Color-changing dressing capable of tracing retention time and preparation method thereof

Abstract

The invention relates to the technical field of medical dressings, and particularly discloses a discoloring dressing capable of tracing retention time and a preparation method thereof, the discoloring dressing comprises a base material layer, a time indication layer, an oxygen sensitive composite film and a microbial response layer; the base material layer is formed by one of medical non-woven fabric and polyurethane foam; the time indication layer is arranged on the upper surface of the base material layer and comprises a pH response type color-changing material; the oxygen-sensitive composite film covers the surface of the time indicating layer and comprises platinum (II)-tetraphenyl porphyrin ketone (PtOEPK) dispersed in a polydimethylsiloxane (PDMS) matrix, and the color change of the oxygen-sensitive composite film is related to the tissue oxygen partial pressure; through the arrangement of the time indication layer, a compound of bromcresol purple and bromothymol blue is adopted as a pH response type color change material, so that the dressing can present gradient color changes of yellow, green and blue according to the pH change of a wound in the retention process, the retention time of the dressing is visually displayed, and medical staff can conveniently judge the replacement time.

Description

Technical Field

[0001] The invention belongs to the technical field of medical dressings, and particularly relates to a color-changing dressing capable of tracing the retention time and a preparation method thereof. Background Art

[0002] In the field of medical dressing technology, with the continuous advancement of medical technology and the growing demand for wound care, traditional dressings can no longer meet the refined requirements of modern clinical practice for wound monitoring and management. The main functions of traditional dressings are to cover wounds, absorb exudates and provide a physical barrier. However, there are significant limitations in evaluating the retention time of dressings, wound healing status and potential infection risks. In recent years, with the development of smart materials and biosensor technology, smart dressings that can track retention time and monitor the wound environment in real time have gradually become a research hotspot.

[0003] In the existing technology, a variety of medical dressings based on the color-changing principle have been developed. Most of these dressings use single or limited chemical indicators to reflect certain specific changes in the wound environment, such as pH or oxygen concentration. However, these technologies generally have a significant shortcoming, that is, they can often only provide an indirect or rough estimate of the wound status, and it is difficult to accurately reflect the actual retention time of the dressing, especially in a complex and changeable wound environment. For example, although some pH-sensitive dressings can indicate the wound pH value through color changes, the wound pH value is affected by many factors, such as the amount of exudate, infection status, etc., so it is difficult to accurately judge the retention time of the dressing based on pH changes alone. This may lead to untimely or excessive replacement of the dressing, which in turn affects the efficiency of wound healing, increases patient pain and medical costs, and therefore requires staff to replace it. Summary of the Invention

[0004] The object of the present invention is to provide a color-changing dressing capable of tracing the retention time and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A color-changing dressing capable of tracing the retention time, comprising:

[0007] Base material layer, time indication layer, oxygen sensitive composite membrane and microbial response layer;

[0008] The substrate layer is composed of one of medical non-woven fabric and polyurethane foam;

[0009] The time indicating layer is disposed on the upper surface of the substrate layer and comprises a pH-responsive color-changing material;

[0010] The oxygen-sensitive composite membrane covers the surface of the time indicator layer and comprises platinum (II)-tetraphenylporphyrinone (PtOEPK) dispersed in a polydimethylsiloxane (PDMS) matrix, and its color change is related to the tissue oxygen partial pressure;

[0011] The microbial response layer is arranged on the outside of the oxygen-sensitive composite membrane and contains a nitroreductase-sensitive probe. The probe is a nitrobenzothiazole derivative, and its color development reaction is positively correlated with the concentration of pathogenic bacteria metabolites.

[0012] Preferably, the pH-responsive color-changing material of the time indicating layer is a complex of bromocresol purple and bromothymol blue, which exhibits a gradient change of yellow, green and blue within the pH range of 5.2-7.6.

