Andrographolide nanoemulsion and preparation method thereof

Abstract

This invention provides an andrographolide nanoemulsion and its preparation method. The andrographolide nanoemulsion has an average particle size of 10.3±2 nm and a zeta potential of 15.2±3 mV. The preparation method includes: dissolving andrographolide in an organic solvent, mixing it with an emulsifier and a co-emulsifier to form an organic phase; injecting the organic phase and deionized water separately into a microreactor for mixing, and collecting the product. Compared with existing technologies, the andrographolide nanoemulsion prepared by this invention has a significantly reduced particle size and a significantly increased zeta potential, exhibiting advantages such as small particle size, uniform distribution, and high stability. Furthermore, the preparation method is simple, efficient, and can be continuously produced, making it suitable for the development of nano-formulations of poorly soluble drugs.

Description

Technical Field

[0001] This invention belongs to the field of pharmaceutical formulation technology, specifically relating to an andrographolide nanoemulsion and its preparation method, and more particularly to an andrographolide nanoemulsion with small particle size and high stability and its continuous preparation method based on a microreactor. Background Technology

[0002] Andrographolide (AND) is a diterpenoid lactone isolated from the leaves of *Andrographis paniculata*. It possesses a variety of remarkable pharmacological effects, including anti-inflammatory, anti-tumor, immunomodulatory, hepatoprotective, choleretic, and anti-Parkinson's disease properties, earning it the nickname "King of Bitter Herbs." However, andrographolide is a poorly soluble drug, exhibiting poor water solubility and low oral bioavailability, which severely limits its clinical application. To address the low bioavailability of andrographolide, researchers have developed various nanodelivery systems, such as solid lipid nanoparticles, chitosan-coated nanocolloids, and nanocrystals. However, these methods typically suffer from uneven particle size distribution, poor stability, complex preparation processes, and difficulties in continuous production.

[0003] Nanoemulsions are nanoscale dispersions formed by two immiscible solutions under the action of surfactants. They possess advantages such as small particle size, good kinetic stability, and improved drug solubility, making them an effective means to improve the bioavailability of poorly soluble drugs. Existing nanoemulsion preparation technologies include low-energy emulsification, ultrasonication, high-pressure homogenization, and microreactor methods. Among these, microreactor technology shows great potential in the field of nanoemulsion preparation due to its high mixing efficiency, fast mass transfer, and strong controllability. However, there are currently no research reports on the preparation of andrographolide nanoemulsions based on microreactor technology. Existing microreactors still have room for improvement in terms of mixing efficiency and particle size control precision, especially for drugs like andrographolide that are prone to aggregation. Achieving nanoemulsion preparation with uniform particle size and high stability remains a technical challenge. Summary of the Invention

[0004] Objective of the Invention: This invention addresses the shortcomings of existing andrographolide nanoformulations, such as poor particle size control, low stability, and complex and difficult-to-continuous preparation processes. It provides an andrographolide nanoemulsion and its preparation method. The andrographolide nanoemulsion prepared by this invention features small particle size (approximately 10 nm), uniform particle size distribution, and high zeta potential (>15 mV). Furthermore, the preparation method is simple, efficient, and can be continuously produced.

[0005] Technical solution: To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides an andrographolide nanoemulsion, wherein the andrographolide nanoemulsion has an average particle size of 10.3±2nm and a zeta potential of 15.2±3mV.

[0007] Preferably, the andrographolide nanoemulsion has an average particle size of 10.3 nm and a zeta potential of 15.2 mV.

[0008] Secondly, the present invention provides a method for preparing the andrographolide nanoemulsion, comprising the following steps:

[0009] (1) Dissolve andrographolide in an organic solvent to obtain a drug solution;

[0010] (2) The drug solution is mixed with an emulsifier and a co-emulsifier to form an organic phase;

[0011] (3) Using deionized water as the aqueous phase, the organic phase and the aqueous phase are mixed in a microreactor;

[0012] (4) Collect the mixed products to obtain andrographolide nanoemulsion.

[0013] As a specific implementation scheme, in step (1), the organic solvent is selected from dimethyl sulfoxide; the concentration of andrographolide in the drug solution is 1.4 to 5.6 mg / mL; preferably, the concentration is 1.4 mg / mL.

