Chitosan nanocapsule as well as preparation method and application thereof

Abstract

The invention relates to the technical field of functional materials, in particular to a chitosan nanocapsule as well as a preparation method and application thereof. The preparation method of the chitosan nanocapsule comprises the following steps: (a) mixing and emulsifying a chitosan solution, an oil-in-water emulsifier and essential oil to form an oil-in-water emulsion, adding an aqueous solution of sodium tripolyphosphate into the oil-in-water emulsion, and stirring to obtain a first mixture; (b) adding the first mixture into an oil phase solvent containing a water-in-oil emulsifier, and stirring to obtain a multiple emulsion; and (c) adding an aqueous solution of a dialdehyde cross-linking agent into the multiple emulsion, carrying out a cross-linking reaction, collecting a solid-phase substance, and drying. The physical / chemical double-crosslinking chitosan nanocapsule is obtained by utilizing physical crosslinking between the chitosan and the sodium tripolyphosphate and chemical crosslinking between the chitosan and the binary aldehyde crosslinking agent, so that the encapsulation efficiency and the encapsulation efficiency of the nanocapsule are remarkably improved; meanwhile, the nanocapsule also has pH responsiveness and has a slow release effect after pH response.

Description

Technical Field

[0001] The present disclosure relates to the technical field of functional materials, and in particular to a chitosan nanocapsule and a preparation method and application thereof. Background Art

[0002] Nanoencapsulation is a technique that encapsulates a core material (such as essential oils, drugs, or bioactive substances) within a shell material to protect it from the external environment. Currently, nanoencapsulation technology has been widely used in many fields, including perfume production, drug delivery, food preservation, and functional fabrics. However, with the continuous development of nanoencapsulation technology and industry, the encapsulation and protective functions of traditional nanocapsules' core materials are no longer able to meet the needs of various fields. Therefore, stimuli-responsive nanocapsules with specialized functions such as targeting and controllability have become a research focus.

[0003] There are many types of common wall materials used for nanocapsules, including natural polymer materials, synthetic polymer materials and inorganic materials. Compared with synthetic polymer materials and inorganic materials, natural polymer materials have good biocompatibility, biodegradability and antibacterial properties. However, natural polymer materials such as chitosan have poor mechanical strength, and low encapsulation rate and encapsulation efficiency. In addition, nanocapsules with chitosan as the wall material experience a burst release phenomenon after stimulation and lose the sustained release effect. Therefore, the development of a nanocapsule that has both high encapsulation rate and encapsulation efficiency, stimulus responsiveness and retention of sustained release effect after stimulation is of great significance for the expansion of the application field of nanocapsules. Summary of the Invention

[0004] The embodiments of the present disclosure at least provide a chitosan nanocapsule and a preparation method and application thereof.

[0005] In a first aspect, the present disclosure provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0006] (a) mixing and emulsifying a chitosan solution, an oil-in-water emulsifier, and an essential oil to form an oil-in-water emulsion, adding an aqueous solution of sodium tripolyphosphate to the oil-in-water emulsion, and stirring to obtain a first mixture;

[0007] (b) adding the first mixture to an oil phase solvent containing a water-in-oil emulsifier, and stirring to obtain a double emulsion;

[0008] (c) adding an aqueous solution of a dialdehyde cross-linking agent to the double emulsion to carry out a cross-linking reaction, collecting the solid phase, and drying it to obtain the chitosan nanocapsules;

[0009] The mass ratio of chitosan in the chitosan solution to sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate is 1:(0.4-1.05); the mass ratio of chitosan in the chitosan solution to the dialdehyde crosslinking agent in the aqueous solution of the dialdehyde crosslinking agent is 1:(1-2.55).

[0010] In an optional embodiment, the mass ratio of the sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate to the dialdehyde cross-linking agent in the aqueous solution of the dialdehyde cross-linking agent is (0.3-0.5):1.

[0011] In an optional embodiment, the chitosan solution has a chitosan concentration of 1 wt% to 5 wt%. Further, the chitosan solution is prepared by dissolving chitosan in an acetic acid aqueous solution; the acetic acid concentration in the acetic acid aqueous solution is 1 wt% to 5 wt%.

[0012] In an optional embodiment, the oil-in-water emulsifier includes Tween 60. Furthermore, in the oil-in-water emulsion, the concentration of the oil-in-water emulsifier is 0.1 wt% to 2 wt%.

[0013] In an optional embodiment, the essential oil is selected from aromatic essential oils. Further, the aromatic essential oil includes at least one of floral, citrus, and herbal essential oils.

[0014] In an optional embodiment, the mass ratio of the essential oil to the chitosan in the chitosan solution is (0.2-2):1.

