An exudate-responsive self-shedding core-shell microgel powder for burn and scald wound surface and a preparation method thereof

Abstract

The present application provides a kind of for burn and scald wound exudate response self-shedding core-shell microgel powder and its preparation method, belong to medical material technical field.The core-shell microgel powder provided by the present application can quickly absorb a large amount of exudate and form a conformal hydrogel in situ after being applied to the wound, providing an ideal wet environment and physical protection for wound healing;Its exudate response characteristics not only can intelligently release active ingredients to actively regulate inflammation and promote repair, but also can achieve gentle self-shedding of the dressing in the later healing stage, greatly improving patient experience and treatment compliance.The product combines efficient liquid management, active therapeutic intervention and painless removal, providing a new and integrated solution for the clinical care of complex exudate wounds such as burns and scalds.

Description

Technical Field

[0001] This invention relates to the field of medical materials technology, and in particular to a self-detaching core-shell microgel powder for exudate response in burn wounds and its preparation method. Background Technology

[0002] Burns, especially deep second-degree burns and above, are among the most common severe traumas in clinical practice. These wounds, due to severe disruption of the skin barrier, lead to significant loss of tissue exudate and are highly susceptible to infection, creating a complex and fragile pathological microenvironment. Effectively managing exudate, controlling infection, and promoting tissue regeneration are key challenges in burn treatment.

[0003] Throughout the development of wound dressings, powdered dressings have consistently held a place due to their advantages such as high specific surface area, good absorbency, ease of use, and suitability for irregular wounds. Traditional powdered dressings, such as certain polysaccharide or inorganic salt powders, primarily manage exudate through physical absorption. However, they often have limited functionality, lack active biological effects, and may form crusts or harden after absorption, easily adhering to newly formed granulation tissue during removal, leading to secondary damage and severe pain.

[0004] With the popularization of the theory of moist healing, hydrogel dressings have received widespread attention for their ability to provide a continuously moist environment and reduce pain. However, some hydrogel dressings suffer from weak initial adhesion, limited absorption capacity for large amounts of exudate, or adhesion problems during removal. In recent years, the strategy of loading active therapeutic ingredients (such as antibacterial agents and growth factors) into dressings to achieve "active treatment" has become a research hotspot. For example, materials that can release gaseous signaling molecules such as nitric oxide and hydrogen are applied to dressings to regulate wound inflammation and promote angiogenesis, showing good potential. However, how to design a material that can achieve intelligent absorption and management of high exudate volumes, precise and continuous release of therapeutic ingredients, and ultimately achieve gentle, non-invasive, and painless removal remains a systemic problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide an exudate-responsive self-detaching core-shell microgel powder for burn wounds and its preparation method, which solves the problems of traditional burn dressings causing secondary damage and pain during removal, and their single function failing to intelligently manage highly inflammatory exudate wounds.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a core-shell microgel powder, wherein the microgel powder has a core-shell structure, and the core in the core-shell structure is a calcium ion pretreated polyacrylamide microsphere;

[0008] The shell in the core-shell structure is a sodium alginate layer loaded with hydrogen donor nanosheets, which are dispersed in the sodium alginate layer.

[0009] Preferably, the hydrogen donor nanosheets are magnesium silicide nanosheets or calcium silicide nanosheets;

[0010] The surface of the hydrogen donor nanosheet is coated with a polyvinylpyrrolidone layer;

[0011] The hydrogen donor nanosheets constitute 10% to 20% of the mass percentage of the core-shell microgel powder.

[0012] The particle size of the polyacrylamide microspheres is 180 micrometers to 280 micrometers;

[0013] The overall particle size of the core-shell microgel powder is 280 micrometers to 360 micrometers.

[0014] The present invention also provides a method for preparing the above-mentioned core-shell microgel powder, comprising the following steps:

[0015] S1. Polyacrylamide microspheres are immersed in an ethanol solution containing calcium ions and then dried to obtain calcium ion pretreated polyacrylamide microspheres.

[0016] S2. The calcium ion pretreated polyacrylamide microspheres are mixed with an aqueous solution of sodium alginate containing hydrogen donor nanosheets and subjected to an ionic crosslinking reaction to form a sodium alginate shell layer loaded with hydrogen donor nanosheets on the surface of the microspheres, thereby obtaining core-shell structured gel particles. The microgel powder has a core-shell structure, wherein the core of the core-shell structure is a calcium ion pretreated polyacrylamide microsphere, and the shell of the core-shell structure is a sodium alginate layer loaded with hydrogen donor nanosheets, wherein the hydrogen donor nanosheets are dispersed in the sodium alginate layer.

[0017] S3. The core-shell structured gel particles are separated, washed, and freeze-dried to obtain the core-shell microgel powder.

[0018] Preferably, in step S1, the polyacrylamide microspheres are prepared by water-in-oil emulsion polymerization, wherein the water-in-oil emulsion polymerization includes adding an aqueous phase containing acrylamide monomer, crosslinking agent and initiator dropwise to an oil phase containing emulsifier for polymerization reaction;

[0019] Alternatively, the polyacrylamide microspheres are prepared by precipitation polymerization, which includes polymerizing acrylamide monomers in a mixed solvent of ethanol and water under nitrogen protection.

[0020] Alternatively, the polyacrylamide microspheres may be prepared by dispersion polymerization, which includes polymerizing acrylamide monomers in a mixed solvent of ethanol and water containing the dispersant polyvinylpyrrolidone.

[0021] Preferably, in step S1, the concentration of calcium ions in the calcium-containing ethanol solution is 40 mg / mL to 60 mg / mL; and the soaking time is 20 hours to 28 hours.

[0022] In step S2, the sodium alginate aqueous solution containing hydrogen donor nanosheets has a sodium alginate mass-volume concentration of 0.1% to 0.3%; the doping amount of the hydrogen donor nanosheets in the sodium alginate aqueous solution containing hydrogen donor nanosheets is 80% to 120% of the mass of sodium alginate; the ionic crosslinking reaction is carried out at room temperature for a reaction time of 0.5 hours to 1.5 hours.

[0023] In step S3, the freeze-drying temperature is -60℃ to -40℃, and the drying time is 40 hours to 56 hours.

[0024] Preferably, in the water-in-oil emulsion polymerization method, the oil phase comprises cyclohexane and a Span-type emulsifier, and the volume ratio of the aqueous phase to the oil phase is 1:2~3; the Span-type emulsifier comprises Span 20 and Span 80, and the mass ratio of Span 20 to Span 80 is 1.5~2.5:1; in the water-in-oil emulsion polymerization method, the rate at which the aqueous phase is added to the oil phase is 50 drops / min~70 drops / min; in the water-in-oil emulsion polymerization method, the polymerization reaction is carried out at 60℃~70℃, the stirring speed is 250 rpm~350 rpm, and the reaction time is 2 hours~4 hours;

[0025] In the precipitation polymerization method, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 3~5:1; in the precipitation polymerization method, the polymerization reaction is carried out at 30℃~40℃, the stirring speed is 250 rpm~350 rpm, and the reaction time is 20 hours~28 hours.

[0026] In the dispersion polymerization method, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 3~5:1; in the dispersion polymerization method, the mass of the dispersant polyvinylpyrrolidone is 0.5%~1.5% of the total mass of the solvent; in the dispersion polymerization method, the polymerization reaction is carried out at 65℃~75℃, the stirring speed is 250 rpm~350 rpm, and the reaction time is 20 hours~28 hours.

