Natural protein-based multifunctional biogel as well as preparation method and application thereof

Abstract

The invention provides a natural protein-based multifunctional biogel and a preparation method and application thereof, and the preparation method comprises the following steps: dissolving gelatin in water to prepare a gelatin solution, cooling and curing to obtain a gel precursor; soaking the gel precursor in water for swelling, and then placing the gel precursor in a first deep eutectic solvent for solvent exchange to obtain gel; the content of gelatin in the gelatin solution is 5-40 wt%; the swelling time in water is greater than or equal to 5 minutes; the preparation method of the gel also comprises the following steps: pretreating degummed silk to obtain silk nanofibers, and dispersing the silk nanofibers in a dispersion solvent to form a dispersion liquid; mixing and stirring gelatin and the dispersion liquid, cooling and curing, and performing swelling-assisted solvent exchange to obtain the gel. The preparation method is green, and the prepared gel is excellent in mechanical property, has electrical conductivity, long-term environmental stability, adhesion, self-healing property and degradability, and can be widely applied to the field of flexible electronics or biomedicine.

Description

Technical Field

[0001] This invention belongs to the field of biogel materials, and relates to a natural protein-based multifunctional biogel, its preparation method and application. Background Technology

[0002] Flexible electronics technology, with its wearable nature and ability to monitor human physiological signals in real time (such as electrocardiogram, electromyography, and movement status), has demonstrated significant application value in smart healthcare, health monitoring, and human-computer interaction. As a core functional material in flexible electronics, gels have become a current research hotspot due to their excellent flexibility, stretchability, biocompatibility, and mechanical and electrical properties that match biological tissues. Compared to synthetic polymers, natural polymers possess unique biocompatibility, biodegradability, sustainability, and renewability. Therefore, natural polymer-based gels (such as gelatin, silk fibroin, and chitosan) have unique advantages in biodegradability, sustainability, and biosafety, making them more suitable for epidermal contact electronic devices. Among these, gelatin is considered an ideal matrix material due to its wide availability, low cost, and excellent gelling properties. However, traditional gelatin gels have the following key defects: 1. Insufficient mechanical properties: The single polymer network structure results in low mechanical strength, poor toughness, and poor fatigue resistance; 2. Lack of electrical conductivity, environmental stability (performance is easily degraded under changes in humidity / temperature), interfacial adhesion, and other multifunctional properties; 3. Conventional crosslinking methods are difficult to simultaneously regulate the multi-scale network structure to achieve synergistic performance improvement.

[0003] In the prior art: CN119656392 A uses animal glue as raw material and introduces polyvinyl alcohol and glycerin to prepare an animal glue composite hydrogel. This material exhibits certain multifunctionality (including adhesion, water retention, biodegradability, biocompatibility, etc.), but its mechanical properties are poor (stress is below 40 kPa). Prior art (1) Zhou et al. (Mormyroidea-inspired electronic skin for active non-contact three-dimensional tracking and sensing, Nature Communication, 2024. DOI: 10.1038 / s41467-024-54249-3) and prior art (2) Lan et al. (Skin-inspired all-natural biogel for bioadhesive interface, Advanced Materials, 2024. DOI: 10.1002 / adma.202401151) used gelatin as a gel base and added functional factors to it to prepare protein-based gels. Compared with the prior art (1), the mechanical properties of the gel in the prior art (2) are improved: the tensile stress increases from 45 kPa to about 1.3 MPa, the tensile strain increases from 170% to about 320%, and it exhibits a certain degree of adhesion to human skin. CN115910627 B uses a blending method to introduce carbon nanotubes into gelatin gel. After the blend liquid gels, it is then soaked in a functional solution to obtain a gel / CNT gel. This gel has good flexibility (tensile strain of 430%), but the tensile stress is only 1.4 MPa.

[0004] In summary, existing gelatin-based gel materials suffer from technical defects such as insufficient mechanical properties and a lack of multifunctionality. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a natural protein-based multifunctional biogel, its preparation method, and its applications. The natural protein-based multifunctional biogel provided by this invention exhibits excellent mechanical properties and can be widely applied in the fields of biomedicine or flexible electronics.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] On the one hand, the present invention provides a method for preparing a natural protein-based multifunctional biogel, the method comprising: dissolving gelatin in water to prepare a gelatin solution, and cooling and solidifying to obtain a gel precursor;

[0008] After the gel precursor was soaked in water to swell, it was placed in a first deep eutectic solvent (DES) for solvent exchange to obtain a natural protein-based multifunctional biogel.

[0009] The gelatin solution contains 5-40 wt% gelatin.

[0010] The soaking time in water for swelling is ≥5 minutes.

[0011] In the above preparation method, preferably, the mass ratio of the gel precursor to water is 1:(20-100); more preferably, the gel precursor needs to be fully swollen when soaked in water for swelling.

