Fibroin-based hydrogel for adhesion and preparation method thereof

Abstract

The invention discloses fibroin-based hydrogel for adhesion and a preparation method thereof, and relates to the technical field of biomedical materials. Comprising the following steps: 1) mixing glycidyl methacrylate and a silk fibroin solution, then heating to chemically modify silk fibroin, and finally dialyzing and purifying to obtain a modified silk fibroin solution; and 2) mixing the silk fibroin solution modified in the step 1) with an acrylic monomer and an initiator, and then carrying out photopolymerization treatment. The tensile strength of the prepared fibroin-based hydrogel for adhesion is 70-310 kPa, the tensile elongation at break is 250%-450%, and the shear adhesive strength to tissues is 20-80 kPa. Compared with the traditional hydrogel, the fibroin-based hydrogel for adhesion prepared by the invention has excellent adhesion, biodegradability and conductivity, and has remarkable advantages in the aspects of wound tissue sealing and wearable and implantable electronic equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedical materials, and particularly relates to a silk fibroin-based hydrogel for adhesion and a preparation method thereof. Background Art

[0002] In the prior art, silk fibroin hydrogels, as biological adhesives or tissue engineering materials, mainly have the following technical problems: Traditional silk fibroin hydrogels have low adhesion strength on the surface of wet tissues (such as visceral organs or wounds), and are easily interfered by interfacial moisture, resulting in adhesion failure and making it difficult to achieve stable and lasting sealing. At the same time, the mechanical strength of the hydrogel (such as tensile modulus, storage modulus) does not match the mechanical properties of human tissues (such as skin, muscle or blood vessels), which may cause stress concentration or interfacial peeling, affecting the repair effect. A single hydrogel is difficult to simultaneously meet the multi-functional requirements such as adaptability. The above problems indicate that existing silk fibroin hydrogels face multi-dimensional bottlenecks in clinical applications, such as adhesion performance, mechanical adaptability, and multi-functional integration, and breakthroughs need to be achieved through material modification and structural design. Summary of the Invention

[0003] The purpose of the present invention is to solve the above problems in the prior art, and provide a silk fibroin-based hydrogel for adhesion and a preparation method thereof.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A preparation method of a silk fibroin-based hydrogel for adhesion, comprising the following steps:

[0006] 1) Mix glycidyl methacrylate and a silk fibroin solution, then heat to chemically modify the silk fibroin, and finally dialyze and purify to obtain a modified silk fibroin solution;

[0007] 2) Mix the modified silk fibroin solution obtained in step 1) with an acrylic acid monomer and an initiator, and then perform photopolymerization treatment to form the silk fibroin-based hydrogel for adhesion.

[0008] In step 1), the heating temperature is 50-90 °C, and the heating time is 10-18 hours.

[0009] In step 1), the mass concentration of the modified silk fibroin solution is 6%-20%.

[0010] In step 2), the mass ratio of the acrylic acid monomer to the modified silk fibroin solution is 5-10:1.

[0011] In step 2), the initiator is α-ketoglutaric acid.

[0012] A silk fibroin-based hydrogel for adhesion, prepared by the above preparation method.

[0013] The tensile strength of the silk fibroin-based hydrogel for adhesion is 70-310 kPa, and the elongation at break is 250%-450%; the shear adhesion strength of the silk fibroin-based hydrogel for adhesion to biological tissues is 20-80 kPa.

[0014] The thickness of the silk fibroin-based hydrogel for adhesion is 1-5 mm.

[0015] The application of a silk fibroin-based hydrogel for adhesion is used as a tissue adhesive or wound sealant in the biomedical field, or a conductive hydrogel sensor for flexible electronic devices.

[0016] The flexible electronic device includes a wearable physiological signal monitoring device or an implantable motion sensor.

