Silk fibroin moisturizing lotion and method for preparing the same

Abstract

This invention provides a sericin moisturizing toner and its preparation method, relating to the field of cosmetic technology. The sericin moisturizing toner of this invention comprises, by mass percentage: 0.15%~1.20% high molecular weight sericin, 0.05%~0.80% low molecular weight hydrolyzed sericin, 0.5%~3.0% betaine, 0.05%~0.50% ectoine, 0.5%~4.0% trehalose, 0.01%~0.15% sodium hyaluronate, 0.005%~0.08% ceramide precursor, 0.02%~0.30% pH buffer, with the balance being water. The mass ratio of high molecular weight sericin to low molecular weight hydrolyzed sericin is 1:(0.15~1.20), and the pH of the toner is 5.0~6.2. This invention realizes the construction of a gradient moisturizing system in a stable, weakly acidic toner system, which consists of "soft surface film formation - stratum corneum hydration - lipid barrier assisted repair". It has good application prospects in moisturizing, soothing and barrier care cosmetics.

Description

Technical Field

[0001] This invention relates to the field of cosmetic technology, and in particular to a sericin moisturizing lotion and its preparation method. Background Technology

[0002] Sericin is a natural protein obtained during the degumming process of silkworms. Rich in hydrophilic amino acids such as serine, aspartic acid, and glycine, it possesses hygroscopic, water-retaining, film-forming, and skin-friendly properties, and has been used in cosmetics such as toners, lotions, emulsions, and creams. Current sericin-based toners typically use natural sericin as a single water-soluble moisturizing ingredient, or fully hydrolyze sericin into small-molecule sericin peptides to improve its permeability in the stratum corneum. These technical solutions primarily focus on the hygroscopic and water-retaining effects of sericin itself, failing to fully utilize the differences in the effects of sericin proteins of different molecular weights on the skin surface and in the stratum corneum, and thus struggling to simultaneously address the multi-layered skincare needs of surface film-forming hydration, stratum corneum moisturization, and barrier repair.

[0003] High molecular weight sericin possesses good flexible film-forming and moisture-retention capabilities; however, in aqueous systems, without proper fractionation and hydration, it is prone to problems such as increased turbidity, flocculation, precipitation, or filtration difficulties due to molecular chain entanglement, local aggregation, or interaction with electrolyte components, affecting the appearance and storage stability of toners. Low molecular weight hydrolyzed sericin exhibits good dispersibility and stratum corneum affinity, but its sustained film-forming ability on the skin surface is insufficient when used alone, resulting in limited long-lasting moisturizing effects. Therefore, using only high molecular weight sericin or only low molecular weight sericin is insufficient to form a stable and well-defined moisturizing system.

[0004] Moisturizing or soothing ingredients such as betaine, trehalose, sodium hyaluronate, and ectoine are widely used in water-based skincare products, while ingredients like phytosphingosine are commonly used in barrier care products. However, these ingredients are usually simply compounded as regular moisturizers or barrier aids, lacking a structured design that matches the molecular weight classification of sericin. Furthermore, lipid barrier-related ingredients such as phytosphingosine exhibit poor dispersion stability in weakly acidic aqueous systems, which can easily affect product clarity, microfiltration permeability, and storage stability if not handled properly.

[0005] Therefore, it is still necessary to develop a sericin moisturizing toner that can exist stably in a weakly acidic aqueous system and can achieve synergistic effects of surface film formation, stratum corneum hydration, and lipid barrier repair. Summary of the Invention

[0006] In view of this, the present invention provides a sericin moisturizing toner and its preparation method. The present invention fractionates the molecular weight of sericin, and after low-temperature swelling of high molecular weight sericin, it is compounded with low molecular weight hydrolyzed sericin, betaine, ectoine, trehalose, sodium hyaluronate, and phytosphingosine under pH 5.0-6.2 conditions. Combined with pre-dispersion or pre-salting and microfiltration sterilization processes, a gradient moisturizing system of "surface flexible film formation - stratum corneum hydration - lipid barrier assisted repair" is constructed in a stable, weakly acidic toner system. This system shows good application prospects in moisturizing, soothing, and barrier care cosmetics.

