A hydrogel microneedle with biocompatibility and mechanical strength, a preparation method and application thereof

Abstract

The application relates to a hydrogel microneedle with biocompatibility and mechanical strength, a preparation method thereof and application, and belongs to the technical field of biomaterials.The hydrogel microneedle comprises Gel and Ser, and the mass ratio is 1:1.The molecular weight of the Gel / Ser hydrogel microneedle is 300000 Da.The method is that Gel and Ser are in-situ synthesized into Gel / Ser pure natural supermolecular soluble hydrogel microneedles under hydrogen bond interaction.The pure natural hydrogel microneedle with biocompatibility and mechanical strength can be used as a drug carrier to load growth factors (GDFx), promote the proliferation, migration and endothelial tube formation of fibroblasts, and further promote the healing of wounds.The pure natural hydrogel microneedle with biocompatibility and mechanical strength prepared by the application is a supermolecular hydrogel formed through intermolecular hydrogen bond interaction, and the reaction condition is easy to obtain and simple to operate.

Description

Technical Field

[0001] This invention belongs to the field of biomaterials technology, specifically relating to a hydrogel microneedle that combines biocompatibility and mechanical strength, its preparation method, and its application. Background Technology

[0002] Wounds, especially chronic wounds, are characterized by slow healing, excessive inflammation, and bacterial infection, posing a significant public health problem and imposing a substantial social and economic burden. Clinical treatment typically involves debridement and topical medication; however, the thickened stratum corneum severely hinders transdermal drug penetration, making it extremely difficult for medications to cross the skin and reducing their effectiveness. Therefore, providing an effective wound-healing agent for patients with chronic wounds is crucial. Considering the characteristics of chronic wound healing, the focus of treatment should be on restoring skin barrier function, reducing infection, providing antioxidant protection, promoting angiogenesis, and facilitating tissue repair.

[0003] Microneedles are arrays of needles with a height of approximately 50–900 μm. Because microneedles can disrupt the stratum corneum and epidermis to create micron-sized drug delivery channels without touching nerve fibers or blood vessels in the epidermis and dermis, microneedling technology can greatly improve drug delivery efficiency and increase the variety of drugs delivered.

[0004] Gelatin and sericin have been proven to promote tissue recovery, and their therapeutic potential in wound treatment is increasingly attracting attention. Compared to other materials, gelatin and sericin possess natural biocompatibility and biodegradability, avoiding the toxic effects of metal ions on the human body, and sericin also exhibits excellent antibacterial properties. Targeting the pathological characteristics of chronic wounds, these materials are combined with hydrogel microneedles to construct a composite hydrogel microneedle system that offers convenient drug delivery, high patient compliance, minimal invasiveness, and accelerated wound healing, providing a novel approach for wound healing and skin dressings.

[0005] Hydrogel microneedles (HMNs), as an emerging type of microneedle, are typically made from cross-linked polymers. The hydrophilic structures in the polymer absorb water from the intercellular spaces and swell after insertion into the skin. The swollen microneedles can then be used to control the transdermal drug delivery rate. Therefore, hydrogel microneedles enable precise controlled drug release, improving drug utilization and reducing treatment discomfort and risks. As an ideal transdermal drug delivery system, HMNs possess excellent properties such as solubility, antibacterial activity, ease of replacement and portability, and customizable sizes. They offer significant advantages in wound healing and, as a drug delivery system, exhibit good adhesion and mechanical properties, promote drug penetration, achieve controlled drug release, improve patient compliance, avoid the first-pass effect, and reduce or eliminate toxic side effects. Summary of the Invention

[0006] The purpose of this invention is to solve the aforementioned problems in the prior art and to provide a hydrogel microneedle that promotes chronic wound healing. This microneedle exerts antibacterial effects, promotes cell proliferation and differentiation, and collagen synthesis through gel and ser. At the same time, it acts as a delivery system to release growth factors (GDFx) and promote wound healing.

[0007] The hydrogel microneedles of this invention combine biocompatibility and mechanical strength, providing natural biocompatibility and biodegradability. They can promote wound closure, tissue regeneration, collagen synthesis, cell proliferation, and angiogenesis under conditions of ordinary wounds and burn wounds, providing new ideas for biomaterial development and wound healing.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A hydrogel microneedle that combines biocompatibility and mechanical strength, the hydrogel microneedle comprising gel and ser in a mass ratio of 1:1.

