Silver ion antibacterial foam dressing and method of manufacturing the same

Abstract

The application discloses a kind of silver ion antibacterial foam dressings and its manufacturing method, belong to medical dressing technical field, manufacturing method includes first preparation silver ion in situ dispersion hydrophilic polyurethane prepolymer, form foaming body by controllable mechanical foaming parameter, again by three-stage gradient drying obtains silver ion containing hydrophilic polyurethane foam layer with water content≤5wt%, finally with glue coating medical breathable polyurethane film presss together composite. Optionally add pharmaceutical grade sodium sulfate micro powder realizes silver ion slow-release cooperation, or water-soluble porogen precise control cell structure. The application uses the above-mentioned silver ion antibacterial foam dressing and its manufacturing method, the prepared dressing silver ion dispersion is uniform, release stable and durable, foam structure is complete and has no defect, with excellent liquid absorption capacity and long-acting antibacterial anti-inflammatory effect, can maintain wound dry environment, accelerate wound healing, suitable for pressure sore, bed sore, diabetic foot and other chronic difficult-to-heal wound clinical nursing.

Description

Technical Field

[0001] This invention relates to the field of medical dressing technology, and in particular to a silver ion antibacterial foam dressing and its manufacturing method. Background Technology

[0002] Chronic wounds (such as pressure sores, diabetic foot ulcers, and lower extremity venous ulcers) are often accompanied by large amounts of exudate and persistent bacterial infection, leading to a prolonged state of inflammation and difficulty in healing. Silver-containing foam dressings, due to their combined antibacterial and exudate management functions, have become the mainstream choice for chronic wound care.

[0003] Currently, the manufacturing processes for silver-containing polyurethane foam dressings mainly fall into two categories: one is the chemical foaming method, such as US8263100B2, which discloses a method of pre-dispersing silver salts in an aqueous phase, then mixing them with isocyanate-terminated polyethers, and using a water-isocyanate reaction to generate CO2 gas for pore formation. This process relies on chemical reaction for pore formation, and the fine control of the pore structure is limited by reaction kinetics. Furthermore, the introduction of silver ions with the aqueous phase makes achieving uniform distribution in the two-phase system technically challenging. The other category is the post-treatment impregnation method, such as impregnating pre-formed polyurethane foam in a silver-containing solution and then drying it to obtain the silver-containing foam dressing. In this method, silver ions mainly adhere to the foam surface and near-surface area, resulting in significant initial release and insufficient antibacterial durability.

[0004] Furthermore, existing silver-containing foam dressings lack quantitative control over the uniformity of the foam cells, resulting in significant differences in the release rate of silver ions in different regions, affecting the stability and predictability of the antibacterial effect. Drying processes generally only target the final moisture content, neglecting the impact of temperature regimes on the chemical state and release behavior of silver ions during drying.

[0005] Therefore, there is an urgent need for a silver ion antibacterial foam dressing with high process controllability, capable of achieving uniform distribution and long-lasting sustained release of silver ions, and its manufacturing method. Summary of the Invention

[0006] The purpose of this invention is to provide a silver ion antibacterial foam dressing and its manufacturing method to solve the above-mentioned problems.

[0007] This invention provides a method for manufacturing a silver ion antibacterial foam dressing, comprising the following steps: S1: Provides a hydrophilic polyurethane prepolymer containing silver ions, wherein silver ions are uniformly dispersed in the hydrophilic polyurethane prepolymer in the form of an aprotic solvent solution of silver salt, the hydrophilic polyurethane prepolymer is prepared by reacting isocyanate, polyol and hydrophilic chain extender, the isocyanate index is 1.5 to 3.5; the aprotic solvent is selected from at least one of acetone, butanone, N,N-dimethylformamide and N-methylpyrrolidone; S2: Mechanically foam the silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1. Add a foaming agent and introduce gas into the silver ion-containing hydrophilic polyurethane prepolymer to form a foam under stirring conditions. Control the foaming temperature to be 20-40℃, the stirring speed to be 500-3000 rpm, and the foaming ratio to be 2:1-6:1. S3: The foam obtained in step S2 is coated onto a substrate and subjected to gradient drying to obtain a hydrophilic polyurethane foam layer containing silver ions with a water content not exceeding 5 wt%. The gradient drying process includes drying at 40–55°C for 5–30 min, drying at 56–70°C for 10–60 min, and finally drying at 71–80°C to the stated water content. The hydrophilic polyurethane foam layer containing silver ions has a porous structure with an average pore size of 50–500 μm and a cell distribution coefficient (CV) value ≤30%. S4: Provides a polyurethane film, with an adhesive layer formed by coating one side surface of the polyurethane film. The polyurethane film is a medical-grade, breathable polyurethane film with a thickness of 10–50 μm and a water vapor permeability of 500–2000 g / (m²). 2 ·24h); S5: The polyurethane film coated with adhesive layer in step S4 and the silver ion-containing hydrophilic polyurethane foam layer obtained in step S3 are bonded together by the adhesive layer.

[0008] Preferably, the hydrophilic polyurethane prepolymer containing silver ions described in step S1 is prepared by mixing the hydrophilic polyurethane prepolymer with an aprotic solvent solution of a silver salt under stirring conditions, wherein the concentration of silver ions in the silver salt solution is 0.01–0.5 mol / L. The silver salt is selected from at least one of silver nitrate, silver perchlorate, silver trifluoromethanesulfonate, and silver tetrafluoroborate, and the silver ion content of the silver salt accounts for 40–80 wt% of the total mass of the silver salt.

[0009] Preferably, the silver ion-containing hydrophilic polyurethane prepolymer in step S1 also contains sodium sulfate micropowder. The sodium sulfate micropowder is introduced in the following way: pharmaceutical-grade sodium sulfate micropowder is directly added to the silver ion-containing hydrophilic polyurethane prepolymer and stirred to disperse evenly; the amount of sodium sulfate micropowder added is 0.1 to 3 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer, and the mass ratio of sodium sulfate micropowder to silver salt is 1:5 to 3:1; the sodium sulfate micropowder is evenly dispersed and embedded in the foam matrix of the silver ion-containing hydrophilic polyurethane foam layer. When in use, it preferentially dissolves after contact with wound exudate, generating local high osmotic pressure inside the foam pore wall, driving the exudate to penetrate and dissolve the silver salt embedded in the matrix, thereby promoting the release of silver ions to the wound.

[0010] Preferably, the silver ion content in the silver ion-containing hydrophilic polyurethane foam layer is expressed as Ag.+ The silver ion content is controlled by the concentration and amount of the silver salt aqueous solution; in step S2, the foaming agent is an organosilicon surfactant, and its addition amount is 0.5-5.0 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer; in step S3, the average pore size of the silver ion-containing hydrophilic polyurethane foam layer is 100-300 μm, and the cell distribution coefficient (CV) is 10%-25%.

