Double-response drug delivery microneedle for wound repair

Abstract

The invention relates to an H2O2 / hypoxia dual-response sectional drug delivery system based on a microneedle structure, which is used for treating burn wounds. The system comprises a soluble microneedle matrix containing sodium percarbonate, H2O2 response microspheres embedded in microneedles and functional components encapsulated in the microspheres. The H2O2 response microspheres are formed by crosslinking polyvinyl alcohol and 1, 4-phenylenediboronic acid through boric acid ester bonds, and a MnO2 nano material with catalase-like activity and hypoxia response drug-loaded micelles formed by self-assembly of nitroimidazole modified hyaluronic acid are encapsulated in the microspheres. After the micro-needle is applied to a burn wound, hydrogen peroxide generated in situ by sodium percarbonate triggers the microspheres to break and release functional components, and MnO2 catalyzes oxygen generation to promote diffusion of drugs to deep tissues; then, under the hypoxic microenvironment formed in the inflammation process, the micelles are discombined to release the medicine, and segmented and sequential medicine delivery is achieved. The invention can break through the physical barrier of the burn wound, improve the deep drug delivery efficiency and reduce the times of dressing change, and is suitable for continuous treatment of the burn wound.

Description

Technical Field

[0001] This invention relates to the field of drug delivery system technology, specifically to a segmented drug delivery system based on a microneedle structure with H2O2 / hypoxia dual response. Technical Background

[0002] Burn wounds exhibit complex pathological characteristics significantly different from ordinary wounds, including eschar formation, microcirculatory disruption, high risk of local infection, elevated levels of reactive oxygen species (ROS), and persistent hypoxia. The eschar and necrotic tissue form a dense barrier, preventing conventional topical medications from effectively penetrating deeper tissues. Simultaneously, excessive H2O2 and ROS prolong inflammation, while the hypoxic environment inhibits tissue repair. Due to the highly dynamic and heterogeneous local microenvironment, drug diffusion within the wound often presents unevenness and limited delivery depth, thus limiting treatment efficacy.

[0003] Microneedling technology, as a drug delivery method capable of penetrating the skin barrier and delivering drugs to the epidermis or dermis, has shown potential in the treatment of various skin diseases and wounds. However, existing microneedles mostly employ a single material matrix and a bulk release mechanism, which has significant limitations in complex wounds such as burns: First, microneedles typically dissolve or release bulk after insertion, lacking a "time-sequential" drug delivery capability that matches the pathological changes of the wound; second, the drugs released by microneedles mainly rely on passive diffusion, making it difficult to form a sufficient diffusion range in deep tissues such as the subeschar layer; third, conventional microneedles cannot integrate multi-level structures and multiple functional materials, thus failing to simultaneously address multiple therapeutic needs such as antibacterial activity, removal of excess ROS, improvement of hypoxia, and promotion of tissue repair.

[0004] Responsive drug delivery materials (such as H2O2-responsive, ROS-responsive, and hypoxia-responsive carriers) have been studied to some extent in wound treatment, but most rely on a single stimulus as a trigger, making it difficult to adapt to the dynamic changes in burn wounds from the peak of infection to the late stage of inflammation and then to tissue repair. Existing H2O2-responsive systems are usually used to eliminate oxidative stress or achieve initial drug release, but they cannot automatically switch treatment modes based on hypoxia signals in the late stage of inflammation; while hypoxia-responsive carriers are mostly used for deep diseases such as tumors, and are prone to insufficient stability in the eschar, exudate, and high H2O2 environment of burn wounds. In addition, these materials often lack a controllable segmented structure and an active mechanism to promote drug diffusion into deeper tissues, making it difficult to achieve a continuous treatment process of "antibacterial first - anti-inflammatory then parallel antioxidant" in a single application.

