Rifampicin amorphous spherulites based on emulsion crystallization regulation and preparation method and application thereof

Abstract

The application discloses rifampicin amorphous spherulites based on emulsion crystallization regulation and a preparation method and application thereof. The preparation method comprises the following steps: dissolving rifampicin in dichloromethane as an oil phase, dissolving glycyrrhizic acid in deionized water as an aqueous phase, adding the oil phase solution into the aqueous phase, forming an oil-in-water emulsion under ultrasonic conditions, removing the organic solvent, and drying to obtain rifampicin amorphous spherulites. The results of X-ray powder diffraction and differential scanning calorimetry tests show that the rifampicin spheroid drug is of amorphous structure. Compared with rifampicin raw materials, the rifampicin amorphous spherulites have excellent lung drug delivery properties, including uniform particle size, high sphericity and excellent flowability, improve the solubility of rifampicin in an in-vitro simulated lung fluid, and are suitable for the treatment of anti-tuberculosis diseases by dry powder inhalation lung drug delivery.

Description

Technical Field

[0001] This invention relates to rifampin, and more particularly to a rifampin amorphous spherulites based on emulsion crystallization regulation, its preparation method and application, which is as an anti-tuberculosis drug delivered via the lungs by dry powder inhalation; belonging to the field of drug delivery systems. Background Technology

[0002] Pulmonary tuberculosis is a highly contagious chronic lung disease with long clinical treatment cycles and significant drug side effects, posing a serious challenge. Rifampin is currently a core first-line drug for the treatment of pulmonary tuberculosis. However, rifampin belongs to the Biopharmaceutical Classification System (BCS) Class II drugs, with extremely poor water solubility, significantly limiting its bioavailability. Traditional administration methods have many drawbacks. For example, oral administration easily causes adverse reactions such as gastrointestinal irritation, nausea, and vomiting, and the first-pass effect in the liver reduces bioavailability; systemic distribution can easily lead to hepatotoxicity and nephrotoxicity. Intravenous injection results in poor patient compliance and makes it difficult to achieve targeted delivery to the lungs, resulting in local drug concentrations that are difficult to reach effective therapeutic levels.

[0003] Pulmonary administration is an ideal non-invasive drug delivery method, allowing drugs to be delivered directly to the lesion site in the lungs through the respiratory tract, increasing local drug concentration and reducing systemic toxicity. However, existing rifampicin formulations are insufficient for pulmonary administration. Its I- and II-crystal forms are the main raw materials for commonly used clinical dosage forms, and are mostly needle-shaped or irregularly shaped crystals. These crystals suffer from impurities, irregular particle size distribution, low bulk density, and poor flowability, leading to severe aggregation and low lung deposition efficiency during dry powder inhalation. Therefore, there is an urgent need to develop novel rifampicin formulations to improve clinical efficacy.

[0004] Chinese invention patent CN108578373B discloses a method for preparing rifampicin-loaded silk fibroin nanospheres: using silk fibroin as a drug carrier, drug-loaded nanospheres are prepared through self-assembly, freeze-thaw, and freeze-drying processes. The product has a small particle size and uniform distribution, and has a certain sustained-release effect, which can reduce the toxic side effects of rifampicin. However, the preparation process of this technology is complex. The pretreatment of silk fibroin requires multiple time-consuming steps such as high-temperature dissolution with LiBr, dialysis desalination, and polyethylene glycol reverse dialysis concentration. The drug loading process also requires freeze-thaw, multiple centrifugation washing, and freeze-drying. The overall process cycle is long, the steps are cumbersome, and the equipment requirements are high. In addition, the freeze-drying step is prone to forming hard agglomerates, and the viscosity of silk fibroin itself can also lead to particle aggregation. Ultimately, the resulting microspheres have serious agglomeration and adhesion, poor dispersibility, and poor powder flowability.

[0005] Chinese invention patent application CN117797123A discloses a method for preparing rifampicin-loaded ethyl cellulose microspheres using electrostatic spraying. Using dichloromethane as a solvent, rifampicin and ethyl cellulose solutions are mixed and ultrasonicated, then electrostatically sprayed and dried to obtain drug-loaded microspheres. The process is mild and simple, producing microspheres with good dispersibility and no adhesion, exhibiting a certain sustained-release effect and reducing drug side effects. However, this technology, using electrostatic spraying, is only suitable for small-batch laboratory preparation. The process has low capacity and stringent equipment requirements, making industrial-scale production impossible. Furthermore, during electrostatic spraying, the droplets are stretched and deformed under a high-voltage electric field, and the rapid evaporation of the solvent leads to uneven shrinkage of the ethyl cellulose film, ultimately forming flat, disc-shaped particles with poor sphericity and insufficient morphological regularity. The large contact area between particles results in friction and adhesion forces far exceeding those of spherical particles, leading to poor powder properties and limiting its application in pharmaceutical formulations.