[0011] Preferably, before mechanical foaming in step S2, a water-soluble porogen is added to the silver ion-containing hydrophilic polyurethane prepolymer. The water-soluble porogen is selected from polyethylene glycol or polyvinylpyrrolidone, with a molecular weight of 400-6000 Da, and the amount added is 1-8 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer. This results in the water-soluble porogen being distributed in the cell walls of the dried silver ion-containing hydrophilic polyurethane foam layer. When in contact with liquid, the water-soluble porogen dissolves and forms microchannels on the cell walls.

[0012] Preferably, the size and distribution density of the microchannels are controlled by adjusting the molecular weight and amount of the water-soluble porogen, thereby controlling the release rate of silver ions; the amount of the water-soluble porogen added does not exceed 80% of its saturated solubility in water at 20-40°C.

[0013] Preferably, in step S3, by controlling the temperature change rate of the gradient drying process, at least 30% of the silver ions in the dried silver ion-containing hydrophilic polyurethane foam layer exist in a coordinated state with the ether oxygen bond and / or urethane group in the polyurethane chain segment; in step S4, the adhesive is a medical-grade pressure-sensitive adhesive; and in step S5, the composite bonding condition is pressing under a pressure of 0.1 to 0.5 MPa.

[0014] A silver ion antibacterial foam dressing is provided, which is prepared by the above-described manufacturing method.

[0015] Preferably, the silver ion antibacterial foam dressing includes: The silver ion-containing hydrophilic polyurethane foam layer has a porous structure with an average pore size of 50–500 μm and a cell distribution coefficient (CV) value ≤30%. Silver ions are uniformly distributed within the silver ion-containing hydrophilic polyurethane foam layer, with the silver ion content expressed as Ag. + It is calculated to be 0.05–2.0 wt%; A polyurethane film layer is disposed on top of a silver ion-containing hydrophilic polyurethane foam layer. This polyurethane film layer is a medical-grade, breathable polyurethane film with a thickness of 10–50 μm and a water vapor permeability of 500–2000 g / (m²). 2 ·24h); An adhesive layer is disposed between the polyurethane film layer and the silver ion-containing hydrophilic polyurethane foam layer, bonding the polyurethane film layer and the silver ion-containing hydrophilic polyurethane foam layer into a single unit.

[0016] Preferably, the average pore size of the silver ion-containing hydrophilic polyurethane foam layer is 100–300 μm, the cell distribution coefficient (CV) is 10%–25%, and the silver ion content is expressed as Ag. + The content is 0.05–1.0 wt%; water-soluble porogens are distributed in the cell walls of the silver ion-containing hydrophilic polyurethane foam layer. The water-soluble porogens are selected from polyethylene glycol or polyvinylpyrrolidone, with a molecular weight of 400–6000 Da. The water-soluble porogens dissolve upon contact with liquid and form microchannels on the cell walls; sodium sulfate is also uniformly dispersed in the foam matrix of the silver ion-containing hydrophilic polyurethane foam layer. The sodium sulfate is embedded in the foam matrix in the form of micro powder. When in use, it preferentially dissolves upon contact with wound exudate, generating an osmotic pressure effect that drives the release of silver ions in the silver ion-containing hydrophilic polyurethane foam layer to the wound; the silver ions in the silver ion-containing hydrophilic polyurethane foam layer are selected from at least one silver salt selected from silver nitrate, silver perchlorate, silver trifluoromethanesulfonate, and silver tetrafluoroborate, and the silver ion content of the silver salt accounts for 40–80 wt% of the total mass of the silver salt.

[0017] Therefore, the present invention, employing the above-mentioned silver ion antibacterial foam dressing and its manufacturing method, has the following beneficial effects: (1) By introducing silver ions into the hydrophilic polyurethane prepolymer in the form of an aprotic solvent solution of silver salt before foaming, and combining it with mechanical foaming process, the silver-containing prepolymer is transformed into a continuous phase of the cell wall. During the subsequent drying process, the silver salt is redeprecipitated in the cell wall matrix as ultrafine crystals, which are highly dispersed and stably embedded in the cell wall matrix rather than attached to the surface. This fundamentally changes the spatial distribution and release kinetics of silver ions, avoiding surface enrichment and burst release. At the same time, through a specific three-stage gradient drying regime, the silver ions are promoted to form coordination bonds with the polar groups of the polyurethane chain segments during the slow solvent removal process at low temperature, forming coordinated silver ions with a stable release rate. The release of coordinated silver ions requires two steps: decoordination and diffusion. The release rate is jointly controlled by the decoordination kinetics and the diffusion rate. Compared with the simple dissolution-diffusion of free silver ions, this further prolongs the antibacterial action time and achieves a continuous and controllable antibacterial effect.

[0018] (2) A mechanical foaming process is adopted, and physical parameters such as stirring rate and foaming ratio are independently controlled to obtain a uniform porous structure with an average pore size of 50-500 μm and a pore distribution coefficient CV value ≤30%. The uniform pore size distribution ensures that the exudate absorption rate and silver ion release rate in each area of ​​the wound are highly consistent, avoiding premature local saturation or uneven antibacterial efficacy. This allows the dressing to effectively lock in fluid and prevent backflow while efficiently absorbing exudate, maintaining a suitable moist environment for the wound. It is especially suitable for chronic wounds with moderate to severe exudate.

[0019] (3) The silver ion-containing foam layer is combined with the outer breathable polyurethane film. The film layer provides a physical barrier and suitable water vapor permeability, further optimizing the wound microenvironment. Through the synergistic effect of antibacterial and exudate management, infection is effectively controlled, and inflammatory mediators such as matrix metalloproteinases that are not conducive to healing are removed in time from the excessive exudate, creating favorable conditions for granulation tissue growth and epithelialization, and significantly shortening the healing cycle of chronic wounds.

[0020] (4) All raw materials are medical grade, the manufacturing process does not produce any known harmful byproducts, the resulting products meet the requirements for biological evaluation of medical devices, are safe and reliable, and are suitable for large-scale industrial production.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of a silver ion antibacterial foam dressing and its manufacturing method according to the present invention. Detailed Implementation

[0023] To better understand the above technical solutions, a detailed description of the solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.

[0025] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.

[0026] This invention provides a method for manufacturing a silver ion antibacterial foam dressing, comprising the following steps: S1: Provides a silver ion-containing hydrophilic polyurethane prepolymer, wherein silver ions are uniformly dispersed in the hydrophilic polyurethane prepolymer in the form of a silver salt aprotic solvent solution, wherein the aprotic solvent is selected from at least one of acetone, butanone, N,N-dimethylformamide, and N-methylpyrrolidone; the hydrophilic polyurethane prepolymer is prepared by reacting isocyanate, polyol, and hydrophilic chain extender, and the isocyanate index is 1.5 to 3.5; the silver ion content in the silver ion-containing hydrophilic polyurethane foam layer is expressed as Ag... + The silver ion content is 0.05–1.0 wt%, and the silver ion content is controlled by the concentration and amount of the aprotic solvent solution of the silver salt. The silver ion-containing hydrophilic polyurethane prepolymer is prepared by mixing the hydrophilic polyurethane prepolymer with the aprotic solvent solution of the silver salt under stirring conditions. The concentration of silver ions in the aprotic solvent solution of the silver salt is 0.01–0.5 mol / L. The silver salt is selected from at least one of silver nitrate, silver perchlorate, silver trifluoromethanesulfonate, and silver tetrafluoroborate. The silver ion content of the silver salt accounts for 40–80 wt% of the total mass of the silver salt.