[0005] In summary, current treatment methods for burn wounds, characterized by a complex pathological environment marked by eschar barrier, intertwined infection and inflammation, and the coexistence of high H2O2 and hypoxia, still have significant limitations. On the one hand, conventional topical preparations and existing microneedle delivery methods struggle to effectively deliver drugs to the subeschar layer and deeper tissues, and the release process lacks regulation tailored to the wound healing stage. On the other hand, existing responsive drug delivery systems often rely on single stimulus signals, making it difficult to meet the continuous treatment needs of different pathological stages within the same drug delivery system. Therefore, there is an urgent need for a drug delivery system that can overcome the physical barriers of burn wounds, utilize wound microenvironment signals for segmented regulation, and improve the efficiency of drug diffusion and delivery in tissues, thereby improving the overall treatment outcome of burn wounds. Summary of the Invention

[0006] The purpose of this invention is to provide a drug delivery system for the treatment of burn wounds, in order to solve the problems in the prior art where drugs have difficulty crossing the eschar barrier, have low delivery efficiency in deep tissues, have uneven drug diffusion, and have difficulty meeting the treatment needs of different healing stages.

[0007] This invention provides an H2O2 / hypoxia dual-response segmented drug delivery system for the treatment of burn wounds. It uses a microneedle structure as a carrier to integrate multiple drug delivery units into the same system. By utilizing the unique pathological microenvironment signals of burn wounds, it achieves segmented release and deep delivery of drugs.

[0008] The drug delivery system includes a soluble microneedle matrix, H2O2-responsive microspheres embedded in the microneedle matrix, and functional components encapsulated within the microspheres. The soluble microneedle matrix is ​​composed of polyvinylpyrrolidone and contains sodium percarbonate; after the microneedles are applied to the burn wound, they dissolve in the tissue fluid, releasing hydrogen peroxide.

[0009] The H2O2-responsive microspheres are formed by cross-linking hyaluronic acid, polyvinyl alcohol, and 1,4-phenylenediboronic acid through borate ester bonds. When the local hydrogen peroxide concentration increases, the borate ester bonds undergo oxidative breakage, thereby causing the microsphere structure to rupture and releasing the internal load.

[0010] The microspheres encapsulate MnO2 nanomaterials with catalase-like activity and hypoxia-responsive drug-loaded micelles. The MnO2 can catalyze the decomposition of hydrogen peroxide to generate oxygen, thereby scavenging excess reactive oxygen species and enhancing the drug's diffusion ability in tissues through oxygen generation.

[0011] The hypoxia-responsive drug-loaded micelles are formed by the self-assembly of hyaluronic acid modified with nitroimidazole and loaded with curcumin. When the burn wound creates a hypoxic microenvironment due to oxygen consumption during the inflammatory process, the nitroimidazole groups undergo a reduction reaction, leading to the disassembly of the micelle structure and the release of curcumin to exert anti-inflammatory and tissue repair-promoting effects.

[0012] Through the above structure and mechanism, the present invention realizes a segmented treatment process that sequentially completes initial antibacterial treatment, oxygen supply-driven drug delivery, and hypoxia-triggered drug release under single application conditions.

[0013] 1. This invention uses a microneedle structure as a drug delivery carrier, which can effectively overcome the physical barrier formed by eschar and superficial necrotic tissue in burn wounds, and deliver the drug delivery unit to the tissue below the wound, improving the accessibility of drugs in deep tissues.

[0014] 2. This invention integrates H2O2-responsive microspheres, an oxygen-generating component with catalase-like activity, and hypoxia-responsive drug-loaded micelles into a microneedle system to construct a segmented drug delivery structure, enabling the drug release process to match the pathological changes of the burn wound from the infection stage to the post-inflammatory stage.

[0015] 3. This invention uses the excess hydrogen peroxide generated in situ in the tissue fluid by sodium percarbonate contained in the microneedles and the hypoxic microenvironment formed during the subsequent inflammatory process as dual triggering conditions to successively induce the rupture of H2O2-responsive microspheres and the disassembly of hypoxia-responsive micelles, thereby realizing the time-sequential initiation and on-demand release of the drug delivery process.