[0017] Compared with the prior art, the beneficial effects achieved by the technical solution of the present invention are:

[0018] In the present invention, glycidyl methacrylate is used to chemically modify silk fibroin solution to obtain glycidyl methacrylate-grafted silk fibroin, and then under ultraviolet irradiation, it is photopolymerized with acrylic acid monomers to form a silk fibroin-based hydrogel for adhesion with a crosslinked network. Due to the stable chemical crosslinked network and abundant carboxylic acid groups of the silk fibroin network, sufficient cohesion and interfacial interaction ensure that the tensile strength of the silk fibroin hydrogel is 70-310 kPa, the elongation at break is 250%-450%, and the shear adhesion strength to tissues is 20-80 kPa. Compared with traditional hydrogels, the multifunctional silk fibroin hydrogel prepared in the present invention has excellent adhesion, biodegradability and conductivity, and shows advantages in wound tissue sealing. The silk fibroin hydrogel of the present invention is beneficial for collecting physiological electricity and human motion signals as a flexible sensor, and has significant advantages in wearable and implantable electronic devices. Description of the Drawings

[0019] Figure 1 Are the stress-strain curves when the mass ratios of acrylic acid and modified silk fibroin solution are 5:5, 6:4, 8:2, 7:3 and 9:1 respectively;

[0020] Figure 2 Are the initial photos (left figure) of the silk fibroin-based hydrogel at room temperature and the photos (right figure) stretched to more than 4 times the original length;

[0021] Figure 3 Are the tensile and compression modulus results when the silk fibroin-based hydrogel is stretched to 4 times the original length at room temperature;

[0022] Figure 4 Are the loading-unloading measurements of the silk fibroin-based hydrogel at different stretching ratios;

[0023] Figure 5 It is the 8 - time continuous cyclic loading - unloading curve of the silk - fibroin - based hydrogel at a tensile strain of 50%, and there is no rest interval between the eight consecutive tests;

[0024] Figure 6 It is a schematic diagram of the 80° peeling test of the silk - fibroin - based hydrogel for measuring the toughness of the biological tissue interface;

[0025] Figure 7 It is the adhesion strength of the silk - fibroin - based hydrogel to pig skin, pig heart, pig large intestine, pig small intestine and pig liver;

[0026] Figure 8 It is the adhesion strength of the silk - fibroin - based hydrogel to glass, steel sheet, polydimethylsiloxane (PDMS), polystyrene (PS) and polyurethane (PU). Detailed implementation mode

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the following further describes the present invention in detail with reference to the drawings and embodiments. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0028] Embodiment 1

[0029] In this embodiment, a degummed silk fibroin solution is prepared: The raw silk cocoons are boiled and degummed in a 1wt% NaHCO3 solution for 30 minutes. During this period, the silk threads are cut with scissors to avoid entanglement as much as possible, and then the samples are thoroughly washed. Subsequently, the silk threads are placed in a boiling 0.5wt% NaHCO3 aqueous solution for 30 minutes. To remove the excess NaHCO3, the silk threads are placed in ultrapure water at 100°C and washed for 30 minutes, and this process is repeated 3 times. After drying at ambient temperature, 10g of degummed silk is dissolved in 60mL of 9.3M lithium bromide solution and placed at 60°C for 1 hour to obtain a silk fibroin solution.

[0030] A modified silk fibroin solution is prepared. 3.5mL of glycidyl methacrylate is added to the silk fibroin solution at a rate of 0.5 mL per minute, and then placed in an oven at 60°C for 12 hours to completely dissolve it into a yellow transparent solution. Subsequently, the obtained solution is filtered and dialyzed with distilled water through a 3000 - cut - off dialysis membrane for 3 days. Silk fibroin has amino acid residues containing active amino groups (-NH2). After the epoxy group of glycidyl methacrylate is opened, it forms a covalent bond with the amino group on the silk fibroin, thereby obtaining a modified silk fibroin solution. The mass concentration of the above - prepared modified silk fibroin is 6.4%.