[0007] The first aspect of this invention provides a sericin moisturizing lotion, comprising, by weight percentage: High molecular weight sericin 0.15%~1.20%, low molecular weight hydrolyzed sericin 0.05%~0.80%, betaine 0.5%~3.0%, ectoine 0.05%~0.50%, trehalose 0.5%~4.0%, sodium hyaluronate 0.01%~0.15%, ceramide precursor 0.005%~0.08%, pH buffer 0.02%~0.30%, balance being water; The mass ratio of high molecular weight sericin to low molecular weight hydrolyzed sericin is 1:(0.15~1.20), and the pH of the lotion is 5.0~6.2.

[0008] Preferably, the high molecular weight sericin has a weight-average molecular weight of 80-300 kDa, and the components with a weight-average molecular weight of 80 kDa or higher account for more than 70% of the total mass of the high molecular weight sericin.

[0009] Preferably, the low molecular weight hydrolyzed sericin has a weight-average molecular weight of 0.5 to 10 kDa, and the components with a weight-average molecular weight of less than 10 kDa account for more than 80% of the total mass of the low molecular weight hydrolyzed sericin.

[0010] Preferably, the sodium hyaluronate has a weight-average molecular weight of 10-800 kDa, more preferably 50-300 kDa.

[0011] Preferably, the ceramide precursor exists in the form of lactate, citrate, cyclodextrin inclusion complex, aqueous dispersion, or liposome predispersant; more preferably, the ceramide precursor is at least one of phytosphingosine, sphingosine, dihydrosphingosine, or tetraacetylphytosphingosine; when phytosphingosine, sphingosine, or dihydrosphingosine is used, it is pre-salted with lactic acid or citrate at a molar ratio of 1:(0.8~1.5), stirred at 25~45°C until transparent or slightly opalescent, and then added to the aqueous phase; when tetraacetylphytosphingosine is used, the tetraacetylphytosphingosine is an aqueous dispersion, cyclodextrin inclusion complex, or D... 90Liposome predispersants with a density of ≤180 nm.

[0012] Preferably, the pH buffer is at least one of citric acid / sodium citrate, lactic acid / sodium lactate, and sodium dihydrogen phosphate / disodium hydrogen phosphate.

[0013] Preferably, the toner further includes 0-0.60% preservative, more preferably 0.20%-0.60%. When it contains preservative, the preservative is at least one of phenoxyethanol, ethylhexylglycerin, 1,2-hexanediol, and capryloyl hydroxamic acid. When it does not contain preservative, the toner is packaged in a disposable sealed container or a non-backflow pump container after being sterilized by 0.22 μm microfiltration.

[0014] Preferably, the lotion shows no visible sediment after being placed at 25°C for 30 days, has a turbidity increase of ≤5.0 NTU, and shows no stratification after centrifugation at 3000 r / min for 30 min.