[0027] The silver ion-containing hydrophilic polyurethane prepolymer also contains sodium sulfate micropowder, which is introduced in the following way: pharmaceutical-grade sodium sulfate micropowder is directly added to the silver ion-containing hydrophilic polyurethane prepolymer and stirred to disperse evenly; the amount of sodium sulfate micropowder added is 0.1-3 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer, and the mass ratio of sodium sulfate micropowder to silver salt is 1:5-3:1; the sodium sulfate micropowder is uniformly dispersed and embedded in the foam matrix of the silver ion-containing hydrophilic polyurethane foam layer. When in use, it preferentially dissolves after contact with wound exudate, generating an osmotic pressure effect that drives the release of silver ions in the silver ion-containing hydrophilic polyurethane foam layer to the wound.

[0028] Specifically, silver salt is dissolved in an aprotic solvent to form a solution, which is then mixed with a hydrophilic polyurethane prepolymer. The aprotic solvent and the prepolymer exhibit good compatibility, forming a homogeneous system after mixing, where silver is uniformly dissolved or highly dispersed in the prepolymer in ionic form. The prepolymer contains numerous ether bonds (COC) and urethane groups (-NH-COO-), these polar groups can react with Ag...+ Through ion-dipole interactions or coordination, silver ions achieve stable molecular-level dispersion on the polymer chain segments, preventing phase separation or silver salt precipitation. Since the system is anhydrous, side reactions of isocyanate groups are avoided, and the viscosity of the prepolymer inhibits the migration and aggregation of silver ions, ensuring uniform silver ion distribution in subsequent foaming and the foam layer.

[0029] The mechanism of action of sodium sulfate micronized powder lies in the significant difference in solubility between it and silver salts. Sodium sulfate has a solubility of approximately 19.5 grams per 100 milliliters in water at 25°C, while the solubility of silver salts such as silver sulfate and silver citrate is typically less than 1 gram per 100 milliliters—a difference of more than an order of magnitude. During manufacturing, pharmaceutical-grade sodium sulfate micronized powder is directly dispersed in a hydrophilic polyurethane prepolymer containing silver ions through stirring, forming a solid microparticle suspension, which is then uniformly embedded within the foam matrix. When the dressing comes into contact with wound exudate, sodium sulfate preferentially dissolves faster than silver salts, creating a high osmotic pressure environment in localized micro-regions within the foam pore walls, forming an osmotic pressure gradient from the inside of the matrix to the outside. This osmotic pressure effect drives water molecules to penetrate the foam matrix more rapidly and simultaneously promotes the diffusion and release of dissolved silver ions from within the matrix along the concentration gradient to the wound surface. This increases the effective release of silver ions and the drug release efficiency without increasing the amount of silver salt used.

[0030] S2: The silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1 is mechanically foamed. A foaming agent is added to the silver ion-containing hydrophilic polyurethane prepolymer and gas is introduced. A foam is formed under stirring conditions. The foaming temperature is controlled at 20-40°C, the stirring speed is 500-3000 rpm, and the foaming ratio is 2:1-6:1. The foaming agent is an organosilicon surfactant, and its addition amount is 0.5-5.0 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer.

[0031] Before mechanical foaming, a water-soluble porogen is added to the silver ion-containing hydrophilic polyurethane prepolymer. The water-soluble porogen is selected from polyethylene glycol or polyvinylpyrrolidone, with a molecular weight of 400-6000 Da, and the addition amount is 1-8 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer. This ensures that the water-soluble porogen is distributed in the cell walls of the dried silver ion-containing hydrophilic polyurethane foam layer. Upon contact with liquid, the water-soluble porogen dissolves and forms microchannels on the cell walls. The size and distribution density of the microchannels are controlled by adjusting the molecular weight and addition amount of the water-soluble porogen, thereby controlling the release rate of silver ions. The addition amount of the water-soluble porogen does not exceed 80% of its saturated solubility in water at 20-40°C.

[0032] Specifically, a foaming agent is added to a silver ion-containing prepolymer, and an inert gas or air is introduced under stirring conditions. Surfactant molecules adsorb at the gas-liquid interface, reducing surface tension and causing the gas to form numerous uniform bubble nuclei within the prepolymer. Continuous stirring causes the bubble nuclei to continuously split, refine, and distribute evenly, ultimately forming a stable wet foam. During this process, the Ag-containing... + The prepolymer forms a continuous phase in the cell walls, Ag + The silver ions are embedded in situ within the polymer matrix of the cell walls, rather than merely adhering to the cell surface. This is fundamentally different from post-processing impregnation methods: in impregnation, silver ions adhere to the inner and outer surfaces of the formed foam only through physical adsorption, while in this invention, the silver ions are three-dimensionally embedded in the polymer matrix. They are only released after the exudate penetrates into the matrix and dissolves, thus altering the release kinetics. Existing chemical foaming relies on the chemical reaction between isocyanate groups and water to generate CO2 gas. Bubble nucleation, growth, and polymer cross-linking and curing occur simultaneously, and the control of cell structure is limited by reaction kinetics. In mechanical foaming, bubble formation and polymer curing are independent in time and mechanism. The foaming ratio, pore size, and pore size distribution can be independently controlled by physical parameters such as stirring rate and gas flow rate, without being constrained by the degree of chemical reaction. This results in a wider process window and higher cell uniformity.

[0033] By adding a water-soluble porogen, the difference in solubility between the porogen and the polyurethane matrix is ​​utilized to construct auxiliary channels for silver ion release within the cell walls. During manufacturing, polyethylene glycol or polyvinylpyrrolidone is dissolved in a silver-ion-containing hydrophilic polyurethane prepolymer, achieving molecular-level dispersion. After mechanical foaming, the porogen is physically encapsulated within the polymer matrix of the cell walls. When the dressing comes into contact with wound exudate, the porogen in the cell walls preferentially dissolves and exudes, leaving microchannels ranging in size from submicron to several micrometers in situ. These microchannels significantly increase the number of pathways and the total specific surface area for exudate to penetrate into the cell wall matrix, allowing more silver ions within the matrix to contact and dissolve in the exudate, thereby increasing the effective release of silver ions without altering the silver ion release mechanism itself. The size and distribution density of the microchannels can be controlled by the molecular weight and dosage of the porogen: a larger molecular weight results in larger pore sizes after dissolution; a higher dosage results in a higher channel distribution density. By limiting the amount added to no more than 80% of the saturated solubility of the porogen at the foaming temperature, it can be ensured that the porogen is completely dissolved in the prepolymer system, forming a uniform molecular-level dispersion, and avoiding undissolved particles from affecting the integrity of the cell structure.

