Drug-loaded magnetic porous alumina composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of material science and biological medicine, and particularly relates to a drug-loaded magnetic porous alumina composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing magnetic nanoparticles with doxorubicin to obtain a suspension; and immersing the nano-porous anodic aluminum oxide in the suspension, drying, coating the surface with a chitosan solution, and drying to obtain the drug-loaded magnetic porous aluminum oxide composite material. The drug-loaded magnetic porous alumina composite material has magnetic response capability and controllable gating performance, so that the drug release mode is changed from traditional passive diffusion to external controllable on-demand release, and the time, space and dosage accuracy of the release process is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the fields of materials science and biomedicine, and more specifically relates to a drug-loaded magnetic porous alumina composite material, its preparation method, and its application. Background Technology

[0002] Doxorubicin (DOX), a commonly used anthracycline chemotherapy drug in clinical practice, has limited its application due to dose-dependent cardiotoxicity and systemic side effects. Therefore, drug delivery systems capable of on-demand release based on external or endogenous stimuli have gained increasing attention. Nanoporous anodic alumina (NAA) is widely used to construct inorganic controlled-release drug carriers due to its regular pore structure, tunable pore size and thickness, and excellent mechanical and chemical stability. To improve the diffusion-dominated release mode of pure NAA, existing research attempts to introduce magnetically responsive structures, multilayer polyelectrolyte membranes, or other surface-modifying materials into the system to achieve enhanced control over the location, timing, and rate of drug release. However, these technical approaches typically suffer from problems such as complex structures, limited response effects, or difficulties in engineering the preparation process.

[0003] Current NAA-based DOX controlled-release systems still face several limitations: First, the diffusion-dominated release behavior of pure NAAs makes it difficult to achieve precise controlled release that is adjustable, can be shut off, or can be triggered multiple times. Second, magnetically responsive systems have limited magnetocaloric efficiency, insufficient composite structural stability, and often struggle to balance drug loading and manufacturing feasibility. Third, existing literature reports that some polymer films used for pore-mouth control (including chitosan-based or other polyelectrolyte multilayer films) may exhibit limited structural durability and decreased interfacial bonding under wet conditions or external stimulus coupling, thus affecting long-term controlled-release performance. Fourth, traditional thin-film construction methods are cumbersome, making it difficult to simultaneously satisfy overall structural stability and response specificity. These issues collectively limit the further application of NAA-based stimulus-responsive controlled-release systems in precision medicine scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide a drug-loaded magnetic porous alumina composite material, its preparation method, and its application, in order to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of this invention is to provide a method for preparing a drug-loaded magnetic porous alumina composite material, comprising the following steps:

[0007] Magnetic nanoparticles were mixed with doxorubicin (DOX) to obtain a suspension;

[0008] The nanoporous anodic alumina was immersed in the suspension, dried, coated with chitosan solution, and then dried to obtain the drug-loaded magnetic porous alumina composite material.

[0009] Furthermore, the doxorubicin was added in the form of an aqueous solution at a concentration of 1 mg / mL.

[0010] Furthermore, the mass ratio of the magnetic nanoparticles to the doxorubicin star is 10:2.

[0011] Furthermore, the nanoporous anodic aluminum oxide is immersed in the suspension for 30 minutes.

[0012] Furthermore, the chitosan solution is prepared by dissolving chitosan in a 0.8 wt% acetic acid solution and magnetically stirring for 2-3 h.

[0013] Optionally, the ratio of chitosan to acetic acid solution is 0.15 g: 15 mL.

[0014] Furthermore, the amount of chitosan solution coated on the surface is 2-3 mL / cm². 2 .

[0015] Furthermore, the drying temperature is 45 °C.

[0016] Furthermore, the preparation steps of the magnetic nanoparticles include:

[0017] Using an iron source and a citric acid-ethanol solution as reactants, an oxide intermediate is obtained through a combustion reaction.

[0018] The oxide intermediate was calcined under an inert atmosphere to obtain a primary magnetic material.

[0019] The primary magnetic material was modified with citric acid solution, then separated, washed, and dried to obtain magnetic nanoparticles.

[0020] Optionally, the concentration of the citric acid-ethanol solution is 50 g / L.

[0021] Optionally, the ratio of the iron source to the citric acid-ethanol solution is 10.5 g: 40 mL.

[0022] Optionally, the iron source includes ferric nitrate nonahydrate.

[0023] Optionally, the combustion reaction involves igniting the reactants until they extinguish naturally.

[0024] Optionally, the calcination treatment is carried out at a temperature of 350 °C, a heating rate of 3 °C / min, and a time of 2 h.

[0025] Optionally, the concentration of the citric acid solution is 0.05 M (aqueous solution).

[0026] Optionally, the ratio of the primary magnetic material to the citric acid solution is 50 mg: 250 mL.

[0027] Optionally, the modification involves ultrasonic treatment for 30 minutes.

