Microneedle with two-phase insoluble structure as well as preparation method and application of microneedle

Abstract

According to the microneedle with the two-phase insoluble structure and the preparation method and application of the microneedle, a two-phase insoluble method is used for controlling drug loading of the needle tip, that is, the needle tip and a substrate are filled with a water phase solution and an organic phase solution respectively, so that the needle tip solution is effectively prevented from diffusing into the substrate, and stable drug loading of the needle tip is achieved. The micro-needle with the two-phase insoluble structure can realize real detection of the drug loading capacity of the micro-needle, and due to the water insolubility of the substrate part, only the needle tip is dissolved in the dissolving process, so that the content of the drug entering a human body can be accurately controlled and measured; meanwhile, the microneedle with the two-phase insoluble structure can effectively prevent the unevenness phenomenon caused by water absorption or water loss in different humidity environments, and guarantee is provided for follow-up accurate drug administration.

Description

[0001] This application claims priority to the earlier Chinese application, application number 2024105739494, filed on May 10, 2024; all its contents are part of this invention. Technical Field

[0002] This invention belongs to the field of microneedle technology, specifically relating to microneedles with a two-phase insoluble structure, their preparation methods, and applications. Background Technology

[0003] Soluble microneedles are a novel transdermal drug delivery technology. Using various polymers as a framework, they carry drugs that can penetrate the stratum corneum and dissolve and permeate within the skin, thus achieving drug delivery. The microneedles range in length from 25 to 2000 μm, with a base diameter of 50 to 300 μm and a tip diameter of 1 to 30 μm, and are arranged in a regular matrix within an area of ​​1 to 5 cm². 2 On the patch.

[0004] Most existing microneedle fabrication processes utilize a mold-based method. This involves mixing the matrix material and drug, filling the mixture into a cured PDMS (polydimethylsiloxane) mold, drying it to form a film, and then demolding to obtain a complete microneedle patch. Furthermore, existing microneedles are typically fabricated entirely from the same matrix material. While there are reports of using different materials for the needle tip and base, both are generally water-soluble. This makes it difficult to ensure stable drug concentration at the needle tip; the drug diffuses along with the matrix material to the needle column or base. Due to the skin's high elasticity, the needle column or base will not penetrate the skin completely; usually only the needle tip can enter and dissolve. Therefore, if the drug diffuses to the needle column or base, the amount of drug entering the body becomes unstable, failing to achieve stable drug delivery at the needle tip.

[0005] Meanwhile, current microneedle content assays often face the challenge of accurately measuring drug loading. Drug loading refers to the actual amount of drug that can penetrate and dissolve in the human body. Since microneedles are typically 700–1000 μm in height, only about 30–70 μm penetrates the body—a very small fraction. Manually removing the needle tip to measure the loading is practically impossible. The common practice is to dissolve the entire microneedle in water before measuring the loading, but this isn't a true measurement of drug loading. Drug at the needle tip may diffuse to the needle column or base, where it cannot penetrate the body, leading to inaccurate results. The actual amount of drug entering the body may be less than the amount obtained from the assay.

[0006] Therefore, there is an urgent need to find a method for preparing soluble microneedles that can carry drugs at the needle tip without diffusing to other parts of the body. This method can ensure that the drug is always stored at the needle tip and is released as the needle tip skeleton material dissolves in the body. This would truly solve the problems of consistent drug loading and stable bioavailability in microneedles, while also allowing for precise control and measurement of the amount of drug entering the human body. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a biphase insoluble microneedle, its preparation method, and its applications. The biphase insolubility method is used to control drug loading at the needle tip. Specifically, the needle tip and substrate are filled with aqueous and organic phase solutions, respectively, effectively preventing the needle tip solution from diffusing into the substrate and achieving stable drug loading. The biphase insoluble structure of the microneedle enables true drug loading detection because the water insolubility of the substrate means that only the needle tip dissolves during the dissolution process, allowing for precise control and measurement of the drug content entering the body. Furthermore, the biphase insoluble structure effectively prevents unevenness caused by water absorption or loss in different humidity environments, ensuring accurate subsequent drug delivery.

[0008] On one hand, the present invention provides a microneedle with a two-phase insoluble structure, the microneedle comprising a tip and a substrate, the tip being prepared using a water-soluble material and the substrate being prepared using a non-water-soluble material.

[0009] This invention provides a method for preparing soluble microneedles with drug-loaded tips that prevent diffusion to other sites. The method utilizes a two-phase insoluble approach to control drug loading at the tip. Two-phase insolubility means that the tip and substrate are filled with an aqueous phase solution and an organic phase solution, respectively. Since most drugs are highly water-soluble, water-soluble polymers are often chosen for the tip matrix material, while a lipid-soluble polymer is chosen for the substrate matrix material. This effectively prevents the tip solution from diffusing into the substrate. Microneedles prepared using the two-phase insolubility method provided by this invention ensure that the drug is stored at the tip and released as the tip matrix material dissolves in vivo. This method solves the problems of consistent drug loading and stable bioavailability in microneedles.