[0014] As a specific implementation scheme, in step (2), the emulsifier is selected from Span 80, polyoxyethylene hydrogenated castor oil or Tween 80, and the co-emulsifier is selected from ethanol, 1,2-propanediol or 1,4-butanediol; preferably, the emulsifier is Tween 80 and the co-emulsifier is 1,4-butanediol.

[0015] The mass ratio of the drug solution, emulsifier, and co-emulsifier is (4-8):(2-4):1; preferably, the mass ratio is 6:3:1.

[0016] As a specific implementation scheme, in step (3), the microreactor includes an outer pipe and an internal baffle located inside the outer pipe; the outer pipe consists of two inlets, one outlet and a mixing channel. The mixing includes injecting the organic phase and the aqueous phase into the two inlets of the outer pipe respectively, and mixing them in the mixing channel.

[0017] As a specific implementation scheme, in step (3), the flow rate ratio of the organic phase to the aqueous phase is 1:4 to 1:20; preferably, the flow rate ratio of the organic phase to the aqueous phase is 1:16.

[0018] As a specific implementation scheme, in step (3), the total flow rate of the organic phase and the aqueous phase is 2.5~20 mL / min; preferably, the total flow rate of the organic phase and the aqueous phase is 5 mL / min; and the mixing temperature is 20~40℃.

[0019] The working principle of the preparation method of this invention is as follows: an organic phase (containing andrographolide and surfactant) is injected through a side tube, and deionized water (antisolvent) is injected through a main tube. The side tube extends into the main tube and bends to form a coaxial coupling structure, allowing the two fluid phases to contact coaxially and achieve thorough mixing. During this process, the solvent dimethyl sulfoxide rapidly diffuses into the aqueous phase, and andrographolide precipitates due to decreased solubility, forming nano-sized aggregates. Simultaneously, the surfactant is rapidly adsorbed onto the newly formed interface, forming a stable nanoemulsion. This nanoemulsion has the characteristics of small average particle size, uniform distribution, and high zeta potential. Under optimized process conditions, the average particle size is 10.3 nm, and the zeta potential is 15.2 mV.

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

[0021] 1) The nanoemulsion has extremely small particle size and uniform distribution. The andrographolide nanoemulsion prepared by the optimal process of this invention has an average particle size of only 10.3 nm, which is much smaller than the andrographolide nano-preparations reported in the prior art (such as solid lipid nanoparticles of about 262 nm and nanocrystals of about 119-137 nm). Moreover, the particle size is stable at about 10 nm under different operating conditions, with uniform distribution and no bimodal or large particle agglomeration.

[0022] 2) Significantly improved stability. The nanoemulsion prepared by the optimal process of this invention has a zeta potential as high as 15.2 mV, which is about 3.33 times that of the 4.53 mV prepared by the traditional beaker method. This indicates that the nanoemulsion has a higher interfacial charge density and electrostatic stability, which is beneficial for long-term storage and in vivo application.

[0023] 3) High preparation efficiency and strong controllability. This invention employs continuous preparation via a microreactor, with extremely short mixing time (milliseconds), timely surfactant adsorption, and effective inhibition of disordered aggregation of andrographolide. By adjusting the flow rate ratio, total flow rate, and prodrug concentration, the particle size and potential of the nanoemulsion can be flexibly controlled, resulting in a wide process window and easy scale-up production.

[0024] 4) The method has good versatility. This invention is not only applicable to andrographolide, but can also provide a reference for the preparation of nanoemulsions of other poorly soluble drugs, and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the preparation process of andrographolide nanoemulsion of the present invention.

[0026] Figure 2 This is a comparison of the particle size distribution of andrographolide nanoemulsions under different surfactant systems.

[0027] Figure 3 The graph shows the changes in average particle size and zeta potential of andrographolide nanoemulsions at different flow rate ratios.

[0028] Figure 4 The graph shows the changes in average particle size and zeta potential of andrographolide nanoemulsions at different prodrug concentrations.

[0029] Figure 5 The graph shows the changes in average particle size and zeta potential of andrographolide nanoemulsions at different total flow rates.

[0030] Figure 6 This is a comparison of the particle size and zeta potential of andrographolide nanoemulsions prepared by the optimized process of this invention and those prepared by the traditional beaker method. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in further detail below with reference to examples. These examples are for illustrative purposes only and should not be considered as limiting the scope of the invention.