[0028] The second technical solution of the present invention provides a drug-loaded magnetic porous alumina composite material, which is prepared by the above-described preparation method.

[0029] The third technical solution of the present invention provides an application of the above-mentioned drug-loaded magnetic porous alumina composite material in the preparation of precise drug delivery and multi-stimulus response drug delivery systems.

[0030] The present invention discloses the following technical effects:

[0031] The drug-loaded magnetic porous alumina composite material provided by this invention overcomes the problems of uncontrollable release and low magnetic response efficiency of existing porous carriers. It has better engineering properties and stronger application adaptability, and has obvious advantages and application value in the fields of precision drug delivery and multi-stimulus response.

[0032] This invention constructs a drug-loaded magnetic porous alumina composite material with magnetic responsiveness and controllable gating properties, transforming the drug release mechanism from traditional passive diffusion to externally controllable on-demand release, significantly improving the temporal, spatial, and dosage accuracy of the release process. Compared with existing technologies, this invention achieves more efficient magnetic triggering response, a more stable gating structure, higher drug loading, and a more controllable release rate, while improving the dispersion of magnetic components and the consistency of the overall structure, thereby enhancing the system's triggering capability. Attached Figure Description

[0033] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0034] Figure 1 The images show the morphology and structure of the magnetic nanoparticles prepared in Example 1. In the images, A is a TEM image with an inset of a particle size distribution histogram; B is a selected area electron diffraction pattern; C is a high-resolution TEM image with an inset of an FFT image; and D is a high-resolution TEM image.

[0035] Figure 2The figures show the XRD patterns of the magnetic nanoparticles, Fe3O4 (PDF#98-000-0294), α-Fe2O3 (PDF#98-000-0240), and M1 and M2 prepared in Example 1. In the figures, (a) shows the XRD patterns of the magnetic nanoparticles, Fe3O4 (PDF#98-000-0294), and α-Fe2O3 (PDF#98-000-0240) prepared in Example 1, and (b) shows the XRD patterns of M1 and M2.

[0036] Figure 3 The image shows the VSM diagram of the magnetic nanoparticles prepared in Example 1.

[0037] Figure 4 The images show the surface morphology and pore size distribution of nanoporous anodic aluminum oxide, where A is the surface SEM image and B is the pore size distribution.

[0038] Figure 5 The images show cross-sectional SEM images of nanoporous anodic aluminum oxide before and after drug loading, where A represents before drug loading and B represents after drug loading.

[0039] Figure 6 In the diagram, A is a schematic diagram of the magnetic field strength of the rectangular permanent magnet used in the magnetically triggered drug release experiment, and B is a finite element simulation diagram.

[0040] Figure 7 Here are the standard fluorescence curves for DOX, where (a) is the fluorescence emission spectrum of DOX solutions at different concentrations, and (b) is the linear fit between the fluorescence intensity of DOX at 593 nm and the concentration.

[0041] Figure 8 The effect of magnetic stimulation (1148 mT) on drug release from the drug-loaded magnetic porous alumina composite material prepared in Example 1 is shown, where A represents short-term release (0-180 minutes) and B represents long-term release (up to 600 hours).

[0042] Figure 9 The images show the drug release curves of drug-loaded magnetic porous alumina composite materials with different chitosan coating thicknesses in Examples 1-3. Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0049] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0050] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0051] The equipment models and manufacturers used in the specific embodiments of this invention are as follows: ultrasonic cleaner (model PS-08A, Shenzhen Hengli Ultrasonic Equipment Co., Ltd.); quartz tube furnace (model HTL1100-60, Hefei Kejing Materials Technology Co., Ltd.); DC power supply (model DC-1760, Hefei Dachun Electronics Co., Ltd.); scanning electron microscope (model S-4800, Hitachi); fluorescence visible spectrophotometer (model F97 Pro, Shanghai Lingguang Technology Co., Ltd.); high-resolution transmission electron microscope equipped with EDS and EELS functions (instrument model JEOL JEM-ARM200F, JEOL).

[0052] The nanoporous anodic aluminum oxide used in the specific embodiments of this invention can be a commercially available product, or it can be prepared by the following method, the steps of which include:

[0053] The aluminum foil was mechanically pre-flattened, and then ultrasonically cleaned in acetone, anhydrous ethanol and deionized water in sequence. Each step lasted 3 minutes and was repeated three times to fully remove surface impurities. After cleaning, it was placed in an electropolishing solution prepared by perchloric acid and ethanol in a volume ratio of 1:4 and electrochemically polished for 6 minutes under a constant voltage of 20 V. After polishing, it was rinsed three times with deionized water to remove residual solution and obtain pretreated aluminum foil.

