Nanocapsules for encapsulating nicotinamide and a method for preparing and using the same

Abstract

The application discloses a kind of nanocapsules of nicotinamide and its preparation method and application, belong to the technical field of cosmetics.The preparation method of the nanocapsules, including the following steps: polyglutamic acid and silver ion solution mixed aqueous solution is added dropwise to the mixed aqueous solution of chitosan and nicotinamide, crosslinking reaction is carried out by mixing stirring, namely obtained.The nanocapsules of nicotinamide prepared by the method, the loading capacity of nicotinamide is 5~12%, and the encapsulation efficiency of nicotinamide is 55~75%.The nanocapsules prepared by the application have good moisturizing, bacteriostatic anti-inflammatory, antioxidant activity effect, and the shelf life of product is long, the preparation method is simple, the raw material used is safe and easy to degrade, and has good biocompatibility;The nanocapsules have high encapsulation efficiency and suitable loading capacity for nicotinamide, which can effectively play the whitening effect, and can ensure low irritation to the skin.

Description

Technical Field

[0001] This invention relates to the field of cosmetic technology, and in particular to a nanocapsule containing nicotinamide, its preparation method, and its application. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Niacinamide (NA) is an amide of vitamin B3 (niacin). It achieves skin whitening by restricting the transfer of melanosomes (melanin) from melanocytes to surrounding keratinocytes. Literature reports that NA also possesses multiple skincare benefits, including anti-inflammatory and anti-aging properties. Due to its relative safety compared to other whitening ingredients, it has gained widespread attention in the cosmetics industry. However, while niacinamide exerts its effects, it can also cause skin irritation, so its content in products needs to be strictly controlled. Studies show that when the niacinamide content in a product is below 2%, it is less irritating to the skin but has poor whitening effects. When the niacinamide content is above 2%, the whitening effect is good, but the skin irritation is significantly increased. Therefore, there is an urgent need for a way to modify niacinamide to reduce irritation, enhance permeability and stability, while ensuring that it can exert its normal activity.

[0004] The paper "Preparation of Oleic Acid (Sodium)-Carboxymethyl Cellulose Sodium Composite Vesicles and Their Application in Encapsulating Nicotinamide" reports the use of composite vesicles formed from oleic acid (sodium) and carboxymethyl cellulose sodium to encapsulate nicotinamide. The prepared composite vesicles achieved nicotinamide loadings exceeding 15%, even reaching nearly 30%. Excessive nicotinamide loading, even with sustained-release properties, could result in an initial nicotinamide release concentration higher than 2%, potentially causing skin irritation. Furthermore, excessive loading and prolonged sustained-release time also lead to nicotinamide waste. In addition, the encapsulation efficiency of the prepared composite vesicles was less than 55%, meaning that a significant amount of nicotinamide was removed during subsequent purification, resulting in waste. Summary of the Invention

[0005] In view of this, the present invention provides a nanocapsule encapsulating niacinamide, its preparation method and application. The nanocapsule reduces skin irritation by releasing niacinamide in a sustained manner and has multiple effects such as good moisturizing, antibacterial and anti-inflammatory, antioxidant activity, whitening and non-irritating. At the same time, the nanocapsule has a high encapsulation rate of niacinamide and a suitable loading amount, which is beneficial for practical application.

[0006] In a first aspect, the present invention provides a method for preparing nanocapsules loaded with nicotinamide, comprising the following steps:

[0007] A mixed aqueous solution of polyglutamic acid and silver ion solution is added dropwise to a mixed aqueous solution of chitosan and nicotinamide, and the mixture is stirred to carry out a cross-linking reaction to obtain the product. In the reaction system of the cross-linking reaction, the concentration of chitosan is 0.3-1 mg / mL and the concentration of polyglutamic acid is 0.1-0.3 mg / mL.

[0008] Preferably, the concentration of silver ions in the crosslinking reaction system is 0.1–0.3 mg / mL.

[0009] Preferably, the volume ratio of the mixed aqueous solution of polyglutamic acid and silver ion solution to the mixed aqueous solution of chitosan and nicotinamide is 5 to 10:1.

[0010] Preferably, the mass ratio of polyglutamic acid to chitosan is 1:2 to 5.

[0011] Preferably, the mass ratio of nicotinamide to the total mass of chitosan and polyglutamic acid is 1:5 to 15.

