Janus dry face mask based on birch emulsion electrospinning and its preparation method

Abstract

Janus dry facial mask based on birch emulsion electrospinning and its preparation method belong to the field of beauty and skin care materials technology. This invention first utilizes green bio-based solvents ethyl lactate or methyl lactate to optimize the extraction of betulinol from birch bark using an ultrasound-assisted method. Then, employing emulsion electrospinning technology and a Janus bilayer structure design, an asymmetric bilayer dry facial mask is constructed: the hydrophobic layer is made of biodegradable polylactic acid electrospinned, acting as a water-locking barrier to delay moisture loss; the hydrophilic layer is made by uniformly dispersing birch bark ethyl lactate extract (oil phase) in a mixed aqueous solution of polyvinyl alcohol and chitosan through high-speed shear emulsification to form a stable O / W type emulsion, followed by electrospinning to create a nanofiber membrane encapsulating active ingredients. The Janus dry facial mask exhibits excellent moisturizing, antioxidant, and anti-inflammatory effects, and requires no preservatives for dry storage and transportation. The process is simple and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of beauty and skin care materials technology, specifically relating to a Janus dry face mask based on birch emulsion electrospinning and its preparation method. Background Technology

[0002] Facial masks are an indispensable part of modern daily skincare. They form a occlusive layer on the skin's surface, promoting the absorption of active ingredients and achieving effects such as moisturizing, whitening, and anti-aging. Currently, most facial masks on the market use ordinary non-woven fabric as the base material, then infuse various skincare essences (such as hyaluronic acid, niacinamide, and plant extracts). To extend shelf life and improve the user experience, these masks often also add chemical preservatives (such as parabens and phenoxyethanol) and various fragrances (including synthetic fragrances or plant essential oils), resulting in poor adhesion and insufficient breathability of the mask fabric. Non-woven fabric has limited absorption capacity for nutrient solutions, making it prone to dripping and causing discomfort. Furthermore, the presence of essence increases the packaging volume and weight of the mask, leading to higher transportation costs. The emergence of dry masks solves these problems. They are stored and transported in a dry state, only needing to be activated before use, making them more portable and hygienic.

[0003] Birch bark extract, especially its key active ingredient betulin, has attracted much attention in the pharmaceutical and cosmetic fields. Studies have confirmed that betulin has significant anti-inflammatory, antioxidant, skin barrier repair, and antibacterial multiple biological activities, and has clear potential for soothing sensitive skin, resisting environmental oxidative stress, and delaying skin aging. Traditional methods for extracting betulin from birch bark mostly use organic solvents. These traditional methods have many drawbacks: (1) High toxicity: The use of toxic solvents such as methanol and chloroform poses a serious risk of solvent residue, affecting the safety of the final product, and is especially unsuitable for pharmaceuticals and cosmetics; (2) Many impurities: Traditional solvents often extract a large amount of pigments, tannins, resins and other impurities at the same time, which makes subsequent purification difficult and increases production costs; (3) Unfriendly to the environment: The use and recycling of petroleum-based or halogenated solvents will put pressure on the environment.

[0004] Ethyl lactate is a highly efficient, green, safe, and selective solvent. It can be synthesized from lactic acid (obtained through carbohydrate fermentation) and ethyl lactate (also biofermented), aligning with the modern trend of "green chemistry." It exhibits significant advantages over traditional solvents in the extraction of betulin. Ethyl lactate is similarly miscible with betulin, a pentacyclic triterpenoid compound with moderate polarity and a large hydrophobic skeleton. The molecular structure of ethyl lactate contains both polar ester groups and nonpolar ethyl groups, classifying it as a moderately polar solvent. This property perfectly matches the chemical properties of betulin, resulting in extremely high solubility for it. Ethyl lactate demonstrates excellent selectivity in the extraction of betulin: birch bark has a complex composition, containing not only betulin but also tannins, pigments, resins, and other components. The good selectivity of ethyl lactate for betulin means that while efficiently dissolving the target compound, it reduces the dissolution of these impurities, simplifying subsequent purification processes.

[0005] However, betulin, as a lipid-soluble molecule, has limited solubility and stability in aqueous systems, posing a significant challenge to its efficient loading and long-term preservation in traditional hydrophilic mask carriers. Simply mixing it directly into water-based formulations easily leads to the release, uneven distribution, or chemical degradation of active ingredients, severely impacting product efficacy and shelf-life stability. Stable integration of this lipid-soluble active ingredient into a hydrophilic fiber network is a major challenge. Electrospinning is an advanced technology capable of preparing micro / nano-scale fibers. The resulting fiber membranes possess characteristics such as large specific surface area, high porosity, and a biomimetic extracellular matrix structure, making them ideal as carriers for skincare ingredients. Direct mixing of polymers and active ingredients into nanofibers allows for uniform distribution of the active ingredients within the nanofibers, increasing the loading capacity; it also enhances the contact area between the skin and the active ingredients, improving skin penetration and adhesion. Current research indicates that Janus masks have outstanding advantages in water retention and moisturizing. Janus materials refer to materials with two sides possessing different chemical properties or functions. Introducing this concept into mask design allows for the development of masks that combine "moisturizing" and "functionality." One layer is designed to be hydrophobic to slow down moisture evaporation and achieve long-lasting hydration; the other layer is designed to be hydrophilic to carry and release water-soluble or emulsion-like active skincare ingredients to perform functional effects such as anti-oxidation and anti-inflammation.