[0054] Pretreated aluminum foil was placed as the anode along with parallel carbon rod cathodes in an electrolyte solution (1 M phosphoric acid / ethanol mixture, with a water to ethanol volume ratio of 1:3). Electrochemical oxidation was performed in the electrolytic cell. Pre-anodization was first carried out for 45 min at a lower voltage (90 V in the phosphoric acid system) to form an initial protective layer, thereby reducing the risk of breakdown and ensuring uniform film growth at a higher voltage (140 V). Subsequently, the voltage was increased to approximately 140 V at a constant boost rate of 2 V per 1 s, and anodization was carried out at this voltage for approximately 5 h to obtain original nanoporous anodic aluminum oxide with straight pores of uniform pore size from top to bottom. Wet chemical etching was performed for 90 min using a 5 wt% H3PO4 aqueous solution to expand the pore size. All oxidation steps were carried out at 0 °C, and the final product was nanoporous anodic aluminum oxide (NAA).

[0055] In some specific embodiments, the present invention provides a method for preparing a drug-loaded magnetic porous alumina composite material, the steps of which include:

[0056] S1. Preparation of magnetic nanoparticles: 2.0 g of citric acid monohydrate was dissolved in 40 mL of anhydrous ethanol to prepare a homogeneous citric acid-ethanol solution with a mass concentration of 50 g / L (0.238 M). Then, 10.5 g of ferric nitrate nonahydrate was added under continuous magnetic stirring and stirred for about 60 min to obtain a homogeneous precursor mixture. The resulting mixture was transferred to a crucible and ignited under ventilation until the system spontaneously combusted and extinguished naturally. The intermediate obtained from the combustion was then calcined in a programmable muffle furnace at 350 °C for 2 h under a nitrogen atmosphere at a heating rate of about 3 °C / min. Approximately 50.0 mg of the calcined magnetic powder was redispersed in a 0.05 M (10.51 g / L) citric acid solution to obtain a stable suspension with a mass concentration of approximately 0.2 mg / mL. This suspension was then ultrasonically treated for 30 minutes. After a period of time, the particles were washed three times with deionized water and residual citric acid was removed by magnetic separation. After drying, well-dispersed magnetic nanoparticles (CA-MNPs) were obtained.

[0057] S2. Weigh 10 mg of magnetic nanoparticles (CA-MNPs) and disperse them in 2 mL of doxorubicin (DOX) aqueous solution with a concentration of 1 mg / mL. Then, perform magnetic stirring, ultrasonic treatment for 30 min, and let it stand for 1 h to form a composite suspension.

[0058] S3. Dissolve chitosan in a 0.8 wt% acetic acid solution and stir magnetically for 2 h to obtain a homogeneous chitosan solution; wherein the ratio of chitosan to acetic acid solution is 0.15 g: 15 mL.

[0059] S4. Immerse the nanoporous anodic aluminum oxide (NAA, circular sheet with a diameter of approximately 3 cm) template in the composite suspension of step S2 for 30 min. After removal, gently wash with deionized water and dry at room temperature. Then, uniformly coat the NAA surface with the chitosan solution of step S3 (coating amount of 2-3 mL / cm). 2 The drug-loaded magnetic porous alumina composite material was dried at 45 °C.

[0060] The drug-loaded magnetic porous alumina composite material prepared by the above method can solve the uncontrollability of release caused by diffusion-based pure NAA, and provide a carrier structure that can achieve externally controllable and adjustable release; it can solve the problems of limited magnetocaloric effect and insufficient structural stability of magnetic response systems, and provide a composite system with higher magnetic response capability and better triggering efficiency; it can solve the problems of complex and poor reproducibility in the preparation of layer-by-layer self-assembled films, and propose a more easily engineered gated construction method; it aims to improve the drug loading capacity of NAA carriers, taking into account both drug loading and controllability; it aims to improve the defects of easy aggregation and poor system stability of magnetic nanoparticles, and provide a magnetic composite system with uniform structure and good dispersion; it aims to broaden the stimulus response window and improve triggering stability.

[0061] This invention first pre-treats the aluminum substrate, including degreasing, cleaning, and electropolishing. Then, a nanoporous alumina (NAA) carrier with a regular vertical pore structure is prepared using an anodic oxidation process in an acidic electrolyte. After obtaining the NAA, magnetic nanoparticles (including a mixture of Fe3O4 and γ-Fe2O3) are mixed with doxorubicin in a certain proportion, allowing doxorubicin to form a stable composite system with the magnetic nanoparticles through adsorption or coating. The resulting doxorubicin-magnetic nanoparticle composite is then introduced into the pore region of the NAA via solution impregnation to achieve simultaneous construction of magnetic response function and drug loading. Subsequently, after the composite is immobilized in the NAA structure, a gated layer is formed on the NAA surface by coating with a chitosan (CHI) solution. This gated layer can achieve different diffusion regulation capabilities by adjusting its concentration, thickness, or number of coatings. Throughout the process, anodizing is a standard step, while the simultaneous introduction of the doxorubicin-magnetic nanoparticle composite and the construction of the chitosan-gated layer are improvements made in this invention and can be adapted to specific application requirements. This invention obtains a composite NAA carrier system that combines magnetic responsiveness, high drug loading capacity, and controllable release characteristics through the above process.