[0012] Preferably, the silver ion solution is prepared by dissolving silver nitrate in water, then adding polyvinylpyrrolidone, stirring and dissolving to obtain the solution.

[0013] Furthermore, the preparation process of the mixed aqueous solution of chitosan and nicotinamide is as follows: add nicotinamide solution to chitosan solution to obtain the solution; the preparation process of chitosan solution is as follows: stir chitosan powder to dissolve in water, add acetic acid, stir until the solution is clear and transparent, let stand until the bubbles completely disappear, adjust the pH to 5.5-6.5 with sodium hydroxide solution, and make up the volume to obtain the solution.

[0014] Preferably, the molecular weight of the polyglutamic acid is 100-1400 kDa; or, the molecular weight of the polyglutamic acid is 1000-1400 kDa.

[0015] Preferably, the mixing and stirring time is 3-5 hours, the rotation speed is 200-300 rpm, and the crosslinking reaction temperature is 25-33℃.

[0016] Preferably, during the cross-linking reaction, the pH of the reaction system is adjusted to 5.5–6.5.

[0017] Preferably, the method further includes a step of dialysis of the solution after the cross-linking reaction, wherein the content of free nicotinamide is monitored during the dialysis process until the content of free nicotinamide in the solution outside the dialysis bag drops below 0.01%.

[0018] Secondly, the present invention provides nanocapsules loaded with nicotinamide prepared by the above preparation method; wherein the loading of nicotinamide is 5-12% and the encapsulation efficiency of nicotinamide is 55-75%.

[0019] Thirdly, the present invention provides the application of the above-mentioned nanocapsules containing nicotinamide in the preparation of cosmetics.

[0020] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0021] (1) The nanocapsules prepared by this invention have good moisturizing, antibacterial and anti-inflammatory and antioxidant effects, and the products have a long shelf life. At the same time, the preparation method is simple, the raw materials used are safe and easy to degrade, and have good biocompatibility.

[0022] (2) The nanocapsules provided by this invention have easily adjustable encapsulation efficiency and loading capacity of niacinamide. Those skilled in the art can adjust the niacinamide content in the microcapsules according to the application purpose and requirements, which is highly flexible. In addition, the nanocapsules provided by this invention have a high encapsulation efficiency and suitable loading capacity for niacinamide, which can effectively exert a whitening effect while ensuring low skin irritation, making them very suitable for use in cosmetics. Attached Figure Description

[0023] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation thereof. Obviously, those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0024] Figure 1 This is the blank γ-PGA / Ag prepared in Example 2 of this invention. + Particle size distribution diagram of / CS nanocapsule solution;

[0025] Figure 2 This is the blank γ-PGA / Ag prepared in Example 2 of this invention. + Scanning electron microscope image of / CS nanocapsule solution;

[0026] Figure 3 This is the γ-PGA / Ag prepared in Example 4 of this invention. + Particle size distribution diagram of / CS-NA2 nanocapsule solution;

[0027] Figure 4 This is the γ-PGA / Ag prepared in Example 4 of this invention. + Scanning electron microscope image of / CS-NA2 nanocapsule solution;

[0028] Figure 5This is the standard curve of nicotinamide in this invention;

[0029] Figure 6 The γ-PGA / Ag prepared in Examples 3-5 of this invention + Moisturizing properties test diagram of / CS-NA nanocapsule solution;

[0030] Figure 7 The γ-PGA / Ag prepared in Examples 3-5 of this invention + Whitening activity test of / CS-NA nanocapsule solution;

[0031] Figure 8 This is the γ-PGA / Ag prepared in Example 4 of this invention. + The sustained-release experimental test diagram of / CS-NA nanocapsule solution, where the NA curve was tested at 25℃. Detailed Implementation

[0032] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0033] This invention provides a method for preparing a nanocapsule solution loaded with nicotinamide, comprising the following steps:

[0034] A mixed aqueous solution of polyglutamic acid and silver ion solution is added dropwise to a mixed aqueous solution of chitosan and nicotinamide, and the mixture is stirred to carry out a cross-linking reaction to obtain the product. In the reaction system of the cross-linking reaction, the concentration of chitosan is 0.3-1 mg / mL and the concentration of polyglutamic acid is 0.1-0.3 mg / mL.