[0010] Furthermore, the water-soluble material used for the needle tip is a material that is soluble in water but insoluble in organic solvents, including any one or more of polymers, sugars, and amino acids.

[0011] Furthermore, the polymer includes any one or more of polyvinylpyrrolidone (PVP), polyacrylamide (PAA), polyvinyl alcohol (PVA), and carboxymethyl cellulose (CMC). These polymers have good water solubility and biocompatibility and can be used to prepare soluble microneedles.

[0012] Furthermore, the sugars include any one or more of trehalose, sucrose, maltose, galactose, sodium hyaluronate, and chondroitin sulfate. Sugars are also a commonly used water-soluble material.

[0013] Furthermore, the amino acid includes any one or more of glycine, alanine, and valine.

[0014] Amino acids are natural, water-soluble materials that can be used to prepare soluble microneedles. Common amino acids include glycine, alanine, and valine. These amino acids have good water solubility and biocompatibility, making them suitable for preparing soluble microneedles.

[0015] In some embodiments, this invention compares the differences in mechanical strength, drug loading, and skin penetration of microneedles prepared from composite framework materials composed of different polymers, sugars, and amino acids. The results show that, compared to tips prepared from PVA, sucrose, and glycine, microneedles prepared using PVP, maltose, or valine as the framework material, or using only one or two of PVA, sucrose, and glycine, have slightly lower mechanical strength. The actual drug loading measured using the drug loading method provided by this invention is also slightly lower than the theoretical value, and the actual drug loading decreases to varying degrees after the microneedles are stored for a certain period. Only by using a combination of PVA, sucrose, and glycine as the framework material can the drug loading of the microneedle tip be effectively improved.

[0016] In some methods, the aforementioned water-soluble material is used to prepare a needle tip solution, which is injected into the micro-needle holes of a PDMS mold under high pressure, and the needle tip is obtained after drying.

[0017] Furthermore, the needle tip also includes a drug, which is a water-soluble drug, including any one or more GLP-1 drugs selected from benaglutide, exenatide, liraglutide, lixinatide, long-acting exenatide encapsulated with polylactic-co-glycolic acid copolymer, abiglutide, duraglutide, smegglutide, and telparatide.

[0018] In some approaches, a single water-soluble matrix material can be used to bind the drug to the needle tip region, or multiple composite matrix materials can be used to compensate for the specific defects of a single matrix material.

[0019] Furthermore, the substrate uses a non-water-soluble material that is soluble in organic solvents or lipids but insoluble in water, including any one or more of polylactic-co-glycolic acid copolymer (PLGA), acrylic resin (EUDRAGIT), dimethylaminoethyl methacrylate (DMAEMA), ethyl cellulose, fatty alcohols, dimethylacetamide (DMA), polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG).

[0020] In some approaches, the substrate region can use materials that are soluble in organic solvents or lipids, or multiple composite materials can be used to compensate for the specific defects of a single material.

[0021] In some embodiments, the base solution is selected as a pharmaceutical-grade acrylic resin. Eudragit is a trade name for a synthetic pharmaceutical excipient, comprising methacrylic acid copolymers and methacrylate copolymers, commonly known as acrylic resins in China. Eudragit is widely used in gastric coating, enteric coating, sustained-release coating, protective coating, sustained-release matrix materials, and matrix adhesive materials for transdermal drug delivery systems. This invention chose Eudragit because of its water insolubility, which allows it to be used to prepare a base solution. The prepared base solution is uniformly coated onto a PDMS mold containing a needle tip solution, and complete drug-loaded microneedles are prepared through degassing and drying.

[0022] By preparing the tip and base of the microneedle using two different materials (water-soluble and water-insoluble), the diffusion of water-soluble drugs from the tip to the base area can be effectively prevented.

[0023] Furthermore, the microneedle also includes a needle column, which is prepared using a water-soluble material, and the molecular weight and / or viscosity of the needle column material is higher than that of the needle tip material.

[0024] Since some drugs are sensitive to organic solvents and cannot directly contact the substrate prepared with organic solvents, needle columns are also required. The needle column area can protect the drug at the needle tip and prevent the drug from denaturing or becoming inactive due to contact with organic solvents in the substrate area. Even if a small amount of drug diffuses into the needle column area, it can act as a buffer and will not come into contact with the organic solvents in the substrate.

[0025] In some methods, the needle tip height is approximately 200 μm, located at the tip of the microneedle; the needle column height is approximately 400 μm, located in the middle of the microneedle; and the base region height is approximately 300 μm, located at the bottom of the microneedle.