[0034] S3: The foam obtained in step S2 is coated onto a substrate and subjected to gradient drying to obtain a hydrophilic polyurethane foam layer containing silver ions with a water content not exceeding 5 wt%. The gradient drying process includes: drying at 40–55°C for 5–30 min, drying at 56–70°C for 10–60 min, and finally drying at 71–80°C to the stated water content. By controlling the temperature change rate of the gradient drying process, at least 30% of the silver ions in the dried hydrophilic polyurethane foam layer containing silver ions are present in a coordinated state with ether oxygen bonds and / or urethane groups in the polyurethane chain segments. The hydrophilic polyurethane foam layer containing silver ions has a porous structure with an average pore size of 50–500 μm and a cell distribution coefficient (CV) value ≤30%; the average pore size of the hydrophilic polyurethane foam layer containing silver ions is 100–300 μm, and the cell distribution coefficient (CV) value is 10%–25%.

[0035] Specifically, step S3 employs a three-stage gradient drying process to achieve long-term sustained release of silver ions. Its mechanism of action consists of the following three stages: The first stage, at a low temperature of 40–55℃, is the silver ion coordination induction period: the foam contains a large amount of aprotic solvent, which evaporates slowly at low temperatures to avoid violent boiling that could damage the cell structure. In this temperature range, the solvent gradually evaporates, and the prepolymer segments gradually shrink from an extended state, releasing Ag... + In a concentrated polymer matrix, Ag coordinates with the ether oxygen bond (COC) and urethane group (-NH-COO-) on the chain segments. + The empty orbitals of Ag accept lone pairs of electrons from oxygen and nitrogen atoms, forming coordinate bonds. Low temperature conditions favor a shift in the coordination equilibrium toward the coordination state (coordination reactions are usually exothermic processes), allowing more Ag to be released. + It exists stably in the polyurethane matrix in a coordinated state.

[0036] The second stage, at a medium temperature of 56–70℃, is the period of coordination state curing and structural stabilization: as the solvent is further reduced, the hydrogen bonds and van der Waals forces between polymer segments increase, and the porous framework structure of the foam gradually stabilizes. (Coordination state Ag) + Locked within a cross-linked polymer network, it forms a stable slow-release reservoir.

[0037] The third stage, the high-temperature range of 71-80℃, is the period of deep solvent removal and residual stress elimination: the water content and residual solvent are reduced to the target value of no more than 5wt% of the final water content, while eliminating residual stress in the foam structure to ensure the dimensional stability of the product.

[0038] After gradient drying, at least 30% of the silver ions exist in a coordinated state. Coordinated Ag +Release requires a decoordination reaction (ligand breakage) before diffusion to the wound surface via the matrix. The release rate is jointly controlled by decoordination kinetics and diffusion rate, compared to free Ag. + Its simple dissolution-diffusion process effectively prolongs the duration of its antibacterial effect.

[0039] S4: Provides a polyurethane film, with an adhesive layer formed by coating one side surface of the polyurethane film. The polyurethane film is a medical-grade, breathable polyurethane film with a thickness of 10–50 μm and a water vapor permeability of 500–2000 g / (m²). 2 •24h); The adhesive is a medical-grade pressure-sensitive adhesive.

[0040] S5: The polyurethane film coated with adhesive layer in step S4 and the silver ion-containing hydrophilic polyurethane foam layer obtained in step S3 are pressed together under a pressure of 0.1 to 0.5 MPa using an adhesive layer.

[0041] Specifically, steps S4-S5 involve bonding the silver ion-containing foam layer to the outer breathable polyurethane film using an adhesive layer. The water vapor permeability of the film layer is 500–2000 g / (m²). 2 (24h) It forms a semi-permeable membrane barrier that is "breathable but not water-permeable," allowing water vapor to pass through the wound and preventing exudate from seeping into the surrounding healthy skin; at the same time, it blocks external moisture and bacteria from entering, maintaining a sterile and moist environment for the wound. The foam layer provides exudate absorption and silver ion release, while the film layer provides physical protection and microenvironment regulation. The two are tightly bonded together by an adhesive layer under a pressure of 0.1–0.5 MPa, forming an integrated structure that is convenient for clinical use.

[0042] A silver ion antibacterial foam dressing is provided, prepared by the above-described manufacturing method. The silver ion antibacterial foam dressing comprises: The silver ion-containing hydrophilic polyurethane foam layer has a porous structure with an average pore size of 50–500 μm and a cell distribution coefficient (CV) value ≤30%. Silver ions are uniformly distributed within the silver ion-containing hydrophilic polyurethane foam layer, with the silver ion content expressed as Ag. + It is calculated to be 0.05–2.0 wt%; A polyurethane film layer is disposed on top of a silver ion-containing hydrophilic polyurethane foam layer. This polyurethane film layer is a medical-grade, breathable polyurethane film with a thickness of 10–50 μm and a water vapor permeability of 500–2000 g / (m²). 2 ·24h); An adhesive layer is disposed between the polyurethane film layer and the silver ion-containing hydrophilic polyurethane foam layer, bonding the polyurethane film layer and the silver ion-containing hydrophilic polyurethane foam layer into a single unit.

[0043] The average pore size of the silver ion-containing hydrophilic polyurethane foam layer is 100–300 μm, the cell distribution coefficient (CV) is 10%–25%, and the silver ion content is mainly Ag. + The content is 0.05–1.0 wt%; water-soluble porogens are distributed in the cell walls of the silver ion-containing hydrophilic polyurethane foam layer. The water-soluble porogens are selected from polyethylene glycol or polyvinylpyrrolidone, with a molecular weight of 400–6000 Da. The water-soluble porogens dissolve upon contact with liquid and form microchannels on the cell walls; sodium sulfate is also uniformly dispersed in the foam matrix of the silver ion-containing hydrophilic polyurethane foam layer. The sodium sulfate is embedded in the foam matrix in the form of micro powder. When in use, it preferentially dissolves upon contact with wound exudate, generating an osmotic pressure effect that drives the release of silver ions in the silver ion-containing hydrophilic polyurethane foam layer to the wound; the silver ions in the silver ion-containing hydrophilic polyurethane foam layer are selected from at least one silver salt selected from silver nitrate, silver perchlorate, silver trifluoromethanesulfonate, and silver tetrafluoroborate, and the silver ion content of the silver salt accounts for 40–80 wt% of the total mass of the silver salt.