[0035] Polyglutamic acid is a natural anionic polymer that reacts with Ag. + Ions have an adsorption effect. Silver ions are non-toxic to the human body and have antibacterial, anti-inflammatory and antiseptic effects. At the same time, the inventors found that adding silver ions can significantly extend the shelf life of the product and keep the active ingredients of the product unchanged.

[0036]

[0037] Polyglutamic acid and chitosan self-assemble through polyelectrolyte interaction to form blank microcapsules, which then encapsulate niacinamide (its structural formula is shown above). On one hand, the encapsulation of niacinamide in nanocapsules formed by polyglutamic acid and chitosan controls its release, achieving a sustained-release effect. This effectively avoids the strong irritation caused by high concentrations of niacinamide coming into contact with human skin in a short time, allowing it to better exert its whitening effect. On the other hand, it enhances the stability of niacinamide under different temperature, pH, and light conditions, maintaining its original activity. Furthermore, polyglutamic acid and chitosan, as the main raw materials for the nanocapsules, are both excellent biocompatibility, biodegradability, and non-toxicity. Polyglutamic acid is a natural anionic polymer, and chitosan is a natural cationic polymer. Both have good biocompatibility, biodegradability, and are non-irritating to the skin. The resulting nanocapsules also have superior moisturizing and hydrating effects.

[0038] Therefore, the nanocapsules prepared by the above method have multiple effects such as good moisturizing, antibacterial and anti-inflammatory, antioxidant activity, whitening and non-irritating.

[0039] The inventors discovered that when the concentration of chitosan is 0.3–1 mg / mL and the concentration of polyglutamic acid is 0.1–0.3 mg / mL, the mixed solution of the above substances is transparent. However, when the concentration of polyglutamic acid exceeds 0.3 mg / mL and / or the concentration of chitosan exceeds 1 mg / mL, a white precipitate is formed in the mixed solution, and the higher the concentration, the more white precipitate is formed.

[0040] In the cross-linking reaction system described in this invention, the concentration of silver ions is 0.1–0.3 mg / mL. An appropriate concentration of silver ions is non-toxic to the human body and can exert its antibacterial and anti-inflammatory effects. The preparation method of the silver ion solution in this invention is as follows: silver nitrate is dissolved in water, then polyvinylpyrrolidone is added and stirred until dissolved. Polyvinylpyrrolidone has excellent stability and dispersibility, which can improve the stability of silver ions and prevent their precipitation or aggregation. Adding a certain amount of polyvinylpyrrolidone (PVP) simultaneously with silver ions can effectively improve the adsorption effect of polyglutamic acid on silver ions and enhance stability.

[0041] In this invention, the volume ratio of the mixed aqueous solution of polyglutamic acid and silver ion solution to the mixed aqueous solution of chitosan and nicotinamide is 5 to 10:1.

[0042] In this invention, the mass ratio of polyglutamic acid to chitosan is 1:2 to 5.

[0043] In this invention, the mass ratio of nicotinamide to the total mass of chitosan and polyglutamic acid is 1:5 to 15. The amount of nicotinamide affects its loading and encapsulation efficiency in the nanocapsules, and is more preferably 1:10.

[0044] The preparation process of the mixed aqueous solution of chitosan and nicotinamide in this invention is as follows: Nicotinamide solution is added to a chitosan solution to obtain the solution. The preparation process of the chitosan solution is as follows: Chitosan powder is dissolved in water by stirring, acetic acid is added, and the solution is stirred until it is clear and transparent. The solution is allowed to stand until the bubbles completely disappear, and the pH is adjusted to 5.5–6.5 with sodium hydroxide solution. The solution is then brought to a final volume. After dissolving chitosan in water, the system is semi-transparent and has a high viscosity. Adding acetic acid (pH = 2–3) makes the chitosan molecules more soluble, and the system gradually becomes clear. Then, sodium hydroxide solution is added to adjust the pH to a weakly acidic environment (pH = 5.5–6.5). Under these conditions, the microcapsules formed by cross-linking exhibit better stability.

[0045] In the mixed aqueous solution of polyglutamic acid and silver ion solution described in this invention, the concentration of polyglutamic acid is 4-5 mg / mL.