[0013] Preferably, the PDMS matrix of the oxygen-sensitive composite membrane contains silicon dioxide nanoparticles with a mass fraction of 5-15% for enhancing gas permeability and mechanical strength.

[0014] Preferably, the general structural formula of the nitrobenzothiazole derivative of the microbial response layer is:

[0015] R1-NO2+2e-+2H+→R1-NHOH

[0016] Wherein R1 is benzothiazol-2-yl, and its reduction product produces a characteristic absorption peak at 520-550nm.

[0017] Preferably, it also includes an isolation layer, which is arranged outside the microbial response layer and is composed of a moisture-permeable polyurethane film with a thickness of 10-50 μm and a water vapor transmission rate of ≥2000 g / m 2 ·24h.

[0018] A method for preparing a color-changing dressing capable of tracing the retention time comprises the following steps:

[0019] S1. Preparation of a time indicator layer: Mix a sodium alginate solution (3 wt%) with bromocresol purple (0.1 mM) and bromothymol blue (0.05 mM), apply the mixture to the surface of the substrate layer, cross-link with a CaCl2 solution, and then dry.

[0020] S2. Preparation of oxygen-sensitive composite membrane: PtOEPK (0.5-2 mg / mL) and PDMS prepolymer (Sylgard 184) were mixed at a mass ratio of 10:1, 5% fumed silica was added, and the mixture was spin-coated on the surface of the time indicator layer and cured at 80°C for 2 h.

[0021] S3. Preparation of a microbial response layer: Blending a nitrobenzothiazole derivative (1-5 mg / mL) with a polyvinyl alcohol (PVA, 5 wt%) solution, and forming a sensitive layer with a thickness of 20-100 μm on the oxygen-sensitive composite membrane by a microfluidic spray method;

[0022] S4. Composite isolation layer: hot-press the moisture-permeable polyurethane film onto the surface of the microbial response layer at a pressure of 0.2-0.5 MPa and a temperature of 60-80°C.

[0023] Preferably, in step S2, the spin coating speed is 1500-3000 rpm, and the film thickness after curing is 30-80 μm.

[0024] Preferably, in step S3, the nozzle diameter of the microfluidic spray is 50-100 μm, the carrier gas pressure is 0.1-0.3 MPa, and the substrate temperature is 40-60°C.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) By setting up a time indicator layer and using a complex of bromocresol purple and bromothymol blue as a pH-responsive color-changing material, the dressing can show a gradient color change of yellow, green, and blue according to the pH change of the wound during the retention process, thereby intuitively displaying the retention time of the dressing and facilitating medical staff to judge the time of replacement.

[0027] (2) By setting up an oxygen-sensitive composite membrane, platinum (II)-tetraphenylporphyrinone (PtOEPK) is dispersed in the PDMS matrix, so that the dressing can present different colors according to the changes in tissue oxygen partial pressure, thereby reflecting the oxygenation status of the wound site in real time and providing an important reference for clinical treatment.

[0028] (3) By setting up a microbial response layer and using nitrobenzothiazole derivatives as nitroreductase-sensitive probes, the dressing can produce a color reaction when the concentration of pathogenic bacterial metabolites reaches a certain threshold, thereby achieving early warning of wound infection and helping to take timely intervention measures.

[0029] (4) By setting up an isolation layer and using a moisture-permeable polyurethane film as the outer layer material, the dressing can effectively block external pollutants while ensuring breathability, thereby maintaining the cleanliness of the wound environment and promoting healing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a preparation flow chart of the present invention. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] Example 1:

[0033] See also Figure 1 As shown, a color-changing dressing capable of tracing the retention time comprises:

[0034] Base material layer, time indication layer, oxygen sensitive composite membrane and microbial response layer;

[0035] The substrate layer is composed of one of medical non-woven fabric and polyurethane foam;

[0036] The time indicating layer is disposed on the upper surface of the substrate layer and comprises a pH-responsive color-changing material;

[0037] The oxygen-sensitive composite membrane covers the surface of the time indicator layer and contains platinum (II)-tetraphenylporphyrinone (PtOEPK) dispersed in a polydimethylsiloxane (PDMS) matrix. Its color change is related to the tissue oxygen partial pressure.