[0062] Example 1

[0063] The preparation steps of the drug-loaded magnetic porous alumina composite material include:

[0064] S1. Preparation of magnetic nanoparticles: 2.0 g of citric acid monohydrate was dissolved in 40 mL of anhydrous ethanol to prepare a homogeneous citric acid-ethanol solution with a mass concentration of 50 g / L (0.238 M). Then, 10.5 g of ferric nitrate nonahydrate was added under continuous magnetic stirring and stirred for approximately 60 min to obtain a homogeneous precursor mixture. The resulting mixture was transferred to a crucible and ignited under ventilation until the system spontaneously combusted and extinguished naturally. The intermediate obtained from the combustion was then calcined in a programmable muffle furnace at 350 ℃ for 2 h under a nitrogen atmosphere at a heating rate of approximately 3 ℃ / min. Approximately 50.0 mg of the calcined magnetic powder was redispersed in a 0.05 M (10.51 g / L) citric acid solution to obtain a stable suspension with a mass concentration of approximately 0.2 mg / mL. This suspension was then ultrasonicated for 30 minutes. After a period of time, the particles were washed three times with deionized water and residual citric acid was removed by magnetic separation. After drying, well-dispersed magnetic nanoparticles (CA-MNPs) were obtained.

[0065] S2. Weigh 10 mg of magnetic nanoparticles (CA-MNPs) and disperse them in 2 mL of doxorubicin (DOX) aqueous solution with a concentration of 1 mg / mL. Then, perform magnetic stirring, ultrasonic treatment for 30 min, and let stand for 1 h to form a CA-MNPs-DOX composite suspension.

[0066] S3. Dissolve 0.15 g of chitosan in 15 mL of 0.8 wt% acetic acid solution and stir magnetically for 2 h to obtain a homogeneous chitosan solution.

[0067] S4. Immerse the nanoporous anodic alumina (NAA, a circular sheet with a diameter of about 3 cm) template in the CA-MNPs-DOX composite suspension of step S2 for 30 min. After taking it out, wash it gently with deionized water and dry it at room temperature. Then, uniformly coat the chitosan solution of step S3 onto the surface of NAA and dry it at 45 °C to obtain the drug-loaded magnetic porous alumina composite material, denoted as NAA-MNPs-DOX.

[0068] Example 2

[0069] The preparation steps of the drug-loaded magnetic porous alumina composite material include:

[0070] S1. Preparation of magnetic nanoparticles: 2.0 g of citric acid monohydrate was dissolved in 40 mL of anhydrous ethanol to prepare a homogeneous citric acid-ethanol solution with a mass concentration of 50 g / L (0.238 M). Then, 10.5 g of ferric nitrate nonahydrate was added under continuous magnetic stirring and stirred for approximately 60 min to obtain a homogeneous precursor mixture. The resulting mixture was transferred to a crucible and ignited under ventilation until the system spontaneously combusted and extinguished naturally. The intermediate obtained from the combustion was then calcined in a programmable muffle furnace at 350 ℃ for 2 h under a nitrogen atmosphere at a heating rate of approximately 3 ℃ / min. Approximately 50.0 mg of the calcined magnetic powder was redispersed in a 0.05 M (10.51 g / L) citric acid solution to obtain a stable suspension with a mass concentration of approximately 0.2 mg / mL. This suspension was then ultrasonicated for 30 minutes. After a period of time, the particles were washed three times with deionized water and residual citric acid was removed by magnetic separation. After drying, well-dispersed magnetic nanoparticles (CA-MNPs) were obtained.

[0071] S2. Weigh 10 mg of magnetic nanoparticles (CA-MNPs) and disperse them in 2 mL of doxorubicin (DOX) aqueous solution with a concentration of 1 mg / mL. Then, perform magnetic stirring, ultrasonic treatment for 30 min, and let stand for 1 h to form a CA-MNPs-DOX composite suspension.

[0072] S3. Dissolve 0.3 g of chitosan in 30 mL of 0.8 wt% acetic acid solution and stir magnetically for 2 h to obtain a homogeneous chitosan solution.

[0073] S4. Immerse the nanoporous anodic alumina (NAA, a circular sheet with a diameter of about 3 cm) template in the CA-MNPs-DOX composite suspension of step S2 for 30 min. After taking it out, wash it gently with deionized water and dry it at room temperature. Then, coat the chitosan solution of step S3 evenly on the surface of NAA in two equal parts. After each coating, dry it at 45 °C to obtain the drug-loaded magnetic porous alumina composite material, denoted as NAA-MNPs-DOX-2.