[0006] Polylactic acid (PLA) has become a research hotspot in the fields of biomedicine and functional materials due to its excellent biodegradability, superior biocompatibility, and tunable mechanical properties. In skin care applications, PLA's hydrophobic properties effectively prevent rapid moisture evaporation, while its micro-nano network structure formed by its fibers has a good physical adsorption capacity for oils and hydrophobic dirt on the skin surface, making it an ideal substrate for constructing the hydrophobic functional layer of face masks. Through electrospinning technology, PLA can be processed into fibrous membranes with high specific surface area, high porosity, and controllable structure, which further enhances its cleaning efficiency and provides a physical basis for the stable composite of bilayer structures. Polyvinyl alcohol (PVA) is rich in hydroxyl groups in its molecular chain, giving it good water solubility, film-forming properties, and spinning processability. It can form a fiber network with high strength and good flexibility. Chitosan (CS) has natural antibacterial and biocompatibility. The amino and hydroxyl groups in its molecules can also interact with a variety of components. PVA and CS form a composite solution through intermolecular hydrogen bonding and other interactions. The synergy between the two not only significantly improves the spinning performance of individual components and the mechanical stability of fiber membranes, but their hydrophilic network also provides an ideal environment for subsequent loading of active ingredients. Summary of the Invention

[0007] The purpose of this invention is to provide a Janus dry facial mask based on betulinum emulsion electrospinning and its preparation method. This invention aims to develop an efficient, safe, environmentally friendly, and easily industrialized method for extracting betulinum alcohol, and to solve the problems of high pollution, high energy consumption, and poor compatibility between fat-soluble active ingredients and hydrophilic matrices in traditional facial mask preparation. Therefore, this invention provides a Janus dry facial mask that integrates functionality and skincare. This mask exists in a dry state, is portable and hygienic, and its preparation method is simple and efficient.

[0008] Firstly, in the extraction stage, this invention utilizes the green bio-based solvents ethyl lactate or methyl lactate to optimize the extraction of betulinol from birch bark using an ultrasound-assisted method. This technique achieves a yield of up to 30%, superior to traditional solvents, and the resulting extract can be directly used in skincare products such as serums and masks.

[0009] Based on this, the present invention employs emulsion electrospinning technology and Janus double-layer structure design to construct an asymmetric double-layer dry mask: the hydrophobic layer is made of biodegradable polylactic acid (PLA) through electrospinning, serving as a water-locking barrier to delay moisture loss; the hydrophilic layer is made by uniformly dispersing birch bark ethyl lactate extract (oil phase) in a mixed aqueous solution of polyvinyl alcohol (PVA) and chitosan (CS) through high-speed shear emulsification to form a stable O / W type emulsion, followed by electrospinning to produce a nanofiber membrane encapsulating active ingredients.

[0010] The core technology of this invention lies in encapsulating fat-soluble active ingredients such as betulinol within hydrophilic fibers through emulsion electrospinning. This solves the compatibility problem between the active ingredients and the hydrophilic matrix, forming a physical barrier to protect them from light and oxygen damage, thus extending the duration of activity retention. Furthermore, activation via spraying during use allows the fiber network to swell or degrade upon contact with water, enabling the immediate release of the active ingredients. Testing has shown that this Janus dry mask exhibits excellent moisturizing, antioxidant, and anti-inflammatory effects. It requires no preservatives for dry storage and transportation, and the process is simple, making it suitable for industrial production.

[0011] This invention first provides a method for extracting betulin from birch bark, the steps of which are as follows:

[0012] (1) Disperse birch bark powder in ethyl lactate or methyl lactate solution to obtain betulin extract:

[0013] Weigh 95-105 mg of birch bark powder (60 mesh) into a 10 mL centrifuge tube, add ethyl lactate or methyl lactate solution at a ratio of 1 g: 10-50 mL, and disperse evenly to obtain birch bark solution; after ultrasonic treatment (power 100-500 W, temperature 35-75℃, time 1-5 min), centrifuge, and the supernatant obtained is betulin extract;

[0014] The present invention discloses a method for preparing Janus dry facial mask based on birch emulsion electrospinning, comprising the following steps:

[0015] (1) Preparation of PLA hydrophobic spinning solution: Dissolve 0.45~0.55g of PLA in a mixed solvent of 3.5~4mL of dichloromethane and 1.5~2mL of DMF, and stir magnetically for 5~8 hours to obtain a transparent PLA hydrophobic spinning solution;

[0016] (2) Preparation of hydrophilic spinning emulsion: Dissolve 1-1.2g of PVA in 8-10mL of deionized water and heat and stir in a water bath at 80-90℃ to obtain a clear solution A; dissolve 0.18-0.22g of CS in a 1% (w / w) acetic acid aqueous solution and stir to obtain a clear solution B; mix clear solution A and clear solution B, wherein the volume percentage of clear solution A is 70-90%, to obtain a PVA / CS mixed aqueous solution; measure 1-1.5mL of betulin. Add 0.1-0.15 g of Tween80 to the extract, slowly add 1-1.5 mL of deionized water at 8000-12000 rpm, and continue shearing for 20-40 min to obtain a homogeneous O / W emulsion; slowly add 1.5-2.5 mL of the O / W emulsion to 4.5-5.5 mL of PVA / CS mixed aqueous solution, and continue shearing at 9000-10000 rpm for 20-30 min to obtain a stable hydrophilic spinning solution;

[0017] (3) Spinning is carried out by sequentially changing the spinning solution. That is, a hydrophobic PLA fiber membrane is first spun on the receiving device, and then a hydrophilic fiber membrane is spun on the surface of the hydrophobic PLA fiber membrane on the same receiving device immediately after completion. The specific steps are as follows: First, the PLA hydrophobic layer spinning solution is electrospun, with a spinning solution volume of 4~6mL, a spinning voltage of 14~16kV, a receiving distance of 15~18cm, a feed speed of 1.5~2mL / h, an ambient temperature of 25~30℃, and a humidity of 40~60%; then the hydrophilic layer spinning emulsion is electrospun, with a spinning solution volume of 6~8mL, a spinning voltage of 14~16kV, a receiving distance of 15~18cm, a feed speed of 0.5~1mL / h, an ambient temperature of 25~35℃, and a humidity of 40~60%; thus, a double-layer fiber membrane is obtained on the receiving device.