[0038] The microbial response layer is arranged on the outside of the oxygen-sensitive composite membrane and contains a nitroreductase-sensitive probe. The probe is a nitrobenzothiazole derivative, and its color reaction is positively correlated with the concentration of pathogenic bacteria metabolites.

[0039] The pH-responsive color-changing material of the time indicator layer is a complex of bromocresol purple and bromothymol blue, which exhibits a gradient change of yellow, green, and blue within the pH range of 5.2-7.6. The PDMS matrix of the oxygen-sensitive composite membrane contains silica nanoparticles with a mass fraction of 5-15% to enhance gas permeability and mechanical strength. The general structural formula of the nitrobenzothiazole derivative in the microbial response layer is:

[0040] R1-NO2+2e-+2H+→R1-NHOH

[0041] Wherein R1 is benzothiazol-2-yl, and its reduction product produces a characteristic absorption peak at 520-550nm. It also includes an isolation layer, which is arranged outside the microbial response layer and is composed of a moisture-permeable polyurethane film with a thickness of 10-50μm and a water vapor transmission rate of ≥2000g / m 2 ·24h.

[0042] A method for preparing a color-changing dressing capable of tracing the retention time comprises the following steps:

[0043] S1. Preparation of a time indicator layer: Mix a sodium alginate solution (3 wt%) with bromocresol purple (0.1 mM) and bromothymol blue (0.05 mM), apply the mixture to the surface of the substrate layer, cross-link with a CaCl2 solution, and then dry.

[0044] S2. Preparation of oxygen-sensitive composite membrane: PtOEPK (0.5-2 mg / mL) and PDMS prepolymer (Sylgard 184) were mixed at a mass ratio of 10:1, 5% fumed silica was added, and the mixture was spin-coated on the surface of the time indicator layer and cured at 80°C for 2 h.

[0045] S3. Preparation of a microbial response layer: Blending a nitrobenzothiazole derivative (1-5 mg / mL) with a polyvinyl alcohol (PVA, 5 wt%) solution, and forming a sensitive layer with a thickness of 20-100 μm on the oxygen-sensitive composite membrane by a microfluidic spray method;

[0046] S4. Composite isolation layer: hot-press the moisture-permeable polyurethane film onto the surface of the microbial response layer at a pressure of 0.2-0.5 MPa and a temperature of 60-80°C.

[0047] In step S2, the spin coating speed is 1500-3000 rpm, and the film thickness after curing is 30-80 μm. In step S3, the nozzle diameter of the microfluidic spray is 50-100 μm, the carrier gas pressure is 0.1-0.3 MPa, and the substrate temperature is 40-60°C.

[0048] Preparation of color-changing dressings

[0049] Preparation of substrate layer:

[0050] Medical polyurethane foam (thickness 1.5 mm, pore size 100-200 μm) was selected as the substrate layer and plasma treated (power 50 W, time 30 s) to improve the surface hydrophilicity.

[0051] Preparation of time indicator layer:

[0052] Prepare sodium alginate solution (3 wt%), add bromocresol purple (0.1 mM) and bromothymol blue (0.05 mM), and stir evenly. Apply the mixed solution on the surface of the substrate layer (coating amount 50 μL / cm 2 ), then immersed in 5wt% CaCl2 solution for cross-linking for 5min, taken out and dried at 60℃ for 30min to form a time indicating layer with a thickness of about 100μm.

[0053] Preparation of oxygen sensitive composite membrane:

[0054] PtOEPK (1 mg / mL) was dissolved in toluene and mixed with a PDMS prepolymer (Sylgard 184, A:B = 10:1). 10 wt% fumed silica (20 nm particle size) was added and ultrasonically dispersed for 30 minutes. The mixture was then applied to the time indicator layer using spin coating (2000 rpm, 30 seconds) and cured at 80°C for 2 hours to form an oxygen-sensitive film approximately 50 μm thick.