[0046] This invention does not impose any particular limitation on the molecular weight of the polyglutamic acid. Polyglutamic acid is formed by the polymerization of D-glutamic acid and L-glutamic acid through γ-glutamyl bonds, thereby forming a polypeptide macromolecule, generally with a molecular weight of 10-2000 kDa. Polyglutamic acid with the above molecular weight can form a complex that satisfies the technical effects of this application. The moisturizing effect of polyglutamic acid has no obvious linear relationship with its molecular weight, and may even decrease with increasing molecular weight and amount. Therefore, the preferred molecular weight of the polyglutamic acid in this invention is 100-1400 kDa, more preferably 1000-1400 kDa, and most preferably 1200 kDa.

[0047] In this invention, the mixing and stirring time is 3-5 hours, and the rotation speed is 200-300 rpm; the temperature of the crosslinking reaction is 25-33℃. The preparation process of the nanocapsules of this invention is carried out at room temperature, resulting in low energy consumption.

[0048] In the cross-linking reaction process described in this invention, the pH of the reaction system is adjusted to 5.5–6.5. Under this pH condition, the molecular structures of the two substances are most stable, which is conducive to their cross-linking reaction. At the same time, this pH value helps maintain the integrity of the microcapsules, improving their drug loading capacity and sustained-release performance.

[0049] This invention also includes a step of dialysis of the solution after the cross-linking reaction. This is to remove unencapsulated free nicotinamide and purify the obtained nanocapsule solution. This invention does not impose special limitations on the dialysis procedure; commonly used dialysis methods in the art can be used. The specifications of the dialysis bag are determined according to the molecular weight. The content of free nicotinamide is monitored during the dialysis process. Specifically, the solution outside the dialysis bag is sampled every 3-4 hours, and the absorbance is measured using a UV spectrophotometer. The free nicotinamide content is calculated to be 0.01% or lower using a standard curve.

[0050] In this invention, the water is preferably double-distilled water or triple-distilled water.

[0051] This invention also provides nanocapsules loaded with nicotinamide prepared by the above-described method; wherein the loading amount of nicotinamide is 5-12%, and the encapsulation efficiency of nicotinamide is 55-75%. This nanocapsule solution has a sustained-release effect on nicotinamide, with an appropriate loading amount ensuring no skin irritation, and a high encapsulation efficiency, allowing more nicotinamide to be effectively encapsulated within the nanocapsules, thus improving the stability of the nanocapsules and facilitating the sustained and quantitative release of the drug.

[0052] This invention also provides the application of the above-mentioned niacinamide-encapsulated nanocapsules in the preparation of cosmetics. Those skilled in the art can adjust the niacinamide content in the microcapsules according to the application purpose and requirements, flexibly meeting various application purposes in a range of whitening products.

[0053] In this invention, the mass content of the nanocapsules containing nicotinamide in the cosmetic is preferably 5-10%, more preferably 10%.

[0054] In this invention, the cosmetic product preferably has the effects of whitening without irritation, moisturizing and hydrating, antibacterial and anti-inflammatory, and antioxidant activity.

[0055] In this invention, the cosmetics are in forms including but not limited to toners, creams, lotions, masks, and gels.

[0056] The present invention does not impose any special restrictions on the preparation method of the cosmetics, and the nanocapsules containing niacinamide can be directly added to the matrix of various whitening, non-irritating, moisturizing, antibacterial and anti-inflammatory, antioxidant and other cosmetics, which is convenient to use.

[0057] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0058] Example 1: Preparation of polyglutamic acid solution, chitosan solution, silver nitrate solution, and nicotinamide solution

[0059] (1) Polyglutamic acid (γ-PGA) solution

[0060] Weigh 250 mg of polyglutamic acid powder and dissolve it in 10 mL of double-distilled water. Stir with a magnetic stirrer at 250 rpm for 45 min at room temperature until the solution is clear and transparent. Transfer the solution to a 50 mL volumetric flask, add double-distilled water to make up to volume, and shake well to obtain a 5 mg / mL polyglutamic acid solution.