[0006] Regarding the preparation of rifampicin crystal forms, Chinese invention patent CN107163065B discloses a method for preparing rifampicin crystal form II. This method employs a solvent-mediated crystal transformation process, dispersing crude rifampicin of crystal form I in organic solvents such as methanol and ethanol to form a suspension. After constant-temperature stirring and crystal transformation, followed by separation and drying, crystal form II is obtained. This process is simple, energy-efficient, and produces a product with a particle size of approximately 130 μm, a bulk density greater than 0.65 g / mL, good flowability and purity, and a yield exceeding 90%. However, due to the direct crystal transformation process using a suspension, the dissolution rate of rifampicin of crystal form I and the nucleation and growth rate of crystal form II are difficult to precisely match during the crystal transformation, easily leading to incomplete conversion of crystal form I and the formation of mixed crystals (I / II). Furthermore, the uncontrollable collision, breakage, and aggregation behavior between particles makes it difficult to control the particle size distribution of the product. Additionally, the solubility of crystal form II itself is generally low, failing to significantly improve the solubility of rifampicin. Summary of the Invention

[0007] This invention provides an engineered method for controlling the emulsion crystallization of rifampicin amorphous spherulites. The amorphous spherulites can achieve highly efficient targeted delivery to the lungs via transpulmonary delivery, significantly improving their solubility. This invention utilizes the surface-active properties of glycyrrhizic acid to construct a confined microenvironment in an oil-in-water emulsion system, controlling the nucleation and growth process of rifampicin, and achieving the controllable preparation of uniform spherical amorphous particles.

[0008] This invention is specifically achieved through the following technical solutions:

[0009] A method for preparing rifampicin amorphous spherulites based on emulsion crystallization control: Rifampicin is dissolved in dichloromethane as the oil phase, glycyrrhizic acid is dissolved in deionized water as the aqueous phase, the oil phase solution is added to the aqueous phase, and an oil-in-water emulsion is formed under ultrasonic conditions. After removing the organic solvent, the emulsion is dried to obtain rifampicin amorphous spherulites.

[0010] To further achieve the purpose of this invention, preferably, the concentration of rifampicin in dichloromethane is 10-60 mg / mL; and the concentration of glycyrrhizic acid in deionized water is 1-10 mg / mL.

[0011] Preferably, the volume ratio of the oil phase to the aqueous phase solution is 1:11 to 1:5.

[0012] Preferably, the ultrasound conditions are: a built-in ultrasound probe, an ultrasound time of 3-5 minutes, an ultrasound power of 400-600 W, and an ultrasound duty cycle of 30%-66%.

[0013] Preferably, the removal of organic solvents involves stirring at 20-60°C under normal pressure for 0.5-1 hour, controlling the stirring rate at 100-600 rpm; the drying is vacuum drying.

[0014] A rifampicin amorphous spherulites based on emulsion crystallization regulation are prepared by the above-mentioned method. The X-ray powder diffraction pattern of the rifampicin amorphous spherulites does not have sharp characteristic diffraction peaks, but presents as broad and diffuse amorphous diffraction peaks.

[0015] Preferably, the amorphous drug has a single glass transition temperature Tg of 101.50°C in differential scanning calorimetry.

[0016] Preferably, the spherical particles exhibit a uniform spherical shape of 1-5 μm under ultra-high resolution field emission electron microscopy, with a polydispersity index of 0.1-0.5, a bulk density of 0.4-0.57 g / cm-3, and an angle of repose of 25°-40°.

[0017] The rifampicin amorphous spherulites based on emulsion crystallization regulation are used in dry powder inhaled anti-tuberculosis treatment drugs.

[0018] Preferably, the dry powder inhaled anti-tuberculosis drug is used for targeted lung administration; the dry powder inhaled anti-tuberculosis drug is a capsule-type powder inhaler, a blister-type powder inhaler, or a reservoir-type powder inhaler; it is adapted to be administered by a passive dry powder inhaler or an active dry powder inhaler.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1) This invention utilizes the water-in-oil emulsion confined environment constructed with glycyrrhizic acid to regulate the nucleation and growth process of rifampicin, thereby obtaining uniform spherical particles with a pure amorphous structure, effectively avoiding mixed crystal phenomenon and significantly improving the solubility of rifampicin.

[0021] 2) The rifampicin amorphous spherulites obtained by this invention have a suitable particle size of 1~5 μm, high sphericity and excellent powder flowability. The bulk density and angle of repose meet the requirements of dry powder inhalation formulations. They have high lung deposition efficiency and are suitable for targeted lung drug delivery.