[0027] Preferably, in step S2, the mass-to-volume ratio of the calcium ion pretreated polyacrylamide microspheres to the sodium alginate aqueous solution containing hydrogen donor nanosheets is 0.05 g / 100 mL to 0.15 g / 100 mL.

[0028] Preferably, in step S3, the separation is carried out by centrifugation at a speed of 4000 rpm to 6000 rpm for a time of 3 to 8 minutes.

[0029] In step S1, the drying is carried out at 35°C to 45°C for 1 to 3 hours.

[0030] The hydrogen donor nanosheets were prepared by ultrasonic-assisted exfoliation.

[0031] The present invention also provides the application of the above-mentioned core-shell microgel powder or the core-shell microgel powder prepared by the above preparation method in the preparation of medical dressings for promoting wound healing.

[0032] Preferably, the wound is a burn wound.

[0033] The beneficial effects of this invention are:

[0034] The core-shell microgel powder provided by this invention can rapidly absorb a large amount of exudate after application to the wound and form an adherent hydrogel in situ, providing an ideal moist environment and physical protection for wound healing. Its exudate-responsive characteristics not only intelligently release active ingredients to actively regulate inflammation and promote repair, but also enable gentle self-removal of the dressing in the later stages of healing, greatly improving patient experience and treatment compliance. This product combines efficient exudate management, proactive treatment intervention, and humane, painless removal, providing a novel, integrated solution for the clinical care of complex exudative wounds such as burns. Attached Figure Description

[0035] Figure 1 The figures show the Transwell migration assay results of HUVEC cells and L929 cells, including (a); statistics of the number of migrating cells in the Transwell assay; (b); scratch healing assay of HUVEC cells and L929 cells; (c); statistics of scratch closure rate of HUVEC cells (d) and L929 cells (e); immunofluorescence staining for tubular formation in HUVEC cells (f); statistics of the number of tubular branching points (g) and total tubular length (h).

[0036] Figure 2Live and dead cell staining after 7 days of co-culture of HUVEC and L929 cells (a); quantitative analysis of cell viability using CCK-8 assay (b); intracellular reactive oxygen species (ROS) staining in HUVEC and L929 cells (c); quantitative analysis of relative ROS fluorescence intensity in HUVEC (d) and L929 cells (e); immunofluorescence staining of macrophage polarization markers (CD206 and CD86) (f); quantitative analysis of macrophage fluorescence intensity of CD206⁺ (g) and CD86⁺ (h); flow cytometry analysis of macrophage polarization (CD86 / CD206) (i); quantitative analysis of macrophage proportions of CD206⁺ (j) and CD86⁺ (k).

[0037] Figure 3 Representative macroscopic images of rat wound healing (a); histological staining of rat skin tissue sections (b).

[0038] Figure 4 The hemolysis rate (a), blood absorption capacity (b), coagulation index (c), and water absorption properties (d) of the microspheres; scanning electron microscopy images of blood cell adhesion and aggregation on the surface of PCS and PCSM (e, f); photothermal heating curves of PA, PCS, and PCSM (g); photothermal cycling curve of PCSM (h); antibacterial properties of PCSM combined with near-infrared light against Staphylococcus aureus and Escherichia coli (j); and inhibition rate of Staphylococcus aureus (i).

[0039] Figure 5 Scanning electron microscope (SEM) images and corresponding optical micrographs of PA, PCS, and PCSM (ac); cross-sectional SEM images of PA and PCS microspheres (d, e); thermogravimetric analysis curves of PA, PCS, and PCSM (f); dynamic process of PCSM self-gelling adhesion and subsequent desorption (g); burst pressure of each microsphere under 0.30 mL PBS (h); burst pressure of PCSM under different conditions (i).

[0040] Figure 6 Transmission electron microscopy images and corresponding elemental distribution maps (C, N, O, Mg, Si) of MNP and MN (a, b); cumulative H2 release curves of MN and MNP over 6 hours (c) and 10 days (d); XPS spectrum of Si 2p region of MNP (RMNP) after reaction (e). Detailed Implementation

[0041] This invention provides a core-shell microgel powder with a core-shell structure. The core of the core-shell structure is a calcium ion-pretreated polyacrylamide microsphere. Polyacrylamide is a high molecular weight polymer synthesized from acrylamide monomers. It can be polymerized into microspheres with a three-dimensional network structure through free radical polymerization and other methods. This material is used in many fields due to its high water absorption and swelling properties. In the specific context of this invention, calcium ion pretreatment aims to impart specific ionic crosslinking sites to the surface of the microspheres.

[0042] The shell of the core-shell structure is a sodium alginate layer supporting hydrogen donor nanosheets, which are dispersed within the sodium alginate layer. Sodium alginate is a linear anionic polysaccharide extracted from natural brown algae. Its molecular chain contains a large number of carboxyl groups, and it can form a hydrogel film or coating through ionic crosslinking in the presence of divalent cations. Hydrogen donor nanosheets refer to two-dimensional sheet materials that can undergo chemical reactions in aqueous environments and release hydrogen gas. In this invention, such nanosheets are dispersed in a sodium alginate layer to utilize the film-forming properties and biocompatibility of sodium alginate to achieve effective loading and encapsulation of the nanosheets.

[0043] Preferably, the hydrogen donor nanosheets are magnesium silicide nanosheets or calcium silicide nanosheets. Both magnesium silicide and calcium silicide are compounds with specific chemical compositions, and they undergo hydrolysis upon contact with water. The surface of the hydrogen donor nanosheets is coated with a polyvinylpyrrolidone (PVP) layer. PVP is a water-soluble polymer commonly used as a dispersant, stabilizer, or coating material. The mass percentage of the hydrogen donor nanosheets in the core-shell microgel powder is 10% to 20%, for example, 12%, 13%, 14%, 15%, 17%, 18%, 20%, etc.; more preferably 10% to 15%, and more preferably 12% to 14%. The polyacrylamide microspheres have a particle size of 180 micrometers to 280 micrometers, for example, 190 micrometers, 200 micrometers, 210 micrometers, 220 micrometers, 230 micrometers, 240 micrometers, 250 micrometers, 260 micrometers, 270 micrometers, etc.; more preferably 200 micrometers to 260 micrometers, and more preferably 220 micrometers to 240 micrometers. The core-shell microgel powder has an overall particle size of 280 micrometers to 360 micrometers, for example, 290 micrometers, 300 micrometers, 310 micrometers, 320 micrometers, 330 micrometers, 340 micrometers, 350 micrometers, etc.; more preferably 300 micrometers to 340 micrometers, and more preferably 310 micrometers to 330 micrometers.

[0044] The present invention also provides a method for preparing the above-mentioned core-shell microgel powder, comprising the following steps:

[0045] S1. Polyacrylamide microspheres are immersed in an ethanol solution containing calcium ions, followed by drying to obtain calcium ion-pretreated polyacrylamide microspheres. In this step, polyacrylamide microspheres are used as the starting material, and their preparation can be carried out using microsphere preparation techniques known in the field of polymer synthesis. The immersion process uses an ethanol solution containing calcium ions to facilitate the interaction between calcium ions and the microspheres. The drying operation is to remove the liquid medium and obtain the pretreated microspheres in solid form.

