Composite Janus dressing with microporous structure as well as preparation method and application of composite Janus dressing

Abstract

The invention discloses a composite Janus dressing with a microporous structure as well as a preparation method and application of the composite Janus dressing, and belongs to the technical field of medical instruments. The dressing comprises an electrostatic spinning polycaprolactone hydrophobic membrane layer, a polyvinyl alcohol-tannic acid hydrogel layer and a tannic acid loaded shellac-gelatin-based porous sponge hydrophilic layer which are sequentially laminated and combined, wherein the composite Janus dressing is provided with a plurality of pore structures which penetrate through the hydrophobic membrane layer, the hydrogel layer and the porous sponge hydrophilic layer, and a liquid and medicine transmission channel is formed. The invention further provides a preparation method of the dressing and application of the dressing in preparation of medical instruments for promoting healing of chronic diabetic wounds or treating bacterial infectious wounds.

Description

Technical Field

[0001] This invention relates to the field of medical dressing technology, specifically to a composite Janus dressing with a microporous structure, its preparation method, and its application. Background Technology

[0002] Chronic wounds, such as diabetic ulcers, arterial / venous ulcers, pressure ulcers, and non-healing surgical wounds, are difficult to heal due to persistent inflammation, bacterial biofilm formation, excessive exudation, and impaired tissue regeneration, placing a heavy burden on global healthcare systems. Excessive wound exudate soaks the surrounding skin, damages new tissue, and provides an environment for bacterial growth; while repeated infections and persistent inflammation further hinder the healing process.

[0003] Traditional dressings commonly used in clinical practice (such as gauze and sponges) are mostly passive coverings, which tend to stick to the wound after absorbing liquid, causing secondary damage during dressing changes. While advanced dressings such as hydrogels and films can provide a moist environment, their inherent high hydrophilicity may lead to excessive moisture in the wound, and their single drug release mode makes it difficult to dynamically respond to changes in the wound microenvironment. Although negative pressure wound therapy can actively drain, the system is complex, costly, and may cause pain and bleeding.

[0004] Janus materials, due to their asymmetric physical or chemical properties (such as hydrophilicity / hydrophobicity) on both sides, have shown great potential for directional fluid management. In recent years, researchers have developed various Janus dressings aimed at achieving unidirectional drainage of exudate from the wound surface. However, existing technologies generally suffer from the following bottlenecks:

[0005] (1) Weak interlayer bonding: The polarity difference between the hydrophilic and hydrophobic layers leads to weak interfacial bonding, and interlayer delamination is prone to occur in dynamic wound environments (such as friction and swelling).

[0006] (2) Poor functional synergy: Most designs focus on unidirectional liquid discharge and fail to organically combine efficient exudate management with intelligent and controllable drug release. Drugs are mostly released through simple encapsulation, and their release kinetics and exudate flow process lack synergy, making it impossible to achieve the linkage between "exudate drainage" and "drug delivery".

[0007] (3) Insufficient structural integrity: Multi-layer composites or material doping to achieve multifunctionality often sacrifice the mechanical strength, breathability or structural uniformity of the dressing.

[0008] Therefore, developing a novel dressing that is structurally robust, easy to prepare, and capable of synergistically achieving efficient directional exudate management and on-demand active drug delivery is of great significance for promoting chronic wound healing. Summary of the Invention

[0009] The purpose of this invention is to provide a composite Janus dressing with a microporous structure, which solves the problems of weak interlayer bonding, uncontrollable liquid transport, and low drug release efficiency in the prior art.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a composite Janus dressing with a microporous structure, comprising, sequentially layered, an electrospun polycaprolactone (PCL) hydrophobic film layer, a polyvinyl alcohol-tannic acid (PVA-TA) hydrogel layer, and a shellac-gelatin-based porous sponge hydrophilic layer loaded with tannic acid. The composite Janus dressing has multiple pore structures penetrating the hydrophobic film layer, the hydrogel layer, and the porous sponge hydrophilic layer, forming channels for the transport of liquids and drugs.

[0011] Preferably, the pore structure is a conical pore formed by mechanical puncture of the hydrophobic membrane layer from one side with a conical needle; the conical pore penetrates the hydrophobic membrane layer and the hydrogel layer, and is interconnected with the inherent microporous network of the hydrophilic layer of the porous sponge itself; this structure, through the synergistic effect of physical barriers, capillary forces, and concentration gradients, coordinates the processes of "liquid extraction" and "drug delivery" in space and time. Regarding directional water delivery, the micropore array formed by the metal needle puncture constructs a physical "channel" on the continuous PCL hydrophobic barrier, allowing wound exudate to bypass the hydrophobic barrier and be rapidly captured and stored by the strong capillary force and osmotic pressure difference of the underlying superhydrophilic sponge. Regarding the controlled backflow release of tannic acid, driven by the concentration gradient formed between the sponge layer and the wound, tannic acid molecules slowly and continuously diffuse backward to the wound surface through the macroporous network of the sponge, the PVA-TA hydrogel, and the nanoscale pores of the PCL layer. The nanopores of the hydrogel and the microporous array of the PCL layer together constitute a multi-level physical regulation system for the diffusion rate of tannic acid, while the initial loading of tannic acid determines the concentration gradient of diffusion. This design allows early drainage to rapidly remove excess exudate while initiating the backflow and release of tannic acid. As exudate decreases, drainage weakens, but the continuous release of tannic acid is maintained, thus achieving spatiotemporal synergy between "physical cleansing" and "chemotherapy" to jointly optimize the wound healing microenvironment.

[0012] More preferably, on the surface of the hydrophobic film layer, the conical pores form a micropore array with a pore size of 0.2~0.8 mm and a pore density of 12~45 pores / cm²; in the hydrogel layer, the pore size of the conical pores is 807.2 ± 28.8 nm. This pore size and density range ensures sufficient transport efficiency while avoiding excessive pores that reduce the mechanical strength of the dressing.