[0074] Example 3

[0075] The preparation steps of the drug-loaded magnetic porous alumina composite material include:

[0076] S1. Preparation of magnetic nanoparticles: 2.0 g of citric acid monohydrate was dissolved in 40 mL of anhydrous ethanol to prepare a homogeneous citric acid-ethanol solution with a mass concentration of 50 g / L (0.238 M). Then, 10.5 g of ferric nitrate nonahydrate was added under continuous magnetic stirring and stirred for approximately 60 min to obtain a homogeneous precursor mixture. The resulting mixture was transferred to a crucible and ignited under ventilation until the system spontaneously combusted and extinguished naturally. The intermediate obtained from the combustion was then calcined in a programmable muffle furnace at 350 ℃ for 2 h under a nitrogen atmosphere at a heating rate of approximately 3 ℃ / min. Approximately 50.0 mg of the calcined magnetic powder was redispersed in a 0.05 M (10.51 g / L) citric acid solution to obtain a stable suspension with a mass concentration of approximately 0.2 mg / mL. This suspension was then ultrasonicated for 30 minutes. After a period of time, the particles were washed three times with deionized water and residual citric acid was removed by magnetic separation. After drying, well-dispersed magnetic nanoparticles (CA-MNPs) were obtained.

[0077] S2. Weigh 10 mg of magnetic nanoparticles (CA-MNPs) and disperse them in 2 mL of doxorubicin (DOX) aqueous solution with a concentration of 1 mg / mL. Then, perform magnetic stirring, ultrasonic treatment for 30 min, and let stand for 1 h to form a CA-MNPs-DOX composite suspension.

[0078] S3. Dissolve 0.45 g of chitosan in 45 mL of 0.8 wt% acetic acid solution and stir magnetically for 2 h to obtain a homogeneous chitosan solution.

[0079] S4. Immerse the nanoporous anodic alumina (NAA, a circular sheet with a diameter of about 3 cm) template in the CA-MNPs-DOX composite suspension of step S2 for 30 min. After taking it out, wash it gently with deionized water and dry it at room temperature. Then, coat the chitosan solution of step S3 evenly on the surface of NAA in three equal parts. After each coating, dry it at 45 °C to obtain the drug-loaded magnetic porous alumina composite material, denoted as NAA-MNPs-DOX-3.

[0080] Comparative Example 1

[0081] Compared with Example 1, the difference lies in the preparation method of the magnetic particles, specifically:

[0082] S1, ferric nitrate nonahydrate (56.56 g) and citric acid monohydrate (22.414 g) were dissolved in 20 mL of distilled water and stirred with a magnetic stirrer (200 rpm). The solution was then placed in a heating hood (450 °C). As the solution was heated, a combustion reaction occurred, accompanied by the release of a large amount of gas. After the combustion reaction was completed, the flask with the valve closed was cooled to room temperature. Distilled water was added to the obtained powder, and the powder was then transferred to a porcelain dish and manually ground to between 10-20 nm to obtain a magnetic particle sample, denoted as M1.

[0083] S2. Weigh 10 mg M1 and disperse it in 2 mL of doxorubicin (DOX) aqueous solution with a concentration of 1 mg / mL. Then, perform magnetic stirring, sonication for 30 min and static soaking for 1 h to form M1-DOX composite suspension.

[0084] S3. Dissolve 0.15 g of chitosan in 15 mL of 0.8 wt% acetic acid solution and stir magnetically for 2 h to obtain a homogeneous chitosan solution.

[0085] S4. Immerse the nanoporous anodic aluminum oxide (NAA, circular sheet with a diameter of about 3 cm) template in the M1-DOX composite suspension of step S2 for 30 min. After taking it out, wash it gently with deionized water and dry it at room temperature. Then, uniformly coat the chitosan solution of step S3 onto the surface of NAA and dry it at 45 °C to obtain the composite material.

[0086] Comparative Example 2

[0087] Compared with Example 1, the difference lies in the preparation method of the magnetic particles, specifically:

[0088] S1, ferric nitrate nonahydrate (56.56 g), and citric acid monohydrate (22.414 g) were dissolved in 20 mL of distilled water and stirred magnetically (200 rpm). The solution was then placed in a microwave oven (2.45 GHz, 800 W). As the solution heated, a combustion reaction occurred, accompanied by the release of a large amount of gas. After the combustion reaction was complete, the flask with the valve closed was cooled to room temperature. Distilled water was added to the obtained powder, which was then transferred to a porcelain dish and manually ground to a particle size between 7-15 nm, yielding a magnetic particle sample, denoted as M2.

[0089] S2. Weigh 10 mg of M2 and disperse it in 2 mL of doxorubicin (DOX) aqueous solution with a concentration of 1 mg / mL. Then, perform magnetic stirring, sonication for 30 min and static soaking for 1 h to form M2-DOX composite suspension.

[0090] S3. Dissolve 0.15 g of chitosan in 15 mL of 0.8 wt% acetic acid solution and stir magnetically for 2 h to obtain a homogeneous chitosan solution.

