Hollow polylactic acid microspheres, and preparation method and application thereof

Abstract

The present application provides a kind of hollow polylactic acid microsphere and its preparation method and application. Its microsphere is the polylactic acid drug-loaded microsphere of micron scale, particle size is 0.1-10 μm, and the encapsulation efficiency is 90%-100%. The present application uses emulsion solvent evaporation method to prepare sustained-release microspheres, and by adjusting the ratio and process parameters, the prepared microspheres are hollow microspheres. In vitro release experiment shows that the microspheres can be well dispersed in water to form a uniform and stable suspension emulsion, greatly improving the drug release performance, and can be used for drug controlled release, pesticide, cosmetic field application.

Description

Technical Field

[0001] This invention relates to the field of biochemical engineering, specifically to hollow polylactic acid microspheres, their preparation methods, and applications. Background Technology

[0002] Polylactic acid (PLA) is a new biodegradable polymer material that has developed rapidly in the 1990s. It can be used as a sustained-release, controlled-release, and targeted delivery system for various types of drugs. As a new drug dosage form, it has advantages such as protecting unstable drugs, improving drug solubility, enhancing drug therapeutic effects, and reducing drug toxicity and side effects. It has great application prospects in the biomedical field.

[0003] Cellulose nanocrystals (CNCs) are typically extracted from cellulose materials via acid hydrolysis. As a naturally derived material, they have attracted much attention due to their excellent physicochemical properties, such as rod-shaped particles, surface charge, ease of surface modification, large surface area, high mechanical strength, biocompatibility, and biodegradability.

[0004] Pickering emulsions are emulsions in which colloidal particles replace surfactant molecules. Compared with traditional surfactant-stabilized emulsions, Pickering emulsions have the following advantages: First, less emulsifier colloidal particles are used, saving raw materials and reducing costs. Second, no surfactants are added, making them friendly to humans and the environment. Third, the external environment has less impact on the emulsion, resulting in higher stability, etc.

[0005] Curcumin is a β-diketone polyphenolic compound extracted from the ginger plant (Curcuma longa). It possesses a wide range of pharmacological effects, including anti-tumor, anti-inflammatory, antioxidant, and liver and kidney protection. With low toxicity and simple extraction, it has become a hot topic in research and development. Plant essential oils are highly concentrated extracts of aromatic plants. They are highly volatile and have small molecules, making them easily absorbed by the body. They help balance bodily functions and have skin-beautifying effects; however, improper storage can easily lead to inactivation.

[0006] Ichthyophthirius multifiliis is a parasite that causes "white spot disease" in fish, often resulting in significant economic losses for aquariums and fish farms. Its life cycle consists of four stages: trophozoite, cyst, cyst, and larva. Curcumin has been shown to inhibit all four stages of the parasite, exhibiting strong bactericidal properties.

[0007] Curcumin or plant essential oils, along with polylactic acid (PLA), are dissolved in the oil phase, and CNC (carbonyl nitrate) is dispersed in the aqueous phase as an emulsifier. A water-in-oil Pickering emulsion is prepared in a fixed ratio, encapsulating the drug within PLA. The resulting drug-loaded microspheres improve the drug's hydrophobic properties, and the formed polymer barrier protects the drug from easy degradation by the external environment, prolonging its residence and duration of action in vitro and improving bioavailability. Furthermore, the application of drug-loaded control systems can be extended to other fields, such as inflammation treatment, cosmetics, and food. Therefore, research on the preparation method of curcumin-loaded control systems is of great significance. However, current research in this area is limited both domestically and internationally. No research has been found on using PLA to encapsulate curcumin for antiparasitic purposes, nor on using PLA to encapsulate plant essential oils to form Pickering emulsions for cosmetic applications.

[0008] Some researchers have used gelatin to prepare porous polylactic acid microspheres for sustained-release peppermint oil flavoring. However, these microspheres have a porous structure and their sustained-release performance is generally poor. Spray drying is also used to obtain micro / nano particles, but it is difficult to control the drug distribution within the particles, and the resulting microspheres are not uniform in size. This can lead to significant product loss due to particle adhesion to the inner wall of the spray drying equipment and / or particle agglomeration. Furthermore, the equipment is bulky, requiring a large initial investment, and the atomizer and powder recovery device are expensive. Summary of the Invention

[0009] In order to overcome the problems existing in the above-mentioned prior art

[0010] One of the objectives of this invention is to provide a hollow polylactic acid microsphere material.