[0016] 4. This invention can complete a multi-stage treatment process with a single application, which helps to reduce the number of dressing changes and the total amount of medication, and reduces the operational burden and patient discomfort during the treatment process. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the microneedle of the present invention. Figure 2 The 1H NMR spectrum of nitroimidazole (NI) modified hyaluronic acid (HA-NI) according to this invention. Figure 3 SEM images of hypoxia-responsive micelles of the present invention. Figure 4 This is the UV spectrum of the conversion of nitroimidazole to aminoimidazole under anaerobic conditions according to the present invention, HA-NI. Figure 5 Optical microscope images of the microspheres of this invention and their particle size distribution. Figure 6 TEM images of micelles encapsulated in microspheres according to the present invention. Figure 7 Optical microscope image of the microspheres of this invention breaking in response to ROS. Detailed Implementation

[0018] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described below with reference to embodiments. It should be understood that the following embodiments are only for explaining this invention and are not intended to limit the scope of protection of this invention; various modifications or substitutions can be made by those skilled in the art without departing from the spirit and substance of this invention, and all such modifications or substitutions should fall within the scope of protection of this invention. Example

[0019] Step 1: Preparation of hypoxia-responsive drug-loaded micelles Cur@HN ① Synthesis of amine-functionalized NI derivatives Ni (0.15 g, 1.3 mmol) was dissolved in dimethylformamide (DMF), and K₂CO₃ (0.28 g, 2.0 mmol) was added. The mixture was stirred at 80 °C for 0.5 h. Then, 6-(Boc-amino)hexyl bromide (0.39 g, 1.4 mmol) was slowly added dropwise, and the mixture was stirred at 80 °C for another 4 h. The reaction mixture was filtered to remove solid impurities and washed with methanol. Residual solvent was removed by rotary evaporation. The product was suspended in deionized water, extracted with ethyl acetate, and the organic layer was collected, dried over sodium sulfate, concentrated, and the solvent was removed by rotary evaporation to obtain the amine-functionalized ni derivative.

[0020] ② Synthesis of grafted polymer HA-NI (HN) The product from step ① (0.31 g, 1.0 mmol) was dissolved in dichloromethane, and 0.5 mL of trifluoroacetic acid was added. The mixture was stirred at room temperature for 3 h. After the solvent was dried under nitrogen, an appropriate amount of methanol was added and the mixture was evaporated to dryness. The mixture was washed three times to obtain the deprotected product 6-(2-nitroimidazole)hexylamine. 0.1 g of HA (molecular weight approximately 200-400 kDa) was dissolved in MES buffer, and EDC (0.192 g, 1 mmol) and NHS (0.115 g, 1 mmol) were added. The mixture was stirred in an ice bath for 30 min. Then, 6-(2-nitroimidazole)hexylamine (molar ratio to HA 1:1) was added, and the mixture was reacted at room temperature for 24 h. The reaction solution was dialyzed against a 1:1 mixture of deionized water and methanol for 1 day and then against deionized water for 2 days. Finally, the product HN was obtained by freeze-drying.

[0021] ③Preparation of Cur@HN 20 mg of HN was completely dissolved in 4 mL of a mixture (DMSO:water = 2:1), and then Cur solution (20 mg / mL) was added dropwise to achieve a HN:Cur mass ratio of 2:1. The mixture was stirred for 3 h. Subsequently, the solution was dispersed dropwise in 10 mL of deionized water under stirring and reacted for 24 h. The resulting product was dialyzed against deionized water for 1 day, and the resulting solution was stored at 4 °C to obtain hypoxia-responsive drug-loaded micelles Cur@HN.

[0022] Step 2: Preparation of H2O2-responsive microspheres Cur@HN / MS A 5.0% PVA solution was prepared, and Cur@HN (5% of the PVA mass) was added and mixed thoroughly. 10 mL of the mixture was taken, and 5 mg of MnO2 was added and mixed thoroughly. Then, 45 mL of white oil containing Span-80 (2.54 g) was added, and emulsification was carried out at 300 rpm for 30 min to form a W / O emulsion. The emulsion was transferred to a three-necked flask, heated to 80 °C with mechanical stirring, and 1,4-phenylenediboric acid solution (0.4 g PDBA dissolved in sodium hydroxide solution by heating) was added dropwise. The reaction was maintained at 80 °C for 5 h. The resulting microsphere emulsion was centrifuged (7000 rpm, 10 min), washed, and dried to obtain Cur@HN / MS.