[0012] In the above preparation method, preferably, the preparation method further includes:

[0013] The degummed silk was pretreated, washed and filtered, dispersed in water, mechanically peeled, and centrifuged to obtain the supernatant. The supernatant was then filtered to obtain silk nanofibers (SNF), which were dispersed in a dispersion solvent to form a silk nanofiber dispersion.

[0014] Gelatin and silk nanofiber dispersion were mixed and stirred to form a homogeneous and viscous solution, which was then cooled and solidified to obtain a biogel precursor.

[0015] After the biogel precursor was soaked in water to swell, it was placed in a first deep eutectic solvent for solvent exchange to obtain a natural protein-based multifunctional biogel.

[0016] The mass ratio of gelatin to silk nanofibers is 1:(0.01-0.1).

[0017] In the above preparation method, preferably, the content of silk nanofibers in the silk nanofiber dispersion is less than 5 wt%.

[0018] In the above preparation method, preferably, the content of silk nanofibers in the silk nanofiber dispersion is 0.4-1.5 wt%.

[0019] In the above preparation method, preferably, the mass ratio of gelatin to silk nanofibers is 1:(0.02-0.06).

[0020] In the above preparation method, preferably, the pretreatment includes placing degummed silk in a pretreatment solution system and stirring to react.

[0021] In the above preparation method, preferably, the mass ratio of the degummed silk to the pretreatment solution system is 1:(50-3000); more preferably, it is 1:(50-200); and even more preferably, it is 1:100.

[0022] In the above preparation method, preferably, the pretreatment solution system includes a second deep eutectic solvent and / or a calcium chloride-ethanol-water ternary solution.

[0023] In the above preparation method, preferably, the second deep eutectic solvent includes one or a combination of two or more of the following: quaternary ammonium salt-based deep eutectic solvent, organic guanidine compound-based deep eutectic solvent, and metal salt-based deep eutectic solvent.

[0024] In this invention, the quaternary ammonium salt-based deep eutectic solvent, the organic guanidine compound-based deep eutectic solvent, and the metal salt-based deep eutectic solvent are classified according to the hydrogen bond acceptors contained in the second deep eutectic solvent.

[0025] In the above preparation method, preferably, the second deep eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor includes one or more of urea, lactic acid, and arginine; the hydrogen bond acceptor includes one or more of choline chloride, guanidine hydrochloride, zinc chloride, and ferric chloride.

[0026] In the above preparation method, preferably, the calcium chloride content in the calcium chloride-ethanol-water ternary solution is 25-50 wt%, and the ethanol content is 20-40 wt%.

[0027] In the above preparation method, preferably, the temperature of the stirring reaction is 40-150℃ and the time is ≥30min.

[0028] In the above preparation method, preferably, the water dispersion includes dispersing the washed and filtered silk fibers into water; the mass ratio of the washed and filtered silk fibers to water is (1-20):100, more preferably 1:100.

[0029] In the above preparation method, preferably, the mechanical peeling step includes: mechanically peeling the dispersion obtained after water dispersion in an ultrasonic pulverizer and / or a high-speed stirrer.

[0030] This invention utilizes an ultrasonic pulverizer and / or a high-speed stirrer for mechanical stripping, and the output power can be adjusted according to actual needs.

[0031] In the above preparation method, preferably, the mechanical peeling time is ≥10 min and the mechanical peeling power is 400-1800W.

[0032] In the above preparation method, preferably, the output power of the ultrasonic pulverizer is 400-1000W and the time is ≥10min; the output power of the high-speed stirrer is 400-1800W and the time is ≥10min; more preferably, the output power of the ultrasonic pulverizer is 600W and the time is 5h; the output power of the high-speed stirrer is 1800W and the time is 15min.

[0033] In the above preparation method, preferably, the centrifugation speed is 1000-2500 r / min and the centrifugation time is ≥30 min; more preferably, the centrifugation speed is 2000 r / min.

[0034] The silk nanofibers obtained by the preparation method in this invention are obtained by first pre-treatment water washing and filtration, water dispersion, and mechanical exfoliation to obtain micro-nano silk fibers, and then by centrifugation and filtration to obtain silk nanofibers (SNF). Compared with the method of directly using deep eutectic solvent (DES) to thermally stimulate the in-situ splitting of silk fibroin fibers to decompose them into silk fibroin micro-nano fibrils (SMNF), the silk nanofibers obtained by the preparation method of this invention have a more uniform diameter distribution. The stress concentration of the natural protein-based multifunctional biogel prepared with this material will be smaller, which is more conducive to improving the mechanical properties of the natural protein-based multifunctional biogel.

[0035] In the above preparation method, preferably, the pH of the dispersing solvent is 4.2 ≤ pH < 7.0, more preferably 4.2-5.2.

