A double-layer hydrogel with intelligent response, its preparation method and application

Abstract

The present invention belongs to the technical field of biomaterials, and discloses an intelligent-responsive double-layer hydrogel, a preparation method thereof and an application. The present invention uses acrylamide, octadecyl methacrylate and carboxymethyl chitosan as raw materials, and prepares a tough hydrogel layer by hydrophobic association; then uses modified hyaluronic acid, N-isopropylacrylamide, acrylamide, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) as raw materials, and prepares a viscous hydrogel layer on the tough hydrogel layer by a continuous in-situ polymerization process; finally, an intelligent-responsive double-layer hydrogel is obtained. The double-layer hydrogel prepared by the present invention can withstand dynamic mechanical movement, be peeled off as needed and has the functions of diagnosis and treatment integrated with antibacterial, which has important clinical significance.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomaterials, and particularly relates to an intelligent-responsive double-layer hydrogel and its preparation method and application. Background Art

[0002] The human skin has a fine hierarchical structure, with complex mechanical and biomedical properties, and plays an important role in preventing bacterial invasion and maintaining human metabolism. Once the skin is severely damaged, the comprehensive barrier function of the skin will be damaged, and microorganisms will invade and cause tissue infections. In severe cases, non-healing wounds will be caused, especially vulnerable joint wounds such as wrists, ankles, elbows, knees, and the back of the neck. For better recovery, the treatment of skin wounds needs to achieve at least two goals: 1) Stop bleeding and prevent blood loss, 2) Prevent infection, permanent damage, and loss of function. Currently, a variety of antibacterial materials have been developed to solve the problem of bacterial infection. However, traditional wound dressings are usually gauze, bandages, or sponges, which only have single functions such as forming a physical barrier or absorbing exudates, and have a weak effect on promoting healing. In addition, during the use of these dressings, fibers or fragments entangle with the wound site, causing inflammation and even leading to secondary injury. An ideal dressing should not only be able to absorb wound exudate, maintain a high humidity of the wound surface, but also protect the wound surface from bacterial infection and have the property of being easily removed.

[0003] In addition, traditional bacterial infection detection technologies mainly rely on extraction and culture, morphological structure observation, fluorescence, biochemical analysis, and immunological and molecular biological methods. These technologies have a long process, require complex equipment and professional technical personnel, and are not convenient for the rapid treatment of bacterial infection. Moreover, even if a bacterial infection is determined, subsequent treatment may not take effect immediately. Therefore, it is of great significance to provide a bacterial detection and diagnosis strategy that integrates rapid diagnosis and effective treatment.

[0004] In recent years, some emerging hydrogels have been widely used as excellent candidate materials in wound dressings, possessing advantages that many other types of wound dressings cannot offer. On the one hand, hydrogels generally have a high water content, a porous structure, good water absorption, can absorb wound exudates, keep the wound environment moist, and will not damage new granulation or epithelial tissues. And the hydrogel with a hierarchical structure inspired by the skin may have great potential in antibacterial dressings. On the other hand, as a wound dressing, the hydrogel should not only have adjustable adhesion and stretchability but also the ability to eliminate bacteria. Adding antibacterial agents is an effective method. However, the abuse of antibiotics has led to multi-drug resistant bacteria, and metal ions and organic antibacterial agents have defects in treating infections. For hydrogels containing photothermal therapy (PTT) agents, light can be converted into local heating, which causes bacterial protein denaturation. Compared with chemotherapy, PTT has a broad-spectrum bactericidal ability, does not lead to the formation of drug-resistant pathogenic bacteria, and is a drug-resistant-free and minimally invasive process.

[0005] Therefore, it is necessary to develop an intelligent responsive hydrogel with integrated diagnosis and treatment functions in anti-infection. Summary of the Invention

[0006] Aiming at the problems and deficiencies existing in the prior art, the purpose of the present invention is to provide an intelligent responsive double-layer hydrogel and its preparation method and application.

[0007] Based on the above purpose, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides an intelligent responsive double-layer hydrogel, including a tough hydrogel layer and a sticky hydrogel layer arranged in a stacked manner; the tough hydrogel layer and the sticky hydrogel layer are connected by an interlocking network structure and hydrogen bonds;

[0009] Both the tough hydrogel layer and the sticky hydrogel layer are vinyl polymer-based hydrogels; among them, the tough hydrogel layer contains carboxymethyl chitosan; the sticky hydrogel layer contains modified hyaluronic acid, a photothermal material, and a thermosensitive material.

[0010] Preferably, the mass fraction of carboxymethyl chitosan in the tough hydrogel layer is 0.1%-4%, preferably 0.1%-1.6%. Further, the carboxymethyl chitosan is an environmentally friendly hydrophilic anionic polysaccharide, and tight hydrogen bonds are formed between the carboxymethyl chitosan chains and polyacrylamide, which limits and increases the mechanical properties of the hydrogel.

[0011] Preferably, the tough hydrogel layer is mainly copolymerized from vinyl hydrophilic monomers and vinyl hydrophobic monomers.

[0012] More preferably, the vinyl hydrophilic monomer in the tough hydrogel layer is at least one of acrylamide (AM), N-methylolacrylamide, acrylic acid (AA), or methacrylic acid (MAA); the mass fraction of the vinyl hydrophilic monomer in the tough hydrogel layer is 15% - 35%. Further, the mass fraction of acrylamide in the tough hydrogel layer is 15% - 35%.

[0013] More preferably, the vinyl hydrophobic monomer is at least one of stearyl methacrylate (SMA), cetyl methacrylate (HMA), or lauryl acrylate (LA); the mass fraction of the vinyl hydrophobic monomer in the tough hydrogel layer is 0.15% - 0.8%. Further, the mass fraction of stearyl methacrylate in the tough hydrogel layer is 0.15% - 0.8%.

[0014] Preferably, the modified hyaluronic acid is obtained by grafting modification of hyaluronic acid with dopamine; the grafting rate of the modified hyaluronic acid is 10% - 40%; the mass fraction of the modified hyaluronic acid in the viscous hydrogel layer is 0.2% - 1.2%, preferably 0.2% - 0.9%. Further, the catechol groups in the modified hyaluronic acid can form rich hydrogen bonds and van der Waals forces with various surfaces, and imine bonds with amino or thiol groups in the skin, etc., which endows the hydrogel with good adhesion.

[0015] Further, the preparation method of the modified hyaluronic acid is as follows: First, dissolve hyaluronic acid (HA) in water or buffer solution to obtain a 0.5% - 2% HA solution; then add 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC-HCl) and N-hydroxysuccinimide (NHS) to the HA solution and stir until it becomes clear to obtain a mixed solution; then, under ice-water bath and inert gas protection conditions, add dopamine hydrochloride to the mixed solution, adjust the pH to 5 - 6, and react at 0 - 4°C for 12 - 16 h to obtain a reaction solution; finally, dialyze the reaction solution in water, filter, and freeze-dry to obtain the modified hyaluronic acid. Among them, the mass ratio of HA, EDC-HCl, NHS, and dopamine hydrochloride is 1∶(0.2 - 0.6)∶(0.1 - 0.4)∶(0.2 - 0.6).