[0031] To prepare a silk fibroin-based hydrogel for adhesion, 20.38% (w / w) acrylic acid, 5.09% (w / w) modified silk fibroin solution, and 1.59% (w / w) α-ketoglutaric acid were thoroughly mixed, with the rest being water. In this example, the mass ratio of acrylic acid monomer to the modified silk fibroin solution was 8:2. Then, it was dried under low pressure in a vacuum dryer for 3 minutes to remove the air bubbles in the mixture. Subsequently, the mixture was poured into a glass mold, and under ultraviolet irradiation from an ultraviolet lamp (SB-100P / FA, Spectroline, USA), free radical polymerization occurred between the glycidyl methacrylate-grafted silk fibroin and the acrylic acid monomer, forming a 1-mm-thick silk fibroin-based hydrogel for adhesion.

[0032] Example 2

[0033] At a temperature of 25 °C, uniaxial tensile and compression tests were carried out using a microtester (5948, Instron, USA) equipped with a 100 N sensor. The silk fibroin-based hydrogel for adhesion was stretched and compressed at a constant speed of 5 mm / min until the hydrogel broke or reached the compression limit of the instrument. The slope of the stress-strain curve at 0 - 5% strain was calculated as the elastic modulus. The stress-strain tests for each silk fibroin-based hydrogel for adhesion were carried out at least five times.

[0034] The tensile properties of hydrogels are the basis for their biomedical applications. In this invention, the deformation and failure properties of silk fibroin-based hydrogels for adhesion under external forces, such as strength, elastic modulus, and fracture toughness, were studied. At room temperature, the stress-strain curves of silk fibroin-based hydrogels for adhesion (with mass ratios of acrylic acid and modified silk fibroin solution being 5:5, 6:4, 8:2, 7:3, and 9:1 respectively) were studied using a micro-force tensile testing machine.

[0035] Figure 1 It was shown that the tensile strain of the hydrogel was closely related to its network structure, including the degree of crosslinking, the hardness of silk fibroin and polyacrylic acid macromolecules, etc. As the content of polyacrylic acid increased, more crosslinking points were introduced into the network of the silk fibroin-based hydrogel for adhesion. When the mass ratio was 7:3, the fracture strength increased to 312 kPa. When the mass ratio further increased to 8:2, the fracture strength decreased to 74.34 kPa, and the tensile strain reached a maximum value of 424.6%. This may be because as the degree of crosslinking points decreased, the network of silk fibroin and polyacrylic acid macromolecules became more uniform. When the mass ratio was 9:1, the tensile strain decreased to 268.3% because the network of the silk fibroin-based hydrogel for adhesion macromolecules was the largest.

[0036] Figure 2 The tensile images of the silk fibroin-based hydrogel for adhesion at an initial state of 10 mm and a tensile strain of 400% were shown.

[0037] Figure 3 The tensile modulus of the silk fibroin-based hydrogel for adhesion was shown to be 0.4 kPa, and the compressive modulus was 107 kPa, which was consistent with the tissue modulus when the silk fibroin-based hydrogel for adhesion contacted the tissue.

[0038] The mechanical hysteresis of the hydrogel under cyclic loading directly reflected its elastic and damping properties under large deformations. As Figure 4 shown, no obvious hysteresis lines were observed in the silk fibroin-based hydrogel for adhesion at different tensile ratios, and the hysteresis lines increased with the increase of strain. Without a rest interval, there was almost no mechanical hysteresis in the silk fibroin-based hydrogel for adhesion at a tensile strain of 50% ( Figure 5 ). The hysteresis curves overlapped to a large extent, and the dissipated energy remained almost unchanged after the first loading cycle, and the strength of the hydrogel remained at ≈98% after eight loading and unloading cycles. This was due to the strong toughness of the double-layer network of polyacrylic acid and silk fibroin.

[0039] Example 3

[0040] A lap shear test was carried out to evaluate the adhesion of the silk fibroin-based hydrogel for adhesion to the tissue.