[0011] The second objective of this invention is to provide a method for preparing hollow polylactic acid microspheres.

[0012] The third objective of this invention is to provide an application of hollow polylactic acid microspheres in the fields of controlled drug release, pesticides, and cosmetics.

[0013] Specifically, the present invention adopts the following technical solution:

[0014] The first aspect of the present invention provides hollow polylactic acid microspheres, wherein the hollow polylactic acid microspheres are micron-sized biodegradable polymer drug-loaded microspheres, wherein the biodegradable polymer includes polylactic acid and cellulose nanocrystals, and the drug is curcumin or plant essential oil. The microspheres have a particle size between 0.1 and 10 μm, an encapsulation rate of 90 to 100%, and the microspheres have a hollow structure.

[0015] By introducing cellulose nanocrystals to activate polylactic acid, its physical processing properties are improved, thereby enhancing the stability and biocompatibility of the microspheres. Furthermore, considering its hollow structure and particle size characteristics, the microspheres also exhibit excellent sustained-release effects.

[0016] Preferably, the plant essential oil is at least one selected from geranium essential oil, grapeseed oil, chamomile, tea tree oil, patchouli oil, peppermint essential oil, and orange essential oil.

[0017] Preferably, the mass ratio of the cellulose nanocrystals, polylactic acid, and the drug is (0.08-0.2):(0.3-0.5):(0.01-0.04).

[0018] A second aspect of the present invention provides a method for preparing the hollow polylactic acid microspheres, characterized by comprising the following steps:

[0019] S1 is used to prepare a polylactic acid organic solution;

[0020] S2 Weigh a certain amount of curcumin or plant essential oil and put it into the S1 solution to dissolve it completely, thus obtaining a polylactic acid drug organic solution;

[0021] S3 is used to prepare an aqueous dispersion of cellulose nanocrystals;

[0022] S4 involves slowly adding the polylactic acid drug organic solvent from S2 into the cellulose nanocrystal aqueous dispersion, followed by ultrasonication under ice bath conditions to obtain a Pickering emulsion.

[0023] S5 involves stirring the Pickering emulsion from S4 to completely evaporate the organic solvent, followed by centrifugation and freeze-drying to obtain the hollow polylactic acid microspheres; or...

[0024] The hollow polylactic acid microspheres were obtained by directly freeze-drying the Pickering emulsion of S4.

[0025] Preferably, in step S1, the solvent in the polylactic acid organic solution is dichloromethane, and the solution concentration is 30–50 mg / mL. Preferably, the mixing time for preparing the solution is 5–30 min.

[0026] Preferably, in step S2, the mass ratio of polylactic acid to the drug is (0.3-0.5):(0.01-0.04).

[0027] Preferably, the drug comprises curcumin or a plant essential oil, wherein the plant essential oil is at least one selected from geranium essential oil, grape seed oil, chamomile, tea tree oil, patchouli oil, peppermint essential oil, and orange essential oil.

[0028] Preferably, when curcumin is used in step S2, steps S2, S4, and S5 are all carried out under light-protected conditions. The reaction temperature of step S2 is 10-30°C, the reaction temperature of step S4 is 0-10°C, and the reaction temperature of step S5 is 10-80°C.

[0029] Preferably, in step S3, the concentration of the cellulose nanocrystal aqueous dispersion is 0.2–1 wt%, such as 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, etc. Preferably, CNC can be dispersed in water, homogenized for 10–30 min, and then sonicated for 5–30 min to prepare a CNC dispersion.

[0030] Preferably, in step S3, sodium chloride is further added to the cellulose nanocrystal aqueous dispersion, wherein the mass ratio of cellulose nanocrystals to sodium chloride is 1:1. Adding sodium chloride can shield the surface charge of the cellulose nanocrystals, making the microspheres more uniform, the emulsion more stable, and the sustained-release effect better.

[0031] Preferably, in step S4, the volume ratio of the polylactic acid drug organic solvent to the cellulose nanocrystal aqueous dispersion is 1:4.

[0032] In step S5, the organic solvent in the emulsion from S4 can be evaporated to obtain a microsphere suspension, which can then be centrifuged and freeze-dried to obtain microspheres. Alternatively, the emulsion with unevaporated organic solvent can be directly placed in a freeze dryer to obtain microspheres. Preferably, the centrifugation conditions are 10000–15000 r / min, centrifugation time is 5–20 min, and temperature is 4–20 °C.