[0010] Furthermore, the molecular weight of the Gel / Ser hydrogel microneedles is 300,000 Da.

[0011] A method for preparing the above-mentioned hydrogel microneedles that combine biocompatibility and mechanical strength, wherein the method comprises: synthesizing pure natural supramolecular soluble hydrogel microneedles of Gel / Ser in situ through hydrogen bonding interaction between Gel and Ser.

[0012] Further, the method specifically involves: weighing Gel and Ser, dissolving them in deionized water, heating and stirring until dissolved to obtain a Gel / Ser mixture, with the concentration of both Gel and Ser being 50 mg / mL; adding 50% volume of the Gel / Ser mixture to a mold, sonicating it in an ultrasonic machine for 50 minutes, centrifuging it at 4500 rpm for 10 minutes after sonication, adding the remaining Gel / Ser mixture, and placing it in an oven for 5 hours to obtain hydrogel microneedles that possess both biocompatibility and mechanical strength.

[0013] Furthermore, the method specifically includes:

[0014] Step 1: Dissolve Gel and Ser in deionized water by heating to obtain a Gel / Ser mixture through hydrogen bonding; the concentration of both Gel and Ser is 50 mg / mL.

[0015] Step 2: Mix the truncated GDF11 growth factor GDFx with a Gel / Ser mixture to obtain Gel / Ser@GDFx; GDFx can be prepared using the method in CN 105770860 B, and the volume ratio of GDFx to Gel / Ser mixture is 1:9999;

[0016] Step 3: Add 200 μL of Gel / Ser@GDFx to the microneedle mold to prepare microneedle tips containing GDFx drug, sonicate for 50 minutes, and add ice (pay attention to temperature control, do not exceed 40℃ to prevent protein degradation) to promote thorough mixing of Gel / Ser@GDFx and shorten the time for the solution to penetrate into the mold.

[0017] Step 4: Add 300 μL of Gel / Ser mixture to the microneedle mold to prepare the microneedle substrate material;

[0018] Step 5: Place the Gel / Ser@GDFx and the mold into a centrifuge and centrifuge at 3500~4500 rpm for 10 minutes to eliminate air bubbles and accelerate mixing. Then place it in a 37℃ oven for 5 hours to dry thoroughly.

[0019] Step 6: Carefully separate the Gel / Ser@GDFx from the mold to obtain pure natural soluble hydrogel microneedles Gel / Ser@GDFx with GDFx at the tip.

[0020] In step 1, the mass ratio of Gel:Ser:H2O is 1:1:20000. When the ratio is less than this, the material cannot be formed into needles, and the adhesion is low and the mechanical strength is insufficient, making it difficult to penetrate the skin. When the ratio is greater than this value, the material also cannot be formed into needles, but the adhesion is too high.

[0021] The hydrogel microneedles Gel / Ser@GDFx prepared by the above preparation method have a significant promoting effect on wound healing.

[0022] The advantages of this invention over the prior art are as follows:

[0023] 1. It has natural biodegradability and biocompatibility, and can be inserted subcutaneously for wound treatment without pain, which can improve patient compliance and achieve full utilization of the drug. In addition, it can achieve drug sustained release and reduce the number of times the patient needs to take the medication.

[0024] 2. Sericin has antibacterial properties, and together with gelatin, they have a good ability to scavenge reactive oxygen species (ROS), providing a foundation for wound healing.

[0025] 3. The all-natural hydrogel microneedles of the present invention, which possess both biocompatibility and mechanical strength, can serve as drug carriers to promote the proliferation, migration, and endothelial tube formation of fibroblasts by loading growth factors (GDFx), thereby further promoting wound healing.

[0026] 4. The pure natural hydrogel microneedles with both biocompatibility and mechanical strength prepared by this invention are supramolecular hydrogels formed by intermolecular hydrogen bonding. The reaction conditions are readily available and the operation is simple. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the synthesis route of Gel / Ser hydrogel microneedles and their role in promoting wound healing.

[0028] Figure 2 This is a schematic diagram of the appearance of Gel / Ser hydrogel microneedles.