[0018] (4) Post-processing: The double-layer fiber membrane obtained in step (3) is dried at 50~60℃ to completely remove the solvent, and then carefully peeled off from the receiving device and cut to obtain Janus dry face mask based on birch emulsion electrospinning.

[0019] In the single-factor experiments (Examples 3-6), the extraction rates of betulin were 15.9%-27.6%. Based on the single-factor experiments, the key factors and their interactions were modeled and optimized using response surface methodology (RSM). The factors and their coding levels for the response surface experiments are shown in Table 1, the results of the response surface experiments are shown in Table 2, and the analysis of variance of the response surface model is shown in Table 3.

[0020] Table 1: Response surface experimental factors and their coding levels

[0021]

[0022] Table 2: Results of Response Surface Methodology Experiment

[0023]

[0024] Table 3: Variance of the response surface model

[0025]

[0026] Note: "*" indicates a significant difference at the 0.05 level (p<0.05); "**" indicates a significant difference at the 0.01 level (p<0.01); "***" indicates a statistically significant difference at the 0.001 level (p<0.001).

[0027] The experimental data (Table 2) were fitted using multiple regression analysis with Design Expert 13 software, yielding the response surface equation: Y = +30.35 + 0.0425A + 0.0908B + 0.0783C + 0.2583D - 0.1275AB - 0.0625AC - 0.4025AD - 0.0475BC - 0.2675BD - 0.3CD - 0.68A 2 -0.5725B 2 -0.7212C 2 -0.7636D 2 The variance analysis of the fitted quadratic polynomial model is shown in Table 3. Table 3 shows that the F-value of this model is 8.18, and the root mean square error (p < 0.0001), indicating that the regression model of the response surface fitting equation is highly significant. The lack-of-fit term (p = 0.3922 > 0.05) is not statistically significant, indicating a good model fit. Based on the above analysis, this model can be used to analyze and predict the total betulinum extract rate from birch bark. Furthermore, Table 3 also shows that the linear term D and the quadratic term A of the model... 2 B 2 C 2 D 2 The p-values ​​were all less than 0.0001, indicating a highly significant level, thus validating the single-factor experiment. The p-values ​​for the interaction terms AB, AD, BD, and CD were less than 0.05, reaching a significant level, while the remaining terms were not significant. This suggests that the interaction between extraction temperature, extraction time, and the solid-liquid ratio with other factors has a significant impact on betulinol from birch bark. The response values ​​were significantly better than the single-factor optimization results, confirming that response surface methodology can effectively reveal the synergistic mechanism of multiple factors and achieve precise process optimization.

[0028] The fiber membrane prepared by this invention exhibits excellent antioxidant and anti-inflammatory properties: ABTS scavenging rate reaches 80%, and DPPH scavenging rate reaches 84%. Figure 19 ). Elisa results ( Figure 18 The results showed that betulin at a concentration of 6 μg / mL inhibited LPS-induced inflammatory responses in macrophages, indicating that birch bark extract possesses certain anti-inflammatory capabilities. Natural antioxidant and anti-inflammatory components were successfully loaded into fibers via electrospinning, endowing the mask material with active antioxidant and anti-inflammatory functions. Attached Figure Description

[0029] Figure 1 The curve showing the effect of ultrasonic temperature on the extraction rate of crude betulin from birch bark;

[0030] The effect of extraction temperature (ultrasonic temperature) on the extraction rate of betulin from birch bark mainly manifests in the promoting effect of heat energy on the solubility and extraction efficiency of betulin. Figure 1It is observed that the extraction rate increases significantly with increasing temperature, reaching its maximum at 65℃. However, the extraction rate decreases with further increases in temperature (above 65℃). This may be because at higher temperatures, the surface tension decreases, resulting in a lower cavitation intensity threshold required for ultrasound, which facilitates the extraction process. However, further increasing the temperature above 65℃ leads to the degradation of the betulin structure due to thermal effects, offsetting the increased mass transfer rate due to the increased temperature, thus resulting in a decrease in the extraction rate of crude betulin from birch bark.

[0031] Figure 2 The curve showing the effect of ultrasonic treatment time on the extraction rate of crude betulin from birch bark;

[0032] Extraction time (ultrasonic treatment time) directly affects the solubility of betulin. During the extraction process, there is a dynamic equilibrium between the dissolution and precipitation of betulin. Figure 2 It was observed that in the initial stage of extraction, the extraction rate of betulin from birch bark increased with prolonged extraction time, reaching its maximum at 4 minutes. Shorter extraction times may result in insufficient release of betulin from the birch bark, leading to a low extraction rate. Appropriately extending the extraction time can improve the solubility of betulin, and continuous cavitation and microbubble implosion exacerbate the rupture of cell walls in the plant material, reducing the restriction of cell structure on the mass transfer process and thus improving the extraction rate. However, with further extension of ultrasonic treatment time, the extraction rate decreased, possibly due to the prolonged ultrasonic treatment time leading to brief periods of high temperature and the release of free radicals, resulting in the degradation of betulin.