[0015] A second aspect of this invention provides a method for preparing the silk fibroin moisturizing lotion, comprising the following steps: S1. The sericin stock solution is fractionated by ultrafiltration or gel filtration to obtain high molecular weight sericin components and sericin components to be hydrolyzed. S2. Enzymatically hydrolyze the sericin component to be hydrolyzed, and after enzyme inactivation, obtain low molecular weight hydrolyzed sericin by ultrafiltration. S3. High molecular weight sericin is swollen in water at 2-15℃ for 2-12 h to obtain a high molecular weight sericin swelling solution. S4. When using phytosphingosine, sphingosine, or dihydrosphingosine, mix it with lactic acid or citric acid at a molar ratio of 1:(0.8~1.5) and stir at 25~45℃ for 10~60 min to form a transparent or slightly opalescent pre-salted dispersion; when using tetraacetyl phytosphingosine, prepare it as a water-dispersible tetraacetyl phytosphingosine, tetraacetyl phytosphingosine cyclodextrin inclusion complex, or D... 90 A pre-dispersion of tetraacetyl phytosphingosine liposomes with a wavelength of ≤180 nm was prepared. Then, betaine, ectoine, trehalose, sodium hyaluronate, low molecular weight hydrolyzed sericin, the pre-salted dispersion or pre-dispersion, and a pH buffer were added to the high molecular weight sericin swelling solution. The mixture was stirred and compounded at 15~30℃, and the pH was adjusted to 5.0~6.2. S5. After 0.45 μm pre-filtration and 0.22 μm microfiltration for sterilization, the product is filled to obtain the cosmetic water.

[0016] Preferably, the enzymatic hydrolysis in S2 uses at least one of neutral protease, alkaline protease, and papain, with a hydrolysis temperature of 35~55℃, a pH of 6.0~8.5, and a hydrolysis time of 1~6 h.

[0017] A third aspect of the present invention provides the use of the aforementioned toner in the preparation of moisturizing, soothing, or barrier-repairing cosmetics.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention uses sericin according to molecular weight, so that high molecular weight sericin mainly plays the role of flexible film formation and surface water retention, while low molecular weight hydrolyzed sericin mainly plays the role of stratum corneum affinity and hydration. This overcomes the problems of unclear action levels of single ungraded sericin, insufficient stability of high molecular weight sericin aqueous solution, and limited long-term film formation and water retention capacity of low molecular weight hydrolyzed sericin.

[0019] This invention combines low molecular weight hydrolyzed sericin with betaine, ectoine, trehalose, and sodium hyaluronate to form a synergistic hydration system between amino acid / peptide moisturizing ingredients and natural moisturizing factors. Under the flexible water-retaining film formed by high molecular weight sericin, the moisture retention capacity of the stratum corneum is improved, thereby connecting surface water retention and stratum corneum hydration, enhancing the continuous moisturizing and soothing effects of the toner.

[0020] This invention further introduces phytosphingosine and improves its dispersion compatibility in aqueous systems through pre-dispersion or weak acid pre-salting, making it compatible with weak acid systems of pH 5.0~6.2, low-temperature swelling process and microfiltration sterilization steps. While maintaining the appearance stability and gentleness of the toner, it provides auxiliary repair support for the skin lipid barrier.

[0021] The preparation method of this invention adopts a process route that combines molecular weight classification, low-temperature swelling, weak acid compounding and microfiltration sterilization, which helps to reduce the risk of high molecular weight sericin aggregation in aqueous solutions, improve the clarity, filtration permeability and storage stability of the system, and is suitable for preparing sericin toners that are transparent to slightly opalescent, have a refreshing feel and multi-layered moisturizing effects. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] The molecular weights of high-molecular-weight sericin and low-molecular-weight hydrolyzed sericin were determined by gel permeation chromatography. Calibration curves were established using protein standards of known molecular weights to determine the weight-average molecular weight and the proportion of components within the corresponding molecular weight range. The particle size of the tetraacetyl phytosphingosine liposome predispersant was determined by dynamic light scattering.

[0024] The turbidity determination method is as follows: Take a sample and place it in a clean cuvette. Measure the initial turbidity using a turbidity meter at 25℃. Seal another sample and place it at 25℃ for 30 days. Measure the turbidity again under the same conditions. At the same time, observe the sample visually and record whether precipitation, flocculation, or stratification occurs.

[0025] The centrifugal stability test method is as follows: take 10 mL of sample and place it in a centrifuge tube, centrifuge at 25℃ and 3000 r / min for 30 min, and observe with the naked eye whether the sample shows layering, precipitation, flocculation or obvious precipitation.