[0029] Figure 3 Scanning electron microscope (SEM) images and elemental analysis diagrams of Gel / Ser hydrogel microneedles with different doping ratios are shown. The mass ratios of Gel to Ser doping are (A) 1:0.5, (B) 1:1 and (C) 1:3.

[0030] Figure 4 Images A and B show the flexibility test results of hydrogel microneedles. Images A and B are photographs taken from different angles during the flexibility test of the hydrogel microneedles.

[0031] Figure 5 The graph shows the number of needles formed by pure gel, pure ser, and gel / ser hydrogel microneedles with different mass ratios (1:0.5, 1:1, and 1:3).

[0032] Figure 6 Infrared spectra of pure gel, pure ser, and gel / ser hydrogel microneedles with different mass ratios (1:0.5, 1:1, and 1:3).

[0033] Figure 7 This is a graph showing the mechanical strength test results of Gel / Ser hydrogel microneedles.

[0034] Figure 8 Images show the penetration depth of Gel / Ser hydrogel microneedles in pigskin. Image A shows the appearance of the Gel / Ser microneedles after staining with rhodamine. Image B is a magnified view of the Gel / Ser microneedles after staining with rhodamine. Image C shows the penetration depth of the microneedles at different depths.

[0035] Figure 9 Images show the irritation test of hydrogel microneedles after they were applied to mouse skin. Images A, B, C, and D show the skin irritation test results after the microneedles were inserted at 0, 2, 4, and 6 minutes, respectively.

[0036] Figure 10 This is a cell viability assay (CCK-8) of Gel / Ser hydrogel microneedles.

[0037] Figure 11Live and dead cell staining (AMPI) and statistical graphs for Gel / Ser@GDFx (GDFx).

[0038] Figure 12 Cell migration experiments and statistical graphs of Gel / Ser@GDFx.

[0039] Figure 13 Tanswell experiments and statistical graphs for Gel / Ser@GDFx.

[0040] Figure 14 Animal experiments and statistical graphs of common wounds on Gel / Ser@GDFx.

[0041] Figure 15 This is a diagram showing the weight record of mice in a typical wound animal experiment.

[0042] Figure 16 Animal experiments and statistical graphs of burn wounds on Gel / Ser@GDFx.

[0043] Figure 17 This is a diagram showing the weight record of mice in an animal experiment involving burn wounds. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0045] This invention presents a personalized design and synthesis of a hydrogel microneedle that combines biocompatibility and mechanical strength. Utilizing the properties of natural polymers such as gelatin (Gel) and sericin (Ser), these two substances are synthesized through hydrogen bonding to form a pure, natural, soluble hydrogel microneedle (Gel / Ser). This biocompatible and mechanically strong hydrogel microneedle has an aesthetically pleasing morphology, is painless upon skin insertion, and can reach a subcutaneous depth of approximately 300 μm, exhibiting excellent therapeutic effects. Growth differentiation factor-11 (GDF11), as a multifunctional cytokine, holds great potential in tissue repair. However, traditional subcutaneous injection suffers from drawbacks such as poor protein stability, insufficient targeting, and short duration of action, resulting in limited efficacy and poor patient compliance. Therefore, there is an urgent need to develop a drug delivery system that can precisely target the drug delivery site and safely and efficiently deliver growth factors, becoming a key challenge in clinical wound healing and other diseases. Based on this background, this invention utilizes truncated GDF11 (GDFx), which demonstrates better therapeutic effects in tissue repair than GDFx. The team employed ultrasonic drying and centrifugal enrichment techniques to precisely target growth differentiation factors to the microneedle tips, enhancing release rates. The core shell structure, by adjusting the ratio of gelatin to sericin, ensures shell toughness and controls swelling and rupture time, solving the problems of premature leakage or uneven release inherent in traditional microneedles. The combination of (Gel / Ser) hydrogel microneedles with GDFx (Gel / Ser@GDFx) exhibits excellent therapeutic effects, including superior biocompatibility, biodegradability, ROS scavenging, antioxidant properties, antibacterial activity, cell proliferation, and controlled drug release, making it a potential drug or cell carrier for the treatment of various wound diseases.