[0032] The microreactor used in this invention includes an outer pipe and an internal baffle located inside the outer pipe. The outer pipe consists of two inlets, one outlet, and a mixing channel, as specifically described in Example 4 of Chinese Patent Application CN114797602A (Application No. CN202210367848.2).

[0033] The preparation method of andrographolide nanoemulsion is as follows ( Figure 1 (as shown)

[0034] (1) Dissolve andrographolide (purity ≥98%) in dimethyl sulfoxide to prepare a drug solution.

[0035] (2) The drug solution is mixed with an emulsifier and a co-emulsifier to form an organic phase.

[0036] (3) The organic phase and the aqueous phase are injected into the two inlets of the external pipe respectively, and the two phases are rapidly mixed in the mixing channel.

[0037] (4) Collect andrographolide nanoemulsion at the outlet of the microreactor.

[0038] Example 1: Optimization of the preparation process

[0039] 1. Screening of surfactant systems

[0040] This example investigated the effects of nine different surfactant systems on nanoemulsion particle size and Zeta potential. Fixed conditions were maintained: total flow rate 5 mL / min, flow ratio 1:4, and andrographolide concentration 1.4 mg / mL. Three emulsifiers (Span 80, polyoxyethylene hydrogenated castor oil, and Tween 80) were cross-combined with three co-emulsifiers (ethanol, 1,2-propanediol, and 1,4-butanediol).

[0041] The results are as follows Figure 2 As shown, the Span 80 system exhibits a broad Zeta potential distribution (-150mV to +150mV) with multiple peaks, indicating high heterogeneity. The polyoxyethylene hydrogenated castor oil system shows large particle size distribution with broad peaks, indicating agglomeration. The Tween 80 system shows only small particle size main peaks, demonstrating good uniformity. The system with 1,4-butanediol as a co-emulsifier exhibits the smallest particle size and highest potential. Therefore, Tween 80 / 1,4-butanediol is selected as the optimal surfactant system.

[0042] 2. Effect of flow rate ratio on nanoemulsions

[0043] This example investigated the effect of flow rate ratios (organic phase:aqueous phase) of 1:4, 1:8, 1:12, 1:16, and 1:20 on nanoemulsions. Fixed conditions were set: Tween 80 / 1,4-butanediol, total flow rate 5 mL / min, and concentration 1.4 mg / mL. A conventional beaker method (same formulation, only volume ratio changed) was used as a control.

[0044] The results are as follows Figure 3 As shown, the average particle size of the nanoemulsions prepared by the microreactor remained around 10 nm at all flow rates, while the particle size fluctuated significantly in the beaker method. The Zeta potential first increased and then decreased with increasing aqueous phase ratio, reaching its highest value at 1:16. Therefore, a flow rate ratio of 1:16 is preferred.

[0045] 3. Effect of prodrug concentration on nanoemulsions

[0046] This example investigated the effects of andrographolide concentrations of 0.7, 1.4, 2.8, 5.6, 11.2, 22.4, and 44.8 mg / mL. Fixed conditions: Tween 80 / 1,4-butanediol, total flow rate 5 mL / min, flow ratio 1:4.

[0047] The results are as follows Figure 4 As shown, the particle size remains stable at around 10 nm when the concentration is between 1.4 and 5.6 mg / mL; the particle size increases significantly and exhibits a bimodal distribution when the concentration is ≥11.2 mg / mL, indicating aggregation. The zeta potential is highest at 1.4 mg / mL. Therefore, the preferred concentration is 1.4 mg / mL.

[0048] 4. Effect of total flow rate on nanoemulsions

[0049] This example investigated the effects at total flow rates of 2.5, 5, 10, and 20 mL / min. Fixed conditions: Tween 80 / 1,4-butanediol, flow rate ratio 1:4, concentration 1.4 mg / mL.

[0050] The results are as follows Figure 5As shown, the particle size remained around 10 nm at all total flow rates; the Zeta potential was highest at 5 mL / min. Therefore, a total flow rate of 5 mL / min is preferred.

[0051] Example 2 Preparation of andrographolide nanoemulsion (optimized process)

[0052] (1) Dissolve andrographolide (purity ≥98%) in dimethyl sulfoxide to prepare a drug solution with a concentration of 1.4 mg / mL.

[0053] (2) The drug solution is mixed with emulsifier Tween 80 and co-emulsifier 1,4-butanediol in a mass ratio of 6:3:1 (drug solution: Tween 80:1,4-butanediol) to form an organic phase.