[0033] A third aspect of this invention provides the application of the hollow polylactic acid microspheres in the fields of controlled drug release, pesticides, and cosmetics.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The hollow polylactic acid microspheres of the present invention are biodegradable drug microspheres, which are stable, environmentally friendly and pollution-free.

[0036] (2) The hollow polylactic acid microspheres of the present invention, compared with porous microspheres, have a longer shell erosion time, a longer sustained release time, and a better sustained release effect, which can last up to 60 days. This prolongs the residence and action time of the drug in vitro, and the hydrophobic properties of the drug are greatly improved, which greatly improves the bioavailability of the drug.

[0037] (3) The preparation method of the present invention yields hollow polylactic acid microspheres. The microspheres have a cavity structure. The internal structure of the microspheres, such as the hollowness and shell thickness, can be changed by changing the drying method of the organic phase, thereby changing the drug release rate.

[0038] (4) The process of the present invention is simple, efficient, easy to operate and easy to achieve large-scale production. The reactants are stable during the reaction process and no by-products are generated. Attached Figure Description

[0039] Figure 1This is a process flow diagram of the present invention;

[0040] Figure 2 This is a SEM image of polylactic acid-loaded curcumin microspheres from Example 1;

[0041] Figure 3 Here is a SEM image of polylactic acid-loaded curcumin microspheres from Example 2;

[0042] Figure 4 This is a SEM image of the internal structure of polylactic acid-loaded curcumin microspheres from Example 1.

[0043] Figure 5 A polarized light microscope image of the Pickering emulsion prepared in Example 1;

[0044] Figure 6 This is a release diagram of polylactic acid-loaded chamomile essential oil microspheres in the sustained-release medium of Example 3;

[0045] Figure 7 This is a release diagram of polylactic acid-loaded curcumin microspheres in a sustained-release medium after solvent evaporation and subsequent drying in Example 1.

[0046] Figure 8 This is a release diagram of polylactic acid curcumin-loaded microspheres directly dried without volatile solvent in Example 2 in a sustained-release medium. Detailed Implementation

[0047] In the description of this invention, unless otherwise explicitly defined, terms such as heating, cleaning, and weighing should be interpreted broadly. Those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0048] In the description of this invention, references to terms such as "some embodiments" and "examples" indicate that the specific methods or materials described in connection with that embodiment or example are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the specific methods and materials described may be combined in any suitable manner in one or more embodiments or examples.

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings, but this does not constitute a limitation on the scope of protection of the present invention.

[0050] Unless otherwise specified, the raw materials used in the following examples are all available from conventional commercial sources; and the processes used are all conventional processes in the art.

[0051] Example 1

[0052] Reference Figure 1Hollow polylactic acid microspheres are prepared by the following method, which includes the following steps:

[0053] S1. Dissolve 0.3g of polylactic acid in 13.25g of dichloromethane at a concentration of 30mg / mL by shaking thoroughly for 20min to obtain a transparent polylactic acid solution in dichloromethane.

[0054] S2 was prepared under light-protected conditions at a temperature of 10-30℃. 0.01g of curcumin was placed in polylactic acid dichloromethane solvent and allowed to dissolve completely to obtain a yellow polylactic acid curcumin organic solution.

[0055] S3 dispersed 0.08g of CNC in 99.2g of deionized water, homogenized the dispersion for 15min and then sonicated for 10min to prepare a CNC dispersion with a mass concentration of 0.2%. Then, 0.08g of sodium chloride was added and sonicated for 5min to obtain a vitamin nanocrystal dispersion with shielded surface charge.

[0056] Under light-protected conditions, 1 part of the organic solvent in S2 was slowly added to 4 parts of CNC dispersion by volume, and the mixture was sonicated for 10 minutes in an ice bath at 0-10℃ to obtain a yellow Pickering emulsion.

[0057] S5 The emulsion of S4 was stirred at room temperature for 24 hours with a stir bar to completely evaporate the dichloromethane, and a CNC emulsion of polylactic acid loaded with curcumin microspheres was obtained.

[0058] CNC-emulsified polylactic acid curcumin-loaded microspheres were collected by low-temperature high-speed centrifugation. The centrifugation conditions were 10,000 r / min for 10 min and 4-20℃.

[0059] The collected product was freeze-dried to obtain CNC-emulsified polylactic acid-loaded curcumin microspheres. SEM images of the microspheres are attached. Figure 2 and 4 As shown.