[0026] In some methods, the needle column can be composed of backbone materials such as water-soluble polymers, polysaccharides, and amino acids.

[0027] In some approaches, needles can use a single water-soluble framework material, or multiple composite framework materials can be used to compensate for the specific defects of a single framework material.

[0028] Furthermore, the molecular weight of the needle column material is 80-1000 kDa, or the viscosity of the needle column material is 2000-20000 mPa·s.

[0029] In some methods, the needle column can be screened by the matrix material, or the mass ratio of the matrix material can be adjusted to increase the solution viscosity or speed up the drying time, thereby avoiding or slowing down the diffusion of the drug in the needle column area.

[0030] In some methods, the needle column should be made of a water-soluble matrix material with a large molecular weight. For the same mass percentage, a larger molecular weight results in a higher viscosity solution. A molecular weight distribution between 80 kDa and 1000 kDa indicates higher viscosity, which can effectively prevent drug diffusion. Simultaneously, a higher molecular weight leads to faster drying, which can also control the drug diffusion rate within the needle column region.

[0031] In some methods, even with the same material selection for the needle column, adjusting the mass ratio of the matrix material can also regulate viscosity, thereby controlling the diffusion rate of the drug in the needle column region.

[0032] In some embodiments, the drug is smegglutide, the water-soluble material used for the needle tip is polyvinyl alcohol, sucrose and glycine, the water-soluble material used for the needle column is polyvinyl alcohol and sucrose, and the water-insoluble material used for the base includes eutectic and ethanol.

[0033] On the other hand, the present invention provides a method for preparing microneedles with a two-phase immiscible structure, the method comprising the following steps:

[0034] (1) A needle tip solution is added to the microneedle patch mold, wherein the needle tip solution is prepared using a water-soluble material;

[0035] (2) After the needle tip solution has dried and solidified, the needle column solution is added. The needle column solution is prepared using a water-soluble material, and the molecular weight and / or viscosity of the material in the needle column solution is higher than that of the material in the needle tip solution.

[0036] (3) After the needle column solution has dried and solidified, add the base solution, which is prepared using a non-water-soluble material;

[0037] (4) Dry and demold to obtain microneedle patches.

[0038] In some embodiments, the microneedle patch mold described in step (1) is a PDMS mold.

[0039] In some methods, a needle tip solution is added to the microneedle patch mold in step (1): the prepared water-soluble needle tip solution is mixed with the drug and injected into the PDMS mold hole to form a needle tip. The water-soluble material of the needle tip solution includes any one or more of polymers, sugars, and amino acids.

[0040] In some methods, step (3) involves adding a base solution: the prepared non-water-soluble base solution is uniformly applied to the holes of the PDMS mold, and then the excess solution is scraped off with a scraper to form a smooth base. The non-water-soluble material of the base solution includes any one or more of polylactic acid-glycolic acid copolymer, acrylic resin, dimethylaminoethyl methacrylate, ethyl cellulose, fatty alcohols, dimethylacetamide, polyvinylpyrrolidone, and polyethylene glycol.

[0041] In another aspect, the present invention provides a method for testing the drug loading capacity of a microneedle patch, wherein the microneedle patch is dissolved in a water-soluble solution, and then the drug content in the water-soluble solution is detected. The microneedle patch uses microneedles as described above or microneedles prepared by the method described above.

[0042] Currently, microneedles face the challenge of accurately measuring drug loading during content detection. Drug loading refers to the amount of drug that actually enters and dissolves in the human body. Since microneedles are typically 700–1000 μm in height, only about 30–70 μm penetrates the body—a very small fraction. Manually removing the needle tip for measurement is practically impossible. The common practice is to dissolve the entire microneedle in water before measurement, but this isn't a true measurement of drug loading. Drug at the needle tip may diffuse to the needle column or base, preventing entry into the body and leading to inaccurate results. The actual amount of drug entering the body may be less than the detected amount. However, the two-phase insoluble structure of the microneedles provided by this invention enables true drug loading detection. Because the base is water-insoluble, only the needle tip dissolves during dissolution, allowing for precise control and measurement of the drug content entering the body.

[0043] In some methods, when the microneedles contain a tip and a column, the soluble microneedle patch can be dissolved in a water-soluble solution to completely dissolve the tip and column, thus allowing only the drug content within the tip and column to be detected.