[0046] S2. The calcium ion-pretreated polyacrylamide microspheres are mixed with an aqueous solution of sodium alginate containing hydrogen donor nanosheets and subjected to an ionic crosslinking reaction. A sodium alginate shell loaded with hydrogen donor nanosheets is formed on the surface of the microspheres, resulting in core-shell structured gel particles. Mixing is usually achieved by stirring, and the ionic crosslinking reaction is based on the interaction between the carboxyl groups of sodium alginate and calcium ions.

[0047] S3. The core-shell structured gel particles are separated, washed, and freeze-dried to obtain the core-shell microgel powder. Separation can be performed using conventional solid-liquid separation methods, washing is to remove impurities, and freeze-drying is used to obtain a dry powder product.

[0048] Preferably, in step S1, the polyacrylamide microspheres are prepared by a water-in-oil emulsion polymerization method, which includes adding an aqueous phase containing acrylamide monomer, a crosslinking agent, and an initiator dropwise to an oil phase containing an emulsifier for polymerization. In this method, the aqueous and oil phases form an emulsion system under the action of the emulsifier, and the monomer polymerizes within the droplets to form microspheres.

[0049] Alternatively, the polyacrylamide microspheres can be prepared by precipitation polymerization, which involves polymerizing acrylamide monomers in a mixed solvent of ethanol and water under nitrogen protection. In this method, the monomers are soluble in the mixed solvent, while the resulting polymer is insoluble in the medium, thus precipitating to form microspheres. Nitrogen protection is used to create an inert atmosphere.

[0050] Alternatively, the polyacrylamide microspheres can be prepared by dispersion polymerization, which involves polymerizing acrylamide monomers in a mixed solvent of ethanol and water containing the dispersant polyvinylpyrrolidone. This method utilizes the dispersant to stabilize the generated polymer particles, dispersing them in the reaction medium.

[0051] Preferably, in step S1, the concentration of calcium ions in the calcium-containing ethanol solution is 40 mg / mL to 60 mg / mL, for example, 42, 45, 48, 50, 52, 55, 58 mg / mL, etc.; more preferably, 45 mg / mL to 55 mg / mL, and even more preferably, 48 mg / mL to 52 mg / mL. The soaking time is 20 hours to 28 hours, for example, 21, 22, 23, 24, 25, 26, 27 hours, etc.; more preferably, 22 hours to 26 hours, and even more preferably, 23 hours to 25 hours.

[0052] In step S2, the sodium alginate aqueous solution containing hydrogen donor nanosheets has a sodium alginate mass-volume concentration of 0.1% to 0.3%, for example, 0.12%, 0.15%, 0.18%, 0.20%, 0.22%, 0.25%, 0.28%, etc.; more preferably, 0.15% to 0.25%, and more preferably, 0.18% to 0.22%. The doping amount of the hydrogen donor nanosheets in the sodium alginate aqueous solution is 80% to 120% of the mass of sodium alginate, for example, 82%, 85%, 86%, 89%, 95%, 98%, 106%, 110%, 117%, etc.; more preferably, 90% to 110%, and more preferably, 95% to 105%. The ionic crosslinking reaction is carried out at room temperature, which typically refers to an ambient temperature of 15°C to 30°C. The reaction time is 0.5 hours to 1.5 hours, for example, 0.6, 0.8, 1.0, 1.2, 1.4 hours, etc.; more preferably 0.8 hours to 1.2 hours, and more preferably 0.9 hours to 1.1 hours.

[0053] In step S3, the freeze-drying temperature is -60℃ to -40℃, for example -58℃, -55℃, -52℃, -50℃, -48℃, -45℃, -42℃, etc.; more preferably -55℃ to -45℃, and even more preferably -52℃ to -48℃. The drying time is 40 hours to 56 hours, for example 42, 44, 46, 48, 50, 52, 54 hours, etc.; more preferably 44 hours to 52 hours, and even more preferably 46 hours to 50 hours.

[0054] Preferably, in the water-in-oil emulsion polymerization method, the oil phase comprises cyclohexane and a Span-type emulsifier. Cyclohexane is an organic solvent. Span-type emulsifiers are a class of nonionic surfactants. The volume ratio of the aqueous phase to the oil phase is 1:2 to 3, for example, 1:2.2, 1:2.5, 1:2.8, etc.; more preferably, 1:2.3 to 1:2.7, and even more preferably, 1:2.5. The Span-type emulsifier comprises Span 20 and Span 80, and the mass ratio of Span 20 to Span 80 is 1.5 to 2.5:1, for example, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, etc.; more preferably, 1.8:1 to 2.2:1, and even more preferably, 2.0:1. In the water-in-oil emulsion polymerization method, the rate at which the aqueous phase is added to the oil phase is 50 drops / min to 70 drops / min, for example, 52, 55, 58, 60, 62, 65, or 68 drops / min; more preferably, 55 drops / min to 65 drops / min, and even more preferably, 58 drops / min to 62 drops / min. In the water-in-oil emulsion polymerization method, the polymerization reaction is carried out at 60°C to 70°C, for example, 62°C, 64°C, 65°C, 66°C, or 68°C; more preferably, 63°C to 67°C, and even more preferably, 64°C to 66°C. The stirring speed is 250 rpm to 350 rpm, for example, 260, 280, 300, 320, or 340 rpm; more preferably, 280 rpm to 320 rpm, and even more preferably, 290 rpm to 310 rpm. The reaction time is 2 hours to 4 hours, such as 2.2, 2.5, 2.8, 3.0, 3.2, 3.5, 3.8 hours, etc.; more preferably 2.5 hours to 3.5 hours, and more preferably 2.8 hours to 3.2 hours.

[0055] In the precipitation polymerization method, the volume ratio of ethanol to water in the mixed solvent is 3-5:1, for example, 3.2:1, 3.5:1, 3.8:1, 4.0:1, 4.2:1, 4.5:1, 4.8:1, etc.; more preferably, 3.5:1-4.5:1, and even more preferably, 3.8:1-4.2:1. In the precipitation polymerization method, the polymerization reaction is carried out at 30℃-40℃, for example, 32℃, 34℃, 35℃, 36℃, 38℃, etc.; more preferably, 32℃-38℃, and even more preferably, 34℃-36℃. The stirring speed is 250 rpm-350 rpm, for example, 260, 280, 300, 320, 340 rpm, etc.; more preferably, 280 rpm-320 rpm, and even more preferably, 290 rpm-310 rpm. The reaction time is 20 hours to 28 hours, such as 21, 22, 23, 24, 25, 26, 27 hours, etc.; more preferably 22 hours to 26 hours, and even more preferably 23 hours to 25 hours.