[0015] In an optional embodiment, during the mixing and emulsification, the stirring speed is 500 to 2000 rpm, and the stirring time is 4 to 12 hours.

[0016] In an optional embodiment, the concentration of sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate is 1 wt% to 10 wt%.

[0017] In an optional embodiment, the aqueous solution of sodium tripolyphosphate is added dropwise to the oil-in-water emulsion, and further, the dropping speed is 0.5 to 2 mL / min.

[0018] In an optional embodiment, the oil-phase solvent includes liquid paraffin, and the water-in-oil emulsifier includes Span 80. Furthermore, the volume ratio of the first mixture to the oil-phase solvent is 1:(3-5); and the concentration of the water-in-oil emulsifier in the oil-phase solvent is 1 wt% to 10 wt%.

[0019] In an optional embodiment, the stirring to obtain the double emulsion has a stirring speed of 500 to 2000 rpm and a stirring time of 5 to 60 min.

[0020] In an optional embodiment, the concentration of the dialdehyde cross-linking agent in the aqueous solution is 2 wt% to 50 wt%. Furthermore, the dialdehyde cross-linking agent includes glutaraldehyde.

[0021] In an optional embodiment, the aqueous solution of the dialdehyde crosslinking agent is added dropwise to the double emulsion, and further, the dropping speed is 0.5 to 2 mL / min.

[0022] In an optional embodiment, the temperature of the cross-linking reaction is 20 to 30° C., and the time of the cross-linking reaction is 10 to 15 hours.

[0023] In an optional embodiment, the solid phase is collected by centrifugation, wherein the centrifugation speed is 8000-10000 rpm and the centrifugation time is 5-15 min.

[0024] In a second aspect, the embodiments of the present disclosure further provide a chitosan nanocapsule, which is prepared by any one of the preparation methods of the chitosan nanocapsule provided in the first aspect.

[0025] In a third aspect, the embodiments of the present disclosure further provide the use of the chitosan nanocapsules provided in the second aspect in functional fabrics.

[0026] The chitosan nanocapsules provided in the embodiments of the present disclosure, as well as their preparation methods and applications, utilize physical crosslinking between chitosan and sodium tripolyphosphate and chemical crosslinking between chitosan and a dialdehyde crosslinking agent to obtain a physical / chemically double-crosslinked chitosan nanocapsule, which significantly improves the encapsulation rate and encapsulation efficiency of the nanocapsule. At the same time, the nanocapsule is also pH-responsive and has a sustained-release effect after pH response.

[0027] Furthermore, the disclosed embodiments adjust the dosage of sodium tripolyphosphate and dialdehyde crosslinking agents to regulate the degree of physical crosslinking and chemical crosslinking, thereby optimizing the balance between the encapsulation rate, encapsulation efficiency, pH responsiveness, and sustained release effect after the response of the nanocapsules.

[0028] In order to make the above-mentioned objects, features and advantages of the present disclosure more obvious and easy to understand, preferred embodiments are given below and described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the embodiments. The drawings herein are incorporated into and constitute a part of the specification. These drawings illustrate embodiments consistent with the present disclosure and, together with the specification, are used to illustrate the technical solutions of the present disclosure. It should be understood that the following drawings only illustrate certain embodiments of the present disclosure and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without inventive effort.

[0030] Figure 1 A comparison chart of the encapsulation efficiency and encapsulation rate of nanocapsules in different embodiments and comparative examples of the present disclosure is shown;

[0031] Figure 2 A comparison of the sustained-release effects of the nanocapsules of different embodiments and comparative examples of the present disclosure is shown;

[0032] Figure 3 Shown are the release curves of Example 3 of the present disclosure under different pH environments;

[0033] Figure 4 The infrared spectra of Example 3 of the present disclosure after release under different pH environments are shown;

[0034] Figure 5 The scanning electron micrographs of Example 3 of the present disclosure after release under different pH environments are shown. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. The components of the embodiments of the present disclosure generally described and shown here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present disclosure is not intended to limit the scope of the present disclosure for protection, but merely represents the selected embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present disclosure.

[0036] The "and / or" mentioned in this article describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone.

[0037] Existing pH-responsive nanocapsules primarily use pH-sensitive materials as their wall materials. However, upon exposure to environmental pH, these pH-sensitive wall materials often completely cleave or dissolve, causing the core material to be fully released in a short period of time, thus losing its sustained-release effect. In some cases, however, pH-responsive nanocapsules are required to accelerate release upon exposure to pH stimulation while still maintaining a certain sustained-release effect to prolong the release of the core material, such as essential oils.