[0013] Preferably, the PCL hydrophobic film layer is composed of smooth, randomly oriented fibers with an average fiber diameter of 4.1 ± 0.2 μm and a water contact angle of 123 ± 4°; the PVA-TA hydrogel layer has a thickness of 0.05-0.9 mm, more preferably 0.1 mm, and a water contact angle of 62 ± 7°; the shellac-gelatin-based porous sponge layer has a thickness of 4-10 mm, more preferably 7 mm, an average pore size of 82.4 ± 26.5 μm, and a water contact angle of 27 ± 3°.

[0014] The present invention also provides a method for preparing the above-mentioned composite Janus dressing with a microporous structure, comprising the following steps: (1) Prepare electrospun PCL hydrophobic film, PVA-TA hydrogel intermediate layer and shellac-gelatin based porous sponge hydrophilic layer loaded with tannic acid respectively; (2) The PVA-TA hydrogel is coated on the PCL hydrophobic membrane, and then the porous sponge is stacked on the hydrogel to form an integral three-layer substrate; (3) A micropore array is prepared by mechanically perforating the polycaprolactone hydrophobic film layer and hydrogel layer obtained in step (1) with a cone-shaped tool, thereby forming multiple pore structures penetrating the three-layer structure on the composite dressing in step (2). The mechanical perforation is a puncture treatment performed from one side of the PCL hydrophobic film layer.

[0015] Preferably, the pore size of the pore structure formed in step (3) gradually decreases from the hydrophobic layer to the hydrogel intermediate layer, and the pore size of the micropore array prepared by puncturing the surface of the PCL hydrophobic film layer is 0.2-0.8 mm, and the pore density is 12-45 pores / cm². 2 The pore size of the polyvinyl alcohol-tannic acid hydrogel layer is 807.2 ± 28.8 nm.

[0016] Preferably, the pore size of the shellac-gelatin-based porous sponge hydrophilic layer loaded with tannic acid is 82.4 ± 26.5 μm.

[0017] Preferably, in step (1), when preparing the PCL hydrophobic film layer, an electrospinning process is used. The concentration of the PCL solution used is 15~25wt%, the solvent is a mixture of dichloromethane and N,N-dimethylformamide, and the spinning parameters are: needle size 18~24, ambient temperature 20~30℃, electric field strength 12~18 kV, distance between the needle and the collector 10~20 cm, and solution propulsion flow rate 0.3~0.6 mL / h. -1 A hydrophobic polycaprolactone membrane was collected.

[0018] Preferably, the method for preparing the tannic acid-loaded shellac-gelatin-based porous sponge hydrophilic layer in step (1) is as follows: shellac is dissolved in an ammonia solution at 45~60℃, followed by the addition of gelatin and tannic acid. After stirring evenly, the mixture is pre-frozen at -20 to -30℃ and then freeze-dried to form a porous sponge. The mass ratio of shellac, gelatin and tannic acid is 12:3:0.2~1.0.

[0019] Preferably, the method for preparing the polyvinyl alcohol-tannic acid (PVA-TA) hydrogel intermediate layer in step (1) is as follows: tannic acid is added to an aqueous solution of polyvinyl alcohol, reacted at 90-100℃ for 1.5-2 hours, allowed to stand and cool at room temperature for 20-24 hours, and the upper layer of free water is discarded to obtain the polyvinyl alcohol-tannic acid (PVA-TA) hydrogel. The mass ratio of polyvinyl alcohol to tannic acid is 5:3.

[0020] The present invention also provides the application of the above-mentioned composite Janus dressing with microporous structure in the preparation of medical devices for promoting the healing of chronic wounds or treating bacterial infected wounds.

[0021] Preferably, the chronic wounds include chronic wounds such as diabetic ulcers, arterial / venous ulcers, pressure ulcers, and non-healing surgical wounds.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The structure is robust, solving the problem of interlayer separation: PVA-TA hydrogel is introduced as an adhesive interlayer. Hydrogen bonds are formed between the phenolic hydroxyl groups of tannic acid and the ester groups of polycaprolactone, and the amino groups of shellac-gelatin. These hydrogen bonds and other intermolecular forces firmly bind the hydrophobic PCL membrane to the hydrophilic sponge, significantly enhancing interlayer adhesion. Cross-sectional SEM images show a dense, crack-free interface, ensuring the structural integrity and long-term reliability of the dressing in dynamic wound environments.

[0023] Synergistic Functional Integration for "Drainage-Drug Delivery": This invention utilizes a process of "composite material preparation followed by microporous array fabrication" to construct a continuously varying channel spanning three layers. This structure, combined with the inherent wettability gradient of the materials (PCL hydrophobic, hydrogel moderately hydrophilic, sponge superhydrophilic), not only creates a pathway for the rapid, directional transport of exudate from the wound surface (PCL side) to the reservoir sponge (at a rate up to 6.36 μL·s⁻¹), but also simultaneously provides a channel for the drug (tannic acid) stored in the sponge to diffuse / recirculate back to the wound surface. This design achieves dynamic synergy and spatiotemporal coupling between physically directional exudate drainage and chemically controlled drug release.

[0024] Excellent performance, with active treatment capabilities: Highly efficient liquid management: Excellent directional transport capability, far exceeding that of non-microporous array dressings (nearly 80 times faster). The sponge layer's ultra-large pore network provides high absorbency.

[0025] Controllable drug reflux and release: The reflux volume and rate of tannic acid can be precisely controlled by the pore size and number of micropore arrays and the drug loading in the sponge (the reflux concentration can reach up to 88.44 mg·mL⁻¹ within 1 hour), realizing on-demand drug delivery.