[0061] (2) Chitosan (CS) solution

[0062] Weigh 250 mg of chitosan powder and dissolve it in 10 mL of double-distilled water. Stir with a magnetic stirrer at 250 rpm for 20 min at room temperature, then add 1 mL of acetic acid and stir at room temperature for 45 min until the solution is clear and transparent. Let it stand for a certain time until the bubbles completely disappear. Adjust the pH with 1 mol / L NaOH solution, stir evenly, transfer to a 50 mL volumetric flask, add double-distilled water to make up to volume, and shake well to obtain a 5 mg / mL chitosan solution.

[0063] (3) Silver nitrate solution (Ag) + )

[0064] Under normal temperature and light-protected conditions, weigh 12.5 mg of silver nitrate solid and dissolve it in 10 mL of double-distilled water. Shake until the solid is completely dissolved, then add 0.5 mg of polyvinylpyrrolidone powder and stir well. Transfer to a 25 mL volumetric flask, add double-distilled water to make up to volume, and shake well to obtain a silver ion solution of 500 μg / mL.

[0065] (4) Nicotinamide solution (NA)

[0066] Weigh 25 mg of nicotinamide and dissolve it in 5 mL of double-distilled water. Stir with a magnetic stirrer at 250 rpm at room temperature for 45 min until the solution is clear and transparent. Transfer the solution to a 25 mL volumetric flask, add double-distilled water to make up to volume, and shake well to obtain a 1 mg / mL nicotinamide solution.

[0067] Example 2: Preparation of blank nanocapsules

[0068] Polyglutamic acid with a molecular weight of 1200 kDa was prepared by mixing a pre-mixed polyglutamic acid solution with a silver nitrate solution at a certain ratio under stirring at room temperature. Double-distilled water was added to the chitosan solution, and the polyglutamic acid and silver ion solution were slowly added dropwise to the chitosan solution, controlling the concentration of silver ions in the system to be 0.25 mg / mL. The mass ratio of polyglutamic acid to chitosan was 1:3, and the concentration of chitosan was 0.5 mg / mL. Blank γ-PGA / Ag was prepared by stirring at room temperature for 4 hours. + / CS nanocapsule solution.

[0069] Figure 1 The blank γ-PGA / Ag prepared for this embodiment + The particle size distribution diagram of the / CS nanocapsule solution shows that the blank nanocapsule particles are concentrated between 100 and 200 nm, and the PDI value is less than 30%, indicating that the blank nanocapsules are uniform in size.

[0070] Figure 2 The blank γ-PGA / Ag prepared for this embodiment + The scanning electron microscope image of the / CS nanocapsule solution shows that the blank nanocapsules are spherical in shape and uniformly and stably dispersed in the solution.

[0071] Example 3

[0072] This embodiment provides a nanocapsule (γ-PGA / Ag) encapsulated with nicotinamide. + The preparation method of the / CS-NA1) solution includes the following steps:

[0073] Polyglutamic acid with a molecular weight of 1200 kDa was prepared by mixing a pre-mixed polyglutamic acid solution with a silver nitrate solution at a certain ratio under stirring at room temperature. Double-distilled water and nicotinamide solution were added to a chitosan solution. The polyglutamic acid and silver ion solution were then slowly added dropwise to the chitosan and nicotinamide mixture, maintaining a silver ion concentration of 0.25 mg / mL. The mass ratio of polyglutamic acid to chitosan was 1:3, and the chitosan concentration was 0.5 mg / mL. The mass ratio of the total mass of polyglutamic acid and chitosan to the mass of nicotinamide was 15:1. The mixture was stirred at room temperature for 4 hours to prepare γ-PGA / Ag. + The / CS-NA1 nanocapsule solution was purified by dialysis until the content of free nicotinamide in the solution outside the dialysis bag was less than 0.01%.

[0074] Example 4

[0075] This embodiment provides a nanocapsule (γ-PGA / Ag) encapsulated with nicotinamide. + The preparation method of ( / CS-NA2) solution includes the following steps:

[0076] Polyglutamic acid with a molecular weight of 1200 kDa was prepared by mixing a pre-mixed polyglutamic acid solution with a silver nitrate solution at a certain ratio under stirring at room temperature. Double-distilled water and nicotinamide solution were added to a chitosan solution. The polyglutamic acid and silver ion solution were then slowly added dropwise to the chitosan and nicotinamide mixture, maintaining a silver ion concentration of 0.25 mg / mL. The mass ratio of polyglutamic acid to chitosan was 1:3, and the chitosan concentration was 0.5 mg / mL. The mass ratio of the total mass of polyglutamic acid and chitosan to the mass of nicotinamide was 10:1. The mixture was stirred at room temperature for 4 hours to prepare γ-PGA / Ag. + The / CS-NA2 nanocapsule solution was purified by dialysis until the content of free nicotinamide in the solution outside the dialysis bag was less than 0.01%.