[0046] In the hydrogel microneedles of this invention, gelatin, as a natural, water-soluble, biodegradable polymer, has degradation products that are easily absorbed without causing inflammatory reactions. Furthermore, its solution can form a gel with a certain degree of hardness and elasticity upon cooling. Because the structure of gelatin is similar to that of biological tissues, it exhibits good biocompatibility. Sericin is mainly composed of proteins, with many long-chain amino acids and numerous polar hydrophilic groups (such as -OH, -COOH, -NH2, etc.) on the surface of the polypeptide chains. These structural features endow sericin with excellent humectant and moisturizing properties. In gelatin, the -NH groups of the imino acid Pro (proline) and the -OH groups of Hyp (hydroxyproline) can form hydrogen bonds with the side chain groups of other amino acids and water molecules. The interaction of these hydrogen bonds helps stabilize the triple-helix-like structure of gelatin. In addition, there are also cross-linking hydrogen bonds between its molecular chains. This cross-linking allows the gelatin aqueous solution to form a gel with a certain degree of hardness and elasticity during cooling. However, due to the poor mechanical properties of gel, this invention chooses to combine it with ser. The two substances are synthesized in situ under the action of hydrogen bonds to form pure natural supramolecular soluble hydrogel microneedles.

[0047] Growth differentiation factor-11 (GDF11), also known as bone morphogenetic protein, is a secreted protein belonging to the transforming growth factor-β superfamily. The TGF-β superfamily includes subfamilies such as transforming growth factor, bone morphogenetic protein, and growth differentiation factors (GDFs), and is widely distributed in animals from nematodes to mammals. It plays a crucial role in immune regulation, cell growth and differentiation, extracellular matrix synthesis and storage, embryonic development, and wound repair. As a highly conserved functional protein, numerous studies have confirmed the broad roles of GDF subfamily members in cell aggregation, migration, adhesion, differentiation, development, angiogenesis, and the protection and repair of neural tissue.

[0048] The precursor protein of GDF11 consists of 407 amino acids. At the peptide bond formed by the carboxyl group of arginine at position 298, it is hydrolyzed into two fragments by furin. The truncated GDF11 can stimulate collagen secretion by fibroblasts and has the function of promoting tissue regeneration.

[0049] This invention synthesizes a pure natural soluble hydrogel microneedle that combines biocompatibility and mechanical strength. The pure natural supramolecular soluble hydrogel microneedle is composed of gel and ser. The gel, as a natural, water-soluble, biodegradable polymer, has degradation products that are easily absorbed without causing inflammatory reactions. Furthermore, its solution forms a gel with a certain degree of hardness and elasticity upon cooling. Because the structure of gelatin is similar to that of biological tissues, it exhibits good biocompatibility. The -NH groups of the imino acid Pro (proline) and the -OH groups of Hyp (hydroxyproline) in the gel can form hydrogen bonds with the side chain groups of other amino acids and water molecules. These hydrogen bond interactions help stabilize the triple-helix-like structure of gelatin. In addition, there are cross-linking hydrogen bonds between its molecular chains. This cross-linking allows the gelatin aqueous solution to form a gel with a certain degree of hardness and elasticity during cooling. Moreover, the main component of the gel is collagen, which can promote tissue repair and skin regeneration, and accelerate wound healing. Sericin (ser) is primarily composed of protein. Its sericin chains contain numerous amino acids with long side chains and many polar hydrophilic groups (such as -OH, -COOH, and -NH2) on the surface of the polypeptide chains. These structural features endow sericin with excellent moisture-regulating and moisturizing properties. Furthermore, due to its low molecular weight, sericin can directly enter cells and react with anionic bacteria, disrupting their internal structure. Its amino groups can convert to cations under acidic conditions, and the positively charged sericin can react with the negatively charged bacterial cell walls, altering cell permeability, inducing the dissolution of proteins and other bacterial components, and ultimately causing bacterial death.

[0050] By adjusting the mass ratio of gel and ser, the reactive oxygen scavenging, mechanical strength, and adhesion properties of the hydrogel microneedles that possess both biocompatibility and mechanical strength can be controlled. When the ratio is 1:0.5, microneedles can be formed, but the mechanical strength is low. When the ratio is 1:1, microneedles can be formed with good mechanical strength. When the ratio is 1:3, the needle formation rate is low, the mechanical strength is too high, and the flexibility is low.