[0036] In the above preparation method, preferably, the dispersing solvent is one or a combination of two or more of the following: citric acid aqueous solution, malic acid aqueous solution, lactic acid aqueous solution, acetic acid aqueous solution, tartaric acid aqueous solution, ascorbic acid aqueous solution, succinic acid aqueous solution, and gluconic acid aqueous solution.

[0037] In this invention, a SNF dispersion is prepared using a slightly acidic aqueous solution as the dispersion medium, and then mixed with gelatin. This allows SNF to exhibit negative charge and gelatin to exhibit positive charge. By utilizing the electrostatic attraction between the two, the interaction between SNF and gelatin is increased, thereby improving mechanical properties.

[0038] In the above preparation method, preferably, the stirring temperature when mixing the gelatin and silk nanofiber dispersion is 50-100℃, more preferably 50-90℃.

[0039] According to a specific embodiment of the present invention, preferably, the preparation method further includes: mixing and stirring gelatin and silk nanofiber dispersion to form a homogeneous and viscous solution, then injecting the solution into a mold for cooling and solidification. Preferably, the mold is a polytetrafluoroethylene (PTFE) mold; more preferably, the mold has a dumbbell-shaped structure, which is more conducive to mechanical testing. The present invention can use a PTFE mold, which is relatively stable and resistant to strong acids and alkalis. Since the gel preparation system of the present invention is relatively mild, other molds commonly used in the art can also be used.

[0040] In the above preparation method, preferably, the first deep eutectic solvent includes a quaternary ammonium salt-based deep eutectic solvent and / or a metal salt-based deep eutectic solvent; more preferably, the first deep eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor, wherein the hydrogen bond donor includes one or more of glycerol, urea, lactic acid, ethylene glycol, glucose, and fructose; and the hydrogen bond acceptor includes one or more of choline chloride, zinc chloride, betaine, acetylcholine, and tetrabutylammonium chloride.

[0041] In the above preparation method, preferably, the first deep eutectic solvent is a choline chloride-glycerol system deep eutectic solvent.

[0042] In the above preparation method, preferably, the preparation method of the choline chloride-glycerol system deep eutectic solvent includes: stirring and mixing choline chloride and glycerol at a molar ratio of 1:2 at 60°C to obtain a homogeneous and transparent first deep eutectic solvent.

[0043] In the above preparation method, preferably, the solvent exchange time is ≥10 min, more preferably 10 min-6 h.

[0044] In the above preparation method, preferably, the cooling and curing temperature is 4℃-30℃ and the time is ≥10min.

[0045] This invention involves preparing a biogel precursor from gelatin (or a mixture of silk nanofibers and gelatin), allowing it to swell sufficiently, and then immersing it in DES solvent for solvent exchange. This solvent exchange is a swelling-assisted solvent exchange. Compared to the biogel precursor, the mechanical properties of the resulting natural protein-based multifunctional biogel are significantly improved after the swelling-assisted solvent exchange.

[0046] Preferably, the above preparation method further includes the following step: stretching induction of the natural protein-based multifunctional biogel.

[0047] In the above preparation method, preferably, the stretching induction conditions include: a stretching speed of 10-300 mm / min, a stretching strain of 50-200%, and ≥5 cycles of stretching, to prepare a natural protein-based multifunctional biogel with aligned fibers.

[0048] Those skilled in the art can routinely choose a stretching instrument for hydrogels for mechanical induction.

[0049] The natural protein-based multifunctional biogel prepared by this invention possesses excellent flexibility and water retention capacity, thus making it suitable for stretch induction. The natural protein-based multifunctional biogel of this invention contains silk nanofibers; therefore, after stretch induction, the silk nanofibers will align in the gel matrix, further enhancing the strength and toughness of the gel.

[0050] On the other hand, the present invention also provides a natural protein-based multifunctional biogel, which is prepared by the above-described preparation method.

[0051] According to a specific embodiment of the present invention, preferably, the gel has a stress ≥ 0.8 MPa, a strain ≥ 155%, an elastic modulus ≥ 0.4 MPa, and a toughness ≥ 0.5 MJ / m. 3 .

[0052] According to a specific embodiment of the present invention, preferably, the gel has a stress ≥ 2.4 MPa, a strain ≥ 231%, an elastic modulus ≥ 0.6 MPa, and a toughness ≥ 2.2 MJ / m. 3 .

[0053] According to a specific embodiment of the present invention, preferably, the gel has a stress ≥ 3.4 MPa, a strain ≥ 268%, an elastic modulus ≥ 1.9 MPa, and a toughness ≥ 3.7 MJ / m. 3 .

[0054] On the other hand, the present invention also provides an application of the above-mentioned natural protein-based multifunctional biogel in the preparation of products in the fields of flexible electronics or biomedicine.

[0055] According to a specific embodiment of the present invention, preferably, the product in the field of flexible electronics or biomedicine includes flexible electronic devices; more preferably, the flexible electronic device includes one or more of epidermal bioelectrodes, flexible strain sensors, or flexible pressure sensors.