[0056] In the dispersion polymerization method, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 3~5:1, for example 3.2:1, 3.5:1, 3.8:1, 4.0:1, 4.2:1, 4.5:1, 4.8:1, etc.; more preferably 3.5:1~4.5:1, more preferably 3.8:1~4.2:1. In the dispersion polymerization method, the mass of the dispersant polyvinylpyrrolidone is 0.5%~1.5% of the total mass of the solvent, for example 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, etc.; more preferably 0.7%~1.3%, more preferably 0.9%~1.1%. In the dispersion polymerization method, the polymerization reaction is carried out at 65℃~75℃, for example 66℃, 68℃, 70℃, 72℃, 74℃, etc.; more preferably 68℃~72℃, more preferably 69℃~71℃. The stirring speed is 250 rpm to 350 rpm, for example, 260, 280, 300, 320, 340 rpm, etc.; more preferably, 280 rpm to 320 rpm, and even more preferably, 290 rpm to 310 rpm. The reaction time is 20 hours to 28 hours, for example, 21, 22, 23, 24, 25, 26, 27 hours, etc.; more preferably, 22 hours to 26 hours, and even more preferably, 23 hours to 25 hours.

[0057] Preferably, in step S2, the mass-to-volume ratio of the calcium ion pretreated polyacrylamide microspheres to the sodium alginate aqueous solution containing hydrogen donor nanosheets is 0.05 g / 100 mL to 0.15 g / 100 mL, for example, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14 g / 100 mL, etc.; more preferably, 0.07 g / 100 mL to 0.13 g / 100 mL, and even more preferably, 0.08 g / 100 mL to 0.12 g / 100 mL.

[0058] Preferably, in step S3, the separation is performed by centrifugation at a speed of 4000 rpm to 6000 rpm, such as 4200, 4500, 4800, 5000, 5200, 5500, or 5800 rpm; more preferably, 4500 rpm to 5500 rpm, and even more preferably, 4800 rpm to 5200 rpm. The centrifugation time is 3 to 8 minutes, such as 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, or 7.5 minutes; more preferably, 4 to 7 minutes, and even more preferably, 4.5 to 6.5 minutes.

[0059] In step S1, the drying is carried out at 35°C to 45°C, for example, 36°C, 38°C, 40°C, 42°C, 44°C, etc.; more preferably, 37°C to 43°C, and even more preferably, 39°C to 41°C. The drying time is 1 hour to 3 hours, for example, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8 hours, etc.; more preferably, 1.5 hours to 2.5 hours, and even more preferably, 1.8 hours to 2.2 hours.

[0060] The hydrogen donor nanosheets were prepared by ultrasonic-assisted exfoliation. Ultrasonic-assisted exfoliation is a method that uses ultrasonic energy to process layered materials in a liquid medium to obtain nanosheets.

[0061] This invention also provides the application of the above-mentioned core-shell microgel powder, or the core-shell microgel powder prepared by the above-mentioned method, in the preparation of medical dressings for promoting wound healing. The core-shell microgel powder of this invention, with its unique powder morphology and liquid-gelling properties, can be directly used clinically as a novel powder dressing, easily adhering to the wound surface through simple application. Furthermore, this microgel powder can also be used as a functional component, physically or chemically combined with other dressing matrices (such as nonwoven fabrics, sponges, films, or traditional gauze) to construct composite dressings with stronger mechanical properties or easier fixation and bandaging, thereby expanding its application scenarios and convenience.

[0062] Preferably, the wound is a burn wound. The core-shell microgel powder provided by this invention is designed to integrate the characteristics of high absorbency, in-situ formation of protective gel, continuous delivery of active ingredients, and gentle desorption in the later stage. It aims to provide a dressing option for burn wounds, especially those with large amounts of exudate and high risk of inflammation, that can achieve intelligent exudate management and actively promote the repair process, thereby improving the clinical dressing change experience and healing effect.

[0063] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0064] The methods for preparing the calcium silicide nanosheets and magnesium silicide nanosheets used in the examples are as follows:

[0065] 100 mg of magnesium silicide powder was added to 20 mL of ethylene glycol and stirred for 30 minutes. Subsequently, the mixture was subjected to pulsed sonication at 425 W for 40 minutes using an ultrasonic cell disruptor (pulse on-time: 6.6 seconds, off-time: 2.2 seconds) to obtain magnesium silicide nanosheets (MN). The resulting product was washed three times with ethanol and then transferred to 30 mL of an ethanol solution containing 150 mg of polyvinylpyrrolidone (PVP) and soaked for 24 hours to obtain PPVP-coated magnesium silicide nanosheets (MNP).

[0066] 100 mg of calcium silicide powder was added to 20 mL of ethylene glycol and stirred for 30 minutes. Subsequently, the mixture was subjected to pulsed sonication at 450 W for 40 minutes using an ultrasonic cell disruptor (pulse on-time: 6.6 seconds, off-time: 2.2 seconds) to obtain calcium silicide nanosheets (CN). The resulting product was washed three times with ethanol and then transferred to 30 mL of an ethanol solution containing 150 mg of polyvinylpyrrolidone (PVP) and soaked for 24 hours to obtain PPVP-coated calcium silicide nanosheets (CNP).

[0067] Example 1

[0068] Preparation of polyacrylamide-sodium alginate core-shell microgel powder (PCSM) loaded with polyvinylpyrrolidone-coated magnesium silicide nanosheets (MNPs)

[0069] (I) Preparation of polyacrylamide microspheres (PA)

[0070] Polyacrylamide microspheres were prepared by water-in-oil (W / O) emulsion polymerization. The specific steps are as follows: (1) Oil phase preparation: 75 g of cyclohexane, 1.2 g of Span 20 and 0.6 g of Span 80 were mixed in a beaker and sonicated for 10 minutes to make them uniform. Then, the mixture was transferred to a three-necked flask for later use. (2) Aqueous phase preparation: 3 g of acrylamide monomer, 0.0375 g of initiator ammonium persulfate and 0.022 g of crosslinking agent N,N'-methylenebisacrylamide were dissolved in 40 mL of deionized water and magnetically stirred at room temperature for 20 minutes until completely dissolved to obtain an aqueous phase solution. (3) Emulsion polymerization: The three-necked flask was placed in a constant temperature oil bath at 65 °C. Under mechanical stirring at 300 rpm, the above aqueous phase solution was slowly added to the oil phase at a rate of about 60 drops / minute using a constant pressure dropping funnel. After the addition was complete, the reaction was continued at 65℃ and 300 rpm for 3 hours to allow the monomers to fully polymerize. (4) Post-treatment: After the reaction was completed, the resulting emulsion was poured into a beaker containing 200 mL of anhydrous ethanol to break the emulsion. After standing, a white solid was observed to precipitate. The solid product was collected by vacuum filtration and washed three times each with anhydrous ethanol and deionized water to thoroughly remove residual monomers, emulsifiers and cyclohexane. The washed product was freeze-dried at -50℃ for 24 hours to obtain white and fluffy polyacrylamide microspheres (PA).

[0071] (II) Preparation of core-shell microgel powder (PCSM) loaded with polyvinylpyrrolidone-coated magnesium silicide nanosheets (MNPs).