[0016] Preferably, the photothermal material is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS); the mass fraction of the photothermal material in the viscous hydrogel layer is 0.2%-1.6%, preferably 0.2%-0.7%. More preferably, the mass fraction of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) in the viscous hydrogel layer is 0.2%-1.6%. Further, the photothermal material forms hydrogen bond interactions with modified hyaluronic acid, acrylamide, etc., and due to the formation of polaron and bipolaron states, it has excellent photothermal conversion performance; because a conductive path is formed in the hydrogel network, the hydrogel has excellent conductivity and can achieve biosensing.

[0017] Preferably, the thermosensitive material includes a heat-shrinking thermosensitive material. Further, the heat-shrinking thermosensitive material is a vinyl thermosensitive monomer; the vinyl thermosensitive monomer is crosslinked in the polymer in a copolymerization manner with a vinyl hydrophilic monomer and a vinyl crosslinking monomer.

[0018] Preferably, the viscous hydrogel layer is mainly composed of a vinyl thermosensitive monomer, a vinyl hydrophilic monomer, and a vinyl crosslinking monomer copolymerized.

[0019] More preferably, the vinyl thermosensitive monomer is at least one of N-isopropylacrylamide, N-ethylacrylamide, N,N-diethylacrylamide, or N-n-propylacrylamide; the mass fraction of the vinyl thermosensitive monomer in the viscous hydrogel layer is 10%-30%. Further, the mass fraction of N-isopropylacrylamide in the viscous hydrogel layer is 10%-30%.

[0020] More preferably, the vinyl hydrophilic monomer in the viscous hydrogel layer is at least one of acrylamide, acrylic acid, N-hydroxymethylacrylamide, or methacrylic acid; the mass fraction of the vinyl hydrophilic monomer in the viscous hydrogel layer is 0%-15%. Further, the mass fraction of acrylamide in the viscous hydrogel layer is 0%-15%.

[0021] More preferably, the mass ratio of the vinyl thermosensitive monomer to the vinyl hydrophilic monomer in the viscous hydrogel layer is 10∶(0-5), preferably 10∶(0-3). Further, the mass ratio of N-isopropylacrylamide to acrylamide is 10∶(0-5), preferably 10∶(0-3).

[0022] More preferably, the vinyl crosslinking monomer is at least one of N,N'-methylenebis(acrylamide), di(ethylene glycol) diacrylate, or 1,4-butanediol diacrylate; the mass fraction of the vinyl crosslinking monomer in the viscous hydrogel layer is 0.02% - 0.08%. Further, the mass fraction of N,N'-methylenebis(acrylamide) in the viscous hydrogel layer is 0.02% - 0.08%.

[0023] The second aspect of the present invention provides a method for preparing the intelligent response double-layer hydrogel described in the first aspect above, including the following steps:

[0024] (1) Prepare a tough hydrogel layer: Add vinyl hydrophilic monomer, vinyl hydrophobic monomer, carboxymethyl chitosan, and initiator to the worm-like micelle solution and stir evenly to obtain a tough layer precursor solution; add the tough layer precursor solution to a reactor and react at 40 - 60 °C to obtain a tough hydrogel layer;

[0025] (2) Prepare a viscous layer precursor solution: First, add modified hyaluronic acid to the photothermal material dispersion to obtain mixture a; under an inert gas atmosphere, add vinyl thermosensitive monomer and vinyl hydrophilic monomer to mixture a and stir evenly to obtain mixture b; add vinyl crosslinking monomer, initiator, and catalyst to mixture b to obtain a viscous layer precursor solution;

[0026] (3) Prepare a double-layer hydrogel: Pour the viscous layer precursor solution onto the upper part of the tough hydrogel layer and react at 2 - 10 °C to obtain a double-layer hydrogel.

[0027] Preferably, in step (1), the worm-like micelle solution is formed by mixing a surfactant and a strong electrolyte salt solution; the preparation steps of the worm-like micelle solution are specifically: add the surfactant to the strong electrolyte salt solution and disperse evenly at 40 - 60 °C to obtain a worm-like micelle solution; the dispersion method is ultrasonic dispersion, and the dispersion time is 20 - 60 min. More preferably, the strong electrolyte salt solution is an aqueous solution of a strong electrolyte salt; the strong electrolyte salt is at least one of potassium chloride (KCl), sodium chloride (NaCl), or calcium chloride (CaCl 2 ) ; the surfactant is sodium dodecyl sulfate (SDS) or / and cetyltrimethylammonium bromide. Further, the mass ratio of the surfactant to the strong electrolyte salt is (0.8 - 2)∶1; the mass fraction of the strong electrolyte salt in the strong electrolyte salt solution is 1% - 3%.

[0028] Preferably, in step (1), the mass-volume ratio of the vinyl hydrophilic monomer to the worm-like micelle solution is (0.8 - 1.8) g∶5 mL.

[0029] Preferably, in step (1), the vinyl hydrophilic monomer is at least one of acrylamide (AM), N-methylol acrylamide, acrylic acid (AA), or methacrylic acid (MAA); the vinyl hydrophobic monomer is at least one of octadecyl methacrylate (SMA), cetyl methacrylate (HMA), or dodecyl acrylate (LA); the mass ratio of the vinyl hydrophobic monomer to the vinyl hydrophilic monomer is (0.01 - 0.05)∶1; the mass fraction of the vinyl hydrophilic monomer in the toughness layer precursor solution is 15% - 30%. Further, the mass ratio of SMA to AM is (0.01 - 0.05)∶1; the mass fraction of AM in the toughness layer precursor solution is 15% - 30%.

[0030] More preferably, in step (1), the initiator is at least one of ammonium persulfate (APS), potassium persulfate (KPS), or sodium persulfate; the mass ratio of the initiator to the vinyl hydrophilic monomer is (0.01 - 0.03)∶1.

[0031] Preferably, in step (1), the mass fraction of carboxymethyl chitosan in the toughness layer precursor solution is 0.1% - 3%, preferably 0.1% - 1.5%.

[0032] Preferably, in step (2), the modified hyaluronic acid is obtained by grafting dopamine onto hyaluronic acid; the grafting rate of the modified hyaluronic acid is 10% - 40%; the mass fraction of the modified hyaluronic acid in the viscous layer precursor solution is 0.2% - 1%, preferably 0.2% - 0.8%.

[0033] Preferably, in step (2), the photothermal material dispersion is prepared by uniformly dispersing the photothermal material in water; the photothermal material is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). More preferably, the mass fraction of the photothermal material in the photothermal material dispersion is 0.3% - 1.8%; the mass fraction of the photothermal material in the viscous layer precursor solution is 0.2% - 1.5%, preferably 0.2% - 0.6%.

[0034] Preferably, in step (2), the vinyl thermosensitive monomer is at least one of N-isopropylacrylamide, N-ethylacrylamide, N,N-diethylacrylamide, or N-n-propylacrylamide; the vinyl hydrophilic monomer is at least one of acrylamide, acrylic acid, N-hydroxymethylacrylamide, or methacrylic acid; the mass ratio of the vinyl thermosensitive monomer to the vinyl hydrophilic monomer is 10∶(0-5), preferably 10∶(0-3); the mass fraction of the vinyl thermosensitive monomer in the precursor solution of the adhesive layer is 10%-25%. Further, the mass ratio of N-isopropylacrylamide to acrylamide is 10∶(0-5), preferably 10∶(0-3); the mass fraction of N-isopropylacrylamide in the precursor solution of the adhesive layer is 10%-25%.