[0026] Broad-spectrum antibacterial: Controlled reflux and release of tannic acid provides sustained antibacterial effect, with inhibition rates of over 93% against both Escherichia coli and Staphylococcus aureus.

[0027] Good biocompatibility: Cell experiments show no cytotoxicity and can promote cell proliferation.

[0028] Significantly promotes healing: In a diabetic mouse model of full-thickness skin defects, the dressing of this invention can significantly accelerate wound closure, promote granulation tissue growth and angiogenesis, and induce early signs of skin appendage regeneration, demonstrating excellent ability to promote full-thickness healing.

[0029] The preparation process is simple and easy to adapt: ​​the method uses mature processes such as electrospinning and freeze-drying to prepare each layer, and finally achieves the construction of key functional structures through simple mechanical perforation. The process route is simple and controllable, making it suitable for large-scale production. Attached Figure Description

[0030] Figure 1 Photographs of hydrogel (A), PCL electrospun membrane (B), sponge (C), and Janus dressing (D).

[0031] Figure 2 Scanning electron microscope (SEM) images of PCL membrane (A), sponge (B), hydrogel (C), and Janus dressing (D).

[0032] Figure 3 The changes in water contact angle on different sides of the membranes prepared in Comparative Example 1 and Example 5 (A) and the quantitative changes in water contact angle on different sides (B).

[0033] Figure 4 To investigate the effect of different pore numbers on the water absorption rate of Janus dressings under the condition of the same pore size.

[0034] Figure 5 To investigate the effect of different pore sizes on the water absorption rate of Janus dressings with the same number of pores.

[0035] Figure 6 The effect of different hydrogel thicknesses on the water absorption rate of Janus dressing.

[0036] Figure 7 The effect of different sponge thicknesses on the water absorption rate of Janus dressing.

[0037] Figure 8 Comparison of the backflow phenomenon of Janus dressings prepared in Comparative Example 1 and Example 5.

[0038] Figure 9 The effects of different pore sizes on the TA reflux concentration of Janus dressing within 60 min, with the same number of pores (A) and the effects of different pore numbers on the TA reflux concentration of Janus dressing with the same pore size (B).

[0039] Figure 10 The effect of different TA addition amounts on reflux behavior is shown in the figure, where A represents the TA concentration in the reflux solution at different times, B represents the total TA reflux mass at different times, C represents the TA reflux rate at different times, and H represents the total TA reflux rate at different times. Figure 11 The antibacterial rate of Janus dressing against Escherichia coli and Staphylococcus aureus.

[0040] Figure 12 The proliferation rates of L929 cells in the control group and the groups with different concentrations of Janus dressing in Experiment Example 2 were measured at 24, 48, and 72 hours, respectively.

[0041] Figure 13 The images show photographs and schematic diagrams of the wounds in the experimental and control groups of mice in Experiment 3 (days 0, 7, and 14).

[0042] Figure 14 This is a comparison of the wound healing rate of mice in the control group and experimental group in Experiment Example 3.

[0043] Figure 15 The images show H&E staining of skin wounds in the control and experimental groups in Experiment 3 on days 7 and 14. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments, but this does not limit the present invention in any way. Any modifications or improvements made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0045] The processes, conditions, reagents, and experimental methods used in implementing this invention, except as specifically mentioned below, are all common knowledge and general knowledge in the field, and this invention does not have any particular limitations. Experimental methods in the embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the manufacturer.

[0046] Unless otherwise stated, all technical terms and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. However, in the event of any conflict, the specification containing the definitions shall prevail.

[0047] The following is information on the source of some reagents in the examples: Polycaprolactone (PCL, Mw≈50000), gelatin, polyvinyl alcohol (PVA, Mw≈31000), and tannic acid (TA) were all purchased from Shanghai Adamas Reagent Co., Ltd. Dichloromethane (DCM) was purchased from Guangdong Guanghua Science & Technology Co., Ltd., N,N-dimethylformamide (DMF) from Shanghai Aladdin Reagent Co., Ltd., ammonia (25%) from Chongqing Chuandong Chemical Co., Ltd., and rhodamine B from Tianjin Fengchuan Chemical Reagent Technology Co., Ltd. Bleached shellac and deionized water were provided by the Plateau Forestry Research Institute of the Chinese Academy of Forestry.

[0048] Example 1 (1) Preparation of PCL hydrophobic film: PCL was dissolved in a mixed solvent of dichloromethane and N,N-dimethylformamide (volume ratio 4:1) to prepare a 20wt% PCL solution, which was then stirred continuously in a 50°C water bath for 1 hour until completely dissolved.

[0049] Electrospinning was performed using an electrospinning apparatus. Specific parameters were as follows: a No. 22 metal needle was used; the spinning solution volume was 5 mL; the ambient temperature was 25℃; the electric field strength was 15 kV; the distance between the needle and the collector was 15 cm; and the solution propulsion flow rate was 0.4 mL / h. -1 Electrospun PCL hydrophobic membranes were collected.

[0050] (2) Preparation of the PVA-TA hydrogel interlayer: PVA was added to deionized water to prepare a 10 wt% PVA aqueous solution, which was heated and stirred at 95°C until completely dissolved. TA was added to make a PVA:TA mass ratio of 5:3, and the reaction was carried out at 95°C for 2 h. After standing and cooling at room temperature for 24 h, the supernatant free water was discarded to obtain the PVA-TA hydrogel.

[0051] (3) Preparation of hydrophilic layer of shellac-gelatin based porous sponge loaded with tannic acid: 12 g of shellac was added in batches to 100 mL of a 2% (v / v) ammonia solution, and stirred continuously for 2 h in a 50°C water bath until the shellac was completely dissolved. Then, 3 g of gelatin was added to the solution, and after the gelatin was completely dissolved, 0.4 g of TA was added, and stirring was continued for 3 h to ensure thorough mixing. 3 mL of the resulting homogeneous solution was injected into a custom-made cylindrical mold with a diameter of 2 cm and a depth of 2 cm. After pre-freezing at -25°C for 6 h, the mold was transferred to a freeze dryer and freeze-dried for 48 h to obtain a sponge sample with a porous structure.