[0044] In some embodiments, this invention has verified that immiscible microneedles have a significant advantage over existing soluble microneedles in terms of drug loading at the needle tip. Results show that the immiscible microneedles provided by this invention achieve excellent drug loading at the needle tip when loading zolmitriptan and smegglutide. Furthermore, the drug loading effect of needle tips prepared using multiple composite matrix materials is better than that of needle tips with a single matrix structure. This is because the immiscible microneedles provided by this invention, in addition to the needle tip region and the base region, also include a needle column region. The needle column region has a higher molecular weight and viscosity than the needle tip region, and dries faster, effectively controlling the drug diffusion rate and preventing the drug from contacting and deactivating with the organic solvent of the base, thereby achieving complete drug loading at the needle tip. In contrast, soluble microneedles prepared using matrix materials such as sodium hyaluronate and citric acid lack a needle column region and therefore can only load chemical drugs such as zolmitriptan, and cannot effectively load protein drugs. Therefore, compared with existing soluble microneedles, immiscible microneedles can be loaded not only with chemical drugs such as zolmitriptan, but also with protein drugs, making them more widely applicable.

[0045] In another aspect, the present invention provides the use of a composition for preparing a reagent to improve the drug loading capacity of a microneedle tip, said composition comprising any one or more of polymers, sugars, and amino acids.

[0046] In another aspect, the present invention provides the use of the microneedles described above or the microneedles prepared by the method described above for preparing microneedle patches that prevent unevenness due to water absorption or loss.

[0047] Because existing microneedles are made entirely of water-soluble materials, the microneedles may curl up during testing or use due to differences in indoor humidity. This greatly affects subsequent skin drug delivery and prevents the microneedles from fully penetrating the skin.

[0048] The microneedles with the two-phase insoluble structure provided by this invention, because the base region is made of water-insoluble material, can greatly reduce the interference of environmental humidity on patch flatness in subsequent use scenarios, thereby enhancing drug delivery efficiency and effectively preventing unevenness due to water absorption or loss in different humidity environments, which is a good protection for subsequent drug delivery.

[0049] The present invention has the following beneficial effects:

[0050] 1. A two-phase insoluble microneedle and its preparation method are provided, wherein the needle tip and the substrate are filled with an aqueous phase solution and an organic phase solution respectively, thereby effectively preventing the needle tip solution from diffusing into the substrate and achieving stable drug loading at the needle tip;

[0051] 2. The microneedles with a two-phase insoluble structure can achieve true drug loading detection. Because the base is water insoluble, only the needle tip will dissolve during the dissolution process, thus allowing for precise control and measurement of the drug content entering the human body.

[0052] 3. The two-phase insoluble structure of the microneedles can also effectively prevent unevenness caused by water absorption or loss in different humidity environments, thus ensuring accurate drug delivery. Attached Figure Description

[0053] Figure 1 This is a flowchart of the fabrication process for a two-phase immiscible microneedle patch.

[0054] Figure 2 These are schematic diagrams showing the different needle shapes and parts of a microneedle;

[0055] Figure 3 This is a photo of the Smegglutinin microneedle patch from method seven;

[0056] Figure 4 This is a schematic diagram showing the mechanical strength test results of the microneedle patch in Method 7;

[0057] Figure 5 The image shows the remaining microneedle patch after dissolving the microneedle patch in the HPLC mobile phase solution (method 7) and shaking it on a shaker for 1 hour.

[0058] Figure 6 This is a schematic diagram showing the comparison between the drug loading content at the needle tip of the microneedle patch in Method 7 and the theoretical value;

[0059] Figure 7 Comparison photos of microneedle patches of Method 7 and ordinary soluble microneedle patches after drying and storage;

[0060] Figure 8 This is a photograph showing the obvious holes formed on the skin of a rat after the microneedle patch of Method 7 was inserted into its back. Detailed Implementation

[0061] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0062] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0063] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0064] Example 1: Smegglutinin microneedles provided by the present invention

[0065] I. Preparation of Smegglutinin Microneedles

[0066] The composition of the semaglutide microneedles provided in this embodiment is shown in Table 1. The microneedle tip is filled with a mixture of GLP-1 class drug and water-soluble matrix material, containing the semaglutide composition, thickener, stabilizer, and water. The microneedle column is filled with a water-soluble matrix material solution, containing no drug components, and contains the matrix material and water. The microneedle base is filled with a non-water-soluble matrix material solution, containing no drug components, and contains pharmaceutical-grade acrylic resin and an ethanol solution.

[0067] Table 1. Formula for Smegglutinin Microneedles I

[0068]

[0069] The preparation method of microneedles is described in [link to documentation]. Figure 1 The flowchart shown illustrates the preparation steps as follows:

[0070] (1) PVA, sucrose, glycine and purified water were added according to the proportions in Table 1, dissolved by stirring in a water bath, and centrifuged to obtain a mixed solution of PVA-sucrose-glycine.

[0071] (2) Add the proportion of smegglutinin in the table above to the PVA-sucrose-glycine mixed solution obtained in step (1), stir to dissolve, then add the methylene blue powder in the above proportion, mix evenly to obtain the needle tip solution.

[0072] (3) Add PVA, sucrose and purified water according to the proportions shown in the table above, stir and dissolve in a water bath, and centrifuge to obtain the needle column solution.