[0035] Preferably, in step (2), the vinyl crosslinking monomer is at least one of N,N'-methylenebis(acrylamide), di(ethylene glycol) diacrylate, or 1,4-butanediol diacrylate; the mass fraction of the vinyl crosslinking monomer in the precursor solution of the adhesive layer is 0.02%-0.05%. Further, the mass fraction of N,N'-methylenebis(acrylamide) in the precursor solution of the adhesive layer is 0.02%-0.05%.

[0036] Preferably, in step (2), the initiator is at least one of ammonium persulfate (APS), potassium persulfate (KPS), or sodium persulfate; the mass ratio of the initiator to the vinyl thermosensitive monomer is (0.03-0.10)∶1.

[0037] Preferably, in step (2), the catalyst is tetramethylethylenediamine; the mass ratio of the catalyst to the vinyl thermosensitive monomer is (0.01-0.03)∶1. Further, the mass ratio of tetramethylethylenediamine to N-isopropylacrylamide is (0.01-0.03)∶1.

[0038] Preferably, in step (2), the stirring condition after adding the vinyl thermosensitive monomer and the vinyl hydrophilic monomer into the mixed solution a is: stirring and dissolving at 300-500 rpm under the condition of an ice-water bath at 0℃.

[0039] More preferably, the reaction time in step (1) is 3-6 h; the reaction time in step (3) is 6-12 h; the inert gas is nitrogen or / and argon.

[0040] The third aspect of the present invention provides the application of the intelligent response double-layer hydrogel described in the second aspect above in medical materials.

[0041] Preferably, the medical materials include medical stent materials such as wound dressing materials.

[0042] The specific operation of using the intelligent-responsive double-layer hydrogel as a wound dressing is as follows: Apply the double-layer hydrogel to the affected area and irradiate it with a near-infrared laser at a wavelength of 808 nm and a power density of 195 mW / cm 2 for 6 - 8 min. After that, the sterilized double-layer hydrogel automatically detaches from the wound.

[0043] In the fourth aspect of the present invention, there is provided the application of the intelligent-responsive double-layer hydrogel described in the second aspect above in biosensor materials. Preferably, the biosensor materials include bacterial sensor materials.

[0044] The specific operation of using the intelligent-responsive double-layer hydrogel as a bacterial sensor material is as follows: Apply the double-layer hydrogel to the affected area, then connect an electrical signal measuring instrument, and obtain the bacterial infection condition of the patient's wound by measuring the change in the conductivity of the double-layer hydrogel.

[0045] Furthermore, the electrical signal measuring instrument is a digital bridge or a digital source meter.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] (1) In the present invention, hydrophilic monomer acrylamide, hydrophobic monomer octadecyl methacrylate, and carboxymethyl chitosan are used as raw materials, and a hydrogel layer with excellent tensile properties and tough toughness is synthesized by hydrophobic association; then, modified hyaluronic acid, thermosensitive monomer N-isopropylacrylamide, hydrophilic monomer acrylamide, and photothermal material poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) are used as raw materials, and a temperature- and enzyme-responsive viscous hydrogel layer is synthesized on the tough hydrogel layer by a continuous in-situ polymerization process; finally, an intelligent-responsive double-layer hydrogel is obtained. The double-layer hydrogel prepared in the present invention is an antibacterial double-layer hydrogel with a diagnosis and treatment integrated function that can withstand dynamic mechanical movement and peel off as needed. In one of the embodiments, the double-layer hydrogel prepared in the present invention can rapidly heat up to about 55 °C under the condition of irradiation with a near-infrared laser at a wavelength of 808 nm and a power density of 195 mW / cm 2 for 6 min, achieving a sterilization efficiency of 99% against Gram-positive bacterium Staphylococcus aureus; moreover, it can undergo a thermal shrinkage phase change while the sterilization is completed, forming a water film between the double-layer hydrogel and the skin, and at the same time, the bonding strength with the skin rapidly decreases, completing a painless peel-off; it can also detect the infection degree of the wound with high sensitivity in Gram-positive bacterium Staphylococcus aureus with a concentration of 10 3 -10 7 CFU / mL.

[0048] (2) The double-layer hydrogel prepared by the present invention has a unique double-layer structure. Due to the porous network structure of the tough hydrogel layer, the viscous layer precursor solution can penetrate the shallowest layer of the tough hydrogel layer to form an interlocked network structure. At the same time, HA-DA in the viscous layer precursor solution also forms a large number of hydrogen bonds with CMC in the tough hydrogel layer, and strong interactions are formed between the two layers. Moreover, due to the differences in the composition and polymerization conditions of the two layers of polymers, different physical and chemical interactions in the polymer matrix endow each layer of hydrogel with different properties, which can simultaneously meet excellent mechanical properties and adhesion properties. Among them, the tight hydrogen bonds formed between carboxymethyl chitosan and polyacrylamide in the tough hydrogel layer ensure the excellent mechanical properties of the composite hydrogel dressing, so that the wound can be prevented from being damaged by external forces; the catechol groups of the modified hyaluronic acid in the viscous hydrogel layer have rich hydrogen bonds and van der Waals forces with various surfaces, and form imine bonds with amino or thiol groups in the skin, etc., which significantly improves the adhesion properties of the viscous hydrogel layer.

[0049] (3) The double-layer hydrogel prepared by the present invention also has a dual temperature and enzyme response function, which can not only detect the bacterial concentration, but also complete the skin surface sterilization effect, realizing the integration of detection, sterilization and antibacterial treatment of traumatic infections. Among them, the ratio of N-isopropylacrylamide to acrylamide in the viscous gel layer effectively regulates the phase transition temperature of the double-layer hydrogel; poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) not only realizes the photothermal conversion effect of the double-layer hydrogel, but also makes it possible to detect the bacterial concentration through the change in conductivity after being compounded with the modified hyaluronic acid. Therefore, the double-layer hydrogel of the present invention can not only be significantly heated under infrared light irradiation, and the temperature can reach about 55 °C, which can quickly kill the bacteria at the wound site without causing the formation of drug-resistant bacteria and avoid wound suppuration; and it has temperature sensitivity. When killing bacteria at high temperature, the adhesion of the dressing changes, realizing the on-demand removal of the dressing, avoiding secondary damage and wound tearing, and can be applied to sports wounds; it can also change significantly in conductivity when Gram-positive bacteria infection occurs, and then can quickly detect wound bacterial infection, monitor the bacterial concentration of joint wounds, and detect the degree of wound infection.