[0033] Figure 3 The curve showing the effect of ultrasonic power on the extraction rate of crude betulinol from birch bark;

[0034] The effect of ultrasonic power on the extraction rate of crude betulin from birch bark is mainly manifested in the cavitation effect generated by ultrasound. This effect enhances the interaction between the solvent and the solid by forming microbubbles and their rapid collapse, thus affecting the solubility and precipitation efficiency of betulin. Figure 3 It was observed that the yield increased significantly as the ultrasonic power increased from 100W to 400W, and then decreased. With increasing ultrasonic power, cavitation, thermal, and mechanical effects contributed to the improved extraction rate. However, due to the influence of ultrasound, excessive ultrasonic power may lead to the degradation of betulin in the solvent.

[0035] Figure 4 The curve showing the effect of the material-to-liquid ratio on the extraction rate of betulinol from birch bark;

[0036] The essence of extracting betulin from crude birch bark involves the diffusion of the target component from the raw material into the surrounding solvent. The primary driving force of this process is the concentration difference between the raw material and the external solvent. The greater the concentration difference, the faster the diffusion rate and the more thorough the extraction. Figure 4 It is known that when the solid-liquid ratio is too low (10 mL / g), the solvent is quickly saturated by the dissolved target components, slowing down or stopping the diffusion process, and the effective components in the raw material cannot be fully extracted. As the solid-liquid ratio increases, the extraction rate increases. However, when the solvent volume increases to a certain level (40 mL / g), further increases in solvent yield negligible improvements in the extraction rate, reaching a plateau. This is because the total amount of extractable components in the raw material is fixed.

[0037] Figure 5 Contour plot (left) and 3D surface plot (right) showing the effect of extraction temperature and extraction time on betulin extraction rate; Figure 5 It can be seen that the extraction rate gradually increases with increasing extraction time, reaches a maximum, and then decreases. This indicates that within a certain range, extending the extraction time can effectively improve extraction efficiency and promote the release of active ingredients. However, when the extraction time is too long, the extraction rate decreases, which may be due to degradation of active ingredients caused by over-extraction or excessive evaporation of the solvent. Similarly, changes in extraction temperature also significantly affect the extraction rate. Within a moderate temperature range, the extraction rate increases significantly, but when the temperature is too high, it may lead to degradation of sample components, thus affecting the extraction effect. The curve in the surface plot (right figure) is relatively steep, indicating that extraction time and extraction temperature have little effect on the response value. The contour lines (left figure) are elliptical in shape. Combined with the results of the analysis of variance, this indicates that the interaction between extraction time and extraction temperature is significant.

[0038] Figure 6 Contour plot (left) and 3D surface plot (right) showing the effects of extraction temperature and ultrasonic power on betulin extraction rate; Figure 6 It can be seen that the extraction rate reaches its maximum at moderate ultrasonic power and extraction temperature, indicating that the optimized combination of these two factors can effectively improve the extraction efficiency. With increasing ultrasonic power, the extraction rate gradually increases, but after reaching a certain critical point, further increases in power lead to a decrease in the extraction rate. This may be due to the degradation of sample components or excessive evaporation of the solvent caused by excessive ultrasonic waves. Simultaneously, increasing the extraction temperature also helps to improve the extraction rate, but excessively high temperatures may lead to the loss of active ingredients. The surface plot (right figure) shows a steep curve, indicating that ultrasonic power and extraction temperature have a relatively small impact on the response value. The contour lines (left figure) are nearly circular in shape. Combined with the analysis of variance results, this indicates that the interaction between ultrasonic power and extraction temperature is not significant.

[0039] Figure 7Contour plot (left) and 3D surface plot (right) showing the effect of extraction temperature and solid-liquid ratio on betulin extraction rate; Figure 7 It is evident that increasing the extraction temperature helps improve the extraction rate, but excessively high temperatures may lead to the loss of active ingredients. Regarding the solid-liquid ratio, when the ratio is too low, the solvent is quickly saturated by the dissolved target components, slowing down or stopping the diffusion process, and preventing the full extraction of active ingredients from the raw material. As the solid-liquid ratio increases, the extraction rate increases. However, once the solvent dosage reaches a certain level, further increases in solvent yield negligible improvements in the extraction rate. The steep curvature of the surface plot (right figure) indicates that extraction temperature and solid-liquid ratio have a significant impact on the response value. The elliptical shape of the contour lines (left figure), combined with the variance analysis results, demonstrates a significant interaction between extraction temperature and solid-liquid ratio.

[0040] Figure 8 Contour plot (left) and 3D surface plot (right) showing the effects of extraction time and ultrasonic power on betulin extraction rate; Figure 8 It can be seen that the extraction rate gradually increases with the increase of ultrasonic power and extraction time, reaching a maximum value and then decreasing. This indicates that within a certain range, increasing ultrasonic power and extending extraction time can effectively improve extraction efficiency and promote the release of active ingredients. However, when the ultrasonic power or extraction time is too high, the extraction rate may decrease. This may be due to the degradation of sample components caused by excessive ultrasonic waves or excessive extraction time, or excessive evaporation of the solvent, thus affecting the extraction effect. The curve in the surface plot (right figure) is relatively steep, indicating that ultrasonic power and extraction time have little effect on the response value. The contour lines (left figure) are nearly circular in shape. Combined with the results of the analysis of variance, this indicates that the interaction between ultrasonic power and extraction time is not significant.