[0038] Based on this, the present disclosure provides a method for preparing chitosan nanocapsules. On the basis of moderate physical crosslinking, moderate chemical crosslinking is introduced to make the nanocapsules responsive to pH stimulation and still retain a certain sustained-release ability after pH stimulation, which helps to broaden the application field of nanocapsules.

[0039] The defects in the above solutions are the results obtained by the inventors after practice and careful research. Therefore, the process of discovering the above problems and the solutions proposed by this disclosure for the above problems below should be the contributions made by the inventors to this disclosure during the disclosure process.

[0040] To facilitate understanding of this embodiment, the preparation method of the chitosan nanocapsules disclosed in the embodiment of the present disclosure is first introduced in detail. The preparation method of the chitosan nanocapsules provided in the embodiment of the present disclosure comprises the following steps:

[0041] (a) mixing and emulsifying a chitosan solution, an oil-in-water emulsifier, and an essential oil to form an oil-in-water emulsion, adding an aqueous solution of sodium tripolyphosphate to the oil-in-water emulsion, and stirring to obtain a first mixture;

[0042] (b) adding the first mixture to an oil phase solvent containing a water-in-oil emulsifier and stirring to obtain a double emulsion;

[0043] (c) adding an aqueous solution of a dialdehyde cross-linking agent to the double emulsion to carry out a cross-linking reaction, collecting the solid phase, and drying it to obtain chitosan nanocapsules;

[0044] The mass ratio of chitosan in the chitosan solution to sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate is 1:(0.4-1.05); the mass ratio of chitosan in the chitosan solution to the dialdehyde cross-linking agent in the aqueous solution of the dialdehyde cross-linking agent is 1:(1-2.55).

[0045] The present disclosure provides a method for preparing chitosan nanocapsules with physical / chemical dual crosslinking and pH responsiveness, which solves the problem that traditional stimulus-responsive nanocapsules release suddenly when stimulated by the environment and lose their sustained-release ability. Specifically, the pH stimulus responsiveness of the nanocapsules is achieved by physical crosslinking between chitosan and sodium tripolyphosphate, and the chemical crosslinking between chitosan and dialdehyde crosslinking agents enables the nanocapsules to maintain the capsule wall from being completely destroyed after being stimulated by pH, thereby accelerating the release of the core material while retaining a certain sustained-release effect. At the same time, the amount of sodium tripolyphosphate and dialdehyde crosslinking agents is regulated to improve the encapsulation rate and encapsulation efficiency of the nanocapsules.

[0046] Under alkaline conditions, the chitosan nanocapsules disclosed herein readily deprotonate the protonated amino groups on the chitosan, eliminating electrostatic interactions with the phosphate groups of sodium tripolyphosphate, accelerating the release of essential oils. Furthermore, because the chemical crosslinks between the chitosan and the dialdehyde crosslinker are maintained and unaffected by pH changes, the nanocapsules maintain their wall structure moderately under alkaline conditions, rather than completely breaking down, resulting in a sustained-release effect.

[0047] In the preparation method disclosed herein, in an oil-in-water emulsion, a chitosan solution serves as a continuous phase, an essential oil serves as a hydrophobic core material, an emulsifier is adsorbed at the oil-water interface, and after an aqueous solution of sodium tripolyphosphate is added, the phosphate groups of the sodium tripolyphosphate and the protonated amino groups of the chitosan are physically cross-linked through electrostatic interaction, initially solidifying to form a chitosan wall. Furthermore, by preparing a double emulsion, the volatilization of the essential oil is reduced, and an aqueous solution of a dialdehyde cross-linking agent is subsequently added to react between the amino groups on the chitosan and the aldehyde groups of the dialdehyde cross-linking agent to form Schiff base bonds, thereby achieving chemical cross-linking, enhancing the mechanical properties of the wall material, and imparting a sustained-release effect to the nanocapsules after pH stimulation.

[0048] Furthermore, the raw materials for preparing chitosan nanocapsules disclosed in the present invention are mostly biomass materials, which are widely available and easily accessible, and can not only achieve better biocompatibility effects, but also help promote the high-value conversion of biomass materials.

[0049] The present invention ensures the pH stimulation responsiveness of the nanocapsules and the sustained release effect after pH stimulation by regulating the amounts of chitosan in the chitosan solution, sodium tripolyphosphate in the sodium tripolyphosphate aqueous solution, and dialdehyde crosslinking agent in the dialdehyde crosslinking agent aqueous solution.

[0050] For example, in different embodiments, the mass ratio of chitosan in the chitosan solution to sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate can be 1:0.4, 1:0.5, 1:0.6, 1:0.8, 1:1, 1:1.05 or a range consisting of any two of them, preferably 1:(0.5-0.7); when the amount of sodium tripolyphosphate exceeds the above range, sodium tripolyphosphate is easily excessively physically cross-linked with chitosan and aggregated, which is not conducive to the coating of essential oils, and affects the cross-linking degree of subsequent chemical cross-linking, resulting in a poor sustained-release effect after pH stimulation; when the amount of sodium tripolyphosphate is too little and below the above range, it is also not conducive to the coating of essential oils, and also leads to poor pH stimulation responsiveness.