[0091] S4. Immerse the nanoporous anodic aluminum oxide (NAA, circular sheet with a diameter of about 3 cm) template in the M2-DOX composite suspension of step S2 for 30 min. After taking it out, wash it gently with deionized water and dry it at room temperature. Then, uniformly coat the chitosan solution of step S3 onto the surface of NAA and dry it at 45 °C to obtain the composite material.

[0092] Test case

[0093] Figure 1 The images show the morphology and structure of the magnetic nanoparticles prepared in Example 1. In the images, A is a TEM image with an inset of a particle size distribution histogram; B is a selected area electron diffraction pattern; C is a high-resolution TEM image with an inset of an FFT image; and D is a high-resolution TEM image.

[0094] Figure 2 The figures show the XRD patterns of the magnetic nanoparticles, Fe3O4 (PDF#98-000-0294), α-Fe2O3 (PDF#98-000-0240), and M1 and M2 prepared in Example 1. In the figures, (a) shows the XRD patterns of the magnetic nanoparticles, Fe3O4 (PDF#98-000-0294), and α-Fe2O3 (PDF#98-000-0240) prepared in Example 1, and (b) shows the XRD patterns of M1 and M2.

[0095] Figure 3 The image shows the VSM diagram of the magnetic nanoparticles prepared in Example 1.

[0096] Depend on Figures 1-3 As can be seen, the magnetic nanoparticles prepared in Example 1 exhibit a near-spherical geometry with an average diameter of approximately 11.3 nm, consistent with the particle size distribution histogram. Figure 1 Selected area electron diffraction (SAED) revealed distinct concentric rings, confirming their polycrystalline nature. High-resolution TEM combined with Fast Fourier Transform (FFT) analysis further verified the ordered lattice orientation, while magnified HRTEM images showed clear lattice fringes with a spacing of approximately 0.26 nm, corresponding to the (311) plane of Fe3O4 (JCPDS No. 98-000-0294). Citric acid and anhydrous ethanol played key roles in the synthesis. Citric acid chelates iron ions, effectively inhibiting agglomeration, while also acting as a carbon source to promote partial reduction. Ethanol acts as both a dispersion solvent and a combustion medium that influences particle crystallization. X-ray diffraction (XRD) was used to further confirm the polycrystalline nature of the particles. Figure 2This further confirmed the crystalline phase. The diffraction peaks matched well with Fe3O4 (PDF#98-000-0294) and α-Fe2O3 (PDF#98-000-0240). Most peaks corresponded to α-Fe2O3, but characteristic signals of Fe3O4 were still observed at 30°, 35.6°, and 43°, indicating a mixed phase of Fe3O4 and α-Fe2O3. Semi-quantitative RIR analysis showed that the relative contents of Fe3O4 and Fe2O3 were approximately 37% and 63%, respectively. The average crystallite size obtained by the Scherrer equation was approximately 9.98 nm, while the particle size measured by TEM was approximately 11.3 nm. This difference stems from the different measurement principles: the size obtained by XRD reflects the average size of the coherent diffraction domain with an ordered lattice structure, which is affected by crystal defects and microstrain, and is therefore tends to be smaller; in contrast, TEM can directly image the entire particle morphology (including amorphous surface layers or coatings), thus yielding a slightly larger size estimate. In summary, the consistency between XRD and TEM confirms that the magnetic nanoparticles possess a clear nanoscale crystallinity, providing structural evidence for their subsequent application in NAA channel-controlled drug release. In Comparative Examples 1 and 2, sample M1 exhibits magnetite (Fe3O4) as the main crystalline phase, with a content of approximately 97%, and only a small amount of maghemite (γ-Fe2O3, approximately 3%). Sample M2's main phase is maghemite (γ-Fe2O3), with a content of approximately 85%, accompanied by small amounts of magnetite (Fe3O4, 11%), ferrous oxide (FeO, 2%), and metallic iron (Fe, 2%), demonstrating a multiphase coexistence characteristic. The average grain size was calculated from the XRD patterns, with samples M1 and M2 having average grain sizes of 23 nm and 5 nm, respectively. Phase composition characterization of the two magnetic nanoparticles, M1, shows that M1 is superior to M2. However, the average grain size of sample M2 is more suitable for biomedical applications because extremely small magnetic iron oxide nanoparticles (d < 4 nm) can be used as contrast agents for magnetic resonance imaging (MRI), while magnetic nanoparticles with a diameter of 10 nm are more efficient for use as MRI contrast agents. The sample prepared in Example 1 has a better magnetic composition than sample M1 in the comparative example, and its size is also better than that of comparative example M2.

[0097] Vibrating Sample Magnetometer (VSM) Figure 3The magnetic properties of the sample were further characterized. The hysteresis loop exhibited a typical S-shaped profile, and remanence and coercivity were negligible, confirming that the nanoparticles exhibit superparamagnetic behavior at room temperature. This finding is consistent with the nanoscale structure revealed by XRD and TEM, enhancing the correlation between particle size and magnetic characteristics. The measured saturation magnetization reached 47.1 emu / g, lower than the theoretical value of pure Fe3O4 (~90 emu / g), but significantly higher than the theoretical value of α-Fe2O3 (~0.8 emu / g). These results indicate that the Fe3O4 phase is the main source of magnetization.