[0050] (4) The intelligent-responsive double-layer hydrogel prepared by the skin-inspired hierarchical structure of the present invention has a promising future in the rapid development of intelligent materials. By utilizing its double-layer structure, various functions required for intelligent antibacterial dressings and biosensors can be achieved. Photothermal sterilization promotes wound healing; excellent adhesion and mechanical properties such as high viscosity and high stretchability can be applied to sports wounds and protect the wound from secondary damage by sharp objects; it can quickly detect Gram-positive bacterial infections, realizing the integrated diagnosis and treatment function of real-time monitoring of bacterial growth and rapid sterilization, and is also simpler and faster than traditional bacterial detection techniques. It has great potential in both antibacterial dressings and biosensors and has important clinical significance.

[0051] Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. Brief Description of the Drawings

[0052] Figure 1 It is a bar chart of the statistical results of the adhesion performance of HA-DA samples with different contents prepared in Examples 8-11 and Comparative Example 2 of the present invention;

[0053] Figure 2 It is a statistical chart of the results of the change of the photothermal performance with time of PEDOT:PSS samples with different contents prepared in Examples 8, 12, 13 and Comparative Example 3 of the present invention;

[0054] Figure 3 It is a bar chart of the results of the change of the adhesion performance of the sample prepared in Example 8 of the present invention before and after near-infrared irradiation on different substrates;

[0055] Figure 4 It is a bar chart of the statistical results of the conductivity of PEDOT:PSS samples with different contents prepared in Examples 8, 12, 13 and Comparative Example 3 of the present invention;

[0056] Figure 5 It is a bar chart of the statistical results of the conductivity of the sample prepared in Example 8 of the present invention under different Staphylococcus aureus contents;

[0057] Figure 6 It is a comparison chart of the bactericidal experiments of the samples prepared in Example 8 and Comparative Example 3 of the present invention against Staphylococcus aureus; in the figure, a and b are the samples prepared in Example 8, and c and d are the samples prepared in Comparative Example 3. Detailed Description of the Invention

[0058] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the following further elaborates on the present invention through examples in conjunction with the accompanying drawings. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0060] The mechanical properties of the tough hydrogel layer of the present invention were measured under a 50 N load sensor by an electronic universal testing machine (UTM2520) in the tensile mode. Specifically: The hydrogel was prepared into a spline with dimensions of 20 mm × 10 mm × 1 mm, and the effective distance between the clamps was measured with a vernier caliper and recorded; a uniaxial tensile test was carried out using the electronic universal testing machine at a tensile rate of 50 mm / min. Three parallel samples were tested in each group, and the stress-strain curve was obtained by calculating the tensile stress and tensile strain. The calculation formula for the tensile stress (σ) is:

[0061]

[0062] where F is the loading force during the tensile process, and A is the cross-sectional area of the sample.

[0063] The calculation formula for the tensile strain (ε) is:

[0064]

[0065] where l 0 is the length of the initial sample, l is the length of the sample after stretching.

[0066] The phase transition temperature of the sticky hydrogel layer of the present invention was tested by DSC using a differential scanning calorimeter DSC-60 Plus (Shimadzu Corporation, Japan). Specifically: 3 - 5 mg of the sample was placed in a crucible, equilibrated at a temperature of 25 °C for 2 min, heated to 65 °C at a rate of 2 °C / min, and then cooled back to 25 °C at the same rate, and the heat flow changes during the cooling and heating processes were recorded.

[0067] The adhesion performance of the intelligent responsive double-layer hydrogel of the present invention was tested by an electronic universal tensile testing machine. Specifically: At room temperature, the sample was placed between two substrates (pig skin), and the two substrates were stretched and separated by the universal tensile testing machine. The stretching speed was controlled at 20 mm / min, and the ratio of the maximum tensile force (N) obtained to the contact area (m 2 ) is the bonding strength.

[0068] The photothermal properties of the intelligent response double-layer hydrogel of the present invention were tested by an infrared thermal imager. Specifically: The sample was prepared into a disc with a diameter of 20 mm and a thickness of 3 mm; it was irradiated under a near-infrared lamp with a wavelength of 808 nm and a power density of 195 mW / cm 2 for 8 min; the infrared thermal imager was used to record the thermal imaging diagram and the corresponding temperature distribution of the hydrogel. During the test, the bottom of the hydrogel dressing was immersed in 100 μL of phosphate buffer solution (PBS) to simulate the human body environment.

[0069] The conductivity of the intelligent response double-layer hydrogel of the present invention was tested by measuring the resistance with a digital source meter. Specifically: The sample was cut into a circle with a diameter of 20 mm and a thickness of 3 mm, and the resistance was measured by a digital source meter, and the conductivity was calculated. The conductivity calculation formula of the sample is:

[0070] .

[0071] (1) Exploring the influence of different carboxymethyl chitosan contents on the mechanical properties of the tough hydrogel layer

[0072] In order to explore the influence of different contents of carboxymethyl chitosan on the mechanical properties of the tough hydrogel layer, the following experiments were carried out respectively, namely Example 1, Example 2, Example 3, and Comparative Example 1. The mass fractions of carboxymethyl chitosan in the tough layer precursor solution were: 1.5%, 1.0%, 0.5%, and 0%, respectively. Then the mechanical properties of the obtained tough hydrogel layer were tested. The results are shown in Table 1.

[0073] Example 1

[0074] This example provides a tough hydrogel layer, and its preparation method includes the following steps:

[0075] (1) Add the surface activator sodium dodecyl sulfate (SDS) and potassium chloride (KCl) to deionized water, and ultrasonically treat for 30 min at 50 °C to obtain a worm-like micelle solution. Among them, the mass fractions of SDS and KCl in the worm-like micelle solution are both 2 wt%.

[0076] (2) Add 1.2 g of acrylamide powder (AM), 0.024 g of stearyl methacrylate (SMA), 0.09 g of carboxymethyl chitosan (CMC), and 0.024 g of initiator ammonium persulfate (APS) to the above solution, and stir evenly to obtain a tough layer precursor solution. In the tough layer precursor solution, the mass fraction of AM is 20%, the mass fraction of SMA is 0.4%, the mass fraction of carboxymethyl chitosan is 1.5%, and the mass fraction of initiator APS is 0.4%.

[0077] (3) Transfer the precursor solution of the tough layer to a polytetrafluoroethylene mold and place it in a vacuum drying oven at 50 °C for 4 h to obtain 5.8 g of the tough hydrogel layer.

[0078] Example 2

[0079] The content of a tough hydrogel layer is basically the same as that of Example 1, except that: in step (2), the addition amount of the carboxymethyl chitosan is 0.06 g, and the mass fraction of the carboxymethyl chitosan in the precursor solution of the tough layer is 1.0%.

[0080] Example 3

[0081] The content of a tough hydrogel layer is basically the same as that of Example 1, except that: in step (2), the addition amount of the carboxymethyl chitosan is 0.03 g, and the mass fraction of the carboxymethyl chitosan in the precursor solution of the tough layer is 0.5%.

[0082] Comparative Example 1

[0083] The content of a tough hydrogel layer is basically the same as that of Example 1, except that: in step (2), the addition amount of the carboxymethyl chitosan is 0 g, and the mass fraction of the carboxymethyl chitosan in the precursor solution of the tough layer is 0%.