[0026] The method for determining the 0.22 μm microfiltration transit time is as follows: Take 100 mL of sample at 25℃, pre-filter it through a 0.45 μm filter membrane, and then filter it through a 0.22 μm polyvinylidene fluoride microporous filter membrane at a filtration pressure of 0.10 MPa. Record the time required for the sample to completely pass through the filter membrane. If significant membrane blockage, a sharp decrease in flow rate, or incomplete sample passage occurs during filtration, it is recorded as filtration difficulty.

[0027] The method for determining the increase in stratum corneum moisture content is as follows: The inner forearm skin is selected as the test area. After equilibration for 30 minutes in an environment with a temperature of 20–22℃ and a relative humidity of 40%–60%, the baseline value is measured; 2.0 mg / cm³ 2 The sample was coated with the appropriate amount of product, and the stratum corneum moisture content was measured using a skin moisture meter at 2 h and 8 h after coating.

[0028] Thirty healthy subjects were selected for transepidermal water loss and stratum corneum moisture content testing. After equilibration for 30 minutes in an environment of 21±1℃ and 50±5% relative humidity, the tests were conducted. The test site was the inner forearm, divided into test areas of 3 cm × 3 cm. Each sample was tested at a concentration of 2.0 mg / cm². 2 Apply evenly. The stratum corneum moisture content was measured using a stratum corneum moisture meter, and the baseline value before use and the values ​​after 2 hours and 8 hours of use were recorded. Transepidermal moisture loss was measured using a transepidermal moisture loss meter, and the baseline value before use and the values ​​after 24 hours of use were recorded.

[0029] The method for determining the residual rate of flexible water-retaining film is as follows: The sample is prepared at 2.0 mg / cm³. 2 The sample was evenly coated onto an artificial skin membrane, an ex vivo stratum corneum model, or a PMMA test plate and dried at 25°C and 50% relative humidity for 1 h to obtain the membrane layer to be tested. The unrinsed sample membrane layer was used as the initial membrane layer, and the membrane layer after rinsing with deionized water at a fixed flow rate for 60 s and drying again was used as the rinsed membrane layer. The residual amount of sericin in the membrane layer was determined by protein staining, BCA protein quantification, or fluorescent labeling.

[0030] Thirty healthy subjects aged 18-55 years participated in the patch test. The skin at the test site showed no obvious erythema, lesions, inflammation, or allergic reactions. The sample was placed in a patch applicator and applied to the skin of the subject's back or inner forearm for 24 hours. After 24 hours of closed application, the patch applicator was removed, and skin reactions were observed at 30 minutes and 24 hours after removal. The erythema score was the higher of the two scores at each observation time point, and the mean ± standard deviation was calculated. The scores were then assigned from 0 to 4, where 0 indicated no erythema or no visible reaction, 1 indicated mild erythema, 2 indicated significant erythema, 3 indicated erythema with papules or edema, and 4 indicated significant edema, vesicles, or a strong positive reaction.

[0031] Unless otherwise stated, all tests were repeated 3 times, and results are expressed as mean ± standard deviation.

[0032] Example 1: A sericin moisturizing toner, comprising the following components by weight percentage: High molecular weight sericin 0.60%, low molecular weight hydrolyzed sericin 0.30%, betaine 1.50%, ectoine 0.20%, trehalose 2.00%, sodium hyaluronate 0.06%, phytosphingosine 0.02%, citric acid / sodium citrate buffer 0.12%, water to 100%.