[0072] The core-shell structure was constructed using ion crosslinking and freeze-drying techniques. The specific steps are as follows: (1) Core layer solidification: 0.5 g of the PA microspheres prepared above were immersed in 20 mL of anhydrous ethanol solution of calcium chloride with a concentration of 50 mg / mL and soaked at room temperature for 24 hours. (2) Shell layer coating: The PA microspheres after calcium ion immersion treatment were centrifuged and dried in an oven at 40 °C for 2 hours to remove ethanol. 0.1 g of the dried microspheres were weighed and slowly and in small amounts added to 100 mL of sodium alginate aqueous solution containing magnesium silicide nanosheets (MNP) coated with polyvinylpyrrolidone. The mass-volume concentration of the sodium alginate aqueous solution was 0.2% (w / v), and the doping amount of MN was 100% of the mass of sodium alginate (i.e., 200 mg of MNP was contained in every 100 mL of 0.2% sodium alginate solution). Stirring at 100 rpm for 1 hour at room temperature allows sodium alginate to undergo ionic cross-linking with calcium ions on the surface of the microspheres, forming a composite hydrogel shell encapsulating MN on the surface of the PA microspheres. (3) Product purification and drying: After the reaction, the mixture was centrifuged at 5000 rpm for 5 minutes to collect the gel particles, and washed three times with deionized water to remove unreacted sodium alginate. The final product was freeze-dried at -50℃ for 48 hours to obtain polyacrylamide-sodium alginate core-shell microgel powder loaded with polyvinylpyrrolidone-coated magnesium silicate nanosheets, denoted as PCSM.

[0073] Example 2

[0074] Preparation of polyacrylamide-sodium alginate core-shell microgel powder (PCSC) loaded with polyvinylpyrrolidone-coated calcium silicide nanosheets (CNP).

[0075] (I) Preparation of polyacrylamide microspheres (PA)

[0076] Polyacrylamide microspheres were prepared by precipitation polymerization: A mixed solvent consisting of 80 mL of anhydrous ethanol and 20 mL of deionized water was added to a flask, and low-speed stirring was initiated. Then, 2.0 g of acrylamide monomer, 0.022 g of N,N'-methylenebisacrylamide, 0.020 g of ammonium persulfate, and 20 μL of tetramethylethylenediamine were weighed and added to the solvent, and stirred until completely dissolved. The water bath temperature was then raised to 35 °C, and stirring was maintained at a uniform speed of 300 rpm while continuously purging with nitrogen for protection. After reacting for 24 hours, the mixture was centrifuged, and the resulting precipitate was repeatedly washed with anhydrous ethanol and centrifuged several times. Finally, the washed white solid was dried in a vacuum drying oven at 40 °C for 12 hours to obtain dried polyacrylamide microsphere powder.

[0077] (II) Preparation of core-shell microgel powder (PCSC) loaded with polyvinylpyrrolidone-coated calcium silicide nanosheets (CNP).

[0078] Core-shell structures were constructed using ion crosslinking and freeze-drying techniques. The specific steps are as follows: (1) Core layer solidification: PA microspheres were immersed in anhydrous ethanol solution of calcium chloride for 24 hours at room temperature. (2) Shell layer coating: PA microspheres treated with calcium ions were centrifuged and dried in an oven at 40°C for 2 hours to remove ethanol. Then, they were slowly and in small amounts added to 100 mL of sodium alginate aqueous solution containing polyvinylpyrrolidone-coated calcium silicate nanosheets (CNP). The mixture was stirred at 100 rpm for 1 hour at room temperature to allow sodium alginate to undergo ion crosslinking with calcium ions on the surface of the microspheres, forming a composite hydrogel shell coating CNP on the surface of the PA microspheres. (3) Product purification and drying: After the reaction, the mixture was centrifuged at 5000 rpm for 5 minutes to collect the gel particles, and washed three times with deionized water to remove unreacted sodium alginate. The final product was freeze-dried at -50°C for 48 hours to obtain polyacrylamide-sodium alginate core-shell microgel powder loaded with calcium silicide nanosheets, denoted as PCSC.

[0079] Example 3

[0080] Preparation of polyacrylamide-sodium alginate core-shell microgel powder (PCSM) loaded with polyvinylpyrrolidone-coated magnesium silicide nanosheets (MNPs)

[0081] (I) Preparation of polyacrylamide microspheres (PA)

[0082] Polyacrylamide microspheres were prepared by dispersion polymerization. First, a mixed solvent of 120 mL anhydrous ethanol and 30 mL deionized water, along with 1.20 g of polyvinylpyrrolidone (PVP), was added sequentially to a flask. The mixture was stirred and heated to 70°C to completely dissolve the PVP. Then, 12.00 g of acrylamide and 0.12 g of N,N'-methylenebisacrylamide were added to this homogeneous solution. Under nitrogen protection, 0.12 g of azobisisobutyronitrile (AIBN) was added. The reaction temperature was maintained at 70°C, and the mixture was stirred at a constant speed of 300 rpm. After reacting for 24 hours, the mixture was centrifuged, and the resulting precipitate was repeatedly washed and centrifuged several times. Finally, the washed white solid was dried in a vacuum drying oven at 40°C for 12 hours to obtain dried polyacrylamide microsphere powder.

[0083] (II) Preparation of core-shell microgel powder (PCSM) loaded with polyvinylpyrrolidone-coated magnesium silicide nanosheets (MNPs).

[0084] The core-shell structure was constructed using ion crosslinking and freeze-drying techniques. The specific steps are as follows: (1) Core layer solidification: PA microspheres were immersed in anhydrous ethanol solution of calcium chloride for 24 hours at room temperature. (2) Shell layer coating: The PA microspheres treated with calcium ions were centrifuged and dried in an oven at 40°C for 2 hours to remove ethanol. Then, they were slowly and in small amounts added to 100 mL of sodium alginate aqueous solution containing magnesium silicide powder (MNP) coated with polyvinylpyrrolidone. The mixture was stirred at 100 rpm for 1 hour at room temperature to allow sodium alginate to undergo ion crosslinking with calcium ions on the surface of the microspheres, forming a composite hydrogel shell coating MNP on the surface of the PA microspheres. (3) Product purification and drying: After the reaction was completed, the mixture was centrifuged at 5000 rpm for 5 minutes to collect the gel particles, and washed three times with deionized water to remove unreacted sodium alginate. The final product was freeze-dried at -50°C for 48 hours to obtain polyacrylamide-sodium alginate core-shell microgel powder loaded with polyvinylpyrrolidone-coated magnesium silicide, denoted as PCSM.

[0085] Experimental Example

[0086] The following experiments were conducted based on the method and product provided in Example 1:

[0087] Cell migration ability was assessed using a Transwell migration assay. The polycarbonate membrane pore size was selected based on cell type: 3.0 μm pores for human umbilical vein endothelial cells (HUVECs) and 8.0 μm pores for L929 cells. Cells were seeded in the upper chamber of a Transwell and cultured at 37°C in a 5% CO2 incubator until cell adhesion occurred. The upper chamber was then replaced with serum-free medium, and the lower chamber was supplemented with medium containing 10% fetal bovine serum (FBS) to create a chemotactic gradient. Experimental groups were supplemented with PA, PCS, and PCSM, respectively, while the control group maintained standard culture conditions. After 24 hours, unmigrated cells were gently wiped from the upper chamber membrane surface with a cotton swab. Cells that migrated to the lower surface were fixed with 4% paraformaldehyde and stained with 0.5% crystal violet for 15 minutes. After washing with PBS and air drying, five fields of view were randomly selected from each well and photographed under 200x magnification using an inverted microscope. The number of migrating cells was counted using ImageJ software. Cell migration ability was further assessed using a wound healing (scratch) assay. L929 cells and HUVECs were mixed at a ratio of 2 × 10⁶ cells per well. 5Cells were seeded at a density of 100 μL in 12-well plates. After the cells merged into a monolayer, a straight scratch was made in the monolayer using a 200 μL pipette tip. After washing away detached cells with PBS, the cells were cultured for 24 hours in complete medium containing PA, PCS, and PCSM. Images were taken before and after treatment using an inverted microscope, and the scratch closure distance was quantitatively analyzed using ImageJ software. For in vitro angiogenesis analysis, 10 μL of Matrigel was added to each well of angiogenesis slides and allowed to solidify at 37 °C for 30 minutes. HUVECs (1 × 10⁶ cells per well) were then seeded. 5 (Number of cells) were seeded on a surface coated with Matrigel. The formation of tubular structures was observed at different time points, and the number of branching points and the total length of the tubular structures were quantitatively analyzed using ImageJ software.