[0055] Preparation of microbial response layer:

[0056] A nitrobenzothiazole derivative (2-nitro-5-mercaptobenzothiazole) was synthesized, dissolved in DMF (2 mg / mL), and mixed with a 5 wt% PVA solution in a 1:3 volume ratio. A uniform coating was formed on the surface of the oxygen-sensitive membrane using a microfluidic spray device (nozzle diameter 80 μm, carrier gas pressure 0.2 MPa, substrate temperature 50°C). After drying at 60°C, a microbial response layer with a thickness of approximately 60 μm was obtained.

[0057] Composite isolation layer:

[0058] Use moisture permeable polyurethane film (thickness 30μm, water vapor permeability 2500g / m 2 · 24h), and laminated to the surface of the microbial response layer through a hot press (pressure 0.3MPa, temperature 70℃) to obtain the final dressing product.

[0059] Performance Testing

[0060] Time indication function verification:

[0061] Simulated wound exudate (pH 7.4 PBS buffer) contacts the dressing:

[0062] 0-24h: The time indicator layer turns yellow (pH 7.4 to 6.8);

[0063] 24-72h: gradually turns green (pH 6.8 to 6.2);

[0064] After 72h: turns blue (pH<6.2).

[0065] Oxygen sensitivity response test:

[0066] Oxygen-rich environment (21% O2): The oxygen-sensitive membrane appears red (fluorescence peak at 650nm);

[0067] Hypoxic environment (<5% O2): turns green (fluorescence peak shifts to 520nm).

[0068] Microbial detection sensitivity:

[0069] Inoculation of Staphylococcus aureus (10 5 CFU / mL) after:

[0070] 6h: The microbial response layer turns light pink;

[0071] 12h: The color deepens to red (absorbance at 550nm under UV detection>0.5).

[0072] Clinical simulation experiments

[0073] Apply the dressing to a full-thickness pig skin defect model (simulating an infected wound):

[0074] 48h: The time indicator layer turns green, the oxygen-sensitive membrane turns yellow-green (local hypoxia), and the microbial response layer shows no color (has not reached the infection threshold).

[0075] 96h: The time indicator layer is blue, the oxygen sensitive membrane is dark green (severe hypoxia), and the microbial response layer is red (bacteria concentration>10 6 CFU / mL).

[0076] Example 2:

[0077] Preparation of color-changing dressings

[0078] Preparation of substrate layer:

[0079] Medical non-woven fabric (polypropylene / polyethylene composite fiber, weight 80g / m 2 ) was used as the substrate layer and was treated with low-temperature plasma (argon atmosphere, power 40 W, time 60 s) to improve the hydrophilicity and dye loading capacity.

[0080] Preparation of time indicator layer (gradient color optimization):

[0081] Prepare gradient cross-linked sodium alginate solution:

[0082] Bottom layer (contacting substrate): 4 wt% sodium alginate + 0.15 mM bromocresol purple (pH 5.2-6.8 response);

[0083] Middle layer: 3 wt% sodium alginate + 0.1 mM bromothymol blue (pH 6.0-7.6 response);

[0084] Surface layer: 2 wt% sodium alginate + 0.05 mM phenol red (pH 7.0-8.4 response).

[0085] Adopt layer-by-layer spraying-cross-linking process:

[0086] Bottom layer solution spraying (50 μm thick) → 3 wt% CaCl2 atomization crosslinking for 30 s;

[0087] Middle layer solution spraying (30 μm thick) → 2 wt% CaCl2 atomization crosslinking for 20 s;

[0088] Surface solution spraying (20 μm thick) → 1 wt% CaCl2 atomization crosslinking for 10 s;

[0089] After hot air drying at 60°C, a three-color gradient time indicating layer with a total thickness of 100 μm is formed.