[0041] The lap shear test was carried out according to the ASTM F2255 25 standard. The bonding substrates were wet fresh porcine tissue / abiotic tissue and the silk fibroin-based hydrogel for adhesion, and the bonding area was set to 1 cm × 1 cm. Before the lap shear test, the surface of the porcine tissue was wiped clean, and then the porcine tissue was allowed to adhere to the porcine tissue / abiotic tissue for 2 seconds. The lap shear test was carried out at a constant speed of 5 mm / min by a microtester (5948, Instron, USA), and the peak stress before separation was regarded as the shear strength. For the silk fibroin-based hydrogel for adhesion used, the mass ratio of acrylic acid and the modified silk fibroin solution was 8:2, and five samples were tested in each group.

[0042] The adhesion performance of the silk fibroin-based hydrogel for adhesion to biological tissue was measured by the lap shear method. Porcine skin has mechanical robustness and is highly similar to human skin, so it was selected as the model tissue to evaluate the adhesion performance. Before adhering the silk fibroin-based hydrogel for adhesion to the porcine skin, the moisture on the tissue surface was gently wiped with a tissue paper. After the silk fibroin-based hydrogel for adhesion contacted the porcine skin for 2 seconds, the shear strength was immediately measured ( Figure 6 ) Compared with the shear strength of the silk fibroin-based hydrogel for adhesion between two in vitro biological tissues such as porcine heart (≈23 kPa), porcine large intestine (≈25 kPa), porcine small intestine (≈38 kPa) and porcine liver (≈41 kPa), the shear strength of porcine skin was the highest, reaching 64 kPa ( Figure 7). Shear measurements were also performed on the adhesion between the silk fibroin-based hydrogel and non-biological tissues and pigskin. The silk fibroin-based hydrogel for adhesion still had good adhesion properties (glass ≈ 14.3 kPa, steel ≈ 15.3 kPa, polydimethylsiloxane (PDMS) ≈ 15.2 kPa, polystyrene (PS) ≈ 16.1 kPa, and polyurethane (PU) ≈ 19.6 kPa), with a slight decrease in shear strength ( Figure 8 ).

Claims

1. A method for preparing a silk-based hydrogel for adhesion, characterized in that: The following steps are involved: 1) Glycidyl methacrylate and silk fibroin solution are mixed, then heated to chemically modify the silk fibroin, and finally dialyzed and purified to obtain a modified silk fibroin solution; 2) The modified silk fibroin solution of step 1) is mixed with acrylic monomer and initiator, and then subjected to photopolymerization treatment to form the aforementioned silk fibroin-based hydrogel for adhesion.

2. The method for preparing a silk-based hydrogel for adhesion according to claim 1, characterized in that: The heating temperature in step 1) is 50-90° C. and the heating time is 10-18 hours.

3. The method for preparing a silk fibroin-based hydrogel for adhesion according to claim 1, characterized in that: In step 1), the mass concentration of the modified silk fibroin solution is 6% to 20%.

4. The method for preparing a silk fibroin-based hydrogel for adhesion according to claim 1, characterized in that: In step 2), the mass ratio of the acrylic acid monomer to the modified silk fibroin solution is 5-10:

1.

5. The method for preparing a silk-based hydrogel for adhesion according to claim 1, characterized in that: In step 2), the initiator is α-ketoglutaric acid.

6. A silk-based hydrogel for adhesion, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

7. The silk-based hydrogel for adhesion according to claim 6, characterized in that: The tensile strength of the adhesion silk-based hydrogel is 70-310 kPa, and the tensile elongation at break is 250%-450%; the shear adhesion strength of the adhesion silk-based hydrogel to biological tissue is 20-80 kPa.

8. The silk-based hydrogel for adhesion according to claim 6, characterized in that: The thickness of the silk-based hydrogel for adhesion is 1-5 mm.

9. The use of a silk-based hydrogel for adhesion according to claim 6, characterized in that: Conductive hydrogel sensors for use in biomedical applications as tissue adhesives, wound sealants, or flexible electronic devices.

10. The use according to claim 9, characterized in that: The flexible electronic device includes a wearable physiological signal monitoring device or an implantable motion sensor.

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