[0044] To provide a clearer and more detailed description of the silver ion antibacterial foam dressing and its manufacturing method provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0045] Example 1 Step S1: Provide a hydrophilic polyurethane prepolymer containing silver ions; A hydrophilic polyurethane prepolymer was mixed uniformly with a silver nitrate N,N-dimethylformamide solution under stirring. Pharmaceutical-grade sodium sulfate powder was then added, and stirring continued to ensure the sodium sulfate powder was uniformly dispersed in the prepolymer, resulting in a hydrophilic polyurethane prepolymer containing silver ions and sodium sulfate powder. The hydrophilic polyurethane prepolymer was prepared by reacting isocyanate, polyether polyol, and a hydrophilic chain extender, with an isocyanate index of 2.0. The concentration of silver ions in the silver nitrate N,N-dimethylformamide solution was 0.05 mol / L. The amount of sodium sulfate powder added was 0.8% by weight of the silver ion-containing hydrophilic polyurethane prepolymer, and the mass ratio of sodium sulfate powder to silver salt was 0.9:1.

[0046] Step S2: Mechanical foaming; An organosilicon surfactant is added as a foaming agent to the silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1, and the amount added is 2.0% by weight of the silver ion-containing hydrophilic polyurethane prepolymer. Mechanical foaming is performed by introducing nitrogen gas at a foaming temperature of 25°C and a stirring speed of 1500 rpm, with the foaming ratio controlled at 3:1, to form a foamed body.

[0047] Step S3: Gradient drying to form a hydrophilic polyurethane foam layer containing silver ions; The foam obtained in step S2 was coated onto a release film and subjected to gradient drying. The gradient drying process consisted of drying at 45°C for 20 minutes, drying at 60°C for 30 minutes, and finally drying at 75°C until the water content was 3.2% by weight, resulting in a silver ion-containing hydrophilic polyurethane foam layer. The average pore size of this silver ion-containing hydrophilic polyurethane foam layer was 185 micrometers, the cell distribution coefficient (CV) was 18.5%, and the silver ion content was 0.35% by weight.

[0048] Step S4: Provide a polyurethane film and apply adhesive; A medical-grade breathable polyurethane film with a thickness of 25 micrometers and a water vapor permeability of 1200 grams per square meter per 24 hours is provided. A medical-grade pressure-sensitive adhesive is uniformly coated on one side surface of the polyurethane film to form an adhesive layer.

[0049] Step S5: Composite into one; The polyurethane film coated with adhesive layer in step S4 and the hydrophilic polyurethane foam layer containing silver ions obtained in step S3 are pressed together under a pressure of 0.3 MPa, and composited into one through the adhesive layer to obtain silver ion antibacterial foam dressing.

[0050] Example 2 Step S1: Provide a hydrophilic polyurethane prepolymer containing silver ions; A hydrophilic polyurethane prepolymer was mixed evenly with an acetone solution of silver trifluoromethanesulfonate under stirring. Then, pharmaceutical-grade sodium sulfate powder was added, and stirring continued to ensure the sodium sulfate powder was uniformly dispersed in the prepolymer, resulting in a hydrophilic polyurethane prepolymer containing silver ions and sodium sulfate powder. The hydrophilic polyurethane prepolymer was prepared by reacting isocyanate, polyether polyol, and a hydrophilic chain extender, with an isocyanate index of 2.5. The concentration of silver ions in the acetone solution of silver trifluoromethanesulfonate was 0.10 mol / L. The amount of sodium sulfate powder added was 1.5% by weight of the silver ion-containing hydrophilic polyurethane prepolymer, and the mass ratio of sodium sulfate powder to silver salt was 1.2:1.

[0051] Step S2: Mechanical foaming; An organosilicon surfactant is added as a foaming agent to the silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1, at a weight percentage of 3.5%. Mechanical foaming is performed by introducing air at a foaming temperature of 30°C and a stirring speed of 2000 rpm, with a foaming ratio controlled at 5:1, to form a foamed body.

[0052] Step S3: Gradient drying to form a hydrophilic polyurethane foam layer containing silver ions; The foam obtained in step S2 was coated onto a release film and subjected to a gradient drying process. The gradient drying process consisted of drying at 50°C for 15 minutes, drying at 65°C for 40 minutes, and finally drying at 78°C until the water content was 2.8% by weight, resulting in a silver ion-containing hydrophilic polyurethane foam layer. The average pore size of this silver ion-containing hydrophilic polyurethane foam layer was 260 micrometers, the cell distribution coefficient (CV) was 22.1%, and the silver ion content was 0.60% by weight.

[0053] Step S4: Provide a polyurethane film and apply adhesive; A medical-grade breathable polyurethane film with a thickness of 25 micrometers and a water vapor permeability of 1200 grams per square meter per 24 hours is provided. A medical-grade pressure-sensitive adhesive is uniformly coated on one side surface of the polyurethane film to form an adhesive layer.

[0054] Step S5: Combine into one unit; The polyurethane film coated with adhesive layer in step S4 and the hydrophilic polyurethane foam layer containing silver ions obtained in step S3 are pressed together under a pressure of 0.3 MPa, and then bonded together with adhesive layer to obtain silver ion antibacterial foam dressing.

[0055] Example 3 Step S1: Provide a hydrophilic polyurethane prepolymer containing silver ions; A hydrophilic polyurethane prepolymer was mixed uniformly with an acetonitrile solution of silver tetrafluoroborate under stirring. Then, pharmaceutical-grade sodium sulfate powder was added, and stirring continued to ensure the sodium sulfate powder was uniformly dispersed in the prepolymer, resulting in a hydrophilic polyurethane prepolymer containing silver ions and sodium sulfate powder. The hydrophilic polyurethane prepolymer was prepared by reacting isocyanate, polyether polyol, and a hydrophilic chain extender, with an isocyanate index of 3.0. The concentration of silver ions in the acetonitrile solution of silver tetrafluoroborate was 0.20 mol / L. The amount of sodium sulfate powder added was 2.0% by weight of the silver ion-containing hydrophilic polyurethane prepolymer, and the mass ratio of sodium sulfate powder to silver salt was 1.5:1.

[0056] Step S2: Mechanical foaming; An organosilicon surfactant is added as a foaming agent to the silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1, at a weight percentage of 1.5%. Mechanical foaming is performed by introducing nitrogen gas at a foaming temperature of 22°C and a stirring speed of 800 rpm, with a foaming ratio controlled at 2.5:1, to form a foamed body.

[0057] Step S3: Gradient drying to form a hydrophilic polyurethane foam layer containing silver ions; The foam obtained in step S2 was coated onto a release film and subjected to gradient drying. The gradient drying process consisted of drying at 42°C for 25 minutes, drying at 55°C for 50 minutes, and finally drying at 72°C until the water content was 4.5% by weight, resulting in a silver ion-containing hydrophilic polyurethane foam layer. The average pore size of this silver ion-containing hydrophilic polyurethane foam layer was 120 micrometers, the cell distribution coefficient (CV) was 14.8%, and the silver ion content was 0.85% by weight.

[0058] Step S4: Provide a polyurethane film and apply adhesive; A medical-grade breathable polyurethane film with a thickness of 25 micrometers and a water vapor permeability of 1200 grams per square meter per 24 hours is provided. A medical-grade pressure-sensitive adhesive is uniformly coated on one side surface of the polyurethane film to form an adhesive layer.