[0022] 3) This invention uses the emulsion solvent evaporation method, which is a mild and simple process with good reproducibility, low organic solvent residue, no special or complicated equipment required, and is easy to scale up for industrial production. Attached Figure Description

[0023] Figure 1 PXRD patterns of rifampicin raw material of Comparative Example 1, rifampicin sample prepared without glycyrrhizic acid of Comparative Example 2, and rifampicin amorphous spherulites obtained in Examples 1-4.

[0024] Figure 2 DSC images of rifampicin raw material for Comparative Example 1, rifampicin sample prepared without glycyrrhizic acid for Comparative Example 2, and rifampicin amorphous spherulites obtained in Examples 1-2.

[0025] Figure 3 The images are scanning electron microscope (SEM) images of rifampicin raw material (a) of Comparative Example 1, rifampicin sample (b) prepared without glycyrrhizic acid of Comparative Example 2, and rifampicin amorphous spherulites (c, d) obtained in Example 3.

[0026] Figure 4 Particle size distribution diagrams of rifampicin raw material obtained in Comparative Example 1, rifampicin sample prepared without glycyrrhizic acid obtained in Comparative Example 2, and rifampicin amorphous spherulites prepared in Examples 2-3.

[0027] Figure 5 This is a comparison of the apparent solubility curves of rifampicin raw material in Comparative Example 1 and the rifampicin amorphous spherulites obtained in Example 4.

[0028] Figure 6 The diagram shows the in vitro simulated lung deposition distribution of rifampicin raw material (Comparative Example 1) and rifampicin amorphous spherulites obtained in Example 2. Detailed Implementation

[0029] To better understand the present invention, the following description, in conjunction with embodiments, further illustrates the present invention. However, it should be noted that the scope of protection claimed by the present invention is not limited to the scope described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Rifampicin is a highly effective first-line anti-tuberculosis drug with potent bactericidal activity against Mycobacterium tuberculosis (Mtb). Its chemical name is 3-[[(4-methyl-1-piperazinyl)imino]methyl]-rifamycin, and its molecular formula is C2. 43 H 58 N4O 12 Molecular weight: 822.95, CAS number: 13292-46-1. The structure is shown in Formula 1: Formula 1;

[0031] However, rifampin has some limitations in clinical application: Rifampin belongs to BCS Class II drugs, has extremely poor water solubility, low bioavailability with traditional oral administration, and is prone to causing gastrointestinal irritation, first-pass effect in the liver, and low distribution in lung tissue; furthermore, existing crystalline rifampin forms are mostly irregular blocky crystals, exhibiting low bulk density, poor flowability, mixed crystals, and uneven particle size, and the crystal structure also results in poor solubility, limiting its clinical efficacy. To overcome these challenges, developing highly effective new rifampin formulations is of great significance for improving the efficacy of anti-tuberculosis treatment.

[0032] Crystals represent an ordered molecular arrangement, while amorphous molecules represent a disordered molecular state. This invention discovers that by utilizing the high solubility of amorphous structures and the excellent powder properties of spherical particles, the pain points in the delivery process of rifampicin can be effectively addressed. Spherical particles are formed from countless disordered molecules. An amorphous structure refers to a drug molecule that does not possess a long-range ordered lattice arrangement, but only maintains a short-range ordered molecular arrangement. Compared to crystalline rifampicin, the amorphous structure does not require overcoming the high lattice energy needed to destroy the lattice, thus enabling rapid dissolution during the dissolution process. This significantly improves the apparent solubility and dissolution rate of the drug in pulmonary fluid, fundamentally solving the core problem of rifampicin's poor water solubility and slow intrapulmonary dissolution as a BCS Class II poorly soluble drug. Spherical particles refer to drug particles with a three-dimensional symmetrical near-spherical morphology. Compared to irregularly shaped particles, they have the smallest interparticle contact area, the lowest friction and adhesion, which can significantly improve the flowability and bulk density of the powder, reduce particle agglomeration and adhesion, and simultaneously improve the dosage accuracy and packing uniformity of dry powder inhalation formulations.

[0033] This invention utilizes an emulsion solvent evaporation method combined with the confinement regulation effect of glycyrrhizic acid to achieve the controllable preparation of rifampicin amorphous spherulites under mild conditions, effectively suppressing the ordered arrangement of crystals and avoiding mixed crystal phenomenon, while obtaining uniform spherical particles that meet the powder performance requirements of lung dry powder inhalation formulations.

[0034] Glycyrrhizic acid (GA), one of the main components of licorice, has the structural formula shown in Formula 2. It possesses good antibacterial, anti-inflammatory, and antioxidant effects, exhibits good biocompatibility and high safety, and is widely used in pharmaceutical formulations. Its molecular formula is C2. 42 H 62 O 16 Molecular weight 822.94, CAS number 1405-86-3.