[0033] Preparation method: S1. Take the sericin stock solution, filter it through a 100 kDa ultrafiltration membrane to obtain high molecular weight sericin components, concentrate and dialyze to remove salt, so that the weight average molecular weight of high molecular weight sericin is 150 kDa. S2. Take the permeate (or the original sericin solution), add neutral protease, and enzymatically hydrolyze for 3 h at 45℃ and pH 7.0. Inactivate the enzyme at 85℃ for 15 min. Collect the permeate through a 10 kDa ultrafiltration membrane, then concentrate and collect the retentate using a 1 kDa ultrafiltration membrane to obtain low molecular weight hydrolyzed sericin with a weight average molecular weight of 3.5 kDa. S3. Add high molecular weight sericin to water and swell at 8°C for 6 hours to obtain a uniform swollen solution; S4. Mix phytosphingosine and lactic acid at a molar ratio of 1:1.1 and stir at 35°C for 30 min to form a transparent to slightly opalescent phytosphingosine lactate pre-salted dispersion. S5. Add betaine, ectoine, trehalose, sodium hyaluronate, low molecular weight hydrolyzed sericin from step S2, pre-salted dispersion of phytosphingosine lactate from step S4, and citric acid / sodium citrate buffer to the swelling solution in step S3 in sequence, stir at 25°C until homogeneous, and adjust the pH to 5.6. S6, after being pre-filtered with 0.45 μm and sterilized by microfiltration with 0.22 μm, is filled into a non-backflow pump container to obtain the final product.

[0034] Example 2 The difference from Example 1 is as follows: 0.20% high molecular weight sericin, 0.08% low molecular weight hydrolyzed sericin, 0.80% betaine, 0.08% ectoine, 0.80% trehalose, 0.02% sodium hyaluronate, 0.008% phytosphingosine, 0.08% citric acid / sodium citrate buffer, and water to 100%.

[0035] Example 3 The difference from Example 1 is as follows: 1.00% high molecular weight sericin, 0.65% low molecular weight hydrolyzed sericin, 2.50% betaine, 0.40% ectoine, 3.50% trehalose, 0.12% sodium hyaluronate, 0.06% phytosphingosine, 0.20% lactic acid / sodium lactate buffer, water to 100%, and pH 5.4.

[0036] Example 4 The difference from Example 1 is that the weight-average molecular weight of the high molecular weight sericin is 220 kDa, the weight-average molecular weight of the low molecular weight hydrolyzed sericin is 6.0 kDa, and the ceramide precursor is 0.03% tetraacetyl phytosphingosine; the tetraacetyl phytosphingosine is a tetraacetyl phytosphingosine hydroxypropyl-β-cyclodextrin inclusion complex, which is added according to the effective content of tetraacetyl phytosphingosine. After stirring with some water at 25°C for 20 min to form a transparent to microemulsified dispersion, it is then added to the high molecular weight sericin swelling solution.

[0037] Example 5 The difference from Example 1 is that the low-temperature swelling temperature of the high molecular weight sericin is 4°C, the swelling time is 10 h, and the pH buffer is a mixture of lactic acid / sodium lactate and citric acid / sodium citrate, with a final pH of 5.2.

[0038] Comparative Example 1 The difference from Example 1 is that no high molecular weight sericin is added, only 0.90% low molecular weight hydrolyzed sericin is added.

[0039] Comparative Example 2 The difference from Example 1 is that low molecular weight hydrolyzed sericin is not added, but only 0.90% high molecular weight sericin is added.

[0040] Comparative Example 3 The difference from Example 1 is that molecular weight fractionation is not performed, and 0.90% of unfractionated sericin is added directly.

[0041] Comparative Example 4 The difference from Example 1 is that: low-temperature swelling is not performed, and high molecular weight sericin is directly added with stirring at 45°C.

[0042] Comparative Example 5 The difference from Example 1 is that phytosphingosine is not added.

[0043] Table 1. Results of stability and appearance tests

[0044] Table 2. Results of tests on moisturizing, film-forming, and barrier-assisted repair.

[0045] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A sericin moisturizing toner, characterized in that, Included by weight percentage: High molecular weight sericin 0.15%~1.20%, low molecular weight hydrolyzed sericin 0.05%~0.80%, betaine 0.5%~3.0%, ectoine 0.05%~0.50%, trehalose 0.5%~4.0%, sodium hyaluronate 0.01%~0.15%, ceramide precursor 0.005%~0.08%, pH buffer 0.02%~0.30%, balance being water; The mass ratio of high molecular weight sericin to low molecular weight hydrolyzed sericin is 1:(0.15~1.20), and the pH of the lotion is 5.0~6.