[0056] In some specific embodiments of the present invention, the natural protein-based multifunctional biogel can be used as an electrode interface material for epidermal bioelectrodes or as a sensing material for flexible strain sensors for long-term, continuous, high-quality monitoring of electrophysiological signals such as electrocardiograms and electromyograms, as well as for human motion monitoring.

[0057] The method for preparing natural protein-based multifunctional biogels provided by this invention can significantly improve the mechanical properties of the prepared gels through a swelling-assisted solvent exchange strategy. This invention further innovates the material system by using natural silk nanofibers as a reinforcing phase. Through the synergistic effect of DES-induced phase separation, a gelatin crosslinking network structure reinforced with natural silk nanofibers is constructed, achieving a performance breakthrough in gelatin gel materials. The natural protein-based multifunctional biogel obtained by the preparation method of this invention uses gelatin, natural silk nanofibers (SNF), and deep eutectic solvent (DES) as core components, and constructs a three-dimensional network structure through physical crosslinking and exogenous nanofiber reinforcement. The natural protein-based multifunctional biogel prepared by this invention possesses the following characteristics: (1) excellent mechanical properties; (2) multifunctional integration: mechanical robustness, conductivity, long-term environmental stability, adhesion, self-healing, and biodegradability.

[0058] Furthermore, the preparation method of this invention does not involve toxic organic solvents or toxic chemical crosslinking agents, making it environmentally friendly and possessing the following technical advantages: (1) Green preparation process: no toxic organic solvents or toxic chemical crosslinking agents; (2) Adjustable performance: the performance of the gel material can be optimized by controlling the SNF content and / or DES component; (3) High industrialization potential: the raw materials are green and abundant, and the process is simple. The gel material prepared by this invention can be widely used in the fields of flexible electronics or biomedicine, including but not limited to epidermal bioelectrodes, flexible strain sensors, flexible pressure sensors, etc., enabling long-term, high-quality monitoring of human electrophysiological signals, detection of human motion, and human-computer interaction. Attached Figure Description

[0059] Figure 1 SEM images of natural silkworm cocoons and silk nanofibers (SNF).

[0060] Figure 2 Infrared spectra of natural silkworm cocoons and silk nanofibers (SNF).

[0061] Figure 3 In the figure, A represents the stress-strain curves of Gel-BioGel and pre-BioGel. Figure 3 In the figure, B represents the stress-strain curves of Gel-BioGel, NPM-BioGel-1, NPM-BioGel-2, and NPM-BioGel-3.

[0062] Figure 3 C in the figure represents the stress-strain curves of DM-BioGel-1, DM-BioGel-2, DM-BioGel-3 and NPM-BioGel-2. Figure 3D in the figure represents the stress-strain curves of pre-BioGel, SED-BioGel-1, SED-BioGel-2, SED-BioGel-3 and NPM-BioGel-2.

[0063] Figure 4 This is a comparison chart of stress, strain, elastic modulus, and toughness between NPM-BioGel-2 and pre-BioGel.

[0064] Figure 5 This demonstrates the fatigue resistance properties of NPM-BioGel-2.

[0065] Figure 6 Stress-strain curves, fracture energy, and SEM images of NPM-BioGel-2, NPM-BioGel-4, NPM-BioGel-5, and NPM-BioGel-6 are displayed.

[0066] Figure 7 This demonstrates the adhesiveness, self-healing properties, UV resistance, and biodegradability of natural protein-based multifunctional biogels.

[0067] Figure 8 Demonstration of the conductivity of natural protein-based multifunctional biogels.

[0068] Figure 9 The stress and strain histograms of NPM-BioGel-2 after being placed in environments of 40°C, room temperature, -20°C, and -60°C for 2 days.

[0069] Figure 10 Demonstrating the antifreeze and water-retention properties of natural protein-based multifunctional biogels; Figure 10 In the diagram, A represents the antifreeze properties of a natural protein-based multifunctional biogel. Figure 10 The B in the figure represents the water retention properties of NPM-BioGel-2, DM-BioGel-1, DM-BioGel-2 and DM-BioGel-3.

[0070] Figure 11 A natural protein-based multifunctional biogel for use in flexible strain sensors.

[0071] Figure 12 The results of monitoring electrocardiogram signals using a natural protein-based multifunctional biogel as an epidermal bioelectrode.