[0077] Figure 3 The γ-PGA / Ag prepared in this embodiment + The particle size distribution diagram of the / CS-NA2 nanocapsule solution shows that γ-PGA / Ag +The particle size of the / CS-NA2 nanocapsules is concentrated between 100 and 200 nm, and the PDI value is less than 30%, resulting in uniformly sized blank nanocapsules.

[0078] Figure 4 The γ-PGA / Ag prepared in this embodiment + Scanning electron microscope image of / CS-NA2 nanocapsule solution. The image shows γ-PGA / Ag + / CS-NA2 nanocapsules are spherical in shape and are uniformly and stably dispersed in solution.

[0079] Example 5

[0080] This embodiment provides a nanocapsule (γ-PGA / Ag) encapsulated with nicotinamide. + The preparation method of ( / CS-NA3) solution includes the following steps:

[0081] Polyglutamic acid with a molecular weight of 1200 kDa was prepared by mixing a pre-mixed polyglutamic acid solution with a silver nitrate solution at a certain ratio under stirring at room temperature. Double-distilled water and nicotinamide solution were added to a chitosan solution. The polyglutamic acid and silver ion solution were then slowly added dropwise to the chitosan and nicotinamide mixture, maintaining a silver ion concentration of 0.25 mg / mL. The mass ratio of polyglutamic acid to chitosan was 1:3, and the chitosan concentration was 0.5 mg / mL. The mass ratio of the total mass of polyglutamic acid and chitosan to the mass of nicotinamide was 5:1. The mixture was stirred at room temperature for 3 hours to prepare γ-PGA / Ag. + The / CS-NA3 nanocapsule solution was purified by dialysis until the content of free nicotinamide in the solution outside the dialysis bag was less than 0.01%.

[0082] Test case

[0083] 1. Determination of encapsulation rate and load capacity:

[0084] Nicotinamide standards were scanned in the wavelength range of 200–400 nm using a UV spectrophotometer to identify the maximum absorption wavelength of nicotinamide, which was then selected as the measurement wavelength. Nicotinamide is known to have absorption peaks around 216 nm and 260 nm. Based on literature, the specific absorption peak at 260 nm was chosen. 1 g of nicotinamide solid was accurately weighed and dissolved in 1 mL of double-distilled water. Based on this, standard stock solutions of 2, 4, 8, 16, 32, 64, 128, 256, and 300 μg / mL were prepared. The absorbance at different concentrations at 260 nm was measured using UV spectrophotometry, and a standard curve of absorbance versus concentration was plotted. Figure 5 ).

[0085] The γ-PGA / Ag +The CS-NA nanocapsule solution was centrifuged at high speed (12000 rpm) for 30 min, the supernatant was collected, diluted by a certain factor, and the absorbance was measured at λ = 260 nm using a UV spectrophotometer. The absorbance was then substituted into the nicotinamide standard curve to calculate the mass of free nicotinamide. The drug loading capacity (DLC) and encapsulation efficiency (EE) of nicotinamide were calculated using the following formulas:

[0086]

[0087]

[0088] Where M1 is the total amount of nicotinamide added, M2 is the amount of nicotinamide not encapsulated in the nanocapsules, and M is the total mass of the nanocapsules.

[0089] Table 1 Encapsulation efficiency (EE) and payload (DLC) data for Examples 1-3

[0090] Example 2 59.27 6.67 Example 3 70.24 10.33 Example 4 60.41 11.35

[0091] As can be seen from Table 1, the encapsulation efficiency of nicotinamide in the nanocapsules of Examples 2 to 4 can reach more than 55%, and the loading amount is 6 to 12%. Among them, Example 3 has the best encapsulation efficiency and a suitable loading amount.