[0051] For example, in different embodiments, the mass ratio of chitosan in the chitosan solution to the dialdehyde cross-linking agent in the aqueous solution of the dialdehyde cross-linking agent can be 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.55 or a range consisting of any two of them, preferably 1:(1.2-1.8); when the dialdehyde cross-linking agent is too much and exceeds the above range, it is easy to excessively chemically cross-link with chitosan, which is not only not conducive to the encapsulation of essential oils, but also affects the pH stimulus responsiveness and the sustained release effect after stimulation; when the dialdehyde cross-linking agent is too little and below the above range, it cannot effectively maintain the capsule wall structure after pH stimulation, affecting the sustained release effect after pH stimulation.

[0052] In some embodiments, the mass ratio of sodium tripolyphosphate in an aqueous solution of sodium tripolyphosphate to the dialdehyde crosslinking agent in an aqueous solution of the dialdehyde crosslinking agent is (0.3-0.5):1, for example, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, or any combination thereof. Further studies have found that regulating the amounts of sodium tripolyphosphate and the dialdehyde crosslinking agent to meet the above conditions improves the encapsulation efficiency and encapsulation rate while accelerating the release of the nanocapsules after pH stimulation and achieving a better sustained-release effect, with a more preferred ratio of (0.35-0.45):1.

[0053] In some embodiments, the chitosan solution has a chitosan concentration of 1 wt% to 5 wt%, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or any combination thereof. Furthermore, the chitosan solution is prepared by dissolving chitosan in an aqueous acetic acid solution; the acetic acid concentration in the aqueous acetic acid solution is 1 wt% to 5 wt%, for example, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, or any combination thereof.

[0054] In some embodiments, the oil-in-water emulsifier includes Tween 60. Furthermore, in the oil-in-water emulsion, the concentration of the oil-in-water emulsifier is 0.1 wt % to 2 wt %, for example, 0.1 wt %, 0.5 wt %, 1 wt %, 1.5 wt %, 2 wt % or any two thereof, thereby further helping to ensure the stability of the emulsion.

[0055] In some embodiments, the essential oil is selected from aromatic essential oils. Further, the aromatic essential oil includes at least one of floral, citrus, and herbal essential oils.

[0056] In some embodiments, the mass ratio of essential oil to chitosan in the chitosan solution is (0.2-2):1, for example, it can be 0.2:1, 0.25:1, 0.5:1, 1:1, 1.5:1, 2:1 or a range consisting of any two of them, which is more conducive to improving the encapsulation efficiency of the nanocapsules, the uniformity of the particle size of the nanocapsules and the sustained-release stability.

[0057] In some embodiments, the essential oil includes, but is not limited to, lavender-coconut oil blend.

[0058] In some embodiments, during the mixing emulsification, the stirring speed is 500 to 2000 rpm, for example, it can be 500 rpm, 800 rpm, 1000 rpm, 1500 rpm, 2000 rpm or a range consisting of any two thereof; the stirring time is 4 to 12 h, for example, it can be 4 h, 6 h, 8 h, 10 h, 12 h or a range consisting of any two thereof.

[0059] In actual operation, the preparation of the oil-in-water emulsion may include: adding an oil-in-water emulsifier to a chitosan solution, stirring evenly, then adding essential oil, and stirring at a stirring speed of 500-2000 rpm for 4-12 hours to form an oil-in-water emulsion.

[0060] In some embodiments, the concentration of sodium tripolyphosphate in the aqueous solution is 1 wt% to 10 wt%, for example, 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt% or any two thereof.

[0061] In some embodiments, the aqueous solution of sodium tripolyphosphate is added dropwise to the oil-in-water emulsion. Further, the rate of addition is 0.5 to 2 mL / min, for example, 0.5 mL / min, 0.8 mL / min, 1 mL / min, 1.2 mL / min, 1.5 mL / min, 1.8 mL / min, 2 mL / min or a range consisting of any two of them. The aqueous solution of sodium tripolyphosphate is added dropwise, which helps to form a uniform three-dimensional network structure between sodium tripolyphosphate and chitosan and form uniform nanoparticles to avoid aggregation. In actual operation, the aqueous solution of sodium tripolyphosphate can be added to the oil-in-water emulsion using a syringe pump, but is not limited to this.