[0088] Transwell migration assays showed that PCSM significantly enhanced the migration ability of HUVEC cells and L929 cells. Figure 1 a, 1b). The scratch healing assay further confirmed that the cell groups treated with PCSM showed a significantly faster migration rate (a, 1b). Figure 1 Furthermore, tubular formation experiments showed that the PCSM group had the highest number of vascular nodes and the longest total tubular length. Figure 1 H2 gas (fh) exhibited strong pro-angiogenic activity. This effect may stem from the fact that H2 gas can reduce cellular inflammatory responses, thereby promoting cell proliferation and migration, and further driving angiogenesis at the wound site.

[0089] In the live and dead cell staining experiment, L929 or HUVECs were seeded in 24-well plates (1 × 10⁶ cells per well). 5Cells were cultured in 500 μL of complete culture medium for 24 hours. Then, sterile PA, PCS, and PCSM (10 mg / mL) were added to each well, gently mixed, and co-cultured for another 24 hours. After washing twice with PBS, 500 μL of live and dead cell staining solution (2 μmol Calcein-AM, 5 μg propidium iodide) was added to each well, and the cells were incubated at 37 °C in the dark for 30 minutes. After PBS washing, cell viability was observed using fluorescence microscopy or confocal microscopy; live cells showed green fluorescence, and dead cells showed red fluorescence. In addition, four groups were established for the CCK-8 experiment: control group (untreated), PA group, PCS group, and PCSM group. A direct co-culture method was used to evaluate the interaction between the material and cells. L929 fibroblasts or human umbilical vein endothelial cells (HUVECs) were seeded at a density of 5,000–10,000 cells per well in 96-well plates and cultured at 37 °C and 5% CO2 for 24 hours. Subsequently, 10 mg / mL of sterilized material was added to each well for direct co-culture. Cell viability was assessed on days 1, 3, and 5: at each time point, 10 mL of CCK-8 reagent was added to 100 mL of culture medium per well, and after incubation for 1 hour, absorbance was measured at 450 nm using a microplate reader.

[0090] HUVECs were seeded in 12-well plates and cultured until adherent. Then, 100 μmol of hydrogen peroxide was added for 30 minutes to induce oxidative stress. Subsequently, the hydrogen peroxide-containing medium was removed and replaced with medium containing PBS, PA, PCS, and PCSM (10 mg / well), respectively, and incubated for another hour. Afterward, the cells were incubated with 10 μmol of serum-free medium for 20 minutes. Following PBS washing, the production of intracellular reactive oxygen species (ROS) was observed and recorded using a fluorescence microscope.

[0091] To evaluate the anti-inflammatory effects of PA, PCS, and PCSM, primary RAW264.7 mouse macrophages were used as an in vitro inflammation model. Cells were cultured at 1 × 10⁶ cells per well. 5 Cells were seeded at a density of [number] cells / well in 24-well plates. After cell adhesion, cells were treated with lipopolysaccharide (LPS, 100 ng / mL) for 24 hours to induce inflammation. After washing with PBS, interleukin-4 (IL-4, 10 ng / mL) was added to the cells, and they were co-cultured with sterile PA, PCS, and PCSM (10 mg / well) for 24 hours. Untreated cells served as a negative control. After treatment, cells were washed with PBS and fixed with 4% paraformaldehyde for 15 minutes.

[0092] To assess macrophage polarization status, immunofluorescence staining was performed on CD86 (M1 marker) and CD206 (M2 marker). Fixed cells were permeabilized with 0.1% Triton X-100 for 10 min and blocked with 5% bovine serum albumin (BSA) for 30 min. Subsequently, cells were incubated overnight at 4°C with fluorescently labeled anti-CD86 and anti-CD206 primary antibodies. After washing, cells were incubated with the corresponding secondary antibodies for 1 h, and the nuclei were counterstained with DAPI. Fluorescence images were acquired using a confocal laser scanning microscope, and quantitative analysis was performed using ImageJ software.

[0093] Simultaneously, flow cytometry was used to quantitatively analyze the expression of CD86 and CD206. Processed cells were collected and analyzed using a BDFACSCanto II flow cytometer. Data were processed using CytExpert software to calculate CD86 expression. + (M1 type) and CD206 + The percentage of (M2 type) macrophages was used to assess the polarization status of macrophages in different treatment groups.

[0094] After co-culturing with the materials for 24 hours, staining of live and dead cells showed that no dead cells were detected in any of the experimental groups. L929 fibroblasts and HUVEC cells were uniformly distributed and maintained their morphology well. Under a fluorescence microscope, the cells emitted green fluorescence without any obvious red signal, indicating that under the experimental conditions, the PA, PCS, and PCSM groups all exhibited high cell viability and no cytotoxicity. Figure 2 a). Cell viability was further assessed using CCK-8 assays on days 1, 3, and 5. Although the control, PA, and PCS groups showed similar proliferation levels, the PCSM group showed significantly enhanced cell growth, especially at later time points. Figure 2 b). To investigate the antioxidant capacity of H2 released by PCSM in the repair of severe burn wounds, H2O2-induced oxidative stress was applied to HUVEC and L929 cells. The results showed that PCSM significantly inhibited the increase in intracellular ROS levels, indicating that H2 release can effectively scavenge ROS and protect cells from oxidative damage. Figure 2 The anti-inflammatory effect of PCSM H2 release was assessed in RAW264.7 macrophages by immunofluorescence staining and flow cytometry. Immunofluorescence results showed that, compared with other groups, the PCSM group had higher expression of CD206 (M2 macrophage marker, green) and lower expression of CD86 (M1 macrophage marker, red). Figure 2Flow cytometry analysis further confirmed that PCSM-treated macrophages showed significantly decreased CD86 expression and significantly increased CD206 expression; while the control group, PA group, and PCS group showed higher CD86 expression and lower CD206 expression. These results indicate that PCSM can effectively promote macrophage polarization towards the anti-inflammatory M2 phenotype (fh). Figure 2 ik).

[0095] All animal experiments were approved by the Animal Ethics and Welfare Committee of Sichuan University (Approval No.: 20220228127). Eight-week-old SD rats were obtained from Lilai Biotechnology Co., Ltd. and housed under standard laboratory conditions. Anesthesia was induced using an induction chamber (China Ruiwode Co., Ltd.) with a mixture of 1.5% isoflurane and 60% oxygen. After shaving the hair on the back, a preheated cauterizing iron at 90°C was applied to the skin for 10 seconds under a pressure of 500g to create a full-thickness burn wound with a diameter of 14 mm.