[0035] Formula 2;

[0036] Glycyrrhizic acid, as a surfactant, dissolves in the aqueous phase. This invention reveals that glycyrrhizic acid contains both hydrophilic and hydrophobic ends in its structure, enabling it to adsorb onto the surface of oil droplets in the aqueous phase. This reduces interfacial tension, forming a stable oil-in-water emulsion system, providing a uniform, confined microenvironment for rifampicin nucleation. This effectively controls particle size and sphericity while preventing particle aggregation and adhesion, providing an ideal template for preparing uniformly dispersed amorphous rifampicin spherulites.

[0037] In this invention, dichloromethane, as the oil-phase solvent, exhibits excellent solubility for rifampin, enabling high drug loading and ensuring uniform dispersion of drug molecules in the oil phase. Rifampin is a lipid-soluble but poorly soluble drug, with a solubility in dichloromethane exceeding 150 mg / mL, meeting the wide concentration range of 10-60 mg / mL required for preparation in this invention. Simultaneously, dichloromethane is virtually immiscible with water, facilitating the construction of a stable, oil-in-water (O / W) emulsion confined microenvironment. In particular, the extremely low solubility of dichloromethane in water allows for the formation of a clear two-phase interface, enabling effective adsorption of glycyrrhizic acid surfactant at the interface and controlling droplet size and morphology. Furthermore, dichloromethane possesses a moderately low boiling point and evaporation rate, crucial for forming a purely amorphous structure in this invention. The excellent compatibility between dichloromethane and glycyrrhizic acid surfactant allows for the formation of a stable emulsion with uniform particle size. This invention achieves its purpose by utilizing the unique physicochemical properties of dichloromethane in conjunction with the emulsion solvent evaporation method of this invention to prepare rifampicin amorphous spherulite structures.

[0038] For pulmonary dry powder inhalation administration, the suitable drug particle size is 1-5 micrometers. This invention, through the regulation of the rifampicin amorphous formation process, prepares rifampicin amorphous spheroids exhibiting a narrow and concentrated particle size distribution, high bulk density and sphericity, and excellent flowability; in vitro antibacterial tests show high antibacterial activity against Mycobacterium tuberculosis; in vivo tests further verify its highly efficient lung-targeting ability.

[0039] Therefore, this invention provides a method for obtaining rifampicin amorphous spherulites based on emulsion crystallization control, employing the following measures: rifampicin is dissolved in dichloromethane as the oil phase, and glycyrrhizic acid, as a surfactant, is dissolved in the aqueous phase. A stable oil-in-water emulsion is formed under ultrasonic conditions. The organic solvent is removed by heating and stirring under normal pressure, and the resulting product is dried to obtain rifampicin amorphous spherulites. In this technical solution, the amounts of relevant raw materials can be obtained through testing in conjunction with the above measures to achieve the purpose of this invention. Preferably, the concentration of rifampicin in dichloromethane is 10-60 mg / mL; more preferably, the concentration of rifampicin in dichloromethane is 30-60 mg / mL. Preferably, the concentration of glycyrrhizic acid in deionized water is 1-10 mg / mL; more preferably, the concentration of glycyrrhizic acid in deionized water is 3-7 mg / mL. Preferably, the volume ratio of the oil phase to the aqueous phase is controlled to be 1:11 to 1:5.

[0040] In the technical measures of this invention, ultrasonic conditions are used to prepare a uniform and stable oil-in-water emulsion. For this purpose, the preferred ultrasonic conditions are an ultrasonic time of 3-5 min, an ultrasonic power of 400-600 W, and an ultrasonic duty cycle of 33%-66%. In the above technical measures, atmospheric pressure heating and stirring are used to remove organic solvents; a stirring temperature of 20-60℃ and a stirring speed of 100-600 rpm are preferred conditions. In the above technical measures, drying removes moisture to form a dry powder.

[0041] The rifampicin amorphous spherulites obtained in this invention, based on emulsion crystallization regulation, exhibit uniform spherical shapes of 1-5 μm under ultra-high resolution field emission electron microscopy, with a particle size of 1-5 μm, a polydispersity index of 0.1-0.5, and a bulk density of 0.4-0.57 g / cm³. -3 The angle of repose is 25 degrees. o ~40 o Its X-ray powder diffraction pattern shows no sharp characteristic diffraction peaks, but only broad and diffuse amorphous diffraction peaks; differential scanning calorimetry analysis shows a single glass transition temperature Tg.

[0042] The present invention also provides the application of the rifampicin amorphous spherulites based on emulsion crystallization regulation in the preparation of dry powder inhaled anti-tuberculosis drugs.

