significant temperature change in the pre-embedded photothermal reagent is clearly visible, and the propagation trajectory of the light source along the hydrogel fiber is clearly observable. This demonstrates that the core-sheath structure hydrogel fiber prepared in Example 5 of this invention can effectively transmit the light source deep into the tissue, possessing the potential as a propagation medium for photothermal therapy.

[0121] The specific testing procedure for controlled drug release was as follows: Nano-ferric oxide was coated with gelatin and tartrazine was added as a simulated drug, then immersed in 100 mL of deionized water. The hydrogel optical fiber prepared in Example 5 was used as the propagation medium of the light source in the water, while the drug without the optical fiber was released freely underwater as a control group. Every 5 minutes, 4 mL of sample was taken and the tartrazine content in the drug was quantitatively analyzed using UV-Vis spectroscopy to assess the release rate. During this process, 4 mL of deionized water was added to each 4 mL sample to maintain a constant system volume.

[0122] like Figure 16 Figure 5 shows a study on the use of hydrogel optical fibers prepared in Example 5 of this invention for controlled drug release. Figure 16 It can be seen that the drug release rate under fiber-optic irradiation is significantly higher than that of the control group without infrared release. This is because the temperature of the photothermal reagent rises under the stimulation of the fiber-optic light source, and the gelatin melts, promoting the accelerated release of the drug.

[0123] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a core-sheath structured slippery hydrogel optical fiber, characterized in that, The method includes: (1) The core layer hydrogel precursor solution is injected into the mold and cured and crosslinked under ultraviolet light to obtain a crosslinked and cured hydrogel fiber core layer. The diameter of the hydrogel fiber core layer is consistent with the inner diameter of the mold. The core layer hydrogel precursor solution was prepared by uniformly mixing an aqueous solution of polyethylene glycol diacrylate and a water-soluble photoinitiator. The molecular weight of the polyethylene glycol diacrylate is 700~20000; In the core layer hydrogel precursor solution, the mass fraction of the polyethylene glycol diacrylate is 15-45 wt%. (2) The cross-linked and cured hydrogel fiber core is immersed in a ferrous ion solution to obtain ferrous ion loaded core fiber; the immersion time is 1~10 min; The ferrous ion solution is prepared by uniformly mixing an aqueous solution of ferrous ions and citric acid; the concentration of ferrous ions in the aqueous solution of ferrous ions is 0.1~0.2 mol / L. (3) The core fiber is immersed in the hydrogel precursor solution to grow a hydrogel sheath to obtain the core-sheath structure wet-slip hydrogel optical fiber; the growth time of the hydrogel sheath is 10~60 s; The sheath hydrogel precursor solution was prepared by uniformly mixing an unsaturated monomer aqueous solution, a water-soluble photoinitiator, and a thermal initiator. The unsaturated monomer aqueous solution is any one or more of acrylamide, N-acryloylglycinamide and N,N-dimethylacrylamide; The mass fraction of the unsaturated monomer aqueous solution is 15~50 wt%; The thermal initiator is any one of ammonium persulfate, potassium persulfate, and sodium persulfate; the mass of the thermal initiator is 0.3~1 wt% of the mass of the unsaturated monomer in the sheath hydrogel precursor solution. The mass of the water-soluble photoinitiator is 0.2 to 1 wt% of the mass of the unsaturated monomer in the sheath hydrogel precursor solution.

2. The preparation method according to claim 1, characterized in that, In step (1), the inner diameter of the mold is 300~3000 μm; the curing and crosslinking time is 5~15 min.

3. The preparation method according to claim 1, characterized in that, In step (2), the ferrous ion aqueous solution is any one or more of ferrous sulfate, ferrous chloride, and ferrous carbonate; the amount of citric acid added to the ferrous ion solution is 0.1~0.3 mol / L.

4. The preparation method according to claim 1, characterized in that, In steps (1) and (3), the water-soluble photoinitiator is any one or more of the following: lithium phenyl-2,4,6-trimethylbenzoyl phosphate, azobisisobutyramidine hydrochloride, sodium phenyl bis-2,4,6-trimethylbenzoyl phosphate, lithium phenyl bis-2,4,6-trimethylbenzoyl phosphate, and polyethylene glycol / phenyl bis-2,4,6-trimethylbenzoylphosphine oxide.

5. A core-sheath structured wet-slip hydrogel optical fiber prepared by the preparation method according to any one of claims 1-4.

6. The application of the core-sheath structure wet-slip hydrogel optical fiber as described in claim 5 in the field of preparing bio-optical fiber materials and biomedical devices.

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