[0062] In some embodiments, the oil-phase solvent includes liquid paraffin, and the oil-in-water emulsifier includes Span 80. Furthermore, the volume ratio of the first mixture to the oil-phase solvent is 1:(3-5), for example, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or a range consisting of any two thereof; the concentration of the oil-in-water emulsifier in the oil-phase solvent is 1wt% to 10wt%, for example, 1wt%, 3wt%, 5wt%, 8wt%, 10wt%, or a range consisting of any two thereof. Regulating the types and amounts of the oil-phase solvent and the oil-in-water emulsifier to meet the above conditions is more conducive to controlling the particle size of the nanocapsules and ensuring the stability of the emulsion.

[0063] In some embodiments, the stirring speed to obtain the double emulsion is 500 to 2000 rpm, for example, 500 rpm, 800 rpm, 1000 rpm, 1500 rpm, 2000 rpm, or a range consisting of any two thereof; the stirring time is 5 to 60 min, for example, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, or a range consisting of any two thereof.

[0064] In actual operation, the preparation of the double emulsion may include: directly pouring the first mixture into an oil phase solvent containing a water-in-oil emulsifier, and continuously stirring at a stirring speed of 500 to 2000 rpm for 5 to 60 minutes to form the double emulsion.

[0065] In some embodiments, the concentration of the dialdehyde crosslinking agent in the aqueous solution is 2 wt% to 50 wt%, for example, 2 wt%, 5 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, or any combination thereof. Furthermore, the dialdehyde crosslinking agent includes glutaraldehyde.

[0066] In some embodiments, the aqueous solution of the dialdehyde crosslinking agent is added dropwise to the double emulsion. Furthermore, the rate of addition is 0.5 to 2 mL / min, for example, 0.5 mL / min, 0.8 mL / min, 1 mL / min, 1.2 mL / min, 1.5 mL / min, 1.8 mL / min, 2 mL / min, or a range consisting of any two thereof. The aqueous solution of the dialdehyde crosslinking agent is added dropwise, which helps to form uniform chemical crosslinks between the dialdehyde crosslinking agent and chitosan. In actual operation, the aqueous solution of the dialdehyde crosslinking agent can be added to the double emulsion using a syringe pump, but is not limited thereto.

[0067] In some embodiments, the cross-linking reaction temperature is 20-30° C., and the cross-linking reaction time is 10-15 hours. In actual operation, the cross-linking reaction is accompanied by stirring at a speed of 500-2000 rpm, but is not limited thereto.

[0068] In some embodiments, the solid phase is collected by centrifugation, preferably at a speed of 8,000 to 10,000 rpm for 5 to 15 minutes.

[0069] In actual operation, the solid phase collected by centrifugation is further washed with anhydrous ethanol and deionized water, and then freeze-dried to obtain chitosan nanocapsules.

[0070] It is understood that unless otherwise specified in the present disclosure, the corresponding temperature is room temperature (25° C.).

[0071] The present disclosure also provides a chitosan nanocapsule, which is prepared by any one of the chitosan nanocapsule preparation methods provided in the present disclosure.

[0072] The chitosan nanocapsules disclosed herein have an encapsulation rate of 8% to 15%, an encapsulation efficiency of 80% to 93%, and can sustain release for more than 36 days at room temperature.

[0073] Compared with acidic conditions, the chitosan nanocapsules disclosed in the present invention have a higher release rate under alkaline conditions and can be sustained for more than 6 days.

[0074] The disclosed embodiments also provide applications of chitosan nanocapsules in functional fabrics.

[0075] The chitosan nanocapsules provided in the embodiments of the present disclosure, as well as their preparation methods and applications, utilize physical crosslinking between chitosan and sodium tripolyphosphate and chemical crosslinking between chitosan and a dialdehyde crosslinking agent to obtain a physical / chemically double-crosslinked chitosan nanocapsule, which significantly improves the encapsulation rate and encapsulation efficiency of the nanocapsule. At the same time, the nanocapsule is also pH-responsive and has a sustained-release effect after pH response.

[0076] Example 1

[0077] This embodiment provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0078] (1) 2.4 g of chitosan was dissolved in 117.6 g of a 2 wt% aqueous acetic acid solution to obtain a chitosan solution. 1.8 g of Tween 60 was added to the chitosan solution and stirred uniformly. 0.534 g of lavender-coconut oil composite essential oil was then added and stirred at 1000 rpm for 6 h to obtain an oil-in-water emulsion.

[0079] (2) Dissolve a certain amount of sodium tripolyphosphate in deionized water to obtain a 4 wt% aqueous solution of sodium tripolyphosphate. Add 24 mL of the aqueous solution of sodium tripolyphosphate dropwise to the oil-in-water emulsion prepared in step (1) at a rate of 1 mL / min (with stirring at 1000 rpm) to obtain a first mixture. Pour the first mixture into 600 mL of liquid paraffin containing 2 wt% of Span 80 and stir at 1000 rpm for 30 minutes to obtain a double emulsion.