[0023] Step 3: Preparation of segmented drug delivery microneedles 0.15 g of polyvinylpyrrolidone (PVP) was dissolved in 500 μL of Cur@HN / MS ethanol solution with a concentration of 32 mg / mL, and 10 mg of sodium percarbonate (SPC) was added. The mixture was then thoroughly mixed to obtain a microneedle precursor solution. The mass percentage of the H2O2-responsive microspheres in the microneedle matrix was approximately 5%.

[0024] When preparing the microneedle patch, 500 μL of precursor solution was injected into the polydimethylsiloxane (PDMS) microneedle mold, and the air in the microneedle pores was removed by multiple vacuum degassing cycles. The patch was then cured at 30 °C for 24 h. After curing, the patch was demolded and dried in a vacuum environment to finally obtain a 12×12 array of microneedles.

[0025] Segmented drug delivery and response process After microneedles are applied to the burn wound, the microneedle matrix dissolves in the tissue fluid, releasing SPC and generating H2O2 in situ, achieving initial antibacterial action. Subsequently, H2O2 triggers the oxidative breakage of borate ester bonds in the microspheres, thereby causing the microsphere structure to rupture and releasing the internal load. The released MnO2 catalyzes the decomposition of H2O2 to generate oxygen, which on the one hand removes excess reactive oxygen species, and on the other hand enhances the drug's diffusion ability in the tissue through oxygen generation. When oxygen consumption during the inflammatory process leads to the formation of a hypoxic microenvironment, the nitroimidazole groups in the HA-NI micelles undergo a reduction reaction under hypoxic conditions, causing the micelle structure to disassemble and release curcumin, thus completing the sequential drug delivery process of "antibacterial → oxygen supply-driven → hypoxic drug release". Example

[0026] This embodiment is basically the same as embodiment 1, except that: In step 1, during the preparation of the grafted polymer HA-NI, the molar ratio of 6-(2-nitroimidazole)hexylamine to HA was adjusted to 2:1, and the remaining steps and conditions were the same as in Example 1. Example

[0027] This embodiment is basically the same as embodiment 1, except that: In step 1, during the preparation of the grafted polymer HA-NI, the molar ratio of 6-(2-nitroimidazole)hexylamine to HA was adjusted to 3:1, and the remaining steps and conditions were the same as in Example 1. Example

[0028] This embodiment is basically the same as embodiment 1, except that: In step 1, during the preparation of Cur@HN, the mass ratio of HN to Cur was adjusted to 4:1, and the remaining steps and conditions were the same as in Example 1. Example

[0029] This embodiment is basically the same as embodiment 1, except that: In step 1, during the preparation of Cur@HN, the mass ratio of HN to Cur was adjusted to 6:1, and the remaining steps and conditions were the same as in Example 1. Example

[0030] This embodiment is basically the same as embodiment 1, except that: In step 2, during the preparation of H2O2-responsive microspheres Cur@HN / MS, the Cur@HN content in the PVA mass was adjusted to 10%, and the remaining steps and conditions were the same as in Example 1. Example

[0031] This embodiment is basically the same as embodiment 1, except that: In step 2, during the preparation of H2O2-responsive microspheres Cur@HN / MS, the Cur@HN content in the PVA mass was adjusted to 15%, and the remaining steps and conditions were the same as in Example 1. Example

[0032] This embodiment is basically the same as embodiment 1, except that: In step 3, during the preparation of segmented drug delivery microneedles, the mass percentage of H2O2-responsive microspheres in the microneedle matrix is ​​adjusted to 10%, and the remaining steps and conditions are the same as in Example 1. Example

[0033] This embodiment is basically the same as embodiment 1, except that: In step 3, during the preparation of segmented drug delivery microneedles, the mass percentage of H2O2-responsive microspheres in the microneedle matrix is ​​adjusted to 15%, and the remaining steps and conditions are the same as in Example 1.

[0034] This comparative example is basically the same as Example 1, except that: Sodium percarbonate (SPC) was not added during the preparation of the microneedle precursor solution, and the remaining raw materials, ratios and preparation conditions were the same as in Example 1.