[0041] Figure 9 Contour plot (left) and 3D surface plot (right) showing the effect of extraction time and solid-liquid ratio on betulin extraction rate; Figure 9 It is evident that increasing the extraction time helps improve the extraction rate, but excessively long extraction times may lead to the loss of active ingredients. Regarding the solid-liquid ratio, when the ratio is too low, the solvent is quickly saturated by the dissolved target components, slowing down or stopping the diffusion process, and the active ingredients in the raw material cannot be fully extracted. As the solid-liquid ratio increases, the extraction rate increases. However, once the solvent dosage reaches a certain level, further increases in solvent yield negligible improvements in the extraction rate. The steep curvature of the surface plot (right figure) indicates that extraction time and solid-liquid ratio have a significant impact on the response value. The elliptical shape of the contour lines (left figure), combined with the variance analysis results, demonstrates a significant interaction between extraction time and solid-liquid ratio.

[0042] Figure 10Contour plot (left) and 3D surface plot (right) showing the effect of ultrasonic power and material-to-liquid ratio on betulin extraction rate; Figure 10 It can be seen that the extraction rate gradually increases with increasing ultrasonic power, but after reaching a certain critical point, further increasing the power leads to a decrease in the extraction rate. This may be due to the degradation of sample components caused by excessive ultrasonic waves or excessive evaporation of the solvent. Regarding the solid-liquid ratio, when the solid-liquid ratio is too low, the solvent is quickly saturated by the dissolved target components. As the solid-liquid ratio increases, the extraction rate increases. However, once the solvent volume increases to a certain level, further increases in solvent yield negligible improvements in the extraction rate. The steep curvature of the surface plot (right figure) indicates that ultrasonic power and solid-liquid ratio have a significant impact on the response value. The contour lines (left figure) are elliptical in shape. Combined with the variance analysis results, this indicates a significant interaction between ultrasonic power and solid-liquid ratio.

[0043] Figure 11 This is a schematic diagram illustrating the preparation and structure of the Janus dry facial mask of the present invention.

[0044] Figure 11 (A) is a schematic diagram of an electrospinning device and its working process, including a high-voltage power supply, spinning solution and receiving device, etc. Figure 11 (B) is a schematic diagram of the Janus dry mask structure, showing the multi-layered design of the dry mask: it consists of a hydrophilic layer and a hydrophobic layer. The hydrophobic layer prevents water from evaporating too quickly or undergoing reverse osmosis, while the hydrophilic layer promotes the rapid absorption and release of water or essence. Figure 11 (C) is a schematic diagram of the directional water transport of Janus dry face mask. The Janus dry face mask designed in this invention realizes directional water transport, that is, water is transported unidirectionally from the hydrophobic layer to the hydrophilic layer, keeping the face mask in contact with the skin moist while avoiding the loss of moisture from the outer layer.

[0045] Figure 12 The image shows a scanning electron microscope (SEM) image of the hydrophilic fiber membrane prepared in Example 8.

[0046] Depend on Figure 12 As can be seen, the hydrophilic fiber membrane prepared in Example 8 has a clearly visible fiber structure with a fiber diameter ranging from nanometer to submicrometer, exhibiting an interwoven network or porous membrane structure; the fiber surface is relatively smooth with no obvious particle adhesion, and the structure is uniform, with the active ingredients encapsulated in the fiber; the fiber dissociates upon contact with water, and the active ingredients are released immediately.

[0047] Figure 13 This is a scanning electron microscope (SEM) image of the hydrophobic fiber membrane prepared in Example 8;

[0048] Depend on Figure 13 As can be seen, the hydrophobic fiber membrane prepared in Example 8 has a clearly visible fiber structure, a relatively smooth fiber surface, and a uniform structure, indicating that the hydrophobic fiber membrane was successfully prepared.

[0049] Figure 14 The Fourier transform infrared (FTIR) spectrum of the hydrophilic fiber membrane prepared in Example 8 is shown below.

[0050] By sequentially introducing chitosan (CS) and birch bark extract (TE) into a polyvinyl alcohol (PVA) substrate membrane, the hydrophilicity and structural stability of the material were significantly enhanced. Infrared spectroscopy analysis showed that with the addition of CS and TE, the hydrophilicity and structural stability of the material at 3300 cm⁻¹ were significantly improved. -1 The OH / NH stretching vibration peak gradually broadened and shifted, indicating that the intermolecular hydrogen bond network was strengthened; simultaneously, the peak at 1650–1550 cm⁻¹... -1 The presence of chitosan-characteristic amide peaks within the range confirms successful integration into the membrane system; this enhanced hydrogen bonding interaction and multifunctional structure improve the membrane's hydrophilicity.

[0051] Figure 15 The water contact angle (WCA) diagrams for the hydrophilic fiber membrane (left) and hydrophobic fiber membrane (right) prepared in Example 8 are shown.

[0052] from Figure 15 As can be seen, the hydrophilic fiber membrane (left image) has a water contact angle of 29°, exhibiting superhydrophilicity, meaning that it will rapidly release active substances upon contact with water for immediate effect; the hydrophobic fiber membrane (right image) has a water contact angle of 117°, exhibiting hydrophobicity. A composite membrane with a Janus structure was successfully prepared, enabling directional water transport.