[0043] Example 1

[0044] A method for obtaining rifampicin amorphous spherulites based on emulsion crystallization control includes the following steps: Rifampicin is dissolved in dichloromethane to prepare an oil phase solution with a concentration of 50 mg / mL; glycyrrhizic acid is dissolved in deionized water to prepare an aqueous phase solution with a concentration of 5 mg / mL; the oil phase solution is slowly added dropwise to the aqueous phase solution at a volume ratio of 1:11; ultrasonic treatment is performed using a built-in ultrasonic probe for 3 minutes (ultrasonic power 500 W, ultrasonic duty cycle 33%) to form a stable oil-in-water emulsion; the resulting emulsion is heated and stirred under normal pressure at a stirring temperature of 30℃ and a stirring speed of 300 rpm; the precipitate is collected by centrifugation, washed with deionized water, and placed in a vacuum drying oven to obtain rifampicin amorphous spherulites. The PXRD pattern of the product is attached. Figure 1 The X-ray powder diffraction pattern showed no sharp characteristic diffraction peaks, only broad and diffuse amorphous diffraction peaks. The results indicate that Example 1 yielded a rifampicin amorphous solid powder.

[0045] Example 2

[0046] A method for obtaining rifampicin amorphous spherulites based on emulsion crystallization control includes the following steps: dissolving glycyrrhizic acid in deionized water to prepare an aqueous solution with a concentration of 7 mg / mL; slowly adding the oil phase solution dropwise to the aqueous phase solution at a volume ratio of 1:5; performing ultrasonic treatment using a built-in ultrasonic probe for 4 minutes (ultrasonic power 500W, ultrasonic duty cycle 50%) to form a stable oil-in-water emulsion; heating and stirring the resulting emulsion under normal pressure at a stirring temperature of 60℃ and a stirring speed of 400 rpm; collecting the precipitate by centrifugation; washing with deionized water; and placing it in a vacuum drying oven to obtain rifampicin amorphous spherulites. SEM images of the product are attached. Figure 2 The crystals were found to be uniformly spherical with a diameter of 1-5 μm under ultra-high resolution field emission electron microscopy, indicating good sphericity. The results showed that the crystals obtained in Example 2 were rifampicin amorphous spherulites.

[0047] Example 3

[0048] A method for obtaining rifampicin amorphous spherulites based on emulsion crystallization control includes the following steps: Rifampicin is dissolved in dichloromethane to prepare an oil phase solution with a concentration of 60 mg / mL; glycyrrhizic acid is dissolved in deionized water to prepare an aqueous phase solution with a concentration of 3 mg / mL; the oil phase solution is slowly added dropwise to the aqueous phase solution at a volume ratio of 1:11; ultrasonic treatment is performed using a built-in ultrasonic probe for 5 minutes (ultrasonic power 600 W, ultrasonic duty cycle 60%) to form a stable oil-in-water emulsion; the resulting emulsion is heated and stirred under normal pressure at a stirring temperature of 40℃ and a stirring speed of 200 rpm; the precipitate is collected by centrifugation, washed with deionized water, and dried in a vacuum drying oven to obtain rifampicin amorphous spherulites. The PXRD pattern of the product is attached. Figure 1 Its X-ray powder diffraction pattern showed no sharp characteristic diffraction peaks, only broad and diffuse amorphous diffraction peaks. The results indicate that Example 3 yielded a rifampicin amorphous solid powder.

[0049] Example 4

[0050] A method for obtaining rifampicin amorphous spherulites based on emulsion crystallization control includes the following steps: Rifampicin is dissolved in dichloromethane to prepare an oil phase solution with a concentration of 20 mg / mL; glycyrrhizic acid is dissolved in deionized water to prepare an aqueous phase solution with a concentration of 5 mg / mL; the oil phase solution is slowly added dropwise to the aqueous phase solution at a volume ratio of 1:5; ultrasonic treatment is performed using a built-in ultrasonic probe for 3 minutes (ultrasonic power 500 W, ultrasonic duty cycle 50%) to form a stable oil-in-water emulsion; the resulting emulsion is heated and stirred under normal pressure at a stirring temperature of 50℃ and a stirring speed of 500 rpm; the precipitate is collected by centrifugation, washed with deionized water, and dried in a vacuum drying oven to obtain rifampicin amorphous spherulites. The PXRD pattern of the product is attached. Figure 1 Its X-ray powder diffraction pattern showed no sharp characteristic diffraction peaks, only broad and diffuse amorphous diffraction peaks. The results indicate that Example 4 yielded a rifampicin amorphous solid powder.

[0051] Comparative Example 1

[0052] Rifampicin API: Commercially available rifampicin API is used directly. It is in stable crystalline form I, as shown in the attached document. Figure 1 As shown.