[0073] (4) Add E100 and anhydrous ethanol according to the proportions shown in the table above, stir to dissolve, and centrifuge to obtain the base solution.

[0074] (5) The needle tip solution obtained in step (2) is injected into the soluble microneedle mold and dried and solidified to form the soluble microneedle tip part.

[0075] (6) The needle column solution obtained in step (3) is injected into the mold in step (5), and after drying and solidification, a soluble microneedle column part is formed.

[0076] (7) The base solution obtained in step (4) is injected into the mold in step (6), and after drying and curing, it is demolded to obtain smegglutide microneedles with a drug content of 2.300 mg.

[0077] Microneedle structures can be like Figure 2 As shown, the left image includes three parts: the needle tip, the needle column, and the base, while the right image includes two parts: the needle tip and the base.

[0078] The specific steps for constructing a two-phase immiscible structure are as follows:

[0079] (1) Prepare PDMS mold microneedles, mix the prepared water-soluble needle tip solution with the drug and inject it into the PDMS mold hole, dry and solidify to form needle tip. The needle tip solution is prepared using water-soluble materials.

[0080] (2) Inject the prepared water-soluble needle column solution into the holes of the PDMS mold, and dry and solidify to form needle columns;

[0081] (3) Apply the prepared water-insoluble base solution evenly into the holes of the PDMS mold, and then use a scraper to scrape off the excess solution to form a smooth base.

[0082] (4) Dry and demold to obtain microneedles.

[0083] II. Determination of drug loading at the needle tip

[0084] The prepared microneedles were dissolved in an HPLC mobile phase solution of acetonitrile-0.1% phosphoric acid aqueous solution and shaken on a shaker for 1 hour. The remaining base portion of the microneedles was then removed. The solution in the centrifuge tube was filtered through a 0.22 mm filter, and 0.2 μL of the test solution was accurately injected into the chromatograph. The drug content in the needle tip was determined to be 2.300 mg.

[0085] Example 2: Preparation of soluble microneedles using different framework materials

[0086] In the process of constructing immiscible microneedles, the framework materials of the needle tip, needle column, and base have a significant impact on the drug loading capacity of the needle tip and the skin insertion effect. To verify the performance differences of the immiscible microneedles prepared from different components provided by this invention, this embodiment sets up the following comparative method to prepare soluble microneedles:

[0087] Method 1: Polyvinylpyrrolidone (PVP) is used instead of PVA as a thickener in the needle tip and needle column areas. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0088] Method 2: Maltose is used instead of sucrose as a stabilizer in the needle tip and needle column areas. The remaining components and proportions are the same as in Table 1 of Example 1, and the preparation steps of the microneedles are the same as in Example 1.

[0089] Method 3: Lysine is used instead of glycine as a stabilizer in the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1, and the preparation steps of the microneedles are the same as in Example 1.

[0090] Method 4: Polylactic acid-glycolic acid copolymer (PLGA) is used as the substrate instead of Euteqi E100 as the skeleton material. The remaining components and proportions are the same as in Table 1 of Example 1. The microneedle preparation steps are the same as in Example 1.

[0091] Method 5: No PVA is added to the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0092] Method 6: No sucrose is added to the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0093] Method 7: Glycine is not added to the needle tip area; the remaining components and proportions are the same as in Table 1 of Example 1; the microneedle preparation steps are the same as in Example 1; the prepared microneedles are as follows. Figure 3 As shown.

[0094] Method 8: No sucrose or glycine is added to the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0095] Method 9: PVA and glycine are not added to the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0096] Method 10: PVA and sucrose are not added to the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0097] Method 11: The microneedles do not contain needle column structures. The remaining components and proportions are the same as in Table 1 of Example 1, and the preparation steps of the microneedles are the same as in Example 1.

[0098] Method 12: Add the chemical drug zolmitriptan to the needle tip area. The remaining components and proportions are the same as in Table 1 of Example 1. The preparation steps of the microneedles are the same as in Example 1.

[0099] Method 13: The soluble microneedles prepared in the best embodiment 8 of the application publication number CN119837818A, entitled "A soluble microneedle patch and its preparation method", are prepared by dissolving zolmitriptan, citric acid and sodium hyaluronate in water to prepare the needle tip, and dissolving polyvinylpyrrolidone, polyethylene glycol and cyclodextrin in anhydrous ethanol to prepare the substrate.

[0100] Method Fourteen: Soluble microneedles are prepared using the matrix material provided in the best embodiment 8 of the invention application publication number CN119837818A entitled "A soluble microneedle patch and its preparation method": the needle tip is prepared by dissolving citric acid and sodium hyaluronate in pure water, and the base is prepared by dissolving polyvinylpyrrolidone, polyethylene glycol and cyclodextrin in anhydrous ethanol, wherein the drug loaded in the needle tip is smegglutinin.