2.

2. The sericin moisturizing lotion according to claim 1, characterized in that, The high molecular weight sericin has a weight-average molecular weight of 80-300 kDa, and the component with a weight-average molecular weight of 80 kDa or higher accounts for more than 70% of the total mass of the high molecular weight sericin; the low molecular weight hydrolyzed sericin has a weight-average molecular weight of 0.5-10 kDa, and the component with a weight-average molecular weight of less than 10 kDa accounts for more than 80% of the total mass of the low molecular weight hydrolyzed sericin; the sodium hyaluronate has a weight-average molecular weight of 10-800 kDa.

3. The sericin moisturizing lotion according to claim 1, characterized in that, The ceramide precursor is at least one of phytosphingosine, sphingosine, dihydrosphingosine, and tetraacetylphytosphingosine.

4. The sericin moisturizing lotion according to claim 3, characterized in that, The ceramide precursor exists in the form of lactate, citrate, cyclodextrin inclusion complex, aqueous dispersion, or liposome predispersant.

5. The sericin moisturizing lotion according to claim 1, characterized in that, The pH buffer is at least one of citric acid / sodium citrate, lactic acid / sodium lactate, and sodium dihydrogen phosphate / disodium hydrogen phosphate.

6. The sericin moisturizing lotion according to claim 1, characterized in that, The lotion also contains 0-0.60% preservatives.

7. The sericin moisturizing lotion according to claim 6, characterized in that, When containing preservatives, the preservatives are at least one of phenoxyethanol, ethylhexylglycerin, 1,2-hexanediol, and capryloyl hydroxamic acid; when not containing preservatives, the lotion is packaged in a disposable sealed container or a non-backflow pump container after being sterilized by 0.22 μm microfiltration.

8. The method for preparing the sericin moisturizing lotion according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. The sericin stock solution is fractionated by ultrafiltration or gel filtration to obtain high molecular weight sericin components and sericin components to be hydrolyzed. S2. Enzymatically hydrolyze the sericin component to be hydrolyzed, and after enzyme inactivation, obtain low molecular weight hydrolyzed sericin by ultrafiltration. S3. High molecular weight sericin is swollen in water at 2-15℃ for 2-12 h to obtain a high molecular weight sericin swelling solution. S4. When using phytosphingosine, sphingosine, or dihydrosphingosine, mix it with lactic acid or citric acid at a molar ratio of 1:(0.8~1.5) and stir at 25~45℃ for 10~60 min to form a transparent or slightly opalescent pre-salted dispersion; when using tetraacetyl phytosphingosine, prepare it as a water-dispersible tetraacetyl phytosphingosine, tetraacetyl phytosphingosine cyclodextrin inclusion complex, or D... 90 A pre-dispersion of tetraacetyl phytosphingosine liposomes with a wavelength of ≤180 nm was prepared. Then, betaine, ectoine, trehalose, sodium hyaluronate, low molecular weight hydrolyzed sericin, the pre-salted dispersion or pre-dispersion, and a pH buffer were added to the high molecular weight sericin swelling solution. The mixture was stirred and compounded at 15~30℃, and the pH was adjusted to 5.0~6.

2. S5. After 0.45 μm pre-filtration and 0.22 μm microfiltration for sterilization, the product is filled to obtain the cosmetic water.

9. The preparation method according to claim 8, characterized in that, The enzymatic hydrolysis in S2 uses at least one of neutral protease, alkaline protease, and papain.

10. The preparation method according to claim 9, characterized in that, The enzymatic hydrolysis temperature is 35~55℃, the pH is 6.0~8.5, and the enzymatic hydrolysis time is 1~6 h.

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