[0053] Figure 16 This is a schematic diagram illustrating the dissolution of the hydrophilic fiber membrane prepared in Example 8;

[0054] like Figure 16 As shown, the hydrophilic fiber membrane can completely dissolve within 3 seconds, achieving the purpose of rapid release of active ingredients. This is because the polymer has high hydrophilicity, which leads to increased interaction between the polymer and the solvent. Rapid solvent absorption causes the matrix to expand, ultimately causing the polymer chain to break away from the helical structure.

[0055] Figure 17The left figure is a bar chart of the effect of different concentrations of compounds on the survival of macrophage Raw246.7 cells in the CCK8 experiment of Example 9. The results show that the concentrations of betulin at 0.06 μg / mL, 0.6 μg / mL and 6 μg / mL have no effect on the survival of macrophages. The concentration of betulin at 60 μg / mL has certain cytotoxicity, which confirms that betulin has good biocompatibility within the experimental concentration range.

[0056] Figure 17 The right figure is a bar graph showing the effect of different concentrations of the compound in Example 9 on the viability of Raw246.7 macrophages induced by LPS (lipopolysaccharide), evaluating the protective effect of Betulin against LPS-induced RAW264.7 cell damage. LPS (lipopolysaccharide) induces polarization in Raw246.7 macrophages, producing a pro-inflammatory phenotype. Compared with the control group treated with DMSO alone, the cell viability in the LPS model group was significantly decreased, indicating that LPS successfully induced cell damage; however, after pretreatment with different concentrations of Betulin, cell viability rebounded in a dose-dependent manner, especially in the medium and high concentration groups (e.g., 6 μg / mL), which significantly antagonized the decrease in cell viability caused by LPS, showing that Betulin has a protective effect on macrophages stimulated by LPS. This indicates that different concentrations of Betulin have an anti-inflammatory effect on macrophages.

[0057] Figure 18 This is a bar graph showing the detection of the inflammatory factor C-reactive protein in the supernatant of macrophages Raw246.7 in Example 10;

[0058] ELISA results showed the relative levels of CRP in the supernatant of RAW264.7 macrophages under different treatment conditions. The results indicated that the basal CRP expression level in the control group (Ctrl) was low, while the CRP level significantly increased after LPS stimulation, indicating that LPS successfully induced the cellular inflammatory response. Compared with the LPS model group, different concentrations of Betulin treatment reduced the relative CRP level to varying degrees in a dose-dependent manner, with the most significant inhibitory effect observed at medium to high concentrations (e.g., 6 μg / mL). This suggests that Betulin can effectively inhibit the release of the LPS-induced macrophage inflammatory factor CRP in vitro, exhibiting anti-inflammatory activity, and that the surface birch bark extract possesses certain anti-inflammatory capabilities.

[0059] Figure 19 The graph shows the antioxidant data of the hydrophilic fiber membranes prepared in Examples 11 and 12.

[0060] Depend on Figure 19It is known that the fiber membrane has excellent antioxidant properties, with an ABTS removal rate of 80% and a DPPH removal rate of 84%. By successfully loading natural antioxidant ingredients into the fiber through electrospinning, the mask material is endowed with active antioxidant function, which helps to alleviate oxidative stress and protect the skin barrier in skin care. Detailed Implementation

[0061] Example 1: Construction of the betulin standard curve

[0062] Accurately measure 2 mg of betulinol standard and dilute to 2 mL with ethanol to prepare a 1 mg / mL betulinol stock solution. Then, sequentially pipette 0.1 mL, 0.2 mL, 0.4 mL, and 0.8 mL of the stock solution into 1.5 mL centrifuge tubes and dilute to 1 mL with ethanol to prepare standard solutions of 0.1, 0.2, 0.4, 0.8, and 1 mg / mL. Chromatographic conditions: C18 column (4.6 mm × 250 mm × 5 μm), acetonitrile-water mobile phase, isocratic elution, column temperature 25°C, injection volume 10 μL, intersample injection delay of 10 min, and detection at 210 nm wavelength. Plot a standard curve with betulinol standard concentration on the x-axis and absorbance A on the y-axis. The linear regression equation for the standard curve is Y = 3211.3X + 14.805, and the correlation coefficient R0 is [missing value]. 2 =0.9999, indicating a good linear fit.

[0063] Example 2: Extraction of betulin from birch bark

[0064] 1) Weigh 100mg of birch bark powder (60 mesh) into a 10mL centrifuge tube, add 2mL of 100% ethyl lactate solution at a material-to-liquid ratio of 1:20 (g / mL), and disperse evenly to obtain birch bark solution;

[0065] 2) Perform ultrasonic treatment (power 300W, temperature 45℃, time 2min). The supernatant obtained by centrifugation after ultrasonic treatment is betulin extract. HPLC analysis showed that the betulin extraction rate reached 25.4%.

[0066] Determination of betulin extraction rate: The absorbance of the sample solution was detected at a wavelength of 210 nm. The betulin extraction rate was calculated by substituting the absorbance into the linear regression equation of the standard curve obtained in Example 1.

[0067] Example 3: Optimization of ultrasonic treatment temperature

[0068] Compared to Example 2, the difference lies in the ultrasonic treatment temperatures of 35, 55, 65, and 75°C, resulting in a betulin extraction rate of 24.5–27.4%.

[0069] Example 4: Optimization of Ultrasonic Processing Time

[0070] Compared with Example 2, the difference is that the ultrasonic treatment time was 1, 3, 4 and 5 min, and the betulin extraction rate was 25.3~27.2%.

[0071] Example 5: Optimization of Ultrasonic Processing Power

[0072] Compared with Example 2, the difference is that the ultrasonic treatment power is 100, 200, 400, and 500W, and the betulin extraction rate is 24.6-26.7%.