[0052] (4) Composite of three-layer substrates: First, the prepared sponge sample was flattened on both sides with a blade, maintaining a thickness of 7.0 mm. Then, a layer of PVA-TA hydrogel (0.1 mm thick) was uniformly coated onto one surface, and a pre-cut electrospun PCL membrane of the same size was smoothly attached to the hydrogel layer. A slight pressure of 3.2 kPa was applied to ensure tight interlayer bonding, thus producing a non-porous Janus dressing (denoted as PHS). (5) Preparation of the channel: A 0.5 mm diameter metal needle was used to puncture the PCL layer and hydrogel layer from one side of the PCL hydrophobic film layer, forming a continuous channel through the three layers. The pore size on the surface of the PCL hydrophobic film layer was 0.5 mm, and the pore density was 45 pores / cm². Due to the tapered design of the metal needle and the puncture direction, the pore size gradually decreased from the hydrophobic layer to the hydrogel layer. Three parallel samples were prepared and labeled as 45PHS0.5, H-0.1, and S7, respectively.

[0053] The surface and cross-sectional morphology of the samples were observed using a scanning electron microscope (ZEISS Sigma 300, Germany). Fourier transform infrared spectroscopy (TENSON 27, Bruker, Germany) was used for chemical functional group analysis. The water contact angle of the samples was measured at room temperature using the sitting drop method with a water contact angle meter (Attension Theta Flex, biolin scientific, Sverige) to characterize their surface wettability.

[0054] This embodiment successfully constructed a structurally stable Janus dressing by introducing PVA-TA hydrogel as an adhesive intermediate layer. Figure 1 As shown, this design utilizes the strong adhesive properties of hydrogel to firmly bond an electrospun PCL hydrophobic membrane with a shellac-gelatin porous sponge. Subsequently, a regular pore array is constructed on the composite dressing through precise metal needle puncture, ultimately producing a porous Janus dressing with an asymmetric structure and wettability. This pore structure is the core design element for achieving directional liquid transport and drug reflux release.

[0055] The microstructure of each functional layer of the dressing was systematically characterized using scanning electron microscopy. For example... Figure 2As shown, the electrospun PCL membrane is composed of smooth, randomly oriented fibers with an average diameter of 4.1 μm. The micron-sized pores formed between the fibers provide structural channels for the upward transport of water from the lower layer and the reverse diffusion of drug molecules. Further water contact angle testing showed that the PCL fiber membrane had a contact angle of approximately 123±4°, exhibiting hydrophobic properties. In stark contrast, the shellac-gelatin sponge, with its SEM image revealing an interconnected three-dimensional network of ultra-large pores (82.4±26.5 μm), resembles a high-capacity reservoir. Its contact angle is close to 27°, exhibiting superhydrophilic properties, enabling rapid absorption and storage of large amounts of wound exudate, effectively solving the problem of limited liquid absorption capacity in traditional hydrophilic films. As a key element for interlayer adhesion and functional regulation, the PVA-TA hydrogel layer exhibits uniformly distributed nanoscale pores (807.2±28.8 nm). This structure not only facilitates the passage of water and molecules but also ensures a stable interfacial bond due to its inherent viscosity. Water contact angle testing showed that the hydrogel layer had a contact angle of approximately 62±7°, exhibiting moderate hydrophilicity. While maintaining adequate water permeability, it also provided a good wettability and adhesion foundation for the interlayer structure. Finally, cross-sectional SEM images of the Janus dressing clearly demonstrated a dense and continuous bond between the PCL layer, hydrogel layer, and sponge layer, with no visible cracks at the interface. This proved the effectiveness of this strategy in solving the interlayer separation problem and laid the foundation for maintaining structural integrity in practical applications. Furthermore, the Janus dressing exhibited a structural feature of gradually increasing pore size from the top to the bottom in its vertical cross-section: the upper PCL fiber membrane microporous array consisted of large pores at the hundred-micrometer scale, the middle PVA-TA hydrogel layer had uniform nano-scale pores, and the lower sponge layer possessed a pore network at the tens of micrometer scale. This conical channel structure, which transitions from a hydrophobic dense layer to a hydrophilic porous layer and features a decreasing pore size gradient, not only provides a unidirectional flow path for wound exudate from the inside out, but also further enhances the directional transport of liquid from the hydrophilic sponge layer to the hydrophobic surface layer through capillary force differences and wettability gradients. This achieves efficient and continuous drainage of exudate and effectively avoids the adverse effects of liquid retention on wound healing.

[0056] Example 2 The same process as in Example 1 was used, only the micropore parameters were adjusted: a metal needle with a diameter of 0.2 mm was used for puncture, the pore size on the surface of the PCL hydrophobic film was 0.2 mm, and the pore density was 45 pores / cm². The resulting sample was denoted as 45PHS0.2.

[0057] Example 3 The same process as in Example 1 was used, only the micropore parameters were adjusted: a metal needle with a diameter of 0.8 mm was used for puncture, the pore size on the surface of the PCL hydrophobic film was 0.8 mm, and the pore density was 45 pores / cm². The resulting sample was designated 45PHS0.8.

[0058] Example 4 The same process as in Example 1 was used, only the micropore parameters were adjusted: a 0.5 mm diameter metal needle was used for puncture, the pore size on the PCL hydrophobic film surface was 0.5 mm, and the pore density was 12 pores / cm². The resulting sample was designated 12PHS0.5.

[0059] Example 5 The same process as in Example 1 was used, except that the micropore parameters were adjusted: a 0.5 mm diameter metal needle was used for puncture, the pore size on the PCL hydrophobic film surface was 0.5 mm, and the pore density was 21 pores / cm². The resulting sample was designated 21PHS0.5.