[0080] (3) A 30 wt% aqueous solution of glutaraldehyde was prepared, and 12 mL of the aqueous solution was added dropwise to the double emulsion prepared in step (2) at a rate of 0.6 mL / min. The mixture was stirred at 1000 rpm for 12 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected, washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0081] Example 2

[0082] This embodiment provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0083] (1) Prepare an oil-in-water emulsion according to step (1) of Example 1.

[0084] (2) Dissolve a certain amount of sodium tripolyphosphate in deionized water to obtain a 6 wt% aqueous solution of sodium tripolyphosphate. Add 24 mL of the aqueous solution of sodium tripolyphosphate dropwise to the oil-in-water emulsion prepared in step (1) at a rate of 1 mL / min (the addition process is accompanied by stirring at 1000 rpm) to obtain a first mixture. Then, pour the first mixture into 600 mL of liquid paraffin containing 2 wt% of Span 80 and stir at 1000 rpm for 30 minutes to obtain a double emulsion.

[0085] (3) A 20 wt% aqueous solution of glutaraldehyde was prepared, and 12 mL of the aqueous solution was added dropwise to the double emulsion prepared in step (2) at a rate of 0.6 mL / min. The mixture was stirred at 1000 rpm for 12 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected, washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0086] Example 3

[0087] This embodiment provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0088] (1) Prepare an oil-in-water emulsion according to step (1) of Example 1.

[0089] (2) Dissolve a certain amount of sodium tripolyphosphate in deionized water to obtain a 6 wt% aqueous solution of sodium tripolyphosphate. Add 24 mL of the aqueous solution of sodium tripolyphosphate dropwise to the oil-in-water emulsion prepared in step (1) at a rate of 1 mL / min (the addition process is accompanied by stirring at 1000 rpm) to obtain a first mixture. Then, pour the first mixture into 600 mL of liquid paraffin containing 2 wt% of Span 80 and stir at 1000 rpm for 30 minutes to obtain a double emulsion.

[0090] (3) A 30 wt% aqueous solution of glutaraldehyde was prepared, and 12 mL of the aqueous solution was added dropwise to the double emulsion prepared in step (2) at a rate of 0.6 mL / min. The mixture was stirred at 1000 rpm for 12 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected, washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0091] Example 4

[0092] This embodiment provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0093] (1) Prepare an oil-in-water emulsion according to step (1) of Example 1.

[0094] (2) Dissolve a certain amount of sodium tripolyphosphate in deionized water to obtain a 6 wt% aqueous solution of sodium tripolyphosphate. Add 24 mL of the aqueous solution of sodium tripolyphosphate dropwise to the oil-in-water emulsion prepared in step (1) at a rate of 1 mL / min (the addition process is accompanied by stirring at 1000 rpm) to obtain a first mixture. Then, pour the first mixture into 600 mL of liquid paraffin containing 2 wt% of Span 80 and stir at 1000 rpm for 30 minutes to obtain a double emulsion.

[0095] (3) A 50 wt% aqueous solution of glutaraldehyde was prepared, and 12 mL of the aqueous solution was added dropwise to the double emulsion prepared in step (2) at a rate of 0.6 mL / min. The mixture was stirred at 1000 rpm for 12 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected, washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0096] Example 5

[0097] This embodiment provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0098] (1) Prepare an oil-in-water emulsion according to step (1) of Example 1.

[0099] (2) Dissolve a certain amount of sodium tripolyphosphate in deionized water to obtain a 10 wt% aqueous solution of sodium tripolyphosphate. Add 24 mL of the aqueous solution of sodium tripolyphosphate dropwise to the oil-in-water emulsion prepared in step (1) at a rate of 1 mL / min (the addition process is accompanied by stirring at 1000 rpm) to obtain a first mixture. Then, pour the first mixture into 600 mL of liquid paraffin containing 2 wt% of Span 80 and stir at 1000 rpm for 30 minutes to obtain a double emulsion.

[0100] (3) A 30 wt% aqueous solution of glutaraldehyde was prepared, and 12 mL of the aqueous solution was added dropwise to the double emulsion prepared in step (2) at a rate of 0.6 mL / min. The mixture was stirred at 1000 rpm for 12 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected, washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0101] Comparative Example 1

[0102] Comparative Example 1 provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0103] (1) Prepare an oil-in-water emulsion according to step (1) of Example 1.