[0059] Step S5: Combine into one unit; The polyurethane film coated with adhesive layer in step S4 and the hydrophilic polyurethane foam layer containing silver ions obtained in step S3 are pressed together under a pressure of 0.3 MPa, and then bonded together with adhesive layer to obtain silver ion antibacterial foam dressing.

[0060] Comparative Example 1 A chemical foaming method was employed, with the following steps: An aqueous phase containing a surfactant and silver nitrate was prepared, wherein the total amount of silver ions was equivalent to that in Example 1. A terminal isocyanate polyether with a functionality of 2.8 was provided. The aqueous phase and the terminal isocyanate polyether were mixed and immediately transferred to a mold. Foaming was achieved by reacting water with the isocyanate to generate carbon dioxide gas. After molding, the foam was dried at a single temperature of 70°C until the water content reached 8.5% by weight, yielding a silver-containing foam layer. This silver-containing foam layer had an average pore size of 310 micrometers, a cell distribution coefficient (CV) of 42.6%, and a silver ion content of 0.33% by weight. This silver-containing foam layer was then laminated with a medical-grade breathable polyurethane film in the same manner as in Example 1 to obtain a foam dressing.

[0061] Comparative Example 2 The post-treatment impregnation method was adopted, with the following steps: using the same hydrophilic polyurethane prepolymer and silicone surfactant as in Example 1, but without adding silver salt, foaming was performed under the same mechanical foaming conditions as in Example 1 to obtain a foamed body. After coating the foamed body, it was dried at a single temperature of 70°C until the water content was 3.0% by weight, obtaining a blank hydrophilic polyurethane foam layer. This blank hydrophilic polyurethane foam layer was impregnated in a silver nitrate aqueous solution, and after removing it, excess liquid was squeezed off. It was then dried at 60°C until the water content was 3.5% by weight, obtaining a silver-containing foam layer. The average pore size of this silver-containing foam layer was 190 micrometers, the cell distribution coefficient (CV) was 20.1%, and the silver ion content (calculated as silver ions) was 0.36% by weight. This silver-containing foam layer was then composited with a medical-grade breathable polyurethane film in the same manner as in Example 1 to obtain a foam dressing.

[0062] Comparative Example 3 Using a single-temperature drying process, step S1: providing a hydrophilic polyurethane prepolymer containing silver ions; A hydrophilic polyurethane prepolymer containing silver ions was prepared using the same method as in Example 1, wherein the concentration of silver ions was 0.05 mol / L and the isocyanate index was 2.0.

[0063] Step S2: Mechanical foaming; Mechanical foaming was performed in the same manner as in Example 1, with a foaming temperature of 25°C, a stirring rate of 1500 rpm, and a foaming ratio of 3:1 to form a foamed body.

[0064] Step S3: Dry at a single temperature to form a hydrophilic polyurethane foam layer containing silver ions; The foam obtained in step S2 was coated onto a release film and dried directly at a single temperature of 70°C until the water content was 3.1% by weight, resulting in a silver ion-containing hydrophilic polyurethane foam layer. The average pore size of this silver ion-containing hydrophilic polyurethane foam layer was 192 micrometers, the cell distribution coefficient (CV) was 19.2%, and the silver ion content was 0.34% by weight.

[0065] Steps S4 and S5: A polyurethane film is provided, an adhesive is applied, and the mixture is laminated in the same manner as in Example 1 to obtain a silver ion antibacterial foam dressing.

[0066] Comparative Example 4 Step S1: Provide a hydrophilic polyurethane prepolymer containing silver ions; A hydrophilic polyurethane prepolymer containing silver ions was obtained by using the same method as in Example 1.

[0067] Step S2: Mechanical foaming; No silicone surfactants are added to the silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1. Nitrogen gas is introduced for mechanical foaming under a stirring speed of 300 rpm. The foaming ratio is controlled at 3:1 and the foaming temperature is 25°C to form a foam.

[0068] Step S3: Gradient drying to form a hydrophilic polyurethane foam layer containing silver ions; The same gradient drying regime as in Example 1 was used: drying at 45°C for 20 minutes, then at 60°C for 30 minutes, and finally at 75°C until the moisture content was 3.4% by weight, to obtain a silver ion-containing hydrophilic polyurethane foam layer. This silver ion-containing hydrophilic polyurethane foam layer had an average pore size of 420 micrometers, a cell distribution coefficient (CV) of 48.3%, and a silver ion content of 0.33% by weight.

[0069] Steps S4 and S5: A polyurethane film is provided, an adhesive is applied, and the mixture is laminated in the same manner as in Example 1 to obtain a silver ion antibacterial foam dressing.

[0070] Performance testing: In the following tests, the samples of each embodiment and comparative example were cut to a size of 5 cm × 5 cm and a thickness of 3 mm. Each test was performed in parallel three times, and the average value of the results was taken.

[0071] Silver ion release performance test: The sample was placed in simulated wound exudate at 37℃. The simulated wound exudate consisted of 0.9% sodium chloride, 0.1% calcium chloride, and 0.05% magnesium chloride by mass / volume percentage, with a pH of 7.4. The release medium was collected at 1 hour, 6 hours, 24 hours, 72 hours, and 168 hours, and the cumulative percentage of silver ions released was measured. The results are shown in Table 1.

[0072] Table 1. Cumulative release rate of silver ions (unit: percentage)

[0073] As shown in Table 1, the cumulative silver ion release rates of Examples 1 to 3 were 12.5%, 14.2%, and 10.8% after 1 hour, respectively; 52.7%, 56.8%, and 48.3% after 24 hours; and 92.1%, 94.6%, and 89.8% after 168 hours, respectively. Comparative Example 2 released 45.3% after 1 hour, reached 89.2% after 24 hours, and was nearly completely released (99.5%) after 168 hours, exhibiting a significant burst release phenomenon. Comparative Example 1 released 28.7% after 1 hour and reached 78.9% after 24 hours, with a release rate significantly faster than the examples. Comparative Example 3 released 26.1% after 1 hour and reached 76.5% after 24 hours, with a sustained-release effect between the examples and Comparative Example 1, but significantly less than the examples. It is evident that the process combination of "introducing silver ions into the prepolymer phase combined with mechanical foaming and gradient drying" can significantly delay the initial release rate of silver ions, achieving a continuous release for up to 7 days.

[0074] Antibacterial performance test: The inhibition zone method was used. Samples were attached to agar plates inoculated with Staphylococcus aureus and incubated at 37°C for 24 hours. The diameter of the inhibition zone was measured. The same sample was continuously transferred to freshly inoculated plates, and measurements were taken daily for 7 consecutive days. The results are shown in Table 2.

[0075] Table 2. Diameter of inhibition zone (Staphylococcus aureus)

[0076] The units in the table above are millimeters.