[0096] Rats were randomly divided into four groups (n=5 per group): (1) burn control group (no treatment); (2) PA treatment group; (3) PCS treatment group; (4) PCSM treatment group. Treatment began on day 1 after injury, and the animals were observed daily. Rats were sacrificed on day 14, and skin tissue samples were collected. The samples were fixed in 4% paraformaldehyde, embedded in paraffin, and then stained with hematoxylin and eosin (H&E) and Masson's trichrome to assess histological changes and collagen deposition.

[0097] A deep second-degree burn model was established by creating a circular wound (14 mm in diameter) on the back skin of rats to evaluate the wound healing effect and potential mechanism of PCSM hydrogel dressing. When the dressing was applied to the wound, both PCS and PCSM absorbed exudate and spontaneously formed adhesive clots on the rat skin surface, further confirming the feasibility of this strategy. Compared with the PA group, PCS group, and untreated burn group, the PCSM-treated wound showed reduced exudate and significantly faster healing speed. Figure 3 (a) indicates that PCSM plays a crucial role in promoting wound healing through absorption of wound exudate and continuous H2 release. On day 14 post-injury, the tissue structure of regenerated tissue was analyzed using H&E staining and Masson's trichrome staining. Results showed that the PCSM group achieved the highest wound closure rate (a). Figure 3 b). The untreated burn group exhibited severe fibrosis and structural damage characteristic of natural healing, while the PCSM group showed active angiogenesis, dermal thickening, and improvement in overall skin structure, highlighting the key role of H2 in promoting tissue repair.

[0098] Skin bleeds very easily after a burn, so an ideal dressing should rapidly promote clotting. Furthermore, the dressing's ability to absorb blood or exudate significantly affects its clotting properties. Hemolysis test ( Figure 4 a) showed that the hemolysis rate in all experimental groups was less than 5% (generally considered a safe range), with the PCSM group exhibiting the lowest hemolysis rate (<2%). This invention further evaluated the blood absorption capacity of PA, PCS, and PCSM. Figure 4 b). PCS had the highest blood absorption rate, while PCSM was slightly lower but the difference was not significant. This characteristic aligns with the targeted design for hyperosmolar burn wounds: the highly absorbent PA core provides strong fluid absorption and retention capabilities, which is further confirmed by the water absorption test. Figure 4 d). The coagulation index (BCI) further confirms the excellent coagulation performance of PCSM. Figure 4 c). Scanning electron microscopy images showed that both PCS and PCSM surfaces had a large number of blood cells adhering to and aggregated. Figure 4 (e, 4f). These results indicate that when PCSM is applied to a bleeding wound, it can rapidly absorb blood and aggregate blood cells, thereby enhancing hemostasis and promoting the wound to successfully pass through the coagulation phase.

[0099] The photothermal properties of PA, PCS, and PCSM under 808 nm laser irradiation were further evaluated. Specifically, 100 mg of each material (PA, PCS, and PCSM) was dispersed in 1 mL of deionized water at a power density of 1.0 W / cm². 2 Temperature changes over time were recorded under 808 nm near-infrared laser irradiation. The results showed that the temperature of the PCSM dispersion increased from 26.4 °C to 52.9 °C within 5 minutes, reaching the effective temperature range for in vitro antibacterial applications. In contrast, neither PA nor PCS showed a significant temperature rise, confirming that the photothermal properties of PCSM are mainly attributed to the incorporation of MNP (…). Figure 4 g). Furthermore, the photothermal stability of PCSM was evaluated through multiple heating-cooling cycles (infrared illumination on time: 5 minutes; off time: 5 minutes). The temperature rise of the PCSM dispersion remained stable throughout five consecutive cycles, indicating its excellent photothermal stability and reusability. Figure 4 h). To further evaluate the photothermal antibacterial properties of PCSM, its antibacterial effects against Staphylococcus aureus and Escherichia coli under near-infrared (NIR) laser irradiation were investigated. The results showed that the combined treatment of PCSM and NIR significantly inhibited the growth of both strains (h). Figure 4 j), the inhibition rate reached 99.5% (j), respectively. Figure 4 i) and 99.6%. The morphology of PA, PCS and PCSM was observed by optical microscopy and SEM, and the core-shell structure of PCS and PCSM was confirmed. Figure 5 The particle sizes of PA, PCS, and PCSM are 223.39 ± 32.01 μm, 318.20 ± 33.69 μm, and 312.09 ± 30.80 μm, respectively. Cross-sectional views of PA and PCS are shown below. Figure 5 (d, e) show distinct morphological characteristics: the PA surface is rough, while the PCS has a smoother surface due to SA coating. TGA further shows that the content of the hydrogen donor MNP in the PCSM is approximately 13.2 wt%. Figure 5 f).

[0100] Ideal wound dressings should adhere immediately, forming a physical barrier to protect the wound. However, strong adhesion often causes secondary damage or pain upon removal. When the core-shell structured microgel in this invention comes into contact with blood or exudate, the microgel rapidly absorbs the liquid and gels, forming a protective physical barrier. To simulate the exudation process of a burn wound, this invention adds methylene blue-stained PBS solution dropwise. When 0.15 mL (3 drops) of PBS is added, the dried PCSM absorbs water, self-gelles, and adheres to the pigskin wound. Figure 5 g, 0.15 mL). After adding 0.30 mL (6 drops) of PBS, PCSM completely transformed from powder into a coagulated gel block. However, further addition of PBS (0.75 mL, 13 drops) caused the gel block to disintegrate into independent hydrogel microspheres. The above phenomena indicate that Ca 2+ Mediated ionic crosslinking enables SA to form a shell on the PA core surface, constituting a core-shell structured microsphere with strong interfacial adhesion. Notably, this microsphere can spontaneously desorb after absorbing sufficient exudate, demonstrating its potential for practical application. Burst pressure tests showed that the average burst pressures of PA, PCS, and PCSM were 73.1, 165.4, and 159.6 mmHg, respectively. Figure 5 h). The values ​​of PCS and PCSM exceeded the normal range of human arterial blood pressure (80-100 mmHg), proving that they could maintain adhesion under physiological pressure. This invention further tested the burst pressure of PCSM under different exudate volumes: the adhesion strength reached its peak when 0.30 mL of exudate was absorbed; beyond this point, the burst pressure of PCSM decreased with increasing absorption, consistent with the weakening trend of adhesion. Figure 5 i). In summary, PCSM possesses spatiotemporally responsive adhesion capabilities, providing a physical barrier in the early and mid-stages of exudate management and achieving painless detachment after fluid saturation.

[0101] This invention successfully prepared magnesium silicide nanosheets (MN) via ultrasonic-assisted exfoliation. However, both pristine Mg₂Si(M) and MN readily react with water, limiting their application in aquatic environments. To address this issue, this invention coats the surface of MN with polyvinylpyrrolidone (PVP) to enhance its short-term stability in water. Figure 6 As shown in Figure a, transmission electron microscopy (TEM) images reveal that the fabricated MNPs possess nanoscale dimensions, which are expected to improve H2 yield. EDS elemental distribution maps further demonstrate that Mg and Si are uniformly distributed on the MNP surface, and the presence of nitrogen (N), a characteristic element of PVP, was detected, confirming the successful PVP coating. In contrast, no significant N element signal was detected in the EDS elemental distribution map of MN. Figure 6 b).