[0092] 2. Evaluation of the moisturizing properties of nano-microcapsule solutions in Examples 3-5: Nano-microcapsules containing nicotinamide and glycerol were prepared into samples with a concentration of 5 mg / mL. The test temperature was room temperature. 100 g of dried color-changing silica gel was placed at the bottom of a desiccator. Approximately 2 g of the solution was weighed into 3 cm diameter weighing dishes and placed in the silica gel desiccator for the moisturizing experiment. The weighing dishes were removed and weighed every 24 hours, and this was repeated 5 times to determine the mass difference between the samples before and after weighing. The moisturizing rate was calculated as follows: Moisturizing rate (%) = H n / H0×100% (where H is the formula) n H0 represents the water content after n days of storage, and H0 represents the water content before storage.

[0093] Figure 6 γ-PGA / Ag from Examples 3-5 +The hydration test results of the / CS-NA nanocapsules show that all three types of microcapsules have good moisturizing effects. Within the first two days of the experiment, the moisturizing content reached 70% or higher. After four days, the moisturizing content decreased slightly but still reached 60% or higher, indicating a relatively superior moisturizing effect. This is mainly because the raw materials composing the nanocapsules are primarily polyglutamic acid and chitosan. Polyglutamic acid contains a large number of three functional groups (carboxyl, carbonyl, and amino) with hydration capabilities, as well as hydrogen bonds. Its moisturizing and water-locking effects are 500 times that of hyaluronic acid. Simultaneously, chitosan itself is a raw material for the synthesis of hyaluronic acid, promoting the production of hyaluronic acid, a skin moisturizing component, and thus also playing a role in moisturizing and anti-wrinkle effects, increasing skin moisture and elasticity. Therefore, all three types of nanocapsules encapsulating niacinamide exhibit good moisturizing effects.

[0094] 3. Evaluation of the whitening activity of nano-microcapsule solutions in Examples 3-5: A specific cell model (mouse melanocyte-keratinocyte co-culture) was cultured in vitro, and the inhibitory effect of the whitening ingredients on melanocyte growth was detected using the CCK-8 assay. The whitening efficacy of the test substances was also evaluated. A certain amount of nano-microcapsules was weighed and dissolved in PBS solution to prepare test samples of different concentrations. Cell suspension was seeded in 96-well plates, approximately 100 μL per well, with three replicates. The culture plates were pre-cultured in an incubator for a period of time (37℃, 5% CO2). Different concentrations of the test substances were added to each well of the culture plate. 10 μL of CCK-8 solution was added to each well, and the culture plates were incubated in an incubator for 1-4 hours. The absorbance (OD) at 450 nm was measured using a microplate reader. The cell viability of the blank group was set at 100%, and the inhibition rate of melanocytes was calculated using the following formula:

[0095] Figure 7 The images show the skin-whitening activity test results of the γ-PGA / Ag+ / CS-NA nanocapsules in Examples 3-5. This experiment investigated the inhibition of melanin production in mouse melanoma cells by the three microcapsules synthesized in Examples 3-5 and by using NA alone, and tested the skin-whitening effect of γ-PGA / Ag+ / CS-NA. The results showed that all three microcapsules and NA had a certain inhibitory effect on melanin production, with higher nicotinamide content resulting in better inhibition.

[0096] 4. Example 4: Sustained-release experiment of nanocapsule solution: The release behavior of nicotinamide nanocapsules at different temperatures was studied by dialysis. 1 mL of nicotinamide solution and γ-PGA / Ag were added... + / CS-NA was added to a dialysis bag and placed in 50 mL of phosphate buffer (pH 7.4), with three replicates. The mixture was shaken at 120 rpm in a constant temperature incubator. The nicotinamide solution was set at 25°C, and the γ-PGA / Ag ratio was also adjusted. +The CS-NA solution was incubated at temperatures of 25℃, 37℃, and 50℃. At time points of 0.5, 1, 3, 6, 12, 24, 48, and 72 h, 1 mL of the release medium was taken out and 1 mL of the same buffer solution was added at the same time. The nicotinamide content in the release medium was determined using a UV spectrophotometer.

[0097] Figure 8 γ-PGA / Ag in Example 4 + The sustained-release experiment of / CS-NA2 nanocapsules shows that free nicotinamide solution can be rapidly released, and after 24 hours, almost all nicotinamide without microcapsule encapsulation is released, while γ-PGA / Ag + / CS-NA nanocapsules have a controlled and sustained-release effect on nicotinamide release. The results showed that the controlled and sustained-release effect was best when the ambient temperature was 25℃ and 30℃.