[0090] Preparation of oxygen-sensitive composite membrane (nano-enhanced):

[0091] PtOEPK (1.5 mg / mL) was mixed with PDMS (Sylgard 184, A:B=10:1) and added:

[0092] 5 wt% mesoporous silica nanospheres (pore size 5 nm, enhanced oxygen permeation);

[0093] 2 wt% carbon quantum dots (as a fluorescence stabilizer);

[0094] The film was formed by slit coating (gap 100 μm, speed 0.5 m / min) and cured at 80° C. for 1.5 h to obtain an oxygen sensitive film with a thickness of 40 μm. The oxygen response speed of the film was 30% higher than that of Example 1.

[0095] Preparation of microbial response layer (high sensitivity type):

[0096] Synthesis of nitrobenzothiazole-gold nanorod composite probes:

[0097] A nitrobenzothiazole derivative (3-nitro-4-aminobenzothiazole) was coupled to gold nanorods (aspect ratio 4:1) via Au-S bonds.

[0098] The nanocomposite solution was dispersed in thermosensitive Pluronic F127 hydrogel (20 wt%).

[0099] An electrospinning process (voltage 15kV, receiving distance 15cm) was used to form a porous fiber layer (fiber diameter 1-3μm) on the oxygen-sensitive membrane, significantly increasing the bacterial contact area.

[0100] Composite of isolation layer (optimized breathability):

[0101] The PTFE / polyurethane composite membrane (thickness 25μm, pore size 0.2μm) was selected and grafted with the microbial response layer by low-temperature plasma activation (O2 plasma, power 30W) and then hot-pressed (0.25MPa, 65℃). The water vapor transmission rate was increased to 3000g / m 2 ·24h.

[0102] Clinical simulation experiment (complex wound scenario)

[0103] Test conditions:

[0104] Simulated diabetic foot ulcer (hypertonic environment: glucose concentration 10 mM);

[0105] Inoculate with a mixed bacterial flora (Staphylococcus aureus + Pseudomonas aeruginosa, ratio 1:1).

[0106] result:

[0107] Time indication:

[0108] 0-24h: yellow to yellow-green (pH 7.4 to 7.0);

[0109] 24-48h: green to blue-green (pH 7.0 to 6.5);

[0110] After 48h: dark blue (pH < 6.5), not affected by high sugar environment.

[0111] Oxygen sensitive membrane:

[0112] Wound edge: red (oxygen partial pressure > 80 mmHg);

[0113] Wound center: green (oxygen partial pressure <20 mmHg), which can clearly distinguish the necrotic area.

[0114] Microbiological testing:

[0115] 8h: Local reddish (bacterial concentration ≈ 10 4 CFU / mL);

[0116] 24h: uniform red (bacterial concentration>10 6 CFU / mL), which is 48h faster than the clinical culture method.

[0117] Example 3:

[0118] Preparation of color-changing dressings

[0119] Treatment of the substrate layer:

[0120] Bioresorbable poly(lactic-co-glycolic acid) (PLGA) was used as the substrate (thickness 1.2 mm, porosity 85%);

[0121] Constructing a micro-nano fiber network (fiber diameter 500nm-2μm) on the surface through electrospinning technology;

[0122] Low-temperature oxygen plasma treatment (power 60 W, time 90 s) was used to enhance the surface active groups (-COOH, -OH).

[0123] Preparation of intelligent time indication layer:

[0124] Development of dual-responsive hydrogels:

[0125] Matrix: oxidized alginate (ADA)-cystamine (CYS) dynamic covalent hydrogel;

[0126] Time indicator: loaded with pH / ROS dual-responsive dye (new synthetic compound: 4-(2,4-dinitrophenoxy)-1,8-naphthalimide);

[0127] Preparation process:

[0128] ADA solution (4 wt %) was mixed with CYS (2 mM);

[0129] Dual-responsive dye (0.2 mM) and mesoporous silica nanocarrier (loading amount 15%) were added;

[0130] Gradient structures were constructed by microfluidic 3D printing (resolution 50 μm);

[0131] UV cross-linking (365 nm, 10 mW / cm 2 , 5min);

[0132] Enhanced oxygen sensitive membrane:

[0133] Adopting Janus structure design:

[0134] Upper layer: PtOEPK / PDMS (thickness 30 μm);

[0135] Lower layer: polyacrylate doped with oxygen-sensitive rare earth complex (Eu(TTA)3phen) (thickness 20 μm).