[0084] Table 1 Influence of different contents of carboxymethyl chitosan on the mechanical properties of the tough hydrogel layer

[0085]

[0086] As can be seen from Table 1, the sample prepared in Comparative Example 1 without adding carboxymethyl chitosan has lower breaking strength and elongation at break. Comparing it with Comparative Examples 1-3, it can be seen that as the content of carboxymethyl chitosan increases, the breaking strength and elongation at break of the sample increase. This is because a tight hydrogen bond is formed between carboxymethyl chitosan and polyacrylamide, thereby significantly increasing the mechanical properties of the hydrogel. It can be seen that the sample prepared in Example 2 has the most suitable mechanical properties, with a breaking strength of 256.05 kPa, an elongation at break of 1966.95%, and a toughness of 2.66 MJ / m 3 . Compared with the sample prepared in Example 2, the increase in the breaking strength of the sample prepared in Example 1 is not obvious, and the elongation at break is 1723.10%, which is lower than that of the sample in Example 2. This may be because the increase in carboxymethyl chitosan leads to its aggregation in the hydrogel network, resulting in a decrease in the mechanical properties of the tough hydrogel layer. In summary, the tough hydrogel layer prepared by the present invention can ensure excellent mechanical properties of the hydrogel dressing, making it applicable to sports wounds.

[0087] (2) Explore the influence of different mass ratios of N-isopropylacrylamide and acrylamide on the phase transition temperature of the viscous hydrogel layer

[0088] To explore the influence of different mass ratios of N-isopropylacrylamide and acrylamide on the phase transition temperature of the viscous hydrogel layer, the following experiments were conducted respectively, namely Example 4, Example 5, Example 6, and Example 7. The corresponding mass ratios of N-isopropylacrylamide and acrylamide are: 10∶3, 10∶2, 10∶1, 10∶0. Then, the phase transition temperature of the obtained viscous hydrogel layer was tested. The results are shown in Table 2.

[0089] Example 4

[0090] This example provides a viscous hydrogel layer, and its preparation method includes the following steps:

[0091] (1) Prepare modified hyaluronic acid HA-DA: First, add 1 g of hyaluronic acid powder (HA) to 100 mL of deionized water, and stir to obtain a uniform hyaluronic acid solution under the conditions of a nitrogen atmosphere and 25 °C. Then, slowly add 575 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC-HCl) and 345 mg of N-hydroxysuccinimide (NHS) to the hyaluronic acid solution, stir for 20 min to obtain a mixed solution. Then, add 569 mg of dopamine hydrochloride to the mixed solution, and adjust the pH with 0.1 N HCl and NaOH to keep the pH between 5 and 6, and react in an ice-water bath environment for 12 h. Immerse in sufficient deionized water, stir and dialyze for 3 days, and freeze-dry the dialyzed product to obtain HA-DA.

[0092] (2) Uniformly disperse PEDOT:PSS solid particles in 3 mL of deionized water to obtain a PEDOT:PSS solution with a mass fraction of 0.4%.

[0093] (3) Dissolve hyaluronic acid grafted with dopamine (HA-DA) in the above PEDOT:PSS solution to obtain a mixed solution a; the mass fraction of HA-DA in the mixed solution a is 0.6%.

[0094] (4) Under a nitrogen atmosphere, N-isopropylacrylamide (NIPAM) and acrylamide (AM) with a mass ratio of 10:3 were added to the mixed solution a, and then stirred at 0 °C in an ice-water bath and 400 rpm until completely dissolved to obtain a mixed solution b; the initiator ammonium persulfate (APS), the crosslinking agent N,N'-methylenebisacrylamide, and TEMED were added to the mixed solution b to obtain a viscous layer precursor solution. Among them, the mass fraction of N-isopropylacrylamide in the viscous layer precursor solution was 20%, the mass fraction of ammonium sulfate (APS) in the viscous layer precursor solution was 1%, the mass fraction of N,N'-methylenebisacrylamide in the viscous layer precursor solution was 0.04%, and the mass fraction of tetramethylethylenediamine in the viscous layer precursor solution was 0.3%.

[0095] (5) The viscous layer precursor solution added with TEMED was quickly transferred to a mold and reacted at 5 °C for 12 h to obtain 3.6 g of a viscous hydrogel layer.

[0096] Example 5

[0097] The content of a viscous hydrogel layer is basically the same as that of Example 4, and the difference lies in that: in step (4), while keeping the total mass of the N-isopropylacrylamide and acrylamide unchanged, the mass ratio of the N-isopropylacrylamide and acrylamide was adjusted to 10:2.

[0098] Example 6

[0099] The content of a viscous hydrogel layer is basically the same as that of Example 4, and the difference lies in that: in step (4), while keeping the total mass of the N-isopropylacrylamide and acrylamide unchanged, the mass ratio of the N-isopropylacrylamide and acrylamide was adjusted to 10:1.

[0100] Example 7

[0101] The content of a viscous hydrogel layer is basically the same as that of Example 4, and the difference lies in that: in step (4), while keeping the total mass of the N-isopropylacrylamide and acrylamide unchanged, the mass ratio of the N-isopropylacrylamide and acrylamide was adjusted to 10:0.

[0102] Table 2 Influence of different mass ratios of NIPAM to AM on the phase transition temperature of the viscous hydrogel layer

[0103]

[0104] First, in the DSC analysis, endothermic peaks were observed for all samples containing poly-NIPAM, indicating that volume phase transitions occurred in the above samples.

[0105] Secondly, as can be seen from Table 2, as the concentration of hydrophilic AM monomer in the hydrogel increases, the transition temperature also increases. For example, the sample prepared in Example 7 undergoes a volume phase transition at 32.1 °C, while the volume phase transition temperature of the sample prepared in Example 4 is higher, reaching 57.1 °C. This is because the higher the AM content, the relatively lower the NIPAM content, the stronger the hydrophilic hydration, and the weaker the hydrophobic hydration. After the viscous hydrogel layer prepared in the present invention reaches the volume phase transition temperature, the volume of the hydrogel shrinks, changing from the swollen hydrated state (hydrophilic state) to the shrunk dehydrated state (hydrophobic state), and the adhesion performance is significantly reduced. Therefore, the viscous layer with a higher phase transition temperature can meet the need for on-demand removal of the dressing after killing bacteria at high temperature, while avoiding secondary damage caused by dressing replacement.

[0106] (III) Exploring the influence of different contents of HA-DA on the adhesion performance of the double-layer hydrogel

[0107] In order to explore the influence of different contents of HA-DA on the adhesion performance of the double-layer hydrogel, the following experiments were respectively carried out, namely Example 8, Example 9, Example 10, Example 11 and Comparative Example 2. The mass fractions of HA-DA in the mixed solution a were: 0.6%, 0.8%, 0.4%, 0.2%, 0%. Then the adhesion performance of the obtained double-layer hydrogel was tested. The results are as Figure 1 shown.

[0108] Example 8

[0109] This example provides an intelligent-responsive double-layer hydrogel, and its preparation method includes the following steps:

[0110] (1) Preparing a tough hydrogel layer:

[0111] i) Add the surfactant sodium dodecyl sulfate (SDS) and potassium chloride (KCl) to ionized water, and ultrasonicate for 30 min at 50 °C to obtain a worm-like micelle solution. Among them, the mass fractions of SDS and KCl in the worm-like micelle solution are both 2 wt%.