[0072] Figure 13 The results of monitoring electromyographic signals using a natural protein-based multifunctional biogel as an epidermal bioelectrode. Detailed Implementation

[0073] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0074] Example 1

[0075] (1) Preparation of natural silk nanofiber dispersion

[0076] Urea and guanidine hydrochloride were weighed at a molar ratio of 2:1 and dissolved completely at 90°C to obtain a transparent and homogeneous urea-guanidine hydrochloride system (DES). Degummed silk was weighed at a mass ratio of 1:100 to the pretreatment solution system and placed in the urea-guanidine hydrochloride system (DES). The mixture was stirred at 90°C for 55 hours. The resulting product was washed, filtered, and thoroughly dried to obtain silk fibers. The silk fibers were dispersed in deionized water at a mass ratio of 1:100 to water and mechanically exfoliated using an ultrasonic pulverizer at 600W for 5 hours to obtain a silk fiber suspension. The silk fiber suspension was centrifuged at 2000 r / min for 30 min, and the supernatant was filtered (filter paper pore size: 0.22 μm) to obtain natural silk nanofibers (SNF). The obtained natural silk nanofibers (SNF) retained the same structure as natural silk fibers (see...). Figure 1 and Figure 2 The obtained natural silk nanofibers of 0g, 0.02g, 0.04g and 0.06g were dispersed in 4g of citric acid aqueous solution (pH=5.2) to obtain natural silk nanofiber dispersions with different natural silk nanofiber contents.

[0077] (2) Preparation of natural protein-based multifunctional biogels

[0078] Weigh 1g of gelatin and place it in the natural silk nanofiber dispersion obtained in step (1) above. Stir and dissolve at 60°C to form a homogeneous viscous solution. Pour the solution into a dumbbell-shaped mold and cool and solidify (temperature: 4°C (refrigerator), time: 1h) to obtain a natural protein-based biogel precursor (denoted as pre-BioGel). Soak pre-BioGel in deionized water for 1 hour to allow it to swell fully. Then soak it in a choline chloride-glycerol system DES for 40min for solvent exchange (DES preparation: choline chloride and glycerol are mixed at a ratio of 1:2 (molar ratio) and stirred at 60°C to obtain a transparent and homogeneous DES). This yields a swelling-assisted natural protein-based multifunctional biogel, denoted as NPM-BioGel. Among them, the samples with silk nanofibers of 0g, 0.02g, 0.04g, and 0.06g respectively, soaked in deionized water for 1 hour and soaked in choline chloride-glycerol DES solvent for 40min in citric acid aqueous solution pH=5.2, are respectively named Gel-BioGel, NPM-BioGel-1, NPM-BioGel-2, and NPM-BioGel-3.

[0079] Comparative Example 1

[0080] Preparation of DES-blended natural protein-based biogels:

[0081] Weigh 0.04g of silk nanofibers and 1g of gelatin, and dissolve them in 4g of citric acid aqueous solution (pH=5.2). Then weigh 0.56g (10wt%), 5.04g (50wt%) and 7.56g (60wt%) of choline chloride-glycerol system DES, respectively, and place them in the above solution. Stir thoroughly to form a homogeneous viscous solution. Pour the solution into a mold and cool to solidify to obtain blended gelatin-based biogels, which are named DM-BioGel-1, DM-BioGel-2 and DM-BioGel-3, respectively.

[0082] Comparative Example 2

[0083] Preparation of direct solvent exchange type natural protein-based biogels:

[0084] Weigh 0.04g of silk nanofibers and dissolve them in 4g of citric acid aqueous solution (pH=5.2). Stir thoroughly to obtain a uniformly distributed silk nanofiber dispersion. Weigh 1g of gelatin and dissolve it in the above natural silk nanofiber dispersion. Stir thoroughly to form a homogeneous viscous solution. Pour the solution into a mold and cool to solidify to obtain a natural protein-based biogel precursor, pre-BioGel. Directly immerse pre-BioGel in choline chloride-glycerol DES solvent for 5min, 20min, and 600min to obtain direct solvent exchange type natural protein-based biogels, which are designated as SED-BioGel-1, SED-BioGel-2, and SED-BioGel-3, respectively.

[0085] Test Example 1

[0086] Mechanical performance testing includes the following indicators: 1. Stress = force / area; 2. Strain = [(fracture length - original length) / original length] × 100%; 3. Elastic modulus: the slope of the initial linear region of the stress-strain curve; 4. Toughness: the integral area of ​​the peak value of the stress-strain curve with the X-axis.

[0087] Compared to pre-BioGel (natural protein-based biogel precursor), Gel-BioGel (without natural silk nanofibers) prepared using a "swelling-assisted" solvent exchange strategy exhibits better mechanical properties, with a stress of 0.8 MPa and a strain of 155% (see...). Figure 3 A) demonstrates that the "swelling-assisted" solvent exchange strategy of the present invention has a positive effect on improving the mechanical properties of pre-BioGel.

[0088] Compared with gel-BioGel, the mechanical properties of swelling-assisted natural protein-based multifunctional biogels containing natural silk nanofibers (NPM-BioGel-1, 2, 3) are significantly improved, with increased tensile stress and tensile strain (see...). Figure 3 (B) in the above demonstrates that the natural protein-based multifunctional biogel containing natural silk nanofibers of the present invention has enhanced and toughening properties.