[0053] Comparative Example 2

[0054] Rifampin was dissolved in dichloromethane to prepare an oil phase solution with a concentration of 40 mg / mL. The oil phase was mixed with pure water at a volume ratio of 1:5 and sonicated using a built-in ultrasonic probe for 3 minutes (ultrasonic power 500 W, ultrasonic duty cycle 50%) to form an oil-in-water emulsion. The resulting emulsion was heated and stirred under normal pressure at a temperature of 40℃ and a stirring speed of 200 rpm for 1 hour. The precipitate was collected by centrifugation and dried in a vacuum drying oven. The PXRD pattern of the obtained product is attached. Figure 1 The X-ray powder diffraction pattern of the sample showed no sharp characteristic diffraction peaks, only broad and diffuse amorphous diffraction peaks. The results indicate that Comparative Example 2 yielded a rifampicin amorphous solid powder. The SEM image of the obtained product is attached. Figure 2 The sample showed a fragmented and irregular state under ultra-high resolution field emission electron microscopy, indicating that Comparative Example 2 yielded an irregular amorphous solid powder of rifampicin.

[0055] The characterization test methods and test results of the embodiments and comparative examples of this invention are as follows:

[0056] This invention uses X-ray powder diffraction (PXRD) to characterize the rifampicin samples of Examples 1-4 and Comparative Examples 1 and 2, as shown in the appendix. Figure 1 The rifampicin active pharmaceutical ingredient in Comparative Example 1 exhibited sharp characteristic crystallization diffraction peaks, with characteristic peak values ​​(2θ±0.2°) of 7.3, 8.6, 11.8, 13.6, 14.3, 16.2, 18.3, 19.2, 20.5, and 21.2. The amorphous rifampicin drugs prepared in Examples 1-4 did not show obvious sharp diffraction peaks in their spectra, but instead exhibited typical broad, diffuse peaks. In Examples 1-4, the concentration of glycyrrhizic acid, drug concentration, oil-water ratio, and ultrasonic conditions were adjusted respectively. PXRD characterization results showed that the amorphous samples prepared under different conditions all exhibited diffuse peaks predominantly, with no obvious crystal characteristic peaks, indicating that the rifampicin obtained in the examples of this invention can form an amorphous form, and also demonstrating that the method of this invention has good repeatability and process applicability.

[0057] Using Examples 1 and 2 as representative embodiments of the present invention, the thermal properties of the rifampicin samples from Examples 1-2 and Comparative Examples 1 and 2 were tested using differential scanning calorimetry. The results are shown in the appendix. Figure 2 The four batches of rifampicin amorphous drug prepared in Examples 1-2 and Comparative Example 2 all showed a single glass transition temperature, close to 100±3℃, further indicating that the obtained solid product was an amorphous structure. Comparative Example 1 showed a sharp exothermic peak characteristic of rifampicin crystal form I, with a temperature between 190-200℃. Figure 2As shown, the specific measured Tg values ​​are as follows: Example 1 underwent a glass transition at 100.4℃; Example 2 underwent a glass transition at 101.9℃; and Comparative Example 2 underwent a glass transition at 102.3℃.

[0058] Taking Example 2 as a representative embodiment of the present invention, the morphology of the rifampicin amorphous spherulites prepared in Comparative Examples 1 and 2 and Example 2 was characterized using field emission scanning electron microscopy (SEM). The results are shown in the appendix. Figure 3 From the morphology, it can be clearly observed that, in Comparative Example 1 (Figure a), the I crystal form of rifampicin raw material is rod-shaped with low sphericity. In Comparative Example 2 (Figure b), without the presence of glycyrrhizic acid, the obtained solid product has poor sphericity, uneven particle size distribution, and high polydispersity. The rifampicin sample obtained in Example 2 is generally a regular spherical or near-spherical particle, without obvious angular, needle-like, or blocky crystal characteristics (from...). Figure 3 As can be seen in c and d), this corroborates the amorphous structure results confirmed by XRD and DSC characterization. Within the glycyrrhizic acid-confined emulsion range, uniformly sized spherulites with diameters of 1-5 μm are formed. The spherulites exhibit an uneven surface morphology and a solid interior. These amorphous spherulites possess high sphericity, a narrow particle size distribution, no obvious agglomeration of large particles or attachment of fine particles, and low polydispersity.

[0059] This invention employs dynamic light scattering (DLS) to characterize the particle size and polydispersity index of rifampicin amorphous spherulites prepared in Examples 2 and 3 and Comparative Examples 1 and 2, as shown in the appendix. Figure 4 The rifampicin amorphous spherulites prepared in Example 2 had a concentrated particle size distribution of 0.8 ± 0.1 μm and a polydispersity index of 0.23; the sample prepared in Example 3 had a particle size of 2.5 ± 0.5 μm and a polydispersity index of 0.28. In contrast, Comparative Example 1 had an extremely wide particle size distribution, with a D50 of approximately 4 ± 1.3 μm and a polydispersity index of 1.024; Comparative Example 2 had a D50 of approximately 3 ± 0.8 μm and a polydispersity index of 0.8154. The test results of Examples 1 and 4 are similar to those of Examples 2 and 4, and are not provided individually. The highly concentrated particle size distribution (1~5 μm) in this embodiment of the invention ensures targeted deposition in the alveolar region during dry powder inhalation, avoiding the retention of large particles in the upper respiratory tract and the exhalation loss of small particles, thereby improving lung delivery efficiency; the low polydispersity index indicates good particle size uniformity and no obvious agglomeration, which is beneficial to improving powder flowability and dispersibility, and adapting to the drug delivery requirements of dry powder inhalation formulations.