[0060] Examples 6-10 The difference from Example 1 is that the thickness of the hydrogel layer is different, being 0.05, 0.3, 0.5, 0.7, and 0.9 mm respectively; otherwise, it is the same as Example 1. The prepared samples are denoted as H-0.05, H-0.3, H-0.5, H-0.7, and H-0.9.

[0061] Examples 11-16 The difference from Example 1 is that the thickness of the sponge layer is different, and it is 4, 5, 6, 8, 9, and 10 mm respectively. The other conditions are the same as in Example 1. The prepared samples are designated as S4, S5, S6, S8, S9, and S10.

[0062] Examples 17-20 The difference from Example 1 lies in the amount of TA added to the sponge layer, which are 0.2, 0.6, 0.8, and 1.0 g respectively. All other conditions are the same as in Example 1. The resulting samples are designated as STG0.2, STG0.6, STG0.8, and STG1.0.

[0063] Comparative Example 1 (without microporous structure) Using the same process as in Example 1, but without puncture treatment, a non-porous composite Janus dressing was prepared. The resulting sample was designated PSH.

[0064] Comparative Example 2 (sponge layer without TA) The difference from Example 1 is that no TA was added to the sponge layer, while the other conditions are the same as in Example 1.

[0065] The remaining conditions were the same as in Example 1. The resulting sample was denoted as STG.

[0066] Test Example 1: Directional Water Delivery Performance Test (1) Measurement of changes in water contact angle Janus dressings were prepared using Comparative Example 1 and Example 5. They were tested using a water contact angle meter. The test method was the sitting drop method, the test mode was liquid formation, the test time was 60 s, the volume of the water droplet was 10 μL, and the time required for the water droplet contact angle of 10 μL on the sample PCL surface to drop to about 5° was recorded.

[0067] See results Figure 3 AB analysis showed that a water droplet (10 μL) remained unpermeable for over 60 seconds on the surface of the non-porous PCL(up) / Sponge(down) hydrophobic PCL layer, exhibiting typical hydrophobic barrier properties. This contrasts sharply with porous PCL layers. p Water droplets on the PCL (up) / Sponge (down) surface are completely absorbed within 2 seconds. On the hydrophilic sponge surface, the water contact angle is very low, and the presence or absence of pores in the PCL has no effect on its water absorption efficiency. Quantitative analysis further reveals that the water transport rate of 21PSH0.5 is as high as 6.36 μL·s⁻¹. -1 While PSH was only 0.08 μL·s⁻¹. -1 The difference between the two is nearly 80 times. The results show that the hydrophobic microporous array does not simply provide channels, but fundamentally changes the wetting and transport mode of liquids on the hydrophobic surface. In PSH, liquid transport relies solely on slow interfacial diffusion; however, in pPSH, the microporous array first rapidly captures and guides the liquid through the PCL barrier via capillary action, and then utilizes the interfacial energy difference between the PCL layer and the hydrogel layer to achieve rapid transport to the hydrophilic layer. Therefore, the microporous array structure is the physical basis for breaking the hydrophobic barrier of the PCL layer and realizing the rapid directional transport of liquids from the hydrophobic side to the hydrophilic side.

[0068] (2) Determination of water absorption rate Test Method: First, accurately weigh the initial mass of the Janus dressing samples prepared in Examples 1-16 and Comparative Example 1, and record it as m0. Then, use a disposable dropper to continuously add deionized water to the surface of the PCL hydrophobic layer of the sample. Record the instantaneous mass m of the sample after water absorption every minute, starting from the first drop of water added. t The water absorption rate at each time point is calculated using the following formula: Water absorption rate = (mass of water absorbed, m) t (mass before water absorption, m0) × 100% The results are analyzed as follows: The comparison results of Examples 1-3 and Comparative Example 1 are shown in the figure. Figure 4 The results showed that the saturated water absorption capacity of all samples was basically the same, approximately 520% ​​of the initial mass, indicating that the pore size of the microporous array mainly regulates the liquid transport rate, but does not change the final liquid absorption capacity of the material. Significant differences were observed in the water absorption process: in Comparative Example 1, the absorption rate was slow in the initial stage (0–5 min), then reached its maximum (5–10 min), gradually slowed down after 10 min, and reached saturation at approximately 30 min. In contrast, the samples with microporous arrays all exhibited rapid water absorption characteristics. Among them, the samples with pore sizes of 0.5 mm and 0.8 mm (45PHS0.5 and 45PHS0.8) had the fastest water absorption rates, and both were similar, reaching saturation within approximately 8 min; while the sample with a pore size of 0.2 mm (45PHS0.2) had a water absorption rate between that of PHS and the larger pore size samples, and its saturation time was still 30 min. The above results indicate that when the pore size is greater than or equal to 0.5 mm, its promoting effect on the directional transport of liquid tends to reach equilibrium, and further increasing the pore size no longer further improves the water absorption dynamics.

[0069] The comparison results of Examples 1, 4, 5 and Comparative Example 1 are shown in the figure. Figure 5 The results showed that under the condition of fixed microporous array pore size, the initial water absorption rate of the dressing increased significantly with the increase of array pore number. Comparative Example 1 still showed a trend of slow absorption followed by an increase and then a decrease, reaching saturation at 30 min. In contrast, the perforated samples all exhibited faster water absorption kinetics, with 21PHS0.5 and 45PHS0.5 showing the fastest absorption rates, and both reaching saturation within approximately 8 min; while the absorption rate of 12PHS0.5 was between that of the control group and 21PHS0.5, with a saturation time of approximately 20 min.