[0073] Example 6: Optimization of the extraction material-liquid ratio

[0074] Compared with Example 2, the difference is that the material-to-liquid ratio is 10, 30, 40, and 50 mL / g, and the betulin extraction rate is 15.9-27.6%.

[0075] Example 7: Response surface methodology optimization for betulin extraction

[0076] Based on the results of the single-factor experiment, the factors with the greatest influence were selected, with the extraction rate of betulin from birch bark as the response value. According to the Box-Behnken design principle, the extraction conditions were optimized using response surface methodology. Compared with Example 2, the extraction rate of betulin could be increased to 30.0% when the extraction experiment was carried out according to the conditions in Table 2.

[0077] Example 8: Preparation process of Janus facial mask

[0078] Preparation of PLA hydrophobic layer spinning solution: Weigh 0.5g of PLA and dissolve it in a mixed solvent of 3.5mL dichloromethane and 1.5mL DMF. Stir magnetically for 6 hours to obtain a 20% (w / v) transparent PLA hydrophobic layer spinning solution.

[0079] Preparation of the hydrophilic spinning emulsion: Weigh 1.2g of PVA and dissolve it in 10mL of deionized water. Stir in a 90℃ water bath until the PVA is completely dissolved to obtain a clear solution A. Weigh 0.2g of CS and dissolve it in 10mL of acetic acid aqueous solution (1% by mass). Stir to obtain a clear solution B. Mix clear solutions A and B in a ratio of 8:2. Continue stirring until a homogeneous solution is obtained to obtain a PVA / CS mixed aqueous solution. Measure 1mL of betulinol extract prepared in Example 2, add 0.1g of Tween 80, and slowly add 1mL of deionized water under high-speed shearing at 10000rpm for 30min until a homogeneous O / W type emulsion is obtained. Slowly add 2mL of the prepared O / W type emulsion to 5mL of PVA / CS mixed aqueous solution and shear at 10000rpm for 30min to obtain a stable hydrophilic spinning solution.

[0080] Sequential electrospinning:

[0081] First, the PLA hydrophobic layer spinning solution was electrospun, and the spinning parameters were set as follows: 5 mL of spinning solution, 15 kV voltage, 15 cm receiving distance, 2 mL / h feed speed, 25 °C ambient temperature, and 50% humidity.

[0082] Subsequently, the process was switched to a hydrophilic spinning emulsion, and the spinning parameters were set as follows: spinning solution 7 mL, voltage 16 kV, receiving distance 15 cm, feed speed 0.5 mL / h, ambient temperature 25 °C, and humidity 50%.

[0083] Post-processing: The prepared double-layer fiber membrane was dried in a 60℃ drying oven for 6 hours, then peeled off from the release paper (which served as the receiving device) and cut into facial shapes to obtain the Janus dry facial mask based on birch emulsion electrospinning. A schematic diagram of its rapid dissolution is shown below. Figure 16 As shown.

[0084] Comparative Example 1

[0085] Single-component PVA and PVA / CS electrospun masks were prepared using the same method as in Example 8.

[0086] Example 9: Determination of the anti-inflammatory ability of lyophilized samples of betulinol extract ( Figure 17 )

[0087] 100 mL of betulinol extract was freeze-dried to collect enough lyophilized powder for anti-inflammatory testing. After freeze-drying, 1 g of solid powder was obtained, containing 600 mg / g of betulinol. Since betulinol is the main anti-inflammatory agent in the crude birch bark extract, different masses of the lyophilized betulinol extract powder were dissolved in ethanol to obtain ethanol solutions of the lyophilized betulinol extract powder, resulting in betulinol concentrations of 0.06 μg / mL, 0.6 μg / mL, 6 μg / mL, and 60 μg / mL. These solutions were then prepared for use.

[0088] Remove the RAW264.7 cell cryovials from the liquid nitrogen tank and quickly place them in a 37°C water bath to thaw rapidly. In a laminar flow hood, transfer the obtained cell suspension to centrifuge tubes, add 5 mL of DMEM medium containing 10% FBS (fetal saponin), centrifuge at 1000 rpm for 5 min, discard the supernatant, resuspend the cells in medium (DMEM medium containing 10% FBS), seed them into culture flasks, and incubate at 37°C in a 5% CO2 incubator. When the cell density reaches 90%, passage the cells. Discard the old medium, pipette the cells to prepare a single-cell suspension, and seed them into fresh medium at a 1:3 volume ratio for further culture. Collect cells in the logarithmic growth phase, trypsinize them, count them, and adjust the cell density to 1×10⁶ cells / mL using DMEM medium containing 10% FBS.5 Cells were seeded at a density of 100 μL / mL into 96-well plates and incubated overnight to allow cell adhesion. After cell adhesion, the culture medium was replaced with serum-free or low-serum (1% FBS) medium for 4 hours for synchronization.

[0089] A control group (without LPS, but with an equal volume of DMEM medium containing 10% FBS) and an experimental group (with LPS to induce an inflammation model, and ethanol solutions of lyophilized betulinol extract powder containing different concentrations of betulinol (0.06 μg / mL, 0.6 μg / mL, 6 μg / mL, and 60 μg / mL) were set up, with three replicates for each concentration. Cells were cultured for 12 h. The CCK-8 assay was used for detection: 10 μL of CCK-8 reagent was added to each well, and after incubation for 4 h, the absorbance at 450 nm was measured using a microplate reader to calculate cell viability.