[0098] Figure 4 The images show the surface morphology and pore size distribution of nanoporous anodic aluminum oxide, where A is a surface SEM image and B is the pore size distribution. Figure 4 As can be seen, the SEM images of the nanoporous anodic alumina surface reveal a highly ordered array of hexagonal pores with circular openings and intact pore walls arranged in a regular pattern. Quantitative analysis of 50 randomly selected pores using ImageJ showed an average diameter of 179 ± 13 nm with a narrow Gaussian distribution, indicating excellent uniformity. The overall porosity of the membrane was 37.55% (±0.38%), indicating stable formation and high reproducibility.

[0099] Figure 5 The images show cross-sectional SEM images of nanoporous anodic alumina before and after drug loading, where A represents before drug loading and B represents after drug loading. As can be seen from the images, Figure 5 The cross-sectional morphology of the nanoporous cationized alumina (NAA) film before and after MNPs-DOX loading was compared. Cross-sectional SEM further confirmed the vertically aligned channels with a depth of approximately 3.9 μm. Based on geometric calculations, the estimated volume of each pore is approximately 0.098 μm³. 3 The internal surface area of ​​each pore is approximately 2.19 μm. 2 The study reveals the formation of NAA (alumina nanoparticles) after anodizing, along with pore enlargement and a highly porous structure featuring vertically aligned nanochannels with uniform pore distribution, forming the main matrix for nanomaterial loading. After introducing the magnetic nanoparticle / DOX composite material, the cross-section of the central region of the porous layer shows the presence of small particles within the nanochannels. These spots appear as distinct spots or deposits on the pore walls, indicating that CA-MNPs-DOX has penetrated deep into the alumina nanopores, rather than remaining merely on the surface.

[0100] The steps for the magnetically triggered drug release experiment are as follows:

[0101] Figure 6In the diagram, A shows a schematic of the magnetic field strength of the rectangular permanent magnets used in the magnetically triggered drug release experiment, and B is a finite element simulation. As shown, the magnet array consists of rectangular permanent magnets arranged in a distinct polarity pattern (alternating north-south). The lateral distribution of magnetic flux density on the magnet surface (from -100 mm to 100 mm) was measured experimentally. The results show that the magnetic field is strongest at the center and gradually weakens towards the edges; this trend is closely related to the structural characteristics of the magnet array. COMSOL Multiphysics simulations of the magnetic vector potential (A) distribution of this magnet configuration provide insight into the field line geometry and local gradient hotspots. This figure indicates the presence of strong local field gradients in these regions. Figure 6 The image visually demonstrates how a carefully arranged array of magnets creates a non-uniform field with distinct high gradient regions near certain magnet surfaces and nodes. These high gradient regions are precisely where the magnetically responsive nanocarriers in nanoporous alumina are expected to experience the maximum force and therefore the most pronounced triggered response. When an external magnetic field is applied, the force exerted on the magnetic nanoparticles is proportional to the product of their magnetization and the field gradient (assuming the particles are fully magnetized).

[0102] According to Lambert-Beer's law, under fixed wavelength conditions, the absorption intensity of a substance is linearly correlated with its concentration. Therefore, within a specific concentration range, the concentration of DOX in a solution can be calculated using the measured fluorescence signal and this law. Thus, it is necessary to first construct a standard curve relating the concentration of DOX in solution to its fluorescence response. In preparing the standard curve, DOX was sequentially prepared into PBS aqueous solutions ranging from 2.5 to 313 ng / mL to form a series of known concentration gradients. Subsequently, the fluorescence intensity of the DOX solutions at each concentration was measured using a fluorescence spectrophotometer (e.g., ... Figure 7 (a) was used to obtain the relationship between the fluorescence signal at 593 nm and concentration. The obtained fluorescence-concentration data were imported into Origin software for linear fitting to obtain the standardized relationship curve between DOX fluorescence value and concentration (e.g., [reference needed]). Figure 7 (b) in the middle.

[0103] To assess drug release behavior, the sample was immersed in 6 mL of PBS solution (pH 7.4). At predetermined time intervals, 1 mL of the release medium was removed and replaced with an equal volume of fresh PBS. Fluorescence measurements were performed using a spectrophotometer (F97 Pro) at excitation wavelengths of 480 nm and emission wavelengths of 593 nm. The results were determined according to the established calibration curve (R...). 2 =0.99918) quantifies the released DOX, thus enabling accurate determination of cumulative release.

[0104] Figure 7Here are the standard fluorescence curves for DOX, where (a) is the fluorescence emission spectrum of DOX solutions at different concentrations, and (b) is the linear fit between the fluorescence intensity of DOX at 593 nm and the concentration.