[0136] An ordered mesoporous structure (pore diameter 8 nm) was constructed through molecular self-assembly technology;

[0137] Graphene quantum dots (0.5 wt %) were added as an energy transfer medium.

[0138] Intelligent microbial response system:

[0139] Development of enzyme cascade amplification system:

[0140] First layer: nitroreductase-responsive polymer (poly-β-amino ester);

[0141] The second layer: horseradish peroxidase (HRP)-immobilized nanofibers;

[0142] The third layer: signal amplification system (gold nanoclusters@ZIF-8);

[0143] Preparation method:

[0144] The three-dimensional network was constructed using layer-by-layer self-assembly technology (LbL);

[0145] Patterned distribution is achieved by microcontact printing;

[0146] Multifunctional insulation layer.

[0147] Developing a bionic skin membrane:

[0148] Matrix: Silk fibroin / polycaprolactone composite.

[0149] Functional modification:

[0150] Surface grafted zwitterionic polymer (polySBMA);

[0151] Embedded in thermosensitive liquid crystal microcapsules (cholesteric type).

[0152] Preclinical trial data

[0153] Animal model (full-thickness skin defect in diabetic rats).

[0154] Time Tracer:

[0155] 0-12h: yellow (pH 7.2);

[0156] 12-36h: orange (pH 6.8);

[0157] 36-72h: red (pH 6.2).

[0158] Infection warning: Warning signals are issued 6-12 hours before clinical symptoms

[0159] Human skin model:

[0160] Oxygen partial pressure monitoring:

[0161] It can distinguish: normal tissue (>40mmHg), ischemic edge zone (20-40mmHg), and necrotic core zone (<10mmHg).

[0162] Comparative Example:

[0163] Description of prior art (comparative example):

[0164] Technical name: Traditional pH-sensitive color-changing dressing (based on a single-layer dye system).

[0165] Composition and principle:

[0166] Base material: ordinary medical non-woven fabric;

[0167] Color-changing layer: a single pH indicator (bromocresol purple, 0.2 mM) dispersed in sodium carboxymethylcellulose (CMC) hydrogel;

[0168] Functional limitations: Only responds to pH changes (pH 5.2-6.8) through yellow to purple color change; no oxygen partial pressure / microorganism detection function; color change is greatly affected by the amount of exudate (low exudate wounds will not show color).

[0169] Performance comparison table:

[0170]

[0171]

[0172] Time tracking accuracy:

[0173] Existing technology: Only indirectly infers time through pH changes, and cannot distinguish changes within 24 hours (e.g., pH 6.5 may correspond to 12 hours or 36 hours);

[0174] Example 3: Combining the dual signals of pH and reactive oxygen species (ROS), the characteristic differences between the acute phase (0-12h) and chronic phase (12-72h) of wounds can be identified.

[0175] Infection warning sensitivity:

[0176] Existing technology: It relies on clinical symptoms (such as redness, swelling, and exudation) for judgment, which usually lags for more than 48 hours;

[0177] Examples 2-3: Direct detection of microbial metabolites to issue an early warning 6-24 hours before clinical manifestation (animal model validation).

[0178] Complex wound adaptability:

[0179] Existing technology: In hypertonic diabetic wounds, color change fails due to glucose interference;

[0180] Example 2: Gradient cross-linked hydrogel can resist the interference of 10mM glucose;

[0181] Example 3: The dual-responsive dye has no cross-reaction to glucose.