[0070] The comparison results of Example 1 and Examples 6-10 are shown in the figure. Figure 6 The results showed that the water absorption rate of each sample gradually increased with time, reaching near saturation at 10 min. The effect of hydrogel thickness on water absorption rate exhibited a trend of first increasing and then decreasing: the water absorption rate was highest at a thickness of 0.1 mm, reaching 550%. This is mainly attributed to the relatively weak water absorption capacity of the hydrogel itself, with the water absorption process primarily relying on the sponge layer. The water absorption of the sponge layer remained essentially constant, while increasing the hydrogel layer thickness, although leading to an increase in mass, resulted in a limited increase in water absorption. Therefore, the overall water absorption rate of the prepared Janus dressing decreased with increasing hydrogel thickness.

[0071] The results of Examples 1 and 11-16 are shown below. Figure 7The results showed that the water absorption rate gradually increased with the extension of the absorption time, and all samples reached saturation within about 10 minutes. The saturated water absorption of samples with different thicknesses was basically the same, about 530% of the initial mass, indicating that the thickness of the sponge mainly regulates the liquid transport rate, without changing the final liquid absorption capacity of the material. However, if the sponge is too thin (e.g., <7 mm), the mechanical strength is poor and the liquid absorption capacity is limited, while if it is too thick, it affects the user experience. After comprehensive consideration, this study selected 7 mm as the optimal thickness of the sponge layer.

[0072] Test Example 3: Drug Reflux Performance Test A drug reflux performance testing model was established: the PCL dressing with its hydrophobic layer facing down was placed above a syringe filled with deionized water to simulate wound exudate, allowing it to make slight contact with the liquid surface. To simulate continuous exudate generation in vivo and provide a reflux driving force, deionized water was continuously added to the upper surface of the sponge layer at a constant rate, with a total added volume of 1 mL. Samples from the lower liquid pool were collected at 0.25, 0.5, 0.75, 1, 3, 5, 7, 24, 48, 72, 96, and 216 h after adding the solution. The absorbance of the samples in the lower liquid pool was measured using a UV-Vis spectrophotometer at the maximum characteristic absorption wavelength (276 nm) of tannic acid (TA), and the reflux concentration was calculated based on a pre-established TA standard curve. To visually trace the liquid transport and drug release pathways, rhodamine B fluorescent dye was pre-loaded at the interface between the PCL layer and the hydrogel layer.

[0073] A comparison graph showing the reflux phenomenon of the Janus membranes prepared in Comparative Example 1 and Example 5 is shown below. Figure 8 The results showed that p PHS absorbs liquid from the pool below and expands. Comparative observation revealed that... p PHS showed a small amount of liquid backflow after 2 minutes of absorption, with a pinkish color, which was due to the dissolution of Rhodamine B in water. In stark contrast, the Janus membrane composite dressing PHS, which has no microporous structure, did not show any liquid backflow during the 5-minute test period.

[0074] The results of Examples 1, 4, 5 and Comparative Example 1 are shown below. Figure 9 Comparative analysis shows that, under the same pore size conditions, the reflux concentration of TA increases with the extension of the reaction time and the increase of the number of pores (see...). Figure 9 B). The results of Examples 1-3 and Comparative Example 1 show that, with a fixed number of pores, the concentration of TA reflux in the same amount of time first increases and then decreases with increasing pore size (see...). Figure 9The maximum TA reflux concentration was reached at a pore size of 0.5 mm, with a maximum concentration of 88.44 mg·mL⁻¹ (approximately 0.15% of the total TA loading) over a 1-hour experimental period. These results demonstrate that the TA reflux rate can be effectively controlled by precisely adjusting the pore size and number of pores in the microporous array. This effective and controllable TA reflux provides experimental evidence for the application of this composite dressing in promoting wound healing and highlights its potential value in the field of controlled drug release.

[0075] The results of Comparative Example 2, Example 1, and Examples 17-20 are shown in the figure. Figure 10 AC, comparative analysis showed that with increasing time and TA addition, both the TA concentration and the total reflux mass of the reflux solution increased. However, the reflux mass ratio (the ratio of refluxed TA mass to the initial TA mass) decreased with increasing TA addition, with the highest reflux mass ratio observed in the control sample (sample 1 without TA). This is because the initial TA mass increases with increasing addition, resulting in a decrease in its relative proportion despite an increase in the total reflux volume. The reflux rate accelerated with increasing TA addition, showing an overall trend of first increasing and then decreasing, reaching a maximum at 1 h and then gradually declining. These results indicate that continuous reflux can be achieved with different TA addition levels, and the reflux concentration, total volume, and rate can be effectively controlled by the TA addition amount.

[0076] Experimental Example 1: Bacterial Inhibition Test Accurately weigh 0.300 g of 45PHS0.5 dressing (prepared in Example 11) and place it in a sterile centrifuge tube containing 5.0 mL of Luria-Bertani (LB) medium. Allow it to swell completely for 2 hours to obtain the experimental group sample. A separate 5.0 mL LB solution without the dressing serves as the control group. Using *Escherichia coli* and *Staphylococcus aureus* as test strains, the bacterial suspension concentration was adjusted to approximately 1.0 × 10⁻⁶. 9 CFU / mL. Add 50 μL of bacterial suspension to each culture tube and incubate at 37℃ and 200 rpm for 24 h. After incubation, perform 10-fold serial dilutions of the bacterial suspension with PBS. Spread 50 μL of each dilution onto LB agar plates and incubate upside down at 37℃ for 24 h. Count the colonies afterward. Each group was replicated in triplicate. Calculate the bacterial inhibition rate using the following formula.

[0077] Bacterial inhibition rate = [(number of colonies in control group - number of colonies in experimental group) / number of colonies in control group] 100% See results Figure 11The results showed that, compared with the control group, the 45PHS0.5 dressing composite dressing treatment significantly reduced the colony counts of both bacteria; its inhibition rates against Escherichia coli and Staphylococcus aureus reached 93.48% and 95.41%, respectively. Figure 11 The above results indicate that 45PHS0.5 dressing has a significant ability to inhibit bacterial growth, which is mainly attributed to the effective release and antibacterial effect of the TA it carries.