[0101] Experimental Example 3: Performance Testing of Two Immiscible Microneedles

[0102] I. Mechanical Strength Test

[0103] Twelve types of soluble microneedles were prepared according to methods one through eleven in Examples 1 and 2, and their mechanical strength was tested using a mechanical pressure testing instrument. The specific method is as follows: A 2x2 matrix (a total of four needles) was cut from the prepared microneedles and placed on a force measuring platform. The platform was fixed and stabilized, and the indenter parameters were adjusted to slowly press down at a stable speed until the microneedles were damaged. The final deformation and pressure values ​​were obtained. The results are shown in the table below.

[0104] Table 2. Mechanical strength test results of microneedles

[0105]

[0106]

[0107] As shown in Table 2, the mechanical strength of soluble microneedles prepared from different framework materials varies considerably. Comparing the 11 microneedles from Example 1 and Methods 1-10, it can be found that microneedles prepared using a single water-soluble material (Methods 8-10) can withstand significantly less mechanical pressure than those from Example 1, and exhibit greater deformation. Furthermore, the mechanical strength of microneedles prepared using two water-soluble materials is also lower than that of those from Example 1. This indicates that the mechanical strength provided by preparing microneedles using only one or two water-soluble materials, or by using multiple composite materials, is insufficient. Using multiple water-soluble materials such as PVP, maltose, and valine to prepare microneedles can significantly improve their mechanical strength.

[0108] Furthermore, comparing the microneedles prepared in Example 1 and Method 11, it can be seen that the microneedles prepared in Method 11 can withstand less mechanical pressure and undergo greater deformation. This is because the microneedles lack a needle column region, resulting in less structural mechanical support. In summary, the preferred method is to use PVA, sucrose, and glycine to prepare the needle tip, PVA and sucrose to prepare the needle column, and Eutec E100 to prepare the substrate.

[0109] II. Determination of drug loading at the needle tip

[0110] Soluble microneedles were prepared according to methods one through fourteen in Examples 1 and 2, respectively, with a theoretical drug loading capacity of 2.300 mg at the tip of each microneedle. Each microneedle was then pressed onto a gelatin surface to dissolve the tip in the gelatin. The tip was then separated from the base using an optical microscope. The drug content in the tip of each microneedle was determined using high-performance liquid chromatography (HPLC). The results are shown in Table 10 (the allowable deviation for content detection is -5%, i.e., the content range is 2.185–2.300 mg). The chromatogram of the microneedles prepared by method seven is shown below. Figure 6 .

[0111] Table 3. Drug loading at the tip of soluble microneedles

[0112]

[0113] As shown in Table 3, the drug loading of microneedles prepared using the same preparation method but with different matrix materials varied. It can be seen that microneedles prepared using the matrix materials of Example 1 and Method 12—namely, the tip material composed of PVA, sucrose, and glycine, the column material composed of PVA and sucrose, and the base material of Eureka E100—achieved complete tip drug loading when loaded with semaglutide. The drug loading of the microneedles measured in Method 12 was slightly lower, possibly because the tip material composed of PVA, sucrose, and glycine was less effective at loading zolmitriptan than semaglutide.

[0114] Comparing the actual values ​​of Example 1 and Methods 1-10, it can be seen that there are certain differences in the results when measuring the drug loading of the prepared microneedles using the same method. Only the actual drug loading of the microneedle tip in Example 1 is closest to the theoretical value; the actual drug loading of the other microneedles is lower than the theoretical value, but all are within the deviation range. This may be because different needle tip framework materials have different drug diffusion rates during the curing and drying process, resulting in a small or trace amount of drug seeping back into the substrate. However, it can still be seen that composite needle tip materials with multiple framework materials are more effective at inhibiting drug diffusion and improving the actual drug loading effect than needle tips with only one or two materials. Only the result of the microneedle tip material in Example 1, after reconstitution and re-measurement, is closest to the theoretical value, indicating the best actual drug loading effect.