[0102] Using the absorbance standard curve of methylene blue (MB) at 664 nm, this invention quantifies the H2 release curves of MN and MNP over 6 hours and 10 days. Figure 6 (c, 6d). The PVP coating slowed the H2 release rate during the first 2 hours of MNP contact with water; as the PVP layer gradually dissolved, the H2 release rate accelerated, thus minimizing premature consumption of MNP. This controlled-release behavior helps retain most of the MN during the inflammatory and proliferative phases of wound healing to maximize its efficacy. Notably, MNP can sustain H2 release for up to 10 days, highlighting its potential in modulating the inflammatory microenvironment and promoting burn wound healing.

[0103] XPS analysis was used to analyze the changes in elemental valence states before and after the reaction of MNP with deionized water (labeled as MNP and RMNP, respectively). In the Si2p spectrum of RMNP ( Figure 6 The characteristic peak corresponding to the Si-O-Si bond appears at 102.1 eV. In contrast, the Si2p spectrum of MNP shows two characteristic peaks: 102.1 eV (Si-O-Si) and 98.4 eV (Si-Mg).

[0104] As demonstrated by the above embodiments, this invention provides a microgel powder with a core-shell structure. This powder can efficiently absorb liquid and transform into an adhesive hydrogel, exhibiting good blood compatibility and procoagulant ability in a simulated wound environment. Experiments have confirmed that this material can continuously release hydrogen gas and active ions such as magnesium and silicon in response to exudate, possessing significant antioxidant stress resistance, regulating macrophage polarization towards a repair phenotype, promoting endothelial cell and fibroblast migration, and angiogenesis. In animal burn models, this material can effectively accelerate wound closure and improve healing quality. Simultaneously, its unique structural design allows it to self-detach after absorbing sufficient liquid, achieving a balance between dressing function and gentle removal characteristics.

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A core-shell microgel powder, characterized in that, The microgel powder has a core-shell structure, and the core in the core-shell structure is a calcium ion pretreated polyacrylamide microsphere. The shell in the core-shell structure is a sodium alginate layer loaded with hydrogen donor nanosheets, which are dispersed in the sodium alginate layer.

2. The core-shell microgel powder according to claim 1, characterized in that, The hydrogen donor nanosheets are magnesium silicide nanosheets or calcium silicide nanosheets. The surface of the hydrogen donor nanosheet is coated with a polyvinylpyrrolidone layer; The hydrogen donor nanosheets constitute 10% to 20% of the mass percentage of the core-shell microgel powder. The particle size of the polyacrylamide microspheres is 180 micrometers to 280 micrometers; The overall particle size of the core-shell microgel powder is 280 micrometers to 360 micrometers.

3. The method for preparing the core-shell microgel powder according to claim 1 or 2, characterized in that, Includes the following steps: S1. Polyacrylamide microspheres are immersed in an ethanol solution containing calcium ions and then dried to obtain calcium ion pretreated polyacrylamide microspheres. S2. The calcium ion pretreated polyacrylamide microspheres are mixed with an aqueous solution of sodium alginate containing hydrogen donor nanosheets and subjected to an ionic crosslinking reaction to form a sodium alginate shell layer loaded with hydrogen donor nanosheets on the surface of the microspheres, thereby obtaining core-shell structured gel particles. The microgel powder has a core-shell structure, wherein the core of the core-shell structure is a calcium ion pretreated polyacrylamide microsphere, and the shell of the core-shell structure is a sodium alginate layer loaded with hydrogen donor nanosheets, wherein the hydrogen donor nanosheets are dispersed in the sodium alginate layer. S3. The core-shell structured gel particles are separated, washed, and freeze-dried to obtain the core-shell microgel powder.

4. The preparation method according to claim 3, characterized in that, In step S1, the polyacrylamide microspheres are prepared by water-in-oil emulsion polymerization, which includes adding an aqueous phase containing acrylamide monomer, crosslinking agent and initiator dropwise to an oil phase containing emulsifier for polymerization reaction. Alternatively, the polyacrylamide microspheres are prepared by precipitation polymerization, which includes polymerizing acrylamide monomers in a mixed solvent of ethanol and water under nitrogen protection. Alternatively, the polyacrylamide microspheres may be prepared by dispersion polymerization, which includes polymerizing acrylamide monomers in a mixed solvent of ethanol and water containing the dispersant polyvinylpyrrolidone.

5. The preparation method according to claim 3, characterized in that, In step S1, the concentration of calcium ions in the calcium-containing ethanol solution is 40 mg / mL to 60 mg / mL; the soaking time is 20 hours to 28 hours. In step S2, the sodium alginate aqueous solution containing hydrogen donor nanosheets has a sodium alginate mass-volume concentration of 0.1% to 0.3%; the doping amount of the hydrogen donor nanosheets in the sodium alginate aqueous solution containing hydrogen donor nanosheets is 80% to 120% of the mass of sodium alginate; the ionic crosslinking reaction is carried out at room temperature for a reaction time of 0.5 hours to 1.5 hours. In step S3, the freeze-drying temperature is -60℃ to -40℃, and the drying time is 40 hours to 56 hours.

6. The preparation method according to claim 4, characterized in that, In the water-in-oil emulsion polymerization method, the oil phase comprises cyclohexane and a Span-type emulsifier, and the volume ratio of the aqueous phase to the oil phase is 1:2~3; the Span-type emulsifier comprises Span 20 and Span 80, and the mass ratio of Span 20 to Span 80 is 1.5~2.5:1; in the water-in-oil emulsion polymerization method, the rate at which the aqueous phase is added to the oil phase is 50 drops / min~70 drops / min; in the water-in-oil emulsion polymerization method, the polymerization reaction is carried out at 60℃~70℃, the stirring speed is 250 rpm~350 rpm, and the reaction time is 2 hours~4 hours; In the precipitation polymerization method, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 3~5:1; in the precipitation polymerization method, the polymerization reaction is carried out at 30℃~40℃, the stirring speed is 250 rpm~350 rpm, and the reaction time is 20 hours~28 hours. In the dispersion polymerization method, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 3~5:1; in the dispersion polymerization method, the mass of the dispersant polyvinylpyrrolidone is 0.5%~1.5% of the total mass of the solvent; in the dispersion polymerization method, the polymerization reaction is carried out at 65℃~75℃, the stirring speed is 250 rpm~350 rpm, and the reaction time is 20 hours~28 hours.

7. The preparation method according to claim 3, characterized in that, In step S2, the mass-to-volume ratio of the calcium ion pretreated polyacrylamide microspheres to the sodium alginate aqueous solution containing hydrogen donor nanosheets is 0.05 g / 100 mL to 0.15 g / 100 mL.

8. The preparation method according to claim 3, characterized in that, In step S3, the separation is carried out by centrifugation at a speed of 4000 rpm to 6000 rpm for a time of 3 to 8 minutes. In step S1, the drying is carried out at 35°C to 45°C for 1 to 3 hours. The hydrogen donor nanosheets were prepared by ultrasonic-assisted exfoliation.

9. The use of the core-shell microgel powder according to any one of claims 1 to 2 or the core-shell microgel powder prepared by the preparation method according to any one of claims 3 to 8 in the preparation of medical dressings for promoting wound healing.

10. The application according to claim 9, characterized in that, The wound is a burn wound.

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