[0112] ii) Add 1.2 g of acrylamide powder (AM), 0.024 g of stearyl methacrylate (SMA), 0.06 g of carboxymethyl chitosan (CMC), and 0.024 g of initiator ammonium persulfate (APS) to the above solution, and stir evenly to obtain a precursor solution for the tough layer. In the precursor solution for the tough layer, the mass fraction of AM is 20%, the mass fraction of SMA is 0.4%, the mass fraction of carboxymethyl chitosan is 1%, and the mass fraction of initiator APS is 0.4%

[0113] iii) Transfer the precursor solution for the tough layer to a polytetrafluoroethylene mold, and place it in a vacuum drying oven at 55 °C for 3 h to obtain the tough hydrogel layer.

[0114] (2) Preparation of the viscous layer precursor solution:

[0115] 1) Preparation of modified hyaluronic acid HA-DA: First, add 1 g of hyaluronic acid powder (HA) to 100 mL of deionized water, and stir to obtain a uniform hyaluronic acid solution under a nitrogen atmosphere at 25 °C. Then, slowly add 575 mg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC-HCl) and 345 mg of N-hydroxysuccinimide (NHS) to the hyaluronic acid solution, and stir for 20 min to obtain a mixed solution. Next, add 569 mg of dopamine hydrochloride to the mixed solution, and adjust the pH with 0.1 N HCl and NaOH to keep the pH between 5 and 6, and react in an ice-water bath environment for 12 h. Immerse in sufficient deionized water, stir and dialyze for 3 days, and freeze-dry the dialyzed product to obtain HA-DA.

[0116] 2) Uniformly disperse PEDOT:PSS solid particles in 3 mL of deionized water to obtain a 0.4% PEDOT:PSS solution by mass fraction.

[0117] 3) Dissolve hyaluronic acid grafted dopamine (HA-DA) in the above PEDOT:PSS solution to obtain a mixed solution a; the mass fraction of HA-DA in the mixed solution a is 0.6%.

[0118] 4) Under a nitrogen atmosphere, add N-isopropylacrylamide (NIPAM) and acrylamide (AM) with a mass ratio of 10:3 to the mixed solution a, and then stir at 0 °C in an ice-water bath and 400 rpm until completely dissolved to obtain a mixed solution b; add the initiator ammonium persulfate (APS), crosslinker N,N'-methylenebis(acrylamide), and TEMED to the mixed solution b to obtain the viscous layer precursor solution. Among them, the mass fraction of N-isopropylacrylamide in the viscous layer precursor solution is 20%, the mass fraction of ammonium persulfate (APS) in the viscous layer precursor solution is 1%, the mass fraction of N,N'-methylenebis(acrylamide) in the viscous layer precursor solution is 0.04%, and the mass fraction of tetramethylethylenediamine in the viscous layer precursor solution is 0.3%.

[0119] (3) Preparation of the intelligent-responsive double-layer hydrogel: Quickly transfer the viscous layer precursor solution added with TEMED to the mold with the tough hydrogel layer prepared in step (1), and react at 5 °C for 12 h to in-situ polymerize to obtain 9.4 g of the intelligent-responsive double-layer hydrogel.

[0120] Example 9

[0121] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that: in step 3) of preparing the viscous layer precursor solution, the mass fraction of HA-DA in mixture a is 0.8 wt%.

[0122] Example 10

[0123] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that: in step 3) of preparing the viscous layer precursor solution, the mass fraction of HA-DA in mixture a is 0.4 wt%.

[0124] Example 11

[0125] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that: in step 3) of preparing the viscous layer precursor solution, the mass fraction of HA-DA in mixture a is 0.2 wt%.

[0126] Comparative Example 2

[0127] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that: in step 3) of preparing the viscous layer precursor solution, the mass fraction of HA-DA in mixture a is 0 wt%.

[0128] From Figure 1 It can be seen that hydrogel samples with different HA-DA contents have different bonding strengths to pigskin. With the increase of the HA-DA content, the bonding strength of the hydrogel to pigskin gradually increases. Among them, the bonding strength of the hydrogel with a HA-DA concentration of 0.6 wt% to pigskin reaches 22.37 kPa. This is because HA-DA in the hydrogel is the main factor affecting the adhesion performance. There are abundant hydrogen bonds and van der Waals forces between the catechol groups in HA-DA and various surfaces, and imines are formed with amino or thiol groups in the skin, which significantly improves the adhesion performance of the hydrogel. Therefore, by fixing the other monomer ratios of the viscous hydrogel layer and adjusting the content of HA-DA, the adhesion of the hydrogel can be improved. However, due to excessive adhesion, it will cause damage to the skin wound, and due to the decrease in the initiator activity caused by the increase of HA-DA, it is difficult to polymerize to form a hydrogel. When the HA-DA concentration increases to 0.8 wt%, the adhesion strength does not increase significantly, but it significantly affects the polymerization of the hydrogel. Therefore, it is more appropriate to choose a hydrogel with a HA-DA concentration of 0.6 wt%, which can not only obtain good adhesion performance, avoid damaging the skin wound, but also will not hinder the formation of the hydrogel.

[0129] (4) Explore the influence of different contents of PEDOT:PSS on the photothermal performance of the double-layer hydrogel

[0130] To investigate the effect of different contents of PEDOT:PSS on the photothermal properties of the double-layer hydrogel, the following experiments were conducted, namely Example 8, Example 12, Example 13, and Comparative Example 3. The mass fractions of PEDOT:PSS in the PEDOT:PSS solution were 0.4%, 0.6%, 0.2%, and 0%, respectively. Then, the photothermal properties of the obtained double-layer hydrogel were tested. The results are as Figure 2 shown.

[0131] Example 12

[0132] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that in step 2) of preparing the viscous layer precursor solution, the mass fraction of PEDOT:PSS in the PEDOT:PSS solution is 0.6 wt%.

[0133] Example 13

[0134] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that in step 2) of preparing the viscous layer precursor solution, the mass fraction of PEDOT:PSS in the PEDOT:PSS solution is 0.2 wt%.

[0135] Comparative Example 3

[0136] The content of an intelligent-responsive double-layer hydrogel is basically the same as that of Example 8, except that in step 2) of preparing the viscous layer precursor solution, the mass fraction of PEDOT:PSS in the PEDOT:PSS solution is 0 wt%.

[0137] It can be Figure 2 seen that for the samples prepared in Example 8, 12, and 13 with the addition of the photothermal material PEDOT:PSS, under 808 nm light irradiation, the temperature can rise rapidly after 2 min; while for the sample prepared in Comparative Example 3 without the addition of PEDOT:PSS, the temperature remains basically unchanged after light irradiation, and even after 8 min, the temperature is only 28 °C. This is because PEDOT:PSS, as a photothermal agent, can effectively convert light into heat, thus being used to construct a photothermal sterilization hydrogel. Moreover, with the increase in the content of PEDOT:PSS, the heating rate of the sample is faster and the temperature is higher, endowing the double-layer hydrogel dressing with excellent photothermal conversion ability. Among them, the temperatures of the samples prepared in Example 8 and 12 can reach above 55 °C after 6 min, and this temperature can kill bacteria, but too high a temperature will cause damage to skin wounds. Therefore, the sample prepared in Example 8 is preferably selected.