[0051] In this invention, the combination of Gel, Ser, and GDFx (Gel / Ser@GDFx) forms a denser network structure, thereby improving the material's mechanical strength, toughness, and elasticity. The addition of Ser significantly alters the porous network structure and crystal structure of the Gel hydrogel, enhancing its swelling capacity. This means that the composite material can reach saturation more quickly when absorbing moisture or bodily fluids, which helps maintain a moist environment for wounds or tissues, thus promoting healing.

[0052] Table 1. Main instruments and equipment used in the experiment

[0053]

[0054] Table 2 Main raw materials and reagents

[0055]

[0056] Example 1:

[0057] 1. Synthesis of hydrogel microneedles with both biocompatibility and mechanical strength

[0058] The preparation method of Gel / Ser hydrogel microneedles is as follows: Weigh 0.05 g of Gel and 0.05 g of Ser, dissolve them in 1000 μL of deionized water, heat and stir until dissolved to obtain Gel / Ser mixture, add 500 μL to a mold, sonicate in an ultrasonic machine for 50 minutes, after sonication, centrifuge at 4500 rpm for 10 minutes, add another 500 μL of Gel / Ser mixture, and finally place in an oven for 5 hours to successfully obtain hydrogel microneedles with both biocompatibility and mechanical strength.

[0059] The preparation method of Gel / Ser@GDFx hydrogel microneedles is as follows:

[0060] Step 1: Dissolve Gel and Ser in deionized water by heating to obtain a Gel / Ser mixture through hydrogen bonding; the concentration of both Gel and Ser is 50 mg / mL.

[0061] Step 2: Mix the truncated GDF11 growth factor GDFx with a Gel / Ser mixture to obtain Gel / Ser@GDFx; GDFx can be prepared using the method in CN 105770860 B, and the volume ratio of GDFx to Gel / Ser mixture is 1:9999;

[0062] Step 3: Add 200 μL of Gel / Ser@GDFx to the microneedle mold to prepare microneedle tips containing GDFx drug, sonicate for 50 minutes, and add ice (pay attention to temperature control, do not exceed 40℃ to prevent protein degradation) to promote thorough mixing of Gel / Ser@GDFx and shorten the time for the solution to penetrate into the mold.

[0063] Step 4: Add 300 μL of Gel / Ser mixture to the microneedle mold to prepare the microneedle substrate material;

[0064] Step 5: Place the Gel / Ser@GDFx and the mold into a centrifuge and centrifuge at 3500~4500 rpm for 10 minutes to eliminate air bubbles and accelerate mixing. Then place it in a 37℃ oven for 5 hours to dry thoroughly.

[0065] Step 6: Carefully separate the Gel / Ser@GDFx from the mold to obtain pure natural soluble hydrogel microneedles Gel / Ser@GDFx with GDFx at the tip.

[0066] 2. Establishment of animal models

[0067] (1) Common wounds

[0068] First, all mice (Kunming mice, male, 8 weeks old) were housed for 3 days to acclimatize to the environment and fasted for 24 hours before the experiment. Then, the mice were randomly divided into 7 groups according to different treatment methods: control group, GDF11 group, GDFx group (prepared using the method specified in authorization number CN105770860B), Gel / Ser group, Gel / Ser@GDF11 group, Gel / Ser@GDFx group, and Prandtl dressing (positive control group). On the first day, a wound of approximately 10 mm was made on the back of each mouse with scissors. The mice in each group then received the corresponding treatment. The dressing was changed every 5 days, and the wound healing progress and the weight of the mice in each group were recorded.

[0069] (2) Burn wound

[0070] First, all mice (Kunming mice, male, 8 weeks old) were housed for 3 days to acclimatize to their environment and fasted for 24 hours before the experiment. Then, the mice were randomly divided into 5 groups according to different treatment methods: burn control group, GDF11 group, GDFx group, Gel / Ser group, Gel / Ser@GDF11 group, Gel / Ser@GDFx group, and Prandtl dressing group (treated with commercially available wound dressing after burns). On the first day, a 10 mm diameter circular severe burn wound was created on the back of the mouse by contacting it with a 300°C cauterization iron for 30 seconds. On the second day, charred tissue was removed, and a 10 mm diameter circular full-thickness skin defect was established. Then, the mice in different groups received the corresponding treatments. Dressings were changed every 5 days, and wound healing progress and the weight of the mice in each group were recorded.