[0054] (3) The organic phase is injected into the side tube inlet of the microreactor, and deionized water is injected into the main inlet. The flow rate ratio of the organic phase to the aqueous phase is set to 1:16, and the total flow rate is set to 5 mL / min. The two phases are rapidly mixed in the microreactor at room temperature of 25°C.

[0055] (4) Collect andrographolide nanoemulsion at the outlet of the microreactor.

[0056] Performance characterization: Particle size and zeta potential were determined using a laser particle size analyzer (DLS, Nano-ZS90, Malvern). The results showed that the average particle size of the obtained andrographolide nanoemulsion was 10.3 nm, and the zeta potential was 15.2 mV.

[0057] Example 3: Comparison with Traditional Methods

[0058] Under optimal conditions (concentration 1.4 mg / mL, Tween 80 / 1,4-butanediol, total flow rate 5 mL / min, flow rate ratio 1:16), the microreactor method of this invention was compared with the beaker method. The beaker method is as follows:

[0059] A 100 mL beaker was used as the nanoemulsion preparation container. A magnetic stirrer was placed in the beaker, and the magnetic stirring speed was 200 rpm. Andrographolide raw material was dissolved in dimethyl sulfoxide to a concentration of 1.4 mg / mL to prepare 5 mL of drug solution. The emulsifier Tween 80 and the emulsifier 1,4-butanediol were added and placed in the beaker. Then, 80 mL of deionized water was quickly added to the beaker, and after stirring for 30 min, the andrographolide nanoemulsion was obtained.

[0060] The results are as follows Figure 6As shown, compared with the beaker method, the nanoemulsion particle size of the present invention is reduced by 42.5%, and the Zeta potential is increased by approximately 3.33 times. This indicates that the microreactor of the present invention effectively inhibits the aggregation of andrographolide through enhanced mixing and rapid interfacial adsorption, forming smaller and more stable nanoemulsions.

Claims

1. A andrographolide nanoemulsion, characterized in that, The average particle size of the andrographolide nanoemulsion is 10.3±2 nm, and the zeta potential is 15.2±3 mV.

2. The andrographolide nanoemulsion according to claim 1, characterized in that, The andrographolide nanoemulsion has an average particle size of 10.3 nm and a zeta potential of 15.2 mV.

3. The method for preparing andrographolide nanoemulsion according to claim 1 or 2, characterized in that, Includes the following steps: (1) Dissolve andrographolide in an organic solvent to obtain a drug solution; (2) The drug solution is mixed with an emulsifier and a co-emulsifier to form an organic phase; (3) Using deionized water as the aqueous phase, the organic phase and the aqueous phase are mixed in a microreactor; (4) Collect the mixed products to obtain andrographolide nanoemulsion.

4. The method for preparing andrographolide nanoemulsion according to claim 3, characterized in that, In step (1), the organic solvent is selected from dimethyl sulfoxide; the concentration of andrographolide in the drug solution is 1.4 to 5.6 mg / mL; preferably, the concentration is 1.4 mg / mL.

5. The method for preparing andrographolide nanoemulsion according to claim 3, characterized in that, In step (2), the emulsifier is selected from Span 80, polyoxyethylene hydrogenated castor oil or Tween 80, and the co-emulsifier is selected from ethanol, 1,2-propanediol or 1,4-butanediol; preferably, the emulsifier is Tween 80 and the co-emulsifier is 1,4-butanediol. The mass ratio of the drug solution, emulsifier, and co-emulsifier is (4-8):(2-4):1; preferably, the mass ratio is 6:3:

1.

6. The method for preparing andrographolide nanoemulsion according to claim 3, characterized in that, In step (3), the microreactor includes an outer pipe and an internal baffle located inside the outer pipe; the outer pipe consists of two inlets, an outlet and a mixing channel.

7. The method for preparing andrographolide nanoemulsion according to claim 3, characterized in that, In step (3), the flow rate ratio of the organic phase to the aqueous phase is 1:4 to 1:20; preferably, the flow rate ratio of the organic phase to the aqueous phase is 1:

16.

8. The method for preparing andrographolide nanoemulsion according to claim 3, characterized in that, In step (3), the total flow rate of the organic phase and the aqueous phase is 2.5~20 mL / min; preferably, the total flow rate of the organic phase and the aqueous phase is 5 mL / min; the mixing temperature is 20~40℃.

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