[0060] Example 2

[0061] Reference Figure 1 Hollow polylactic acid microspheres are prepared by the following method, which includes the following steps:

[0062] S1. Dissolve 0.3g of polylactic acid in 13.25g of dichloromethane at a concentration of 30mg / mL by shaking thoroughly for 20min to obtain a transparent polylactic acid solution in dichloromethane.

[0063] S2 was prepared under light-protected conditions at a temperature of 10-30℃. 0.01g of curcumin was placed in polylactic acid dichloromethane solvent and allowed to dissolve completely to obtain a yellow polylactic acid curcumin organic solution.

[0064] S3 dispersed 0.08g of CNC in 99.2g of deionized water, homogenized the dispersion for 15min and then sonicated for 10min to prepare a CNC dispersion with a mass concentration of 0.2%. Then, 0.08g of sodium chloride was added and sonicated for 5min to obtain a CNC dispersion with shielded surface charge.

[0065] Under light-protected conditions (S4), 1 part of the organic solvent from S2 was slowly added to 4 parts of the CNC dispersion by volume, and the mixture was sonicated for 10 minutes in an ice bath at 0-10°C to obtain a yellow Pickering emulsion.

[0066] S5: Freeze-dry the yellow Pickering emulsion from S4 to obtain CNC-emulsified polylactic acid-loaded curcumin microspheres; SEM images of the microspheres are shown below. Figure 3 As shown.

[0067] Example 3

[0068] Reference Figure 1 Hollow polylactic acid microspheres are prepared by the following method, which includes the following steps:

[0069] S1. Dissolve 0.3g of polylactic acid in 13.25g of dichloromethane at a concentration of 30mg / mL by shaking thoroughly for 20min to obtain a transparent polylactic acid solution in dichloromethane.

[0070] S2 was prepared under light-protected conditions and at a temperature of 10-30℃. 0.01g of chamomile essential oil was placed in polylactic acid dichloromethane solvent and allowed to dissolve completely to obtain an organic solution of chamomile curcumin.

[0071] S3 dispersed 0.08 g of CNC in 99.2 g of deionized water, homogenized the dispersion for 15 min, and then sonicated for 10 min to prepare a CNC dispersion with a mass concentration of 0.2%. Then, 0.08 g of sodium chloride was added, and the mixture was sonicated for 5 min to obtain a vitamin nanocrystal dispersion with shielded surface charge.

[0072] S4 is prepared by slowly adding 1 part of the organic solvent from S2 to 4 parts of the CNC dispersion according to the volume ratio, and then sonicating for 10 minutes under ice bath conditions at 0-10℃ to obtain Pickering emulsion.

[0073] S5 The emulsion of S4 was stirred at room temperature for 24 hours with a stir bar to completely evaporate the dichloromethane, and a CNC emulsion of polylactic acid loaded with chamomile microspheres was obtained.

[0074] CNC-emulsified polylactic acid-loaded chamomile microspheres were collected by low-temperature high-speed centrifugation. The centrifugation conditions were 12,000 r / min for 15 min and 4-20℃.

[0075] The collected product was freeze-dried to obtain CNC-emulsified polylactic acid-loaded chamomile microspheres.

[0076] Example 4

[0077] The types and amounts of materials used in this example are the same as those in Example 1. The only difference between this example and Example 1 is that the mass of polylactic acid in step S1 is 0.5g and the solution concentration is 30mg / mL.

[0078] Compared with Example 1, this example has a more superior sustained-release effect.

[0079] SEM image of CNC emulsified polylactic acid curcumin-loaded microspheres obtained in Example 1 is shown below. Figure 2 and 4 As shown, Figure 3 The image shows the SEM image of the microspheres obtained in Example 2. Figure 5 The image shown is a polarized light microscope image of the polylactic acid-loaded curcumin microsphere Pickering emulsion prepared in Example 1, combined with... Figure 2-5 It can be seen that the droplets in the Pickering emulsion are uniformly dispersed, and the prepared microspheres are also uniform in size, with a particle size between 0.1 and 10 μm, an encapsulation efficiency of 90% to 100%, and are hollow microspheres. Furthermore, compared to… Figure 2 and Figure 3 It can be observed that, under otherwise unchanged conditions, the microspheres in Example 2 with non-volatile dichloromethane have a greater internal hollowness, a thinner shell, and a larger volume than the microspheres in Example 1 with volatile dichloromethane. This is further evidenced by the fact that pressing the microspheres in Example 1 with a toothpick resulted in no significant change, while pressing the microspheres in Example 2 caused them to partially deflate. This demonstrates that the preparation method of the present invention can alter the internal structure of the microspheres, such as hollowness and shell thickness, by changing the drying method of the organic phase.