[0071] Figure 1 A schematic diagram illustrating the synthesis route of hydrogel microneedles that combine biocompatibility and mechanical strength, and their role in promoting wound healing.

[0072] Figure 2 This is a schematic diagram of the appearance of hydrogel microneedles.

[0073] Figure 3 Scanning electron microscopy (SEM) images of hydrogel microneedles exhibiting both biocompatibility and mechanical strength. Images A, B, and C show hydrogel microneedles with ratios of 1:0.5, 1:1, and 1:3, respectively. Mapping scans revealed that these microneedles contain only C, N, and O elements, indicating they are purely natural hydrogel microneedles with excellent biocompatibility. The total number of microneedles is 213, with a needle height of 580 μm, a tip-to-tip distance of 600 μm, a substrate diameter of 300 μm, and a patch diameter of 14 mm.

[0074] Figure 3 Figures A and B show the flexibility test of a 1:1 supramolecular hydrogel, which demonstrates that the hydrogel microneedles have good flexibility.

[0075] Figure 4 The flexibility of the hydrogel microneedles was tested. Figures A and B show that the hydrogel microneedles have good flexibility.

[0076] Figure 5 The number of needles formed by hydrogel microneedles with different ratios that combine biocompatibility and mechanical strength was tested. The ratios were gelatin:sericin 1:0.5, 1:1 and 1:3 (mass ratio), and 4 mL of deionized water. It was found that the 1:1 ratio produced the most needles.

[0077] Figure 6 Infrared spectra of Gel and Ser.

[0078] Figure 7Mechanical strength testing was conducted on hydrogel microneedles at a 1:1 scale, demonstrating both biocompatibility and mechanical strength. The mechanical strength test involved plotting pressure-displacement curves using a universal testing machine. In short, the patch was placed on the lower platform of the machine. Subsequently, the upper platform, equipped with sensors, gradually moved towards the patch at a controlled rate of 1 mm / min. The force applied to the patch was recorded in real time during the test. The hydrogel microneedles exhibited good mechanical strength; the HMNs had a hardness of 25 N / needle, and a force of approximately 1 N was sufficient to penetrate the skin, indicating that the microneedles prepared in this invention possessed good mechanical strength sufficient for skin penetration.

[0079] Figure 8 To test the penetration depth of hydrogel microneedles in pigskin, which possess both biocompatibility and mechanical strength. Figure A shows the appearance of the microneedles after Rhodamine staining; Figure B is a magnified view of the microneedles after Rhodamine staining; Figure C shows the penetration depth of the hydrogel microneedles as captured by confocal microscopy. A 1:1 mixture of hydrogel microneedles and Rhodamine B fluorescent dye was inserted into pigskin, embedded using OCT, and subjected to transverse frozen sectioning. HMNs were observed to reach a subcutaneous depth of up to 300 μm, demonstrating good penetration performance.

[0080] Figure 9 This study tested the irritation of hydrogel microneedles after they were applied to the skin of mice. Figures A, B, C, and D show the skin irritation after microneedle insertion at 0, 2, 4, and 6 minutes, respectively. Hair was removed first, then Gel / Ser was applied to the backs of KM mice, with pressure applied for 3 minutes, followed by 3 minutes before microneedle removal. The healing of the micropores left by the microneedles on the rat's back was observed to visually assess the skin irritation caused by microneedle application. Skin recovery was recorded at specified time points: at 0 minutes after patch removal, the microneedle array pores on the rat's back skin were observed, with no bleeding, erythema, or swelling observed. After microneedle patch removal, the traces of micropores and skin inflammation were observed at 0, 2, 4, and 6 minutes. The time it took for the micropores to become invisible to the naked eye and for the skin to roughly return to its pre-microneedle patch state were also recorded.

[0081] Figure 10 The experiment used CCK-8 assays to detect the viability of hydrogel microneedles. Different concentration gradients were set up: 6.25, 12.5, 25, 50, and 100 mg / mL. It was observed that cell viability decreased with increasing concentration, reaching its lowest point at 100 mg / mL.