[0060] Taking Example 4 as an example, the present invention uses an apparent solubility assay to determine the solubility behavior of rifampicin amorphous spherulites in simulated lung fluid medium PBS (pH 7.4). The solubility behavior of the rifampicin amorphous spherulites prepared in Example 4 of the present invention and the commercially available rifampicin active pharmaceutical ingredient of Comparative Example 1 were characterized. The results are shown in the appendix. Figure 5 In the initial dissolution stage, the drug concentration of amorphous spherulites increases rapidly over time, exhibiting a clear rapid dissolution characteristic, eventually reaching a dissolution plateau at approximately 3000 min, with an equilibrium solubility of approximately 1450 μg / mL. In contrast, rifampicin active pharmaceutical ingredient has a faster initial dissolution rate, but the overall drug concentration increase is limited, and it reaches a plateau at approximately 300 min, with an equilibrium solubility of only about 450 μg / mL, only about one-third that of amorphous spherulites. The high dissolution rate and high apparent solubility of the amorphous spherulites of this invention effectively overcome the dissolution difficulties caused by the high lattice energy of crystalline rifampicin, enabling it to dissolve rapidly in the pulmonary fluid environment and maintain a high drug concentration. This provides sufficient drug exposure for alveolar epithelial absorption after pulmonary administration, which is beneficial for improving local therapeutic effects and pulmonary bioavailability.

[0061] Taking Example 2 as an example, this invention uses a two-stage impinger to characterize the in vitro lung deposition properties of rifampicin amorphous spherulites prepared in Example 2. The test conditions meet the requirements for in vitro deposition determination of dry powder inhalation preparations in the General Chapter of the Chinese Pharmacopoeia: the flow rate of the device is set at 60 L / min, and the collection solutions of the first stage (upper respiratory tract simulation stage) and the second stage (lung deposition stage) are methanol-water mixtures of 8:2. After administration according to the prescribed method, the drug content in the two stage collection solutions is measured, and the fine particle fraction (FPF, i.e., the percentage of drug deposited in the second stage relative to the total administered dose) is calculated. The results are shown in the appendix. Figure 6The fine particle fraction (FPF) of the rifampicin amorphous spherulites prepared in Example 2 was 45.93 ± 3.00%, while the FPF of the rifampicin active pharmaceutical ingredient in Comparative Example 1 was only 5.05 ± 0.14%. The higher fine particle fraction of the rifampicin amorphous spherulites prepared in this embodiment indicates that most particles can bypass the inertial trapping of the oropharynx with the airflow and successfully enter the lung simulation stage; while the extremely low FPF of the other formulation indicates that its particles are mostly trapped in the upper respiratory tract due to their large size, poor flowability, or tendency to agglomerate, making it difficult for them to reach the lungs. Furthermore, the emptying rate (ED) refers to the percentage of drug actually sprayed from the dry powder inhaler relative to the total loaded dose, directly reflecting the device's emptying capacity and the accuracy of the clinical dosage. The Chinese Pharmacopoeia requires that the emptying rate of dry powder inhalation formulations should not be less than 80%. As shown in the figure, the emptying rate of the active pharmaceutical ingredient in Comparative Example 1 was 81.2%, barely meeting the pharmacopoeia's acceptable limit; while the emptying rate of the rifampicin amorphous spherulites prepared in Example 2 of this invention was as high as 94.3%, significantly better than the comparative example. Recovery rate (RD) refers to the percentage of total drug recovered from the collection liquids of each stage of the inhalation device and the two-stage impactor, relative to the total administered dose. It is used to verify the reliability of the test method and reflects the degree of non-specific loss of drug during delivery. The pharmacopoeia requires a total recovery rate of not less than 85%. The test results show that the total recovery rates of Comparative Example 1 and Example 2 were 94.7% and 96.8%, respectively, both meeting the pharmacopoeia requirements. Overall, the results indicate that the test method is reliable. The particle size obtained in this invention is concentrated in the range of 1~5μm, which is within the suitable particle size range for pulmonary inhalation. Furthermore, it exhibits high sphericity, good dispersibility, and excellent airflow following, thus demonstrating excellent pulmonary deposition efficiency.