[0089] Compared with DM-BioGel-1, DM-BioGel-2, and DM-BioGel-3 (DES blended natural protein-based biogels), NPM-BioGel-2, a swelling-assisted natural protein-based multifunctional biogel containing natural silk nanofibers, exhibits significantly increased tensile stress and better overall mechanical properties (see [link to product description]). Figure 3 C) demonstrates that the "swelling-assisted solvent exchange" strategy of the present invention achieves better results than the "blending" strategy.

[0090] Compared with pre-BioGel, SED-BioGel-1, SED-BioGel-2, and SED-BioGel-3 (direct solvent exchange type natural protein-based biogels), NPM-BioGel-2, a swelling-assisted natural protein-based multifunctional biogel containing natural silk nanofibers, exhibits better overall mechanical properties (see...). Figure 3 In point D), the biogel prepared by the "direct solvent exchange method" has better mechanical properties than the precursor pre-BioGel (i.e., the sample without solvent exchange). However, compared with the "swelling-assisted solvent exchange" strategy proposed in this invention, the natural protein-based multifunctional biogel prepared by the "swelling-assisted solvent exchange" strategy of this invention has superior mechanical properties.

[0091] like Figure 4 As shown, the pre-BioGel precursor exhibits a stress of 0.1 MPa, a strain of 61%, a modulus of 0.3 MPa, and a toughness of 51 kJ / m. 3 Compared to pre-BioGel, the swelling-assisted natural protein-based multifunctional biogel containing natural silk nanofibers (NPM-BioGel-2) exhibits significantly improved mechanical properties, with marked increases in stress, strain, elastic modulus, and toughness. Specifically, NPM-BioGel-2 exhibits a stress of 3.4 MPa, a strain of 268%, an elastic modulus of 1.9 MPa, and a toughness of 3.7 MJ / m. 3 (See Figure 4 This demonstrates that the natural protein-based multifunctional biogel prepared using the method of this invention exhibits superior mechanical properties. Furthermore, tensile loading-unloading cyclic testing was conducted on NPM-BioGel-2, a swelling-assisted natural protein-based multifunctional biogel containing natural silk nanofibers. After 10,000 cycles at a tensile speed of 200 mm / min, the gel remained stable, demonstrating its fatigue resistance (see...). Figure 5 ).

[0092] The above results demonstrate that the natural silk nanofibers and the swelling-assisted solvent exchange strategy of the present invention play an important role in the preparation of natural protein-based multifunctional biogels.

[0093] Test Example 2

[0094] Stretch induction can enhance the mechanical properties of natural protein-based multifunctional biogels:

[0095] The NPM-BioGel-2 prepared in Example 1 was fixed in the fixture of an advanced electrodynamic measuring instrument. Under the conditions of tensile speed of 50 mm / min and tensile strain of 100%, it was cyclically stretched 20 times, 50 times, and 100 times, respectively, to obtain high-strength and tough natural protein-based multifunctional biogels with aligned fibers, which were designated as NPM-BioGel-4, 5, and 6, respectively. The fracture energy was calculated using the formula: (the integral area of ​​the stress-strain curve of the unnotched sample at the same fracture point as the notched sample with the X-axis) × the original length of the sample.

[0096] Compared to the unstretched natural protein-based multifunctional biogel (NPM-BioGel-2), the tensile stresses of NPM-BioGel-4, 5, and 6 were all increased. Specifically, the tensile stress of NPM-BioGel-5 increased from 3.4 MPa to 4.8 MPa compared to NPM-BioGel-2 (see...). Figure 6 In section A), the elastic modulus increased from 1.6 MPa to 6.9 MPa, and the fracture energy increased from 12.5 KJ / m. 2 Increased to 24.1 KJ / m 2 (See Figure 6 (B) indicates that stretching induction can enhance the mechanical properties of the natural protein-based multifunctional biogel of this invention. Compare the SEM images of NPM-BioGel-2 (see [image B]). Figure 6 SEM images of C and NPM-BioGel-5 (see C) Figure 6 As shown in D), after stretching induction, the gel fibers of NPM-BioGel-5 are aligned in the gel matrix, thus further improving the strength and toughness of the gel through stretching induction.

[0097] Test Example 3

[0098] The adhesive properties, self-healing properties, UV resistance, biodegradability, and electrical conductivity of natural protein-based multifunctional biogels are as follows:

[0099] The natural protein-based multifunctional biogel of this invention exhibits good adhesion to human skin due to hydrogen bonds, ionic bonds, electrostatic attraction, and van der Waals forces (see [link to invention]). Figure 7 In section A, the 90° peel test was conducted, and the sample was a rectangular specimen with a length of 30 mm and a width of 5 mm. Due to the dynamic physical cross-linking of the natural protein-based multifunctional biogel of this invention, it can achieve self-healing after standing at 60°C for 2 minutes (see...). Figure 7In section B, the self-healing sample was first placed at 60°C for 2 minutes, then at room temperature for 2 hours, followed by a tensile test. The gelatin used in this invention has advantages of UV resistance and biodegradability, and the resulting natural protein-based multifunctional biogel exhibits excellent UV resistance (see...). Figure 7 The C value in the figure was measured using a UV-Vis spectrophotometer (the sample was a circular thin film with a diameter of 30 mm) and its biodegradability (see [reference]). Figure 7 In step D, the NPM-BioGel-2 film is placed on the soil surface for degradation by soil microorganisms. Simultaneously, the DES used in this invention contains a large amount of freely mobile Cl... - Therefore, the natural protein-based multifunctional biogel of this invention exhibits good electrical conductivity (see...). Figure 8 The test was conducted using an electrochemical workstation, and the test method was the three-electrode method.

[0100] Test Example 4

[0101] Environmental stability, freeze resistance, and water retention of natural protein-based multifunctional biogels:

[0102] The natural protein-based multifunctional biogel of this invention utilizes a "swelling-assisted solvent exchange" strategy to replace water molecules within the gel with DES, promoting the formation of strong interactions within the gel and thus exhibiting high-temperature stability (see...). Figure 9 ), freeze resistance (see Figure 10 A) and water retention (see Figure 10 (See section B). The natural protein-based multifunctional biogel of this invention, after being left to stand at -20°C for two days, can still be freely bent and twisted, exhibiting excellent antifreeze properties (see section B). Figure 10 (A) and exhibits good water retention (see A). Figure 10 (B) in the middle. Figure 9 The data in the first column for NMP-BioGel-2 represents the initial values ​​for the gel's performance testing. The specific test methods for high-temperature stability, freeze resistance, and water retention are as follows: 1. High-temperature stability and freeze resistance: NMP-BioGel-2 was placed in environments of 40℃ / -20℃ / -60℃ for 2 days respectively, then removed and subjected to mechanical testing; 2. Water retention: NMP-BioGel-2 was placed at room temperature, and its weight was measured at different time intervals. The rate of weight change was used to evaluate its water retention capacity; the less the mass decrease, the stronger the water retention capacity.

[0103] Application Example 1

[0104] Natural protein-based multifunctional biogels are used to fabricate flexible strain sensors:

[0105] The natural protein-based multifunctional biogel prepared in this invention can be used as a sensing material to construct flexible strain sensors, as demonstrated by the NMP-BioGel-2 prepared in Example 1. The gel was applied to the test site on the human body, and then connected to a Keithley source meter using copper foil and wires for application testing. The device constructed from the NMP-BioGel-2 prepared in this embodiment of the invention exhibits high sensitivity, wide detection range, and cycle stability, and can be used for wearable detection of large-scale human movements (such as nodding, joint movements, walking, etc.) and subtle movements (such as vocal cord vibration, breathing, etc.) (see [link to example]). Figure 11 ).

[0106] Application Example 2

[0107] Natural protein-based multifunctional biogels for epidermal bioelectrodes:

[0108] Using the multifunctional biogel of this invention as an electrode interface material, epidermal bioelectrodes can be constructed. In this application example, the gel portion of a commercial Ag / AgCl electrode was removed, and the NMP-BioGel-2 prepared in this invention was cut into corresponding shapes and placed in the original position of the commercial gel for application testing. Epidermal bioelectrodes were constructed using the NMP-BioGel-2 prepared in Example 1 for monitoring electrocardiogram (ECG) signals. Due to the excellent deformation resistance, adhesion, conductivity, and environmental stability of the multifunctional biogel prepared in this invention, the epidermal bioelectrodes constructed using it can perform high-quality monitoring of human electrophysiological signals (ECG, EMG) in a wide temperature range (3℃-30℃), and can be worn continuously for several hours with stable output signal quality. The results are shown in […]. Figure 12 , Figure 13 The multifunctional biogel of this invention, when used as an electrode material, has a higher signal-to-noise ratio compared to conventional commercial gel electrodes, such as... Figure 12 As shown in B in the figure. Furthermore, due to its excellent environmental stability, this multifunctional biogel electrode can still be used for accurate and efficient monitoring of electrophysiological signals even after being placed at room temperature for 13 days (see Figure B). Figure 12 (D in the middle).

[0109] In summary, this invention provides a natural protein-based multifunctional biogel, its preparation method, and its application. It significantly improves the mechanical properties of the prepared gel through a swelling-assisted solvent exchange strategy. Furthermore, through material system innovation, it uses natural silk nanofibers as a reinforcing phase and constructs a gelatin crosslinking network structure reinforced by natural silk nanofibers through the synergistic effect of DES-induced phase separation, achieving a performance breakthrough in gelatin gel materials. The gel material prepared by the method of this invention possesses the following characteristics: (1) excellent mechanical properties; (2) multifunctional integration: conductivity, long-term environmental stability, adhesion, self-healing, and biodegradability. The preparation method of this invention has the following technical advantages: (1) green preparation process: no toxic organic solvents or toxic chemical crosslinking agents; (2) adjustable performance: material performance is optimized by controlling the SNF content and / or DES component; (3) high industrialization potential: abundant and green raw material sources and simple process. The gel material prepared by this invention can be widely used in the fields of biomedicine and flexible electronics, including but not limited to wearable epidermal bioelectrodes and flexible strain sensors, and is suitable for long-term and efficient monitoring of human electrophysiological signals, detection of human motion, and human-computer interaction.