[0082] Figure 11Live / dead cell staining (AM / PI) for Gel / Ser@GDFx. We set up a control group, Gel / Ser group, GDF11 group, GDFx group, Gel / Ser@GDF11 group, Gel / Ser@GDFx group, and Prandtl dressing group (positive control). The results showed that the cells in the Gel / Ser@GDFx group had better cell biocompatibility.

[0083] Figure 12 Cell migration assay for Gel / Ser@GDFx. Compared with other groups, the Gel / Ser@GDFx group showed significant cell migration in the control group, Gel / Ser group, GDF11 group, GDFx group, Gel / Ser@GDF11 group, Gel / Ser@GDFx group, and Prandtl dressing group (positive control).

[0084] Figure 13 The Tanswell assay for Gel / Ser@GDFx showed a significant advantage in the Gel / Ser@GDFx group, with markedly enhanced cell migration and a substantial increase in the number of cells crossing the chamber membrane compared to the control group. This indicates that the Gel / Ser@GDFx group has a positive promoting effect on cell migration.

[0085] Figure 14 Animal experiments were conducted on routine wounds treated with Gel / Ser@GDFx. Compared with other groups, the Gel / Ser@GDFx group showed the greatest degree of wound healing, indicating that the combination of the hydrogel and the drug significantly promotes the skin wound repair capacity.

[0086] Figure 15 This is a record of mouse weight in a routine wound animal experiment. It can be seen that the mice's weight gradually increased from day 1 to day 14, indicating that the mice are growing well.

[0087] Figure 16 Animal experiments were conducted on burn wounds treated with Gel / Ser@GDFx. Compared with other groups, the Gel / Ser@GDFx group showed the greatest degree of wound healing, indicating that the combination of this hydrogel and the drug significantly promotes the repair capacity of skin wounds, not only for ordinary wounds but also for burn wounds.

[0088] Figure 17 This is a record of the body weight of mice used in an animal experiment involving burn wounds. It can be seen that the mice's body weight gradually increased from day 1 to day 14, indicating that the mice are growing well.

Claims

1. A method for preparing a hydrogel microneedle with biocompatibility and mechanical strength, characterized by: The hydrogel microneedles comprise gelatin (Gel) and sericin (Ser) in a mass ratio of 1:1; the method is as follows: gel and ser are synthesized in situ as pure natural supramolecular soluble hydrogel microneedles by hydrogen bonding. The method is as follows: Weigh Gel and Ser, dissolve them in deionized water, heat and stir until dissolved to obtain a Gel / Ser mixture, the concentration of both Gel and Ser is 50 mg / mL; add 50% volume of the Gel / Ser mixture to the mold, sonicate in an ultrasonic machine for 50 minutes, after sonication, centrifuge at 4500 rpm for 10 minutes, after centrifugation, add the remaining Gel / Ser mixture, and place in an oven for 5 hours to obtain hydrogel microneedles with both biocompatibility and mechanical strength; The method is specifically as follows: Step 1: Dissolve Gel and Ser in deionized water by heating to obtain a Gel / Ser mixture through hydrogen bonding; the concentration of both Gel and Ser is 50 mg / mL. Step 2: Mix the truncated GDF11 growth factor GDFx with the Gel / Ser mixture to obtain Gel / Ser@GDFx; the volume ratio of GDFx to Gel / Ser mixture is 1:9999; Step 3: Add 200 μL of Gel / Ser@GDFx to the microneedle mold to prepare microneedle tips containing GDFx drug, sonicate for 50 minutes, and place in an ice bath to promote thorough mixing of Gel / Ser@GDFx and shorten the time for the solution to penetrate into the mold; Step 4: Add 300 μL of Gel / Ser mixture to the microneedle mold to prepare the microneedle substrate material; Step 5: Place the Gel / Ser@GDFx and the mold into a centrifuge and centrifuge at 3500~4500 rpm for 10 minutes. Then place them in a 37℃ oven for 5 hours to dry thoroughly. Step 6: Carefully separate the Gel / Ser@GDFx from the mold to obtain pure natural soluble hydrogel microneedles Gel / Ser@GDFx with GDFx at the tip.

Images