[0062] The test and characterization results of Examples 1-4 and Comparative Examples 1-2 show that the rifampicin amorphous spheroids prepared in this invention have a regular spherical morphology, high sphericity, and a concentrated particle size distribution of 1-5 μm. This significantly improves the problems of irregular crystal form, wide particle size distribution, easy aggregation, and poor flowability of commercially available rifampicin active pharmaceutical ingredient (API), which helps to greatly improve the drug deposition efficiency in the lungs. Simultaneously, the apparent solubility of the rifampicin amorphous spheroids in simulated lung fluid is significantly higher than that of the API, demonstrating that the amorphous structure effectively overcomes the dissolution bottleneck of crystalline rifampicin and improves the drug's solubility, indicating its potential for higher pulmonary bioavailability. In vitro simulated lung deposition experiments using a dual-stage impactor show that the fine particle fraction (FPF) of the amorphous spheroids is significantly higher than that of the API sample, demonstrating a significant improvement in its targeted deposition efficiency in the lungs, effectively reducing upper respiratory tract retention, and minimizing local irritation and drug waste. The amorphous spherulites prepared in the examples showed stable and excellent performance in terms of crystal purity, powder properties, dissolution behavior and lung deposition efficiency, verifying the precise control effect of the emulsion solvent evaporation method of the present invention on particle nucleation, growth and crystal form.

[0063] This invention optimizes the performance of rifampicin formulations and enhances their clinical application value. The prepared rifampicin amorphous spherulites have superior physical powder properties, better solubility, and lung-targeted deposition efficiency. These advantages make it highly valuable for clinical application in the treatment of pulmonary tuberculosis with rifampicin dry powder inhalation.

[0064] As can be seen from the above, the rifampicin amorphous spherulites prepared by the glycyrrhizic acid emulsion crystallization regulation of this invention provide an important basis for the development of lung-targeted anti-tuberculosis drug delivery systems and provide a feasible new solution for efficient and low-toxicity lung inhalation therapy for pulmonary tuberculosis.

[0065] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing rifampicin amorphous spherulites based on emulsion crystallization regulation, characterized in that: Rifampicin was dissolved in dichloromethane as the oil phase, and glycyrrhizic acid was dissolved in deionized water as the aqueous phase. The oil phase solution was added to the aqueous phase, and an oil-in-water emulsion was formed under ultrasonic conditions. After removing the organic solvent, the emulsion was dried to obtain amorphous rifampicin spherulites.

2. The method for preparing rifampicin amorphous spherulites based on emulsion crystallization control according to claim 1, characterized in that, The concentration of rifampicin in dichloromethane is 10-60 mg / mL; the concentration of glycyrrhizic acid in deionized water is 1-10 mg / mL.

3. The method for preparing rifampicin amorphous spherulites based on emulsion crystallization control according to claim 1, characterized in that, The volume ratio of the oil phase to the aqueous phase solution is 1:11 to 1:

5.

4. The method for preparing rifampicin amorphous spherulites based on emulsion crystallization control according to claim 1, characterized in that, The ultrasound conditions are as follows: built-in ultrasound probe, ultrasound time of 3-5 minutes, ultrasound power of 400-600 W, and ultrasound duty cycle of 33%-66%.

5. The method for preparing rifampicin amorphous spherulites based on emulsion crystallization control according to claim 1, characterized in that, The removal of organic solvents is carried out by stirring at 20-60℃ under normal pressure for 0.5-1 hour, with the stirring rate controlled at 100-600 rpm; the drying is vacuum drying.

6. A rifampicin amorphous spherulites based on emulsion crystallization regulation, characterized in that, The rifampicin amorphous spherulites prepared by any one of claims 1-5 exhibit no sharp characteristic diffraction peaks in their X-ray powder diffraction patterns, but rather broad and diffuse amorphous diffraction peaks.

7. The rifampicin amorphous spherulites based on emulsion crystallization control according to claim 6, characterized in that, The amorphous drug has a single glass transition temperature Tg of 101.50 °C in differential scanning calorimetry.

8. The rifampicin amorphous spherulites based on emulsion crystallization control according to claim 6, characterized in that, The spherical particles exhibit a uniform spherical shape of 1-5 μm under ultra-high resolution field emission electron microscopy, with a polydispersity index of 0.1-0.5 and a bulk density of 0.4-0.57 g / cm³. -3 The angle of repose is 25 degrees. o ~40 o .

9. The application of rifampicin amorphous spherulites based on emulsion crystallization control as described in claim 6 in the preparation of dry powder inhaled anti-tuberculosis drugs.

10. The application of rifampicin amorphous spherulites based on emulsion crystallization control according to claim 9 in the preparation of dry powder inhaled anti-tuberculosis drugs, characterized in that, The dry powder inhaled anti-tuberculosis drug is used for targeted lung delivery; the dry powder inhaled anti-tuberculosis drug is a capsule-type powder inhaler, a blister-type powder inhaler, or a reservoir-type powder inhaler; it is compatible with passive dry powder inhalers or active dry powder inhalers for delivery.

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