Claims

1. A method for preparing a natural protein-based multifunctional biogel, wherein, The preparation method includes: Gelatin was dissolved in water to prepare a gelatin solution, which was then cooled and solidified to obtain a gel precursor. After the gel precursor was soaked in water to swell, it was placed in a first deep eutectic solvent for solvent exchange to obtain a natural protein-based multifunctional biogel. The gelatin solution contains 5-40 wt% gelatin. The soaking time in water for swelling is ≥5 minutes.

2. The preparation method according to claim 1, wherein, The preparation method further includes: The degummed silk was pretreated, washed and filtered, dispersed in water, mechanically peeled, and centrifuged to obtain the supernatant. The supernatant was then filtered to obtain silk nanofibers, which were dispersed in a dispersion solvent to form a silk nanofiber dispersion. Gelatin and silk nanofiber dispersion were mixed and stirred, and then cooled and solidified to obtain a biogel precursor. After the biogel precursor was soaked in water to swell, it was placed in a first deep eutectic solvent for solvent exchange to obtain a natural protein-based multifunctional biogel. The mass ratio of gelatin to silk nanofibers is 1:(0.01-0.1).

3. The preparation method according to claim 2, wherein, The pretreatment includes placing degummed silk in a pretreatment solution system and stirring to react; Preferably, the mass ratio of the degummed silk to the pretreatment solution system is 1:(50-3000); Preferably, the pretreatment solution system comprises a second deep eutectic solvent and / or a calcium chloride-ethanol-water ternary solution; Preferably, the second deep eutectic solvent includes one or a combination of two or more of the following: quaternary ammonium salt-based deep eutectic solvent, organic guanidine compound-based deep eutectic solvent, and metal salt-based deep eutectic solvent; Preferably, the second deep eutectic solvent comprises a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor comprises one or more of urea, lactic acid, and arginine; the hydrogen bond acceptor comprises one or more of choline chloride, guanidine hydrochloride, zinc chloride, and ferric chloride. Preferably, the temperature of the stirring reaction is 40-150℃ and the time is ≥30min.

4. The preparation method according to claim 2, wherein, The water dispersion includes dispersing washed and filtered silk fibers into water; And / or, the mechanical peeling time is ≥10 min.

5. The preparation method according to claim 2, wherein, The pH of the dispersion solvent is 4.2 ≤ pH < 7.0; Preferably, the dispersing solvent is one or a combination of two or more of the following: citric acid aqueous solution, malic acid aqueous solution, lactic acid aqueous solution, acetic acid aqueous solution, tartaric acid aqueous solution, ascorbic acid aqueous solution, succinic acid aqueous solution, and gluconic acid aqueous solution.

6. The preparation method according to claim 2, wherein, The stirring temperature during the mixing of the gelatin and silk nanofiber dispersion is 50-100℃.

7. The preparation method according to claim 1 or 2, wherein, The first deep eutectic solvent includes quaternary ammonium salt-based deep eutectic solvents and / or metal salt-based deep eutectic solvents; Preferably, the first deep eutectic solvent includes a hydrogen bond donor and a hydrogen bond acceptor; the hydrogen bond donor includes one or more of glycerol, urea, lactic acid, ethylene glycol, glucose, and fructose; the hydrogen bond acceptor includes one or more of choline chloride, zinc chloride, betaine, acetylcholine, and tetrabutylammonium chloride. Preferably, the first deep eutectic solvent is a choline chloride-glycerol system deep eutectic solvent; And / or, the solvent exchange time is ≥10 min; And / or, the cooling and curing temperature is 4℃-30℃, and the time is ≥10min.

8. The preparation method according to claim 1 or 2, wherein, The preparation method further includes the following step: stretching induction of the gel; Preferably, the conditions for tensile induction include: a tensile speed of 10-300 mm / min, a tensile strain of 50-200%, and ≥5 cycles of tensile testing.

9. A natural protein-based multifunctional biogel, prepared by the preparation method according to any one of claims 1-8.

10. The application of the natural protein-based multifunctional biogel according to claim 9 in the preparation of products in the fields of flexible electronics or biomedicine; Preferably, the products in the field of flexible electronics or biomedicine include flexible electronic devices; Preferably, the flexible electronic device includes one or more of the following: epidermal bioelectrode, flexible strain sensor, or flexible pressure sensor.

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