[0104] (2) A certain amount of sodium tripolyphosphate was dissolved in deionized water to obtain a 6 wt% aqueous solution of sodium tripolyphosphate. 24 mL of the aqueous solution of sodium tripolyphosphate was added dropwise to the oil-in-water emulsion prepared in step (1) at a rate of 1 mL / min. After the addition was completed, the mixture was stirred at 1000 rpm for 4 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected and washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0105] Comparative Example 2

[0106] Comparative Example 2 provides a method for preparing chitosan nanocapsules, comprising the following steps:

[0107] (1) Prepare an oil-in-water emulsion according to step (1) of Example 1.

[0108] (2) The oil-in-water emulsion prepared in step (1) was poured into 600 mL of liquid paraffin containing 2 wt% of Span 80, and stirred at a stirring speed of 1000 rpm for 30 min.

[0109] (3) A 30 wt% aqueous solution of glutaraldehyde was prepared, and 12 mL of the aqueous solution was added dropwise to the material obtained in step (2) at a rate of 0.6 mL / min. The mixture was stirred at 1000 rpm for 12 h. The mixture was then centrifuged at 9000 rpm for 10 min. The solid phase was collected, washed with anhydrous ethanol and deionized water, and freeze-dried to obtain chitosan nanocapsules.

[0110] Experimental example

[0111] The encapsulation efficiency and encapsulation rate of the chitosan nanocapsules prepared in Examples 1 to 5 and Comparative Examples 1 to 2 were tested respectively. The results are as follows: Figure 1 From the above test results, it can be seen that the chitosan nanocapsules of the embodiments of the present disclosure have higher encapsulation efficiency and encapsulation rate than the chitosan nanocapsules of the comparative example.

[0112] According to Examples 1, 3 and 5 of the present disclosure, when the amount of sodium tripolyphosphate is low, it cannot fully cross-link with chitosan, resulting in a limited degree of coating of the essential oil; when the amount of sodium tripolyphosphate is high, it excessively cross-links with chitosan to form a flocculent precipitate, affecting the coating of the essential oil.

[0113] According to Examples 2, 3 and 4 of the present disclosure, when the amount of glutaraldehyde is low, it cannot fully cross-link with chitosan, which easily leads to leakage of essential oil; when the amount of glutaraldehyde is too high, it is excessively cross-linked with chitosan, resulting in reduced encapsulation rate and encapsulation efficiency.

[0114] The sustained-release performance of the chitosan nanocapsules of Example 3 and Comparative Examples 1 to 2 was further tested. The specific test method included taking chitosan nanocapsules of the same mass and placing them in a dry environment at room temperature for 36 days, and testing the amount of essential oil residue in the chitosan nanocapsules after different periods of time. The test results are shown in Tables 1 and Figure 2 .

[0115] Table 1 Residual amount of essential oil in chitosan nanocapsules of different embodiments and comparative examples

[0116]

[0117] Figure 2 3 is a comparison chart of the sustained-release effects of the chitosan nanocapsules of Example 3, Comparative Example 1 and Comparative Example 2. As can be seen from the figure, the chitosan nanocapsules of Example 3 show a significantly prolonged release effect, indicating that the chitosan nanocapsules of Example 3 have excellent sustained-release effects.

[0118] The responsiveness of the chitosan nanocapsules of Example 3 to different pH environments was further tested. The specific test method included taking the chitosan nanocapsules of Example 3 of the same mass and placing them in an acidic medium (conventional phosphate buffer) of pH = 4, a medium (conventional phosphate buffer) of pH = 7, and an alkaline medium (conventional phosphate buffer) of pH = 10 at room temperature, respectively. The residual amount of essential oil in the chitosan nanocapsules at different times was tested. The test results are shown in FIG. Figure 3 .from Figure 3 As can be seen from the results, the chitosan nanocapsules of Example 3 release the essential oil faster in alkaline media than in acidic and neutral media. This is because chitosan is more easily deprotonated and loses its positive charge in alkaline media compared to acidic and neutral media. This eliminates the electrostatic interaction between chitosan and sodium tripolyphosphate, reducing the degree of cross-linking in the capsule wall. Therefore, the essential oil diffuses more easily, resulting in a faster release rate on a macroscopic scale.

[0119] The chitosan nanocapsules of Example 3 were dried after being released for 33 days under different pH conditions and then subjected to infrared spectroscopy and scanning electron microscopy tests. The test results were as follows: Figure 4 and Figure 5 .from Figure 4 It can be seen that compared with the samples released in pH = 4 and pH = 7 media, the samples released in pH = 10 medium have a higher release rate at 1546 cm -1 The absorption peak at 100 nm disappeared, indicating that the physical cross-linking between chitosan and sodium tripolyphosphate disappeared, further verifying the pH responsiveness of the chitosan nanocapsules in Example 3. Figure 5As can be seen from the results, the chitosan nanocapsules of Example 3 maintain their geometric shape and microstructural integrity in media with varying pH values. In alkaline media, although the physical crosslinks in the chitosan nanocapsules of Example 3 disappear, the chemical crosslinks between chitosan and glutaraldehyde are unaffected by pH changes, thus maintaining the capsule morphology. This also enables the chitosan nanocapsules of Example 3 to retain a certain sustained-release performance after pH stimulation.