[0115] Furthermore, comparing the drug loading at the needle tip with that of Example 1 and Methods 11, 13, and 14 reveals that the actual drug loading at the microneedle tips prepared by Methods 11 and 14 is significantly lower than the deviation range, and the actual drug loading at the microneedle tip of Method 13 is also slightly less than the theoretical value. Analysis suggests that GLP-1 drugs like semaglutide, being protein drugs, are highly sensitive. Once they diffuse to the substrate and come into contact with anhydrous ethanol, they may be directly inactivated, leading to a significant reduction in the drug loading at the needle tip. Compared to Example 1, the microneedle of Method 11 lacks a needle column region, with the needle tip directly contacting the substrate. This may cause semaglutide to come into contact with the anhydrous ethanol on the substrate and become inactivated, thus reducing the drug loading at the needle tip. Similarly, the microneedles of Methods 13 and 14 use sodium hyaluronate and citric acid as needle tip materials to load the drug, and PVP and PEG dissolved in anhydrous ethanol as the substrate, consisting only of the needle tip and substrate portions. Furthermore, in Method Fourteen, the semaglutide drug in the needle tip is inactivated upon contact with the substrate. In contrast, when zolmitriptan is loaded onto the microneedle tip in Method Thirteen, zolmitriptan, being a chemical drug, is inherently stable and does not experience significant loss or inactivation even when adhering to the substrate surface; therefore, the actual drug loading is not significantly reduced. In comparison, the microneedle provided in Example 1 of this invention includes a tip region, a column region, and a substrate region. The column region, acting as an intermediate buffer layer, has a higher molecular weight and viscosity than the tip region, resulting in faster drying and effective control of drug diffusion rate, preventing drug inactivation due to contact with the organic solvents of the substrate. Simultaneously, the structure of the tip region, column region, and substrate region, combined with the tip material of PVA, sucrose, and glycine, the column material of PVA and sucrose, and the substrate material of Eureka E100, achieves complete drug loading at the needle tip. Therefore, in achieving complete drug loading from the needle tip, the immiscible microneedles provided by this invention have a significant advantage over existing soluble microneedles.

[0116] In summary, by using the polymers, sugars, and amino acids provided by this invention to prepare the microneedle tip, the polymers and sugars to prepare the needle column, and the non-water-soluble material to prepare the substrate, the resulting microneedles can effectively improve the drug loading capacity at the tip. Furthermore, they can be loaded not only with chemical drugs such as zolmitriptan but also with GLP-1 protein drugs, thus broadening their application range. Specifically, PVA, sucrose, and glycine are preferred for preparing the needle tip, PVA and sucrose for preparing the needle column, and E100 for preparing the substrate.

[0117] III. Microneedle Morphology Observation

[0118] Soluble microneedles prepared according to methods 1-14 in Examples 1 and 2, along with ordinary soluble microneedles, were stored in a dry environment at 25°C and 30% relative humidity for one hour. The 15 types of microneedles were then compared. The results showed that the microneedle patches from Example 1 and methods 1-3, 7, 11, and 12 remained flat, while the ordinary soluble microneedle patches and the microneedle patches from methods 13 and 14 showed significant curling. The microneedle patches from methods 4-6 and 8-10 exhibited slight curvature. Specifically, the microneedles prepared in method 7 were compared with ordinary microneedles. Figure 7 This demonstrates that the microneedle patch prepared by the method provided by the present invention can greatly reduce the interference of environmental humidity on the patch flatness, effectively prevent unevenness due to water absorption or loss in different humidity environments, and provide good protection for subsequent drug administration.

[0119] IV. Effects of microneedle insertion into rat skin

[0120] SD rats were anesthetized, and their backs were shaved. Soluble microneedles prepared according to methods one through fourteen in Examples 1 and 2 were inserted into the rats' backs. The needles were pressed for 30 seconds and fixed with medical tape (3M) for 20 minutes. The microneedles were then removed and the skin condition was observed.

[0121] The results showed that the prepared microneedles could all penetrate the skin effectively. Among them, Example 1 and Method 12 showed the best results, while Method 7 showed the following results. Figure 8 As shown, these microneedle patches can remain flat, while the microneedles of Example 1 and Method 12 have higher mechanical strength and can withstand higher mechanical pressure, allowing for perfect skin adhesion after insertion. However, compared to Example 1, the microneedles of Methods 13 and 14 exhibited incomplete puncture. This is partly because the base layer of these microneedles is easily dissolved by bodily fluids after puncture, leading to a decrease in mechanical strength and a lack of stable support; and partly because these microneedle patches have varying degrees of curvature, resulting in poor skin adhesion. Therefore, it is preferable to use the water-soluble material provided in Example 1 of this invention to prepare the needle tip and the non-water-soluble material to prepare the base, significantly improving the drug delivery effect of the microneedles.

[0122] Example 4: Advantages of the needle tip drug loading determination method provided by the present invention

[0123] Since existing soluble microneedles have water-soluble tips and substrates, the drug loading at the tip can only be determined by reconstituted with gelatin to separate the tip and substrate. However, the two-phase immiscible microneedles provided by this invention can not only be determined using existing methods but also directly using the drug loading determination method provided by this invention. To illustrate the significant advantages of the drug loading determination method provided by this invention for measuring the drug loading at the tip of two-phase immiscible microneedles, this embodiment further compares the water-soluble drug loading determination method provided in Example 1 with the gelatin-based drug loading determination method provided in Example 3. The selected microneedles included two semaglutide microneedles prepared in Example 1 and two microneedles prepared using methods four and thirteen in Example 2. The theoretical drug loading value for each type of microneedle was 2.300 mg. The drug loading of the two microneedles was determined according to the methods of Example 1 and Example 3, respectively. The results of the two methods are compared in the table below.