[0105] Figure 8 The effect of magnetic stimulation (1148 mT) on drug release from the drug-loaded magnetic porous alumina composite material prepared in Example 1 is shown in the figure. A represents short-term release (0-180 minutes), and B represents long-term release (up to 600 hours). As can be seen from the figure, based on the drug release experiment results, the magnetic field (1148 mT) significantly accelerated the drug release rate during the short-term release phase. At 180 minutes, the cumulative release in the control group reached 38.05% ± 0.65%, while under magnetic stimulation it increased to 57.43% ± 0.75%, showing a statistically significant difference (t-test, p < 0.001). The release characteristics of the two groups gradually converged over a longer period. However, the time required for complete release differed greatly. Under magnetic stimulation, the complete release time was 384 hours (16 days), while without a magnetic field, complete release was delayed to approximately 600 hours (25 days). These results indicate that the magnetic field not only promotes the rapid release of weakly bound or free DOX in the initial stage but also shortens the overall release window.

[0106] Figure 9 The figures show drug release curves for drug-loaded magnetic porous alumina composites with different chitosan coating thicknesses in Examples 1-3. The figures show that, under non-magnetic conditions, the drug release rate gradually decreases with increasing CS layer number. At 150 minutes, the cumulative release of the monolayer and bilayer coatings reached approximately 62% and 56%, respectively, while the trilayer coating showed only approximately 21%, with statistically significant differences between groups (one-way ANOVA, p < 0.001). This indicates that the CS layers effectively inhibited the initial burst release, and the inhibitory effect increased with increasing layer thickness. However, this level was still significantly lower than that of the monolayer and bilayer groups without magnetic stimulation, suggesting that while the barrier effect of the thicker film can be partially compensated by magnetic triggering, it cannot be completely overcome. In summary, the number of CS layers significantly modulates drug release kinetics by adjusting diffusion resistance and interfacial interactions. Monolayer and bilayer coatings cannot completely eliminate burst release but exhibit stronger responsiveness to magnetic triggering, while the trilayer coating significantly inhibits the burst effect but weakens the magnetic response. These findings highlight the need for a reasonable balance between burst suppression and magnetic responsiveness in practical applications, enabling the design of customized release systems to meet therapeutic requirements.

[0107] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0108] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a drug-loaded magnetic porous alumina composite material, characterized in that the steps include... include: Magnetic nanoparticles were mixed with doxorubicin to obtain a suspension; The nanoporous anodic alumina was immersed in the suspension, dried, coated with chitosan solution, and then dried to obtain the drug-loaded magnetic porous alumina composite material.

2. The preparation method according to claim 1, characterized in that, The doxorubicin was added in the form of an aqueous solution at a concentration of 1 mg / mL; And / or, the mass ratio of the magnetic nanoparticles to the doxorubicin star is 10:

2.

3. The preparation method according to claim 1, characterized in that, The nanoporous anodic aluminum oxide was immersed in the suspension for 30 minutes. And / or, the chitosan solution is prepared by dissolving chitosan in a 0.8 wt% acetic acid solution and magnetically stirring for 2-3 h.

4. The preparation method according to claim 3, characterized in that, The ratio of chitosan to acetic acid solution is 0.15 g: 15 mL.

5. The preparation method according to claim 1, characterized in that, The amount of chitosan solution coated on the surface is 2-3 mL / cm. 2 ; And / or, the drying temperature is 45 °C.

6. The preparation method according to claim 1, characterized in that, The preparation steps of the magnetic nanoparticles include: Using an iron source and a citric acid-ethanol solution as reactants, an oxide intermediate is obtained through a combustion reaction. The oxide intermediate was calcined under an inert atmosphere to obtain a primary magnetic material. The primary magnetic material was modified with citric acid solution, then separated, washed, and dried to obtain magnetic nanoparticles.

7. The preparation method according to claim 6, characterized in that, The concentration of the citric acid-ethanol solution is 50 g / L; And / or, the ratio of the iron source to the citric acid-ethanol solution is 10.5 g: 40 mL; And / or, the iron source includes ferric nitrate nonahydrate.

8. The preparation method according to claim 6, characterized in that, The combustion reaction involves igniting the reactants until they extinguish naturally. And / or, the calcination treatment is performed at a temperature of 350 °C, a heating rate of 3 °C / min, and a time of 2 h; And / or, the concentration of the citric acid solution is 0.05 M; And / or, the ratio of the primary magnetic material to the citric acid solution is 50 mg: 250 mL; And / or, the modification is ultrasonic treatment for 30 min.

9. A drug-loaded magnetic porous alumina composite material, characterized in that, The drug-loaded magnetic porous alumina composite material is prepared by the preparation method described in any one of claims 1-8.

10. The application of the drug-loaded magnetic porous alumina composite material according to claim 9 in the preparation of precision drug delivery and multi-stimulus responsive drug delivery systems.

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