[0120] According to the above test results, the present invention utilizes the physical crosslinking between chitosan and sodium tripolyphosphate and the chemical crosslinking between chitosan and a dialdehyde crosslinking agent to obtain a physical / chemical dual crosslinked chitosan nanocapsule, which significantly improves the encapsulation rate and encapsulation efficiency of the nanocapsule. At the same time, the nanocapsule is also pH-responsive and has a sustained-release effect after pH response.

[0121] Finally, it should be noted that the above-described embodiments are only specific implementation methods of the present disclosure, which are used to illustrate the technical solutions of the present disclosure, rather than to limit them. The scope of protection of the present disclosure is not limited thereto. Although the present disclosure has been described in detail with reference to the above-described embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily conceive of changes to the technical solutions described in the above-described embodiments within the technical scope disclosed in the present disclosure, or replace some of the technical features therein with equivalents. Such modifications, changes, or replacements do not deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure, and should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the scope of protection of the claims.

Claims

1. A method for preparing chitosan nanocapsules, characterized in that: The steps include: (a) mixing and emulsifying a chitosan solution, an oil-in-water emulsifier, and an essential oil to form an oil-in-water emulsion, adding an aqueous solution of sodium tripolyphosphate to the oil-in-water emulsion, and stirring to obtain a first mixture; (b) adding the first mixture to an oil phase solvent containing a water-in-oil emulsifier, and stirring to obtain a double emulsion; (c) adding an aqueous solution of a dialdehyde cross-linking agent to the double emulsion to carry out a cross-linking reaction, collecting the solid phase, and drying it to obtain the chitosan nanocapsules; The mass ratio of chitosan in the chitosan solution to sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate is 1:(0.4-1.05); the mass ratio of chitosan in the chitosan solution to the dialdehyde crosslinking agent in the aqueous solution of the dialdehyde crosslinking agent is 1:(1-2.55).

2. The preparation method according to claim 1, characterized in that The mass ratio of the sodium tripolyphosphate in the aqueous solution of sodium tripolyphosphate to the dialdehyde cross-linking agent in the aqueous solution of the dialdehyde cross-linking agent is (0.3-0.5):

1.

3. The preparation method according to claim 1, characterized in that In the chitosan solution, the concentration of chitosan is 1wt% to 5wt%; The preparation of the chitosan solution comprises: dissolving chitosan in an acetic acid aqueous solution; the concentration of acetic acid in the acetic acid aqueous solution is 1 wt% to 5 wt%.

4. The preparation method according to claim 1, characterized in that The oil-in-water emulsifier includes Tween 60; In the oil-in-water emulsion, the concentration of the oil-in-water emulsifier is 0.1 wt% to 2 wt%.

5. The preparation method according to claim 1, characterized in that The essential oil is selected from aromatic essential oils; The mass ratio of the essential oil to the chitosan in the chitosan solution is (0.2-2):

1.

6. The preparation method according to claim 1, characterized in that Has at least one of the following characteristics: (1) In the aqueous solution of sodium tripolyphosphate, the concentration of sodium tripolyphosphate is 1 wt% to 10 wt%; (2) The aqueous solution of sodium tripolyphosphate is added dropwise to the oil-in-water emulsion; the rate of the addition is 0.5 to 2 mL / min.

7. The preparation method according to claim 1, characterized in that Has at least one of the following characteristics: (1) The oil phase solvent includes liquid paraffin, and the water-in-oil emulsifier includes Span 80; (2) The volume ratio of the first mixture to the oil phase solvent is 1:(3-5); (3) In the oil phase solvent, the concentration of the water-in-oil emulsifier is 1 wt% to 10 wt%.

8. The preparation method according to claim 1, characterized in that Has at least one of the following characteristics: (1) In the aqueous solution of the dialdehyde cross-linking agent, the concentration of the dialdehyde cross-linking agent is 2 wt% to 50 wt%; (2) The dialdehyde cross-linking agent includes glutaraldehyde; (3) The aqueous solution of the dialdehyde crosslinking agent is added dropwise to the double emulsion; the dropping speed is 0.5 to 2 mL / min.

9. A chitosan nanocapsule, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the chitosan nanocapsules according to claim 9 in functional fabrics.

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