[0124] Table 4 Comparison of results from two methods for determining drug loading at the microneedle tip

[0125]

[0126] As shown in Table 4, the drug loading at the tip of all three microneedles could be determined using the gelatin method. However, only the semaglutide microneedle prepared in Example 1 showed a drug loading at the tip that was closest to the theoretical value, consistent with the verification results of Example 3, proving that the microneedle in Example 1 achieved complete drug loading at the tip. When using the water-soluble method to determine the drug loading at the tip, the drug loading at the tip of the microneedles in Example 1 and Method 4 could be accurately measured. Comparing the water-soluble method results of Example 1 and Method 13, it can be found that existing water-soluble microneedles cannot have their actual drug loading at the tip determined using the water-soluble method provided by this invention. This is because the tip and base material of the microneedle in Method 13 are both water-soluble. When the microneedle is placed in an aqueous solution, the entire microneedle dissolves. Therefore, only the drug loading of the entire microneedle can be measured, and the actual drug loading at the tip cannot be determined.

[0127] Furthermore, compared to the water-soluble method provided by this invention, the gelatin method for determining the drug loading of microneedles requires separating the needle tip from the substrate. Before dissolution, an optical microscope or scanning electron microscope is needed to observe the drug distribution at the needle tip to aid in determining the drug loading. This method demands a high level of operator skill, as the microscopic manipulation itself is difficult and prone to error, and the process is cumbersome. In contrast, the water-soluble method provided by this invention only requires placing the two-phase immiscible microneedles in an aqueous solution. Due to the water insolubility of the substrate, only the needle tip dissolves during the dissolution process, allowing for precise measurement of the actual drug loading at the needle tip. This effectively avoids the detection risks caused by operator subjective error, significantly improving detection efficiency and quality. Therefore, the needle tip drug loading determination method provided by this invention has significant advantages for determining the drug loading of two-phase immiscible microneedles.

[0128] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A microneedle with a two-phase insoluble structure, characterized in that, It includes a needle tip and a substrate, the needle tip comprising a water-soluble material that is soluble in water but insoluble in organic solvents, and the substrate comprising a non-water-soluble material that is soluble in organic solvents or lipids but insoluble in water.

2. The microneedle as described in claim 1, characterized in that, The water-soluble material includes any one or more of polymers, sugars, and amino acids.

3. The microneedle as described in claim 1, characterized in that, The non-water-soluble materials include any one or more of polylactic acid-glycolic acid copolymer, acrylic resin, dimethylaminoethyl methacrylate, ethyl cellulose, fatty alcohols, dimethylacetamide, polyvinylpyrrolidone, and polyethylene glycol.

4. The microneedle as described in claim 2, characterized in that, The polymer includes any one or more of polyvinylpyrrolidone, polyacrylamide, polyvinyl alcohol, and hydroxymethyl cellulose; the sugar includes any one or more of trehalose, sucrose, maltose, galactose, sodium hyaluronate, and chondroitin sulfate; and the amino acid includes any one or more of glycine, alanine, and valine.

5. The microneedle as described in claim 4, characterized in that, The needle tip also includes a drug, which includes any one or more GLP-1 drugs selected from benaglutide, exenatide, liraglutide, lixinatide, long-acting exenatide encapsulated in polylactic-co-glycolic acid copolymer, abiglutide, duraglutide, smegglutide, and telparatide.

6. The microneedle as described in claim 5, characterized in that, The microneedle also includes a needle column, which is a water-soluble material, and the molecular weight and / or viscosity of the water-soluble material of the needle column is higher than that of the material at the needle tip.

7. The microneedle as described in claim 6, characterized in that, The molecular weight of the water-soluble material in the needle column is 80-1000 kDa, or the viscosity of the water-soluble material in the needle column is 2000-20000 mPa·s.

8. The method for preparing the two immiscible microneedles according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) A needle tip solution is added to the microneedle patch mold, wherein the needle tip solution is prepared using a water-soluble material; (2) After the needle tip solution has dried and solidified, the needle column solution is added, wherein the needle column solution is prepared using a water-soluble material; (3) After the needle column solution has dried and solidified, add the base solution, which is prepared using a non-water-soluble material; (4) Dry and demold to obtain microneedle patches.

9. A method for testing the drug loading capacity of a microneedle patch at the needle tip, characterized in that, The microneedle patch is dissolved in a water-soluble solution, and the drug content in the water-soluble solution is then detected; the microneedle patch is prepared using the microneedles as described in any one of claims 1 to 7 or the microneedles prepared by the method described in claim 8.

10. Use of a composition for preparing a reagent to improve the drug loading capacity at the tip of a microneedle, characterized in that, The composition includes any one or more of polymers, sugars, and amino acids.

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