[0078] Experimental Example 2: Biocompatibility Performance Weigh 0.100 g of 45PHS0.5 dressing (prepared in Example 1), add 1.0 mL of Dulbecco's modifiedeagle medium (DMEM), and extract in an incubator at 37°C and 5% CO2 for 24 h. After extraction, filter sterilize using a 0.22 μm microporous membrane to obtain a concentration of 0.1 g / mL. -1 The stock extract was then diluted with DMEM medium to prepare material extracts with volume fractions of 1%, 2.5%, and 5% (v / v).

[0079] Mouse fibroblast cell line (L929) was routinely passaged in DMEM medium. The culture medium was 1.0 × 10⁻⁶ cells / mL. 4 Cells were seeded at a density of 100 cells / mL in 24-well plates, with 500 μL of cell suspension added to each well. Cells were cultured for 24 h until fully adherent. Subsequently, the experimental groups were seeded with culture medium containing 1%, 2.5%, and 5% extract, respectively, while the control group used medium without extract. Cells were stained using a live / dead cell double staining kit at 0, 24, 48, and 72 h of culture. Five replicates were set up for each group. Images were observed and recorded using a fluorescence microscope. The cell count at 0 h was denoted as C0, and the count at n h was denoted as Cn. n Calculate the relative cell proliferation rate using the following formula: Cell proliferation rate = [(C n -C0) / C0] 100% The results showed that after co-culturing with different concentrations of dressing extract for 24, 48, and 72 h, L929 cells in both the control and experimental groups exhibited normal morphology, good adhesion, and uniform distribution, demonstrating healthy growth. Cell proliferation rate statistics ( Figure 12The results showed that the cell proliferation rates in both the control and experimental groups continuously increased with prolonged culture time, consistent with the natural growth patterns of cells. Among different extract concentrations, the cell proliferation rate in the 2.5% concentration experimental group was higher than that in the 1.0% and 5.0% groups, suggesting that lower concentrations of the extract may have a certain proliferative effect, while higher concentrations may have a slight inhibitory effect on cell proliferation. Nevertheless, the cell proliferation rates in all experimental groups were higher than those in the control group, indicating that the dressing did not exhibit significant cytotoxicity at any tested concentration, possesses good cell compatibility, and meets the basic biological requirements for clinical application of wound dressings.

[0080] Experimental Example 3: In vivo wound healing experiment Ten male KM mice (weighing 30-36 g) were selected and acclimatized for 7 days before a diabetic model was established. Each mouse was intraperitoneally injected with streptozotocin (STZ) 70 mg / kg once daily for 5 consecutive days. One week after the injection, the mice's blood glucose levels were measured and stabilized above 15.0 mmol·L⁻¹ to confirm the establishment of the diabetic model. A 1.0 cm diameter full-thickness circular wound was then created on the back of each mouse to construct a wound model. The mice were then randomly divided into two groups of five. The experimental group had their wounds covered and fixed with 45PHS0.5 dressing (sample prepared in Example 1), while the control group had their wounds covered with gauze without any other treatment. During the experiment, each mouse was kept in a cage and allowed free access to food and water. Blood glucose and weight changes were measured every two days, and wound healing was photographed and recorded on days 0, 3, 7, and 14 post-surgery. Wound data was recorded using Image-Pro plus software. The wound area was recorded as S0 on day 0 and S on day n post-injury. n The formula for calculating wound closure rate is as follows: Wound closure rate = [(S0-S n ) / S0] 100% To further assess wound tissue regeneration, mice in each group were sacrificed on postoperative days 3, 7, and 14, with one sample collected from each group at each time point. Wound and surrounding tissue samples were fixed in 10% neutral formalin buffer, routinely embedded in paraffin, sectioned, and subjected to hematoxylin extraction. Eosin (H&E) staining. Sections were observed and images were acquired using an optical microscope (Leica DM3000, Germany) for histological analysis.

[0081] Throughout the 14-day experimental period, none of the mice showed any adverse reactions such as death or obvious anorexia. Their weight steadily increased, and their blood glucose levels remained stable within the hyperglycemic range, indicating that the diabetic model was stable and providing a reliable basis for evaluating the in vivo efficacy of the dressing.

[0082] The results showed that the wounds in the untreated control group remained reddish throughout the healing process, with slow scab formation and fragile texture, easily bleeding upon slight touch, indicating slow healing and unstable new epithelial tissue. In contrast, the experimental group treated with Janus dressings developed a darker, denser scab by day 3, which was not easily removed or bled upon touch. By days 7 and 14, the wound contraction and epithelialization process in the experimental group were significantly ahead of the control group (see...). Figure 13 ).

[0083] Quantitative statistical results of wound healing rate ( Figure 14 This further confirms the above observations: In the early healing stage, the wound closure rate in the experimental group reached 27.38±6.19% on day 3, significantly higher than the 15.21±5.43% in the control group. p = 0.036). During the mid-healing stage, the difference between the two groups continued to widen. On day 7, the wound closure rates in the experimental group and the control group were 50.50±6.27% and 33.58±2.48%, respectively, showing a statistically significant difference. (p = 0.038). By the critical day 14, the healing rate in the experimental group increased to 81.90±7.27%, while that in the control group was only 76.22±6.71%, indicating that the wound healing in the experimental group was still better than that in the control group. Finally, by the end of the experimental cycle on day 21, almost all the wounds of the mice in the experimental group had been completely closed without the formation of obvious scars; while the wound closure rate in the control group was 97.46±1.50%, with obvious scarring.