[0138] Furthermore, to verify the effect of near-infrared light irradiation on the bonding strength of the double-layer hydrogel, the following experiment was also conducted: at a wavelength of 808 nm and a power density of 195 mW / cm2 Before illumination under near-infrared light and 6 min after illumination, the samples prepared in Example 8 were placed on different substrates (skin, rubber, glass), and the two substrates were stretched and separated using a universal tensile testing machine, and the bonding strength was recorded. The results are as Figure 3 shown.

[0139] As Figure 3 can be seen, before NIR illumination, the samples prepared in Example 8 had high bonding strengths with skin, rubber, and glass. Among them, the bonding strength with skin reached 23.3 KPa, indicating that this double-layer hydrogel adhesive dressing can bond to the skin and be applied to sports wounds without falling off. However, after NIR illumination, the bonding strength between the sample and the skin decreased rapidly, and at this time, the double-layer hydrogel adhesive dressing could be very easily separated from the skin. This is because the temperature of the hydrogel containing the photothermal material PEDOT:PSS increased after illumination, reaching the volume phase transition temperature. The hydrogel dehydrated and shrank in volume, resulting in a smaller contact area with the skin, and a water film was formed between the hydrogel dressing and the skin, causing the bonding strength between the sample and the skin to decrease rapidly. Moreover, before and after NIR illumination, the tough hydrogel layer and the sticky hydrogel layer in the double-layer hydrogel did not separate. This is because the tough hydrogel layer has a porous network structure, and the precursor solution of the sticky layer can penetrate the shallowest layer of the tough hydrogel layer and polymerize to form an interlocked network structure. At the same time, HA-DA in the precursor solution of the sticky layer can also form a large number of hydrogen bonds with CMC in the tough hydrogel layer, forming a strong interaction between the two layers. Therefore, after killing bacteria by photothermal effect, the hydrogel dressing can be removed as needed as a whole without causing secondary damage to the wound surface.

[0140] (V) Exploring the effect of different contents of PEDOT:PSS on the conductivity of the double-layer hydrogel

[0141] To explore the effect of different contents of PEDOT:PSS on the conductivity of the double-layer hydrogel, the following experiments were conducted, namely Example 8, Example 12, Example 13, and Comparative Example 3 above. The mass fractions of PEDOT:PSS in the PEDOT:PSS solution were 0.4%, 0.6%, 0.2%, and 0%, respectively. Then, the conductivity of the obtained double-layer hydrogel was tested. The results are as Figure 4 shown.

[0142] PEDOT:PSS is a polymer with high conductivity, and the conductive material PEDOT:PSS in the hydrogel sample determines the conductivity of the sample. From Figure 4It can be seen that the conductivity of samples with different PEDOT:PSS contents is different. As the content of PEDOT:PSS increases, the conductivity of the samples also increases. The sample prepared in Comparative Example 3 has a low conductivity of 0.072 mS / cm because it does not contain PEDOT:PSS. However, good conductivity is crucial for its bacterial detection performance. The sample prepared in Example 8 has excellent conductivity, reaching 0.506 mS / cm. Considering the photothermal properties of the hydrogel, the sample prepared in Example 8 with a PEDOT:PSS concentration of 0.4 wt% is selected, which not only ensures good photothermal properties but also has excellent conductive properties to ensure sensitive detection of bacteria.

[0143] Furthermore, to explore the influence of different bacterial contents on the bacterial detection function of the double-layer hydrogel, the following experiment was conducted: The sample prepared in Example 8 was cut into a circular shape with a diameter of 20 mm and a thickness of 3 mm, and co-cultured with a 10 3 CFU / mL Staphylococcus aureus suspension. The resistance was measured by a digital source meter at 0 h, 0.5 h, 1 h, 2 h, 4 h, and 6 h respectively, and the conductivity was calculated. The results are as Figure 5 shown.

[0144] It can be Figure 5 seen that as the co-culture time of the double-layer hydrogel sample of the present invention with the bacterial suspension increases, the conductivity gradually increases significantly. For example, when not co-cultured with bacteria, the initial conductivity of the hydrogel is 0.506 mS / cm. After 30 min of culture, the conductivity is 0.698 mS / cm, indicating that it has a high sensitivity to Staphylococcus aureus. This is because as Staphylococcus aureus multiplies, more hyaluronidase is produced, which in turn degrades the hyaluronic acid network in the hydrogel to a certain extent, causing the hydrogel to change partially from the gel state to the sol state, promoting the movement of electrons in PEDOT:PSS, and significantly reducing the resistance, thus realizing the specific detection of Staphylococcus aureus. In addition, when the hydrogel sample is also co-cultured with a 10 4 -10 7 CFU / mL Staphylococcus aureus suspension, the same trend appears after 30 min, and the conductivity decreases significantly. According to the above results, the double-layer hydrogel of the present invention can detect bacteria after being cultured at a concentration as low as 10 3 CFU / mL for 30 min, indicating its great potential in detecting the degree of wound infection.

[0145] Furthermore, to explore the influence of near-infrared light irradiation on the bactericidal performance of the double-layer hydrogel, the following experiment was also conducted: Step ① Immerse the samples prepared in Example 8 and Comparative Example 3 into 10 7Co-cultured with Staphylococcus aureus suspension at a concentration of CFU / mL for 2 h; Step ② Then irradiate the sample with a near-infrared laser with a wavelength of 808 nm and a power density of 195 mW / cm 2 for 6 min; Step ③ Then add sterile ultrapure water to the sample and ultrasonicate for 2 min. Collect the adhered bacteria on the hydrogel to obtain a bacterial suspension. Dilute it with PBS solution and spread it on a solid medium. Place it in a constant temperature incubator at 37 °C and culture for 24 h. Record the number of colonies C formed; Step ④ At the same time, the sample after co-culture was not irradiated with near-infrared laser, and the total number of colonies B was obtained directly under dark conditions by using the treatment process of Step ③; Step ⑤ Finally, calculate the sterilization efficiency through the formula R = (B - C) / B × 100%. Use the sample prepared in Comparative Example 3 as a positive control, perform the same treatment as above, obtain the total number of colonies, and calculate the sterilization efficiency. In this study, Staphylococcus aureus was used as a model bacterium. The results are as Figure 6 shown in and Table 3.

[0146] Table 3 Effect of Near-Infrared Light Irradiation on the Sterilization Efficiency of Double-Layer Hydrogel

[0147]

[0148] It can be seen from Figure 6 that there are a large number of Staphylococcus aureus colonies on the samples of Example 8 + Dark, Comparative Example 3 + Dark, and Comparative Example 3 + NIR, while there are no bacterial colonies on the sample of Example 8 + NIR. This shows that the sample of Example 8 has good bactericidal performance under near-infrared light irradiation. As can be seen from Table 3, the sample of Comparative Example 3 has no bactericidal activity. After the sample of Example 8 is irradiated with near-infrared light, its photothermal antibacterial activity is significantly improved. After irradiation for 6 min, it is sterile, and the killing rate of Staphylococcus aureus can reach more than 99%.