[0077] As shown in Table 2, the inhibition zone diameters of Examples 1 to 3 on day 7 were 14.5 mm, 15.3 mm, and 14.0 mm, respectively, maintaining effective antibacterial activity. Comparative Example 2's inhibition zone shrank to 3.5 mm on day 5 and had no inhibition zone on day 7, indicating an antibacterial effective period of less than 5 days. Comparative Example 1's inhibition zone on day 7 was only 4.1 mm, showing a significant decrease in antibacterial activity. Comparative Example 3's inhibition zone on day 7 was 7.8 mm, a significant decrease compared to the other examples. The Pseudomonas aeruginosa test also confirmed this trend, as shown in Table 3 below. Example 1 maintained a 12.5 mm inhibition zone on day 7, while Comparative Example 2 had no inhibition zone. It is evident that the products in these examples have a significant advantage in extending the effective antibacterial time, with an effective antibacterial period of more than 7 days.

[0078] The inhibition zone test of Pseudomonas aeruginosa was performed on Example 1 and Comparative Example 2, and the results are shown in Table 3.

[0079] Table 3. Diameter of inhibition zone (Pseudomonas aeruginosa)

[0080] The units in the table above are millimeters.

[0081] Exudate absorption and liquid retention performance tests: The sample was immersed in simulated wound exudate at 37℃ for 30 minutes, and the absorption ratio was measured. The absorption ratio is the ratio of the mass of the sample after absorbing exudate to its initial dry mass, expressed in grams per gram (g / g). The absorbed sample was then placed under a pressure of 40 mmHg for 5 minutes, and the amount of liquid re-exuded from the sample was measured in grams per 100 square centimeters (g / cm²). Simultaneously, the water vapor transmission rate on one side of the polyurethane film was measured in grams per square meter per 24 hours (g / m²). The results are shown in Table 4.

[0082] Table 4 Absorption and Liquid Locking Properties

[0083] As shown in Table 4, the absorption rates of Examples 1 to 3 were 15.8 g / g, 18.2 g / g, and 13.5 g / g, respectively, all higher than the 11.2 g / g of Comparative Example 1. Regarding liquid retention performance, the reabsorption amounts of Examples 1 to 3 were 0.8 g / 100 cm², 1.1 g / 100 cm², and 0.6 g / 100 cm², respectively, all significantly lower than the 2.5 g / 100 cm² of Comparative Example 1 and the 2.8 g / 100 cm² of Comparative Example 4. This demonstrates that the uniform cell structure obtained through mechanical foaming simultaneously improves both absorption capacity and liquid retention ability, while chemical foaming (Comparative Example 1) and non-uniform cell structure (Comparative Example 4) both lead to increased reabsorption, increasing the risk of skin maceration around the wound.

[0084] Cell uniformity and silver ion release uniformity tests: Samples from Example 1, Comparative Example 1, and Comparative Example 4 were each cut into four equal-area regions. The cumulative silver ion release rate of each region was tested over 24 hours, and the coefficient of variation of the release rate in each region was calculated. Simultaneously, the pore distribution coefficient (CV) of the samples was determined. The results are shown in Table 5.

[0085] Table 5 Release Uniformity

[0086] As shown in Table 5, the CV value of Example 1 was 18.5%, and the 24-hour release rate ranged from 51.2% to 54.8% in the four regions, with a coefficient of variation of only 3.2%, indicating highly consistent release behavior. Comparative Example 1 had a CV value of 42.6%, with release rates ranging from 68.3% to 85.7% in each region and a coefficient of variation of 12.8%, showing a difference in release rates exceeding 17 percentage points within each region. Comparative Example 4 had a CV value of 48.3%, with release rates ranging from 62.5% to 80.4% in each region and a coefficient of variation of 14.5%. These data demonstrate that quantitative control of the CV value is crucial for ensuring the consistency of silver ion release in different regions of the product. The CV value limit of ≤30% effectively solves the problem of uneven local release caused by uneven pore size.

[0087] Biocompatibility testing: Cytotoxicity tests were performed on the samples from Example 1 according to GB / T16886.5, and the relative cell viability was determined using L929 cells and the MTT assay; skin irritation and sensitization tests were performed according to GB / T16886.10. The results are shown in Table 6.

[0088] Table 6 Biocompatibility

[0089] As shown in Table 6, the relative cell viability of Example 1 was 92.5%, higher than the 70% qualification standard; the skin irritation index was 0.2, lower than the 1.0 qualification standard; and the sensitization reaction was negative. These data indicate that the product of this invention has low cytotoxicity, no skin irritation or sensitization, and meets the safety requirements for medical dressings in the GB / T16886 series standards.

[0090] Therefore, this invention employs the aforementioned silver ion antibacterial foam dressing and its manufacturing method. Silver ions are introduced into the hydrophilic polyurethane prepolymer phase before foaming. Through mechanical foaming, the silver-containing prepolymer is transformed into a continuous phase within the cell walls. Silver ions are uniformly embedded within the cell wall matrix rather than adhering to the surface, fundamentally altering the spatial distribution and release kinetics of silver ions. Release tests show that the product of this invention releases only 12.5% ​​after 1 hour, 52.7% after 24 hours, and continuous release is still detectable after 168 hours (7 days), extending the effective antibacterial time to over 7 days and improving antibacterial durability by more than 2 times. Simultaneously, EDS energy dispersive spectroscopy analysis confirms that silver elements are uniformly distributed in the foam cross-section, solving the problem of silver concentration gradients from the surface to the interior in the impregnation method.

[0091] This invention upgrades drying from a simple dehydration step to a key process for regulating the kinetics of silver ion release. Current drying methods only target the final moisture content, neglecting the impact of temperature on the chemical state and release behavior of silver ions. This invention employs a three-stage gradient drying process. The slow dehydration at low temperatures provides sufficient coordination time for silver ions to interact with the ether oxygen bonds and urethane groups on the polyurethane segments, ensuring that at least 30% of the silver ions remain stably in the polymer matrix in a coordinated state. The release of coordinated silver ions requires a two-step process of decoordination and diffusion. The release rate is jointly controlled by decoordination kinetics and diffusion rate, significantly extending the duration of antibacterial activity compared to the simple dissolution and diffusion of free silver ions. Comparative Example 3, dried at a single temperature of 70°C, showed a silver ion release rate of 26.1% after 1 hour, compared to only 12.5% ​​in this invention; 76.5% after 24 hours, compared to 52.7% in this invention; and a significant decrease in antibacterial activity after 7 days compared to this invention. This demonstrates the crucial role of gradient drying in regulating the silver ion release rate.

[0092] By limiting the CV value to ≤30%, the high uniformity of the pore structure was ensured, thereby guaranteeing consistent exudate permeation rates and silver ion release rates across all regions. Example 1, with a CV value of 18.5%, had a coefficient of variation of only 3.2% for 24-hour silver ion release rates in different regions. In contrast, Comparative Example 4, with a CV value exceeding the limit (48.3%), exhibited a wide range of release rates (62.5%–80.4%) across different regions, with a coefficient of variation of 14.5%, indicating a localized release rate difference exceeding 17 percentage points. Clinically, this difference suggests that some areas may experience antibacterial failure due to insufficient silver concentration, while others may exhibit excessively high silver concentrations leading to cytotoxicity.