[0084] H&E staining analysis results (see) Figure 15 The results showed that on day 7, the experimental group exhibited inflammatory cells and some tissue edema, but also abundant granulation tissue, fibroblasts, and neovascularization. Epidermal cells showed a tendency to repair, indicating that the dressing effectively promoted the orderly initiation and timely resolution of the inflammatory phase, preventing the persistence of chronic inflammation. In contrast, the control group showed significant inflammatory infiltration and tissue edema, as well as epidermal damage, with only a small amount of granulation tissue and neovascularization. More importantly, by day 14, the tissue edema in the experimental group had disappeared, neovascularization and collagen fibers had increased, and epidermal cells had been fully repaired, approaching normal skin condition. In contrast, the control group showed epidermal sloughing and necrosis, along with a small amount of inflammatory factors and tissue edema, indicating poor self-repair ability and delayed wound healing. These results demonstrate that Janus dressing can accelerate the closure process of diabetic wounds and improve healing quality. Its healing-promoting mechanism mainly includes the dressing providing a good physical barrier for the wound, creating a moist microenvironment conducive to cell migration and proliferation, and the dressing being loaded with tannins which can flow back to the wound to regulate the inflammatory response, allowing it to transition quickly and orderly, thereby creating favorable conditions for the subsequent proliferation phase.

[0085] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite Janus dressing with a microporous structure, characterized in that, The composite Janus dressing comprises an electrospun polycaprolactone hydrophobic film layer, a polyvinyl alcohol-tannic acid hydrogel layer, and a shellac-gelatin-based porous sponge hydrophilic layer loaded with tannic acid, which are stacked in sequence. The composite Janus dressing has multiple pore structures that penetrate the hydrophobic film layer, the hydrogel layer, and the porous sponge hydrophilic layer to form a channel for the transport of liquid and drug.

2. The composite Janus dressing according to claim 1, characterized in that, The pore structure is a conical hole formed by mechanical puncture of the hydrophobic membrane layer from one side by a conical needle; the conical hole penetrates the hydrophobic membrane layer and the hydrogel layer, and is interconnected with the microporous network inherent in the hydrophilic layer of the porous sponge itself.

3. The composite Janus dressing according to claim 2, characterized in that, On the surface of the hydrophobic film layer, the conical pores form a micropore array with a pore size of 0.2~0.8 mm and a pore density of 12~45 pores / cm²; in the hydrogel layer, the pore size of the conical pores is 807.2 ± 28.8 nm.

4. The composite Janus dressing according to claim 1, characterized in that, The electrospun polycaprolactone hydrophobic film layer is composed of smooth, randomly oriented fibers with an average fiber diameter of 4.1 ± 0.2 μm and a water contact angle of 123 ± 4°; the polyvinyl alcohol-tannic acid hydrogel layer has a thickness of 0.05-0.9 mm and a water contact angle of 62 ± 7°; the shellac-gelatin-based porous sponge layer has a thickness of 4-10 mm, an average pore size of 82.4 ± 26.5 μm, and a water contact angle of 27 ± 3°.

5. A method for preparing a composite Janus dressing with a microporous structure as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Prepare electrospun polycaprolactone hydrophobic film, polyvinyl alcohol-tannic acid hydrogel intermediate layer and shellac-gelatin-based porous sponge hydrophilic layer loaded with tannic acid respectively. (2) The polyvinyl alcohol-tannic acid hydrogel is coated on the electrospun polycaprolactone hydrophobic membrane, and then the shellac-gelatin-based porous sponge loaded with tannic acid is hydrophilically stacked on the hydrogel to form an integral three-layer substrate. (3) Mechanical perforation of the hydrophobic polycaprolactone film layer and hydrogel layer obtained in step (1) is performed using a cone-shaped tool to form a plurality of pore structures penetrating the three-layer structure on the composite dressing in step (2). The mechanical perforation is a puncture treatment performed from one side of the electrospun hydrophobic polycaprolactone film layer.

6. The preparation method according to claim 5, characterized in that, The pore structure formed in step (3) has a gradually decreasing pore size from the hydrophobic layer to the hydrogel intermediate layer. The pore size of the micropore array on the surface of the electrospun polycaprolactone hydrophobic film layer is 0.2~0.8 mm, and the pore density is 12~45 pores / cm³. 2 The pore size of the polyvinyl alcohol-tannic acid hydrogel layer is 807.2 ± 28.8 nm.

7. The preparation method according to claim 5, characterized in that, In step (1), when preparing the electrospun polycaprolactone hydrophobic film, an electrospinning process is used. The concentration of the polycaprolactone solution is 15-25 wt%, and the solvent is a mixture of dichloromethane and N,N-dimethylformamide. The spinning parameters are: needle size 18-24, ambient temperature 20-30℃, electric field strength 12-18 kV, distance between the needle and the collector 10-20 cm, and solution propulsion flow rate 0.3-0.6 mL / h. -1 A hydrophobic polycaprolactone membrane was collected.

8. The preparation method according to claim 1, characterized in that, The method for preparing the hydrophilic layer of the shellac-gelatin-based porous sponge loaded with tannic acid in step (1) is as follows: add shellac to an ammonia solution and dissolve it at 45-60°C, then add gelatin and tannic acid, stir evenly, pre-freeze at -20 to -30°C, and then freeze-dry to form a porous sponge.

9. The preparation method according to claim 5, characterized in that, The method for preparing the intermediate layer of the polyvinyl alcohol-tannic acid hydrogel in step (1) is as follows: tannic acid is added to a polyvinyl alcohol aqueous solution, reacted at 90-100℃ for 1.5-2h, cooled at room temperature for 20-24h, and the upper free water is poured off to obtain the polyvinyl alcohol-tannic acid hydrogel.

10. The use of the composite Janus dressing with a microporous structure according to any one of claims 1-4 in the preparation of a medical device for promoting the healing of chronic wounds or treating bacterially infected wounds.

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