[0149] In summary, the present invention effectively overcomes the deficiencies in the prior art and has high industrial utilization value. The role of the above embodiments is to illustrate the substantial content of the present invention, but does not limit the protection scope of the present invention. Those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and protection scope of the technical solutions of the present invention.

Claims

1. A double-layer hydrogel with intelligent response, characterized in that, it includes a tough hydrogel layer and a sticky hydrogel layer which are stacked; the tough hydrogel layer and the sticky hydrogel layer are connected by an interlocking network structure and hydrogen bonds; both the tough hydrogel layer and the sticky hydrogel layer are vinyl polymer-based hydrogels; wherein, the tough hydrogel layer contains carboxymethyl chitosan; the sticky hydrogel layer contains modified hyaluronic acid; the tough hydrogel layer is mainly copolymerized from vinyl hydrophilic monomers and vinyl hydrophobic monomers; the modified hyaluronic acid is obtained by grafting dopamine onto hyaluronic acid; the sticky hydrogel layer also contains a heat-shrinking thermosensitive material; the mass fraction of carboxymethyl chitosan in the tough hydrogel layer is 0.1% - 4%; the vinyl hydrophilic monomer in the tough hydrogel layer is at least one of acrylamide, N-hydroxymethylacrylamide, acrylic acid or methacrylic acid; the mass fraction of the vinyl hydrophilic monomer in the tough hydrogel layer is 15% - 35%; the vinyl hydrophobic monomer is at least one of octadecyl methacrylate, cetyl methacrylate or dodecyl acrylate; the mass fraction of the vinyl hydrophobic monomer in the tough hydrogel layer is 0.15% - 0.8%; the mass fraction of the modified hyaluronic acid in the sticky hydrogel layer is 0.2% - 1.2%; the sticky hydrogel layer also contains a photothermal material; the photothermal material is poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid); the heat-shrinking thermosensitive material is a vinyl thermosensitive monomer; the sticky hydrogel layer is mainly copolymerized from a vinyl thermosensitive monomer, a vinyl hydrophilic monomer and a vinyl crosslinking monomer.

2. The double-layer hydrogel with intelligent response according to claim 1, characterized in that, the grafting rate of the modified hyaluronic acid is 10% - 40%; the mass fraction of the photothermal material in the sticky hydrogel layer is 0.2% - 1.6%; the vinyl thermosensitive monomer is at least one of N-isopropylacrylamide, N-ethylacrylamide, N,N-diethylacrylamide or N-n-propylacrylamide; the vinyl hydrophilic monomer in the sticky hydrogel layer is at least one of acrylamide, acrylic acid, N-hydroxymethylacrylamide or methacrylic acid; the mass ratio of the vinyl thermosensitive monomer to the vinyl hydrophilic monomer in the sticky hydrogel layer is 10∶(1 - 5); the mass fraction of the vinyl thermosensitive monomer in the sticky hydrogel layer is 10% - 30%; the vinyl crosslinking monomer is at least one of N,N'-methylenebis(acrylamide), di(ethylene glycol) diacrylate or 1,4-butanediol diacrylate; the mass fraction of the vinyl crosslinking monomer in the sticky hydrogel layer is 0.02% - 0.08%.

3. A preparation method of the double-layer hydrogel with intelligent response according to claim 1 or 2, characterized in that, it includes the following steps: (1) Preparation of a tough hydrogel layer: A vinyl hydrophilic monomer, a vinyl hydrophobic monomer, carboxymethyl chitosan, and an initiator are added to a worm-like micelle solution and stirred evenly to obtain a precursor solution for the tough layer; The precursor solution for the tough layer is added to a reactor and reacted at 40-60 °C to obtain a tough hydrogel layer; (2) Preparation of a viscous layer precursor solution: First, modified hyaluronic acid is added to a photothermal material dispersion to obtain mixture a; Under an inert gas atmosphere, a vinyl thermosensitive monomer and a vinyl hydrophilic monomer are added to mixture a and stirred evenly to obtain mixture b; A vinyl crosslinking monomer, an initiator, and a catalyst are added to mixture b to obtain a viscous layer precursor solution; (3) Preparation of a double-layer hydrogel: The viscous layer precursor solution is poured onto the upper part of the tough hydrogel layer and reacted at 2-10 °C to obtain a double-layer hydrogel.

4. The preparation method according to claim 3, characterized in that, in step (1), the mass fraction of the carboxymethyl chitosan in the precursor solution for the tough layer is 0.1%-3%; In step (2), the modified hyaluronic acid is grafted and modified by dopamine; The mass fraction of the modified hyaluronic acid in the viscous layer precursor solution is 0.2%-1%; The photothermal material dispersion is prepared by uniformly dispersing a photothermal material in water; The photothermal material is poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid); The mass fraction of the photothermal material in the viscous layer precursor solution is 0.2%-1.5%; The vinyl thermosensitive monomer is at least one of N-isopropylacrylamide, N-ethylacrylamide, N,N-diethylacrylamide, or N-n-propylacrylamide; In step (2), the vinyl hydrophilic monomer is at least one of acrylamide, N-hydroxymethylacrylamide, acrylic acid, or methacrylic acid; In step (2), the mass ratio of the vinyl thermosensitive monomer to the vinyl hydrophilic monomer is 10∶(1-5).

5. The preparation method according to claim 4, characterized in that, in step (1), the vinyl hydrophilic monomer is at least one of acrylamide, N-hydroxymethylacrylamide, acrylic acid, or methacrylic acid; The vinyl hydrophobic monomer is at least one of octadecyl methacrylate, cetyl methacrylate, or dodecyl acrylate; In step (1), the mass ratio of the vinyl hydrophobic monomer to the vinyl hydrophilic monomer is (0.01-0.05)∶1; The mass fraction of the vinyl hydrophilic monomer in the precursor solution for the tough layer is 15%-30%; In step (2), the mass fraction of the vinyl thermosensitive monomer in the viscous layer precursor solution is 10%-25%; The grafting rate of the modified hyaluronic acid is 10%-40%; The vinyl crosslinking monomer is at least one of N,N'-methylenebis(acrylamide), di(ethylene glycol) diacrylate, or 1,4-butanediol diacrylate; The mass fraction of the vinyl crosslinking monomer in the viscous layer precursor solution is 0.02%-0.05%.

6. The preparation method according to claim 5, characterized in that, The worm-like micelle solution is formed by mixing a surfactant and a strong electrolyte salt solution; the strong electrolyte salt solution is an aqueous solution of a strong electrolyte salt; the mass ratio of the surfactant to the strong electrolyte salt is (0.8-2):1; the mass fraction of the strong electrolyte salt in the strong electrolyte salt solution is 1%-3%; the initiator is at least one of ammonium persulfate, potassium persulfate or sodium persulfate; the catalyst is tetramethylethylenediamine.

7. Application of the intelligent response double-layer hydrogel according to claim 1 or 2 in medical materials.

8. Application of the intelligent response double-layer hydrogel according to claim 1 or 2 in biosensor materials.

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