[0093] The formulation consists of three components: medical-grade polyurethane, silver salt, and a small amount of surfactant. All raw materials are mature medical-grade materials already available in similar marketed products. Biocompatibility evaluation is simple, there is no risk of cross-reaction among multiple components, production costs are controllable, and it is easy to achieve large-scale production. The overall performance of the product reaches and in some aspects surpasses the level of existing similar products. Long-lasting antibacterial effect: The cumulative release rate of silver ions was 92.1% after 168 hours, and the diameter of the inhibition zone remained at 14.5 mm after 7 days, which was significantly better than Comparative Example 1 and Comparative Example 2. Highly efficient absorption: Absorption rate of 15.8g / g, with a reabsorption rate of only 0.8g / 100cm³. 2 It is significantly superior to the chemical foaming method in Comparative Example 1; Uniform release: The coefficient of variation of the release rate in each area over 24 hours is 3.2%, ensuring consistent antibacterial effect in all areas of the wound; Biosafety: Relative cell survival rate 92.5%, skin irritation index 0.2, negative sensitization reaction, and all indicators meet the GB / T16886 series standards.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for manufacturing a silver ion antibacterial foam dressing, characterized by, Includes the following steps: S1: Provides a hydrophilic polyurethane prepolymer containing silver ions, wherein silver ions are uniformly dispersed in the hydrophilic polyurethane prepolymer in the form of an aprotic solvent solution of silver salt, the hydrophilic polyurethane prepolymer is prepared by reacting isocyanate, polyol and hydrophilic chain extender, the isocyanate index is 1.5 to 3.5; the aprotic solvent is selected from at least one of acetone, butanone, N,N-dimethylformamide and N-methylpyrrolidone; S2: Mechanically foam the silver ion-containing hydrophilic polyurethane prepolymer obtained in step S1. Add a foaming agent and introduce gas into the silver ion-containing hydrophilic polyurethane prepolymer to form a foam under stirring conditions. Control the foaming temperature to be 20-40℃, the stirring speed to be 500-3000 rpm, and the foaming ratio to be 2:1-6:

1. S3: The foam obtained in step S2 is coated onto the substrate and subjected to gradient drying treatment to obtain a hydrophilic polyurethane foam layer containing silver ions with a water content of no more than 5 wt%. The gradient drying treatment includes drying at 40-55°C for 5-30 min, drying at 56-70°C for 10-60 min, and finally drying at 71-80°C to the stated water content. S4: Provide a polyurethane film, and apply an adhesive to one side surface of the polyurethane film to form an adhesive layer. The polyurethane film is a medical-grade breathable polyurethane film. S5: The polyurethane film coated with adhesive layer in step S4 and the silver ion-containing hydrophilic polyurethane foam layer obtained in step S3 are bonded together by adhesive layer.

2. The method for manufacturing a silver ion antibacterial foam dressing according to claim 1, characterized in that, The hydrophilic polyurethane prepolymer containing silver ions in step S1 is prepared by mixing the hydrophilic polyurethane prepolymer with an aprotic solvent solution of silver salt under stirring conditions. The concentration of silver ions in the silver salt solution is 0.01-0.5 mol / L.

3. The method for manufacturing a silver ion antibacterial foam dressing according to claim 2, characterized in that, In step S1, the silver ion-containing hydrophilic polyurethane prepolymer also contains sodium sulfate micropowder. The sodium sulfate micropowder is introduced in the following way: pharmaceutical grade sodium sulfate micropowder is directly added to the silver ion-containing hydrophilic polyurethane prepolymer and stirred to disperse evenly; the amount of sodium sulfate micropowder added is 0.1 to 3 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer, and the mass ratio of sodium sulfate micropowder to silver salt is 1:5 to 3:1; the sodium sulfate micropowder is evenly dispersed and embedded in the foam matrix of the silver ion-containing hydrophilic polyurethane foam layer.

4. The method for manufacturing a silver ion antibacterial foam dressing according to claim 1, characterized in that, In step S2, the foaming agent is an organosilicon surfactant, and its addition amount is 0.5 to 5.0 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer; in step S3, the average pore size of the silver ion-containing hydrophilic polyurethane foam layer is 100 to 300 μm, and the cell distribution coefficient CV value is 10% to 25%.

5. The method for manufacturing a silver ion antibacterial foam dressing according to claim 1, characterized in that, Before mechanical foaming in step S2, a water-soluble porogen is added to the silver ion-containing hydrophilic polyurethane prepolymer. The water-soluble porogen is selected from polyethylene glycol or polyvinylpyrrolidone, with a molecular weight of 400-6000 Da, and the amount added is 1-8 wt% of the mass of the silver ion-containing hydrophilic polyurethane prepolymer.

6. The method for manufacturing a silver ion antibacterial foam dressing according to claim 5, characterized in that, The amount of water-soluble porogen added shall not exceed 80% of its saturated solubility in water at 20–40°C.

7. The method for manufacturing a silver ion antibacterial foam dressing according to claim 1, characterized in that, In step S4, the adhesive is a medical-grade pressure-sensitive adhesive; in step S5, the bonding condition is to press the adhesive together under a pressure of 0.1 to 0.5 MPa.

8. A silver ion antibacterial foam dressing, characterized in that, It is obtained by the manufacturing method according to any one of claims 1-7.

9. The silver ion antibacterial foam dressing according to claim 8, characterized in that, include: The silver ion-containing hydrophilic polyurethane foam layer has a porous structure with an average pore size of 50-500 μm, a pore distribution coefficient CV value of ≤30%, and silver ions uniformly distributed in the silver ion-containing hydrophilic polyurethane foam layer, with a silver ion content of 0.05-2.0 wt% as Ag + ​ A polyurethane film layer is arranged on the upper side of the silver ion-containing hydrophilic polyurethane foam layer, the polyurethane film layer is a medical-grade breathable polyurethane film, the thickness is 10-50 μm, the water vapor transmission rate is 500-2000 g / (m 2 ·24h); An adhesive layer is disposed between the polyurethane film layer and the silver ion-containing hydrophilic polyurethane foam layer, bonding the polyurethane film layer and the silver ion-containing hydrophilic polyurethane foam layer into a single unit.

10. A silver ion antibacterial foam dressing according to claim 9, characterized in that, The cell walls of the silver ion-containing hydrophilic polyurethane foam layer contain a water-soluble porogen selected from polyethylene glycol or polyvinylpyrrolidone, with a molecular weight of 400-6000 Da. Sodium sulfate is also uniformly dispersed in the foam matrix of the silver ion-containing hydrophilic polyurethane foam layer, and the sodium sulfate is embedded in the foam matrix in the form of micro powder. The silver ions in the silver ion-containing hydrophilic polyurethane foam layer are selected from at least one silver salt selected from silver nitrate, silver perchlorate, silver trifluoromethanesulfonate, and silver tetrafluoroborate, and the silver ion content of the silver salt accounts for 40-80 wt% of the total mass of the silver salt.

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