[0090] Example 10: Determination of C-reactive protein content in anti-inflammatory response ( Figure 18 )

[0091] Collect the cell culture supernatant from Example 9 and detect the C-reactive protein content according to the ELISA kit instructions.

[0092] Example 11: Determination of DPPH free radical scavenging ability ( Figure 19 ):

[0093] Take 2×2cm 2 In Example 8, the birch bark emulsion electrospun dry face mask was dissolved in 1 mL of deionized water in a 5 mL centrifuge tube to obtain a face mask solution.

[0094] Weigh 0.015 g of DPPH into a black centrifuge tube, add 95% (v / v) anhydrous ethanol to a final volume of 10 mL, and sonicate until completely dissolved. Take 0.5 mL of the mask solution into a black centrifuge tube, add 0.5 mL of DPPH solution to the black centrifuge tube, mix well, and react for 40 min. Measure the absorbance at 517 nm. A decrease in absorbance indicates that the dry mask has the ability to fight DPPH free radicals. Perform three biological replicates.

[0095] Example 12: Determination of ABTS free radical scavenging ability ( Figure 19 )

[0096] Weigh 0.0384 g of ABTS into a black centrifuge tube, add distilled water to a final volume of 10 mL to obtain an ABTS aqueous solution; weigh 0.0066 g of potassium persulfate into a black centrifuge tube, add distilled water to a final volume of 10 mL to obtain a potassium persulfate solution; take equal volumes of the ABTS aqueous solution and potassium persulfate solution into black centrifuge tubes, and let them stand in a refrigerator at 4°C for 24 h to obtain an ABTS stock solution; dilute the ABTS stock solution with water to make its absorbance at 734 nm wavelength 0.70; take 0.5 mL of the mask solution prepared in Example 11 into a black centrifuge tube, add 0.5 mL of the ABTS aqueous solution, mix well, and react for 30 min; measure its absorbance at 734 nm wavelength; a decrease in absorbance indicates that the dry mask has the ability to resist ABTS free radicals. Three biological replicates were performed.

Claims

1. A method for preparing Janus dry facial mask based on birch emulsion electrospinning, comprising the following steps: (1) Preparation of PLA hydrophobic spinning solution: Dissolve 0.45~0.55g of PLA in a mixed solvent of 3.5~4mL of dichloromethane and 1.5~2mL of DMF, and stir magnetically for 5~8 hours to obtain a transparent PLA hydrophobic spinning solution; (2) Preparation of hydrophilic spinning emulsion: Dissolve 1-1.2g of PVA in 8-10mL of deionized water and heat and stir in a water bath at 80-90℃ to obtain a clear solution A; dissolve 0.18-0.22g of CS in a 1% (w / w) acetic acid aqueous solution and stir to obtain a clear solution B; mix clear solution A and clear solution B, wherein the volume percentage of clear solution A is 70-90%, to obtain a PVA / CS mixed aqueous solution; measure 1-1.5mL of betulin. Add 0.1-0.15 g of Tween80 to the extract, slowly add 1-1.5 mL of deionized water at 8000-12000 rpm, and continue shearing for 20-40 min to obtain a homogeneous O / W emulsion; slowly add 1.5-2.5 mL of the O / W emulsion to 4.5-5.5 mL of PVA / CS mixed aqueous solution, and continue shearing at 9000-10000 rpm for 20-30 min to obtain a stable hydrophilic spinning solution; (3) Spinning is carried out by sequentially changing the spinning solution. That is, a hydrophobic PLA fiber membrane is first spun on the receiving device, and then a hydrophilic fiber membrane is spun on the surface of the hydrophobic PLA fiber membrane on the same receiving device immediately after completion, so as to obtain a double-layer fiber membrane on the receiving device. (4) Post-processing: The double-layer fiber membrane obtained in step (3) is dried at 50~60℃ to completely remove the solvent, and then carefully peeled off from the receiving device and cut to obtain Janus dry face mask based on birch emulsion electrospinning.

2. The method for preparing Janus dry facial mask based on birch emulsion electrospinning as described in claim 1, characterized in that: Weigh 95-105 mg of birch bark powder into a 10 mL centrifuge tube, add ethyl lactate or methyl lactate solution at a ratio of 1 g: 10-50 mL, disperse evenly to obtain birch bark solution; after ultrasonic treatment, centrifuge, and the supernatant obtained is betulin extract.

3. The method for preparing Janus dry facial mask based on birch emulsion electrospinning as described in claim 2, characterized in that: The ultrasonic treatment power is 100~500W, the temperature is 35~75℃, and the time is 1~5min.

4. The method for preparing Janus dry facial mask based on birch emulsion electrospinning as described in claim 1, characterized in that: The PLA hydrophobic fiber membrane is spun on the receiving device by electrospinning the PLA hydrophobic layer spinning solution. The spinning solution volume is 4~6mL, the spinning voltage is 14~16kV, the receiving distance is 15~18cm, the feed speed is 1.5~2mL / h, the ambient temperature is 25~30℃, and the humidity is 40~60%.

5. The method for preparing Janus dry facial mask based on birch emulsion electrospinning as described in claim 1, characterized in that: The hydrophilic fiber membrane is spun on the surface of a PLA hydrophobic fiber membrane on the same receiving device by electrospinning the hydrophilic layer spinning emulsion. The spinning liquid volume is 6~8mL, the spinning voltage is 14~16kV, the receiving distance is 15~18cm, the feed speed is 0.5~1mL / h, the ambient temperature is 25~35℃, and the humidity is 40~60%.

6. A Janus dry facial mask based on birch emulsion electrospinning, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 5.

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