[0035] Since Comparative Example 1 does not contain SPC, it lacks the triggering source of "in-situ release / generation of H2O2 in tissue fluid" after application. Therefore, it is difficult to effectively start the first stage process of "H2O2 triggering microsphere rupture and releasing internal load", thus affecting the continuous start of the subsequent segmented drug delivery chain.

[0036] This comparative example is basically the same as Example 1, except that MnO2 is not added during the microsphere preparation process; the other raw materials, conditions and steps are kept the same.

[0037] Although Comparative Example 2 can still generate H2O2 in tissue fluid by SPC and trigger the oxidative breakage of borate bonds in microspheres, it lacks the component of "catalyzing the decomposition of H2O2 to produce oxygen and remove excess reactive oxygen species" because the microspheres do not contain MnO2. Therefore, it is difficult to achieve the synergistic effect of "oxygen production to promote diffusion + removal of ROS" as described in the examples, and the promotion effect of segmented drug delivery is relatively limited.

Claims

1. A dual-responsive drug delivery microneedle for wound repair, characterized in that, The microneedle comprises: (1) a soluble microneedle base composed of polyvinylpyrrolidone (PVP) and containing sodium percarbonate (SPC), which can release hydrogen peroxide (H2O2) in tissue fluid after being applied to a burn wound; (2) H2O2-responsive microspheres embedded in the microneedle base, which are formed by cross-linking polyvinyl alcohol (PVA) and 1,4-phenyldiboronic acid (PDBA) through borate ester bonds and undergo structural disruption to release internal loads under the action of H2O2; (3) MnO2 nanomaterials encapsulated inside the H2O2-responsive microspheres, which have a catalase-like activity and can catalyze the decomposition of H2O2 to produce oxygen and eliminate excess active oxygen; (4) hypoxia-responsive drug-loaded micelles encapsulated inside the microspheres, which are formed by self-assembly of nitroimidazole (NI) modified hyaluronic acid (HA-NI) and loaded with curcumin; When the oxygen consumption during the inflammation period at the wound site causes a local hypoxic environment, the HA-NI micelles undergo structural disassembly or degradation to release curcumin, thereby achieving the effects of anti-inflammatory and promoting tissue repair.

2. The microneedle of claim 1, wherein The mass percentage of the H2O2-responsive microspheres in the microneedle base is 5%-15%.

3. The microneedle according to claim 1 or 2, characterized by, The mass of the hypoxia-responsive micelles inside the microspheres accounts for 5%-15% of the mass of PVA.

4. The microneedle according to any one of the preceding claims, wherein The particle size of the H2O2-responsive microspheres is 5-30 μm.

5. The microneedle according to any one of the preceding claims, wherein The H2O2-responsive microspheres have a core-shell structure, in which the MnO2 nitroimidazole modified hyaluronic acid micelles are mainly dispersed in the core region.

6. The microneedle according to any one of the preceding claims, wherein The H2O2-responsive microspheres achieve H2O2-triggered structural disruption through oxidizable cleavage of borate ester bonds.

7. The microneedle according to any one of the preceding claims, wherein The oxygen produced by the reaction of MnO2 with H2O2 can generate a propelling force in the needle channel formed by the microneedle, thereby enhancing the diffusion distance of the released drug in the tissue.

8. The microneedle according to any one of the preceding claims, wherein, The nitroimidazole groups in the HA-NI micelles are reduced by intracellular reductases under hypoxic conditions, causing the micelles to change from hydrophobic to hydrophilic and disassemble, thereby releasing curcumin.

9. The microneedle according to any one of the preceding claims, wherein After the microneedle is applied to the wound, it sequentially achieves: (1) SPC releases H2O2 to produce initial antibacterial effect; (2) H2O2 triggers microsphere disruption and releases MnO2 and hypoxia-responsive micelles; (3) MnO2 catalyzes the production of oxygen by H2O2 and promotes the diffusion of drugs to deeper layers; (4) In the hypoxic environment caused by inflammation oxygen consumption, the micelles disassemble to release curcumin, thereby completing the time-sequential drug delivery process of "antibacterial → oxygen supply and promotion → hypoxic drug release".

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