[0080] Figure 6 This is a release diagram of the polylactic acid-loaded chamomile essential oil microspheres from Example 3 in a sustained-release medium. Figure 7 This is a release diagram of polylactic acid-loaded curcumin microspheres from Example 1 in a sustained-release medium, after solvent evaporation and drying. Figure 8 This is a release diagram of polylactic acid-loaded curcumin microspheres in a sustained-release medium, as shown in Example 2. Figure 6-8 It can be seen that the polylactic acid microspheres prepared in the embodiments of the present invention all have good sustained-release effects, especially the microspheres loaded with curcumin, which have even better sustained-release effects. Figure 7 Polymer-loaded drug microspheres prepared with volatile organic phases can continuously release drugs in sustained-release media for more than a month, while Figure 8 The slow-release effect is better when the solvent in the middle is dried directly, and it can last for up to 60 days.

[0081] This invention employs an emulsification solvent evaporation method to prepare sustained-release microspheres. By adjusting the ratio and process parameters, hollow microspheres are prepared. In vitro release experiments show that the microspheres can be well dispersed in water to form a uniform and stable suspension, greatly improving the drug's water insolubility. Polymer-loaded drug microspheres prepared by volatile organic phase continuously release drugs in the sustained-release medium for more than one month. Polylactic acid microspheres prepared by directly placing the non-volatile organic phase into a freeze dryer have an even longer continuous release time in the sustained-release medium, reaching several months or more. This indicates that the prepared hollow polylactic acid microspheres can significantly extend the drug's retention and action time outdoors, thereby greatly improving the drug's bioavailability.

[0082] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be noted that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A hollow polylactic acid microsphere, characterized by: The hollow polylactic acid microspheres are micron-sized biodegradable polymer drug-loaded microspheres. The biodegradable polymer is composed of polylactic acid and cellulose nanocrystals. The drug is curcumin or plant essential oil. The microsphere particle size is between 0.1 and 10 μm, the encapsulation rate is 90 to 100%, and the microspheres have a hollow structure. The mass ratio of the cellulose nanocrystals, polylactic acid, and the drug is (0.08–0.2):(0.3–0.5):(0.01–0.04). The method for preparing the hollow polylactic acid microspheres includes the following steps: S1 Prepare a polylactic acid organic solution; S2 Weigh a certain amount of curcumin or plant essential oil and put it into the S1 solution to dissolve it completely, thus obtaining a polylactic acid drug organic solution; S3 is used to prepare an aqueous dispersion of cellulose nanocrystals. S4 The polylactic acid drug organic solvent in S2 is slowly added to the cellulose nanocrystal aqueous dispersion, and the mixture is ultrasonicated under ice bath conditions to obtain Pickering emulsion; S5. The Pickering emulsion from S4 is directly freeze-dried to obtain the hollow polylactic acid microspheres.

2. The hollow polylactic acid microspheres according to claim 1, characterized in that: The plant essential oil is at least one of geranium essential oil, grapeseed oil, chamomile, tea tree oil, patchouli oil, peppermint essential oil, and orange essential oil.

3. The hollow polylactic acid microspheres according to claim 1, characterized in that: In step S1, the solvent in the polylactic acid organic solution is dichloromethane, and the solution concentration is 30-50 mg / mL.

4. The hollow polylactic acid microspheres according to claim 1, characterized in that: When curcumin is used in step S2, steps S2, S4, and S5 are all carried out under light-protected conditions. The reaction temperature of step S2 is 10-30℃, and the reaction temperature of step S4 is 0-10℃.

5. The hollow polylactic acid microspheres according to claim 1, characterized in that: In step S3, the concentration of the aqueous dispersion of cellulose nanocrystals is 0.2wt% to 1wt%.

6. The hollow polylactic acid microspheres according to claim 1, characterized in that: In step S3, sodium chloride is also added to the aqueous dispersion of cellulose nanocrystals, wherein the mass ratio of cellulose nanocrystals to sodium chloride is 1:

1.

7. The hollow polylactic acid microspheres according to claim 1, characterized in that: In step S4, the volume ratio of polylactic acid drug organic solvent to cellulose nanocrystal aqueous dispersion is 1:

4.

8. The use of hollow polylactic acid microspheres as described in any one of claims 1-7 in the preparation of controlled-release drugs, pesticides, and cosmetics.

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