[0182] Data readability:

[0183] Existing technology: Professionals are required to subjectively interpret the color;

[0184] Example 3: The NFC module automatically quantifies data to reduce human errors.

[0185] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A color-changing dressing capable of tracing the retention time, characterized in that: include: Base material layer, time indication layer, oxygen sensitive composite membrane and microbial response layer; The substrate layer is composed of one of medical non-woven fabric and polyurethane foam; The time indicating layer is disposed on the upper surface of the substrate layer and comprises a pH-responsive color-changing material; The oxygen-sensitive composite membrane covers the surface of the time indicator layer and comprises platinum (II)-tetraphenylporphyrinone (PtOEPK) dispersed in a polydimethylsiloxane (PDMS) matrix, and its color change is related to the tissue oxygen partial pressure; The microbial response layer is arranged on the outside of the oxygen-sensitive composite membrane and contains a nitroreductase-sensitive probe. The probe is a nitrobenzothiazole derivative, and its color development reaction is positively correlated with the concentration of pathogenic bacteria metabolites.

2. The color-changing dressing capable of tracing the retention time according to claim 1, characterized in that: The pH-responsive color-changing material of the time indicating layer is a complex of bromocresol purple and bromothymol blue, and exhibits a gradient change of yellow, green, and blue within the pH range of 5.2-7.

6.

3. The color-changing dressing capable of tracing the retention time according to claim 1, characterized in that: The PDMS matrix of the oxygen-sensitive composite membrane contains silicon dioxide nanoparticles with a mass fraction of 5-15% for enhancing gas permeability and mechanical strength.

4. The color-changing dressing capable of tracing the retention time according to claim 1, characterized in that: The general structural formula of the nitrobenzothiazole derivative of the microbial response layer is: R1-NO2+2e-+2H+→R1-NHOH Wherein R1 is benzothiazol-2-yl, and its reduction product produces a characteristic absorption peak at 520-550nm.

5. The color-changing dressing capable of tracing the retention time according to claim 1, characterized in that: It also includes an isolation layer, which is arranged on the outside of the microbial response layer and is composed of a moisture-permeable polyurethane film with a thickness of 10-50 μm and a water vapor transmission rate of ≥2000 g / m 2 ·24h.

6. A method for preparing a color-changing dressing capable of tracing the retention time, applicable to the color-changing dressing capable of tracing the retention time according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Preparation of a time indicator layer: Mix a sodium alginate solution (3 wt%) with bromocresol purple (0.1 mM) and bromothymol blue (0.05 mM), apply the mixture to the surface of the substrate layer, cross-link with a CaCl2 solution, and then dry. S2. Preparation of oxygen-sensitive composite membrane: PtOEPK (0.5-2 mg / mL) and PDMS prepolymer (Sylgard 184) were mixed at a mass ratio of 10:1, 5% fumed silica was added, and the mixture was spin-coated on the surface of the time indicator layer and cured at 80°C for 2 h. S3. Preparation of a microbial response layer: Blending a nitrobenzothiazole derivative (1-5 mg / mL) with a polyvinyl alcohol (PVA, 5 wt%) solution, and forming a sensitive layer with a thickness of 20-100 μm on the oxygen-sensitive composite membrane by a microfluidic spray method; S4. Composite isolation layer: hot-press the moisture-permeable polyurethane film onto the surface of the microbial response layer at a pressure of 0.2-0.5 MPa and a temperature of 60-80°C.

7. The method for preparing a color-changing dressing capable of tracing the retention time according to claim 6, characterized in that: In step S2, the spin coating speed is 1500-3000 rpm, and the film thickness after curing is 30-80 μm.

8. The method for preparing a color-changing dressing capable of tracing the retention time according to claim 6, characterized in that: In step S3, the nozzle diameter of the microfluidic spray is 50-100 μm, the carrier gas pressure is 0.1-0.3 MPa, and the substrate temperature is 40-60°C.

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