[0098] 5. Skin Irritation Experiment of Nanocapsules in Examples 3-5: Three types of nanocapsules loaded with different amounts of nicotinamide were used in the experiment. Each nanocapsule was prepared to a specific concentration and excipients were added to form creams. A specific amount of nicotinamide was weighed, prepared to a specific concentration, and excipients were added to form creams (the nicotinamide content was equivalent to that of nanocapsules with a loading of 6.67%). BALB / c mice (6-8 weeks old, 18-22g) were used as experimental animals. The experimental procedure was as follows: Twenty healthy mice were selected, ear-tagged, and randomly divided into four groups of five mice each. After the mice adapted to their environment, their backs were shaved (along both sides of the spine). In three groups, 20mg of microcapsules were applied to the shaved area on the left side and 20mg of excipients to the right side. In the remaining group, 20mg of nicotinamide was applied to the shaved area on the left side and 20mg of excipients to the right side. All were covered with sterile and non-irritating gauze. Each group of five mice was further divided into five categories, and the application was performed sequentially for 6h, 12h, 24h, 48h, and 72h, followed by washing with warm water. Visually inspect the application site for redness, swelling, or edema. Calculate the average score of the skin reaction at each observation time point and evaluate the intensity of stimulation according to the table below, thereby observing its irritation to the skin.

[0099] Table 2. Average scores and irritation intensity evaluation of skin reaction scores.

[0100]

[0101] Table 3. Results of skin irritation experiments on nano-capsules of Examples 3-5.

[0102]

[0103] According to the experimental results in Table 3, compared with nicotinamide alone, the microencapsulated nicotinamide cream had no irritating effect on mice.

[0104] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing nanocapsules loaded with nicotinamide, characterized in that, Includes the following steps: A mixed aqueous solution of polyglutamic acid and silver ions is added dropwise to a mixed aqueous solution of chitosan and nicotinamide, and the mixture is stirred to carry out a cross-linking reaction, thus obtaining the product. In the reaction system of the cross-linking reaction, the concentration of chitosan is 0.3~1 mg / mL, the concentration of polyglutamic acid is 0.1~0.3 mg / mL, and the concentration of silver ions is 0.1~0.3 mg / mL. During the mixing and stirring process of the cross-linking reaction, the pH of the reaction system is adjusted to 5.5~6.

5. The volume ratio of the mixed aqueous solution of polyglutamic acid and silver ion solution to the mixed aqueous solution of chitosan and nicotinamide is 5~10:1; the mass ratio of polyglutamic acid to chitosan is 1:2~5; and the mass ratio of nicotinamide to the total mass of chitosan and polyglutamic acid is 1:5~15. The silver ion solution is prepared by dissolving silver nitrate in water, then adding polyvinylpyrrolidone and stirring until dissolved.

2. The preparation method according to claim 1, characterized in that, The molecular weight of the polyglutamic acid is 100~1400kDa.

3. The preparation method according to claim 1, characterized in that, The molecular weight of the polyglutamic acid is 1000~1400kDa.

4. The preparation method according to claim 1, characterized in that, The preparation process of the mixed aqueous solution of chitosan and nicotinamide is as follows: add nicotinamide solution to chitosan solution to obtain the solution; the preparation process of chitosan solution is as follows: stir chitosan powder into water, add acetic acid, stir until the solution is clear and transparent, let stand until the bubbles completely disappear, adjust the pH to 5.5~6.5 with sodium hydroxide solution, and make up the volume to obtain the solution.

5. The preparation method according to claim 1, characterized in that, The mixing and stirring time is 3-5 hours, and the rotation speed is 200-300 rpm.

6. The preparation method according to claim 1, characterized in that, It also includes a step of dialysis of the solution after the cross-linking reaction, wherein the dialysis process monitors the content of free nicotinamide until the content of nicotinamide drops below 0.01%.

7. The nicotinamide-loaded nanocapsules prepared by the preparation method according to any one of claims 1 to 6, characterized in that, The nicotinamide-encapsulated nanocapsules contain 5-12% nicotinamide and have an encapsulation efficiency of 55-75%.

8. The application of the nicotinamide-encapsulated nanocapsules as described in claim 7 in the preparation of cosmetics.

Images