CN112206345A

CN112206345A - Sustained-release multi-crosslinking hydrogel dressing and preparation method and application thereof

Info

Publication number: CN112206345A
Application number: CN202011090660.5A
Authority: CN
Inventors: 张海娇; 张怡; 刘春香; 马德美; 刘艳青
Original assignee: Tianqing Stem Cell Co ltd
Current assignee: Tianqing Stem Cell Co ltd
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2021-01-12
Anticipated expiration: 2040-10-13
Also published as: CN112206345B

Abstract

A slow-release multi-crosslinking hydrogel dressing and a preparation method and application thereof relate to the field of wound repair materials, in particular to a hydrogel dressing and a preparation method and application thereof. The hydrogel dressing aims to solve the problems that the physical properties of the existing hydrogel dressing are unstable before and after use and difficult to maintain, and nutrient substances required by wound recovery cannot be supplemented in time, so that the wound recovery period is prolonged. The dressing includes a first gel layer, a second gel layer, and a third gel layer. The method comprises the following steps: preparing a first gel layer, preparing a second gel layer on the first gel layer, and preparing a third gel layer on the first gel layer and the second gel layer. The three layers of gel of the hydrogel dressing are matched, so that the structure is easier to maintain, and the physical properties are stable before and after use. Provides growth factors required by wound recovery, accelerates wound healing, has long-acting and slow-release effects, and has an effective period of 20 days. The invention is used for promoting wound repair.

Description

Sustained-release multi-crosslinking hydrogel dressing and preparation method and application thereof

Technical Field

The invention relates to the field of wound repair materials, in particular to a hydrogel dressing and a preparation method and application thereof.

Background

The traditional view points that the wound healing needs a dry environment and the action of oxygen, the dry and clean wound surface is beneficial to the wound healing, and the traditional gauze dressing or the direct exposure of the wound is generally used, namely the dry healing principle. In fact, however, the oxygen utilization of human beings requires the oxygen and action of hemoglobin, while atmospheric oxygen is not directly available to the wound. Dry healing also suffers from a number of drawbacks and deficiencies, including the tendency to dehydrate wounds, form crusts, and impede epithelial cell crawling; the traditional dressing is easy to adhere to the new granulation tissue of the wound, and the dressing is damaged again when being replaced, so that the wound is painful, and the healing speed is slow; the leakage is rapid, the dressing needs to be frequently replaced, the temperature and the humidity of the wound cannot be kept, the healing time is prolonged, and the nursing workload is increased; the wound surface has no barrier to the outside, and the invasion of bacteria cannot be effectively prevented.

At present, the wound healing idea with better effect is wet healing, wherein the wet wound healing is mainly to maintain the environment with proper moisture and proper temperature of the wound by applying a closed dressing and (or) liquid medicine under the aseptic condition, and the mode is favorable for the formation of wound epithelial cells and promotes the growth of granulation tissues and the wound healing. Among them, the hydrogel dressing is a hot material of the current closed dressing, however, different hydrogels have different characteristics, and among them, the biggest problems are: firstly, the hydrogel shape and structure are not easy to maintain, and more chemical substances are added. For example, gels that rely solely on calcium ions for crosslinking with sodium alginate are brittle, less subject to stress, and less rigid when applied to the surface of the body with calcium ions lost; secondly, hydrogels can only provide a healing environment and cannot essentially provide a healing promoting substance, for example, most gels on the market only provide a relatively closed and breathable healing environment for wounds, but do not add any nutrients to supply the healing needs.

Disclosure of Invention

The invention provides a sustained-release multi-crosslinking hydrogel dressing and a preparation method and application thereof, aiming at solving the problems that the physical properties of the existing hydrogel dressing are unstable before and after use and difficult to maintain, and nutrient substances required by wound recovery cannot be supplemented in time, so that the wound recovery period is prolonged.

The hydrogel dressing for wound repair of the present invention comprises a first gel layer, a second gel layer, and a third gel layer; wherein the first gel layer is a calcium alginate gel layer, the second gel layer is a carboxymethyl chitosan gel layer, and the third gel layer is a methacrylated carboxymethyl chitosan gel layer; the second gel layer is located above the first gel layer, and a third gel layer is covered on the second gel layer and the side surfaces of the first gel layer and the second gel layer.

The invention also provides a preparation method of the hydrogel dressing, which comprises the following steps:

firstly, continuously stirring and reacting a carboxymethyl chitosan aqueous solution with the mass concentration of 1.2-1.5% and a methacrylic anhydride aqueous solution with the mass concentration of 1.9-2.2% for 24-26 h under the conditions of alkalinity and ice bath, then carrying out vacuum drying to obtain methacrylated carboxymethyl chitosan, and storing at-80 ℃;

mixing a sodium alginate aqueous solution and an sPL solution to obtain a mixed solution A, pouring the mixed solution A into a mold, freezing for 30-60 min, adding a pre-cooled calcium chloride aqueous solution into the frozen mold, allowing the calcium chloride aqueous solution to highly exceed the mixed solution A, and continuously crosslinking at 4 ℃ for 20-40min to obtain a first gel layer, namely a calcium alginate gel layer;

mixing the carboxymethyl chitosan aqueous solution with the sPL solution to obtain a mixed solution B, pouring the mixed solution B into a mold above a first gel layer, adding a glutaraldehyde aqueous solution into the mold until the mixed solution B is higher than the mixed solution B, and crosslinking for 15-20 min at 65-70 ℃ to form a second gel layer above the first gel layer; wherein the first gel layer is the same size as the second gel layer;

taking out the first gel layer and the second gel layer together, putting the two layers of gel into a new mold with the size larger than that of the first gel layer, enabling the first gel layer to face downwards, adding the mixed solution C into the new mold, enabling the height of the mixed solution C to be 1-2 mm higher than that of the second gel layer, and performing crosslinking under an ultraviolet lamp to form a third gel layer; obtaining the hydrogel dressing;

the mixed solution C is a mixed solution composed of methacrylic acid carboxymethyl chitosan, polyvinyl alcohol, an initiator 2549, boric acid and glycerol according to a mass ratio of (5-10) to 2.5:0.01:1: 1.

Furthermore, the volume ratio of the carboxymethyl chitosan aqueous solution to the methacrylic anhydride aqueous solution in the step one is 1 (1.2-1.3).

Further, the pH of the alkaline condition in the first step is 8 to 10.

Furthermore, in the second step, the mass concentration of the sodium alginate aqueous solution is 1.8-2.2%, and the concentration of the calcium chloride aqueous solution is 190-210 mmol/L.

Furthermore, the volume of the sPL solution in the mixed solution A in the second step is 2.5-10% of the total volume of the mixed solution A.

Furthermore, the mass concentration of the carboxymethyl chitosan aqueous solution in the step three is 1.4-1.6%.

Furthermore, the volume of the sPL solution in the mixed solution B in the third step is 5-25% of the total volume of the mixed solution B.

Furthermore, the mass concentration of the glutaraldehyde aqueous solution in the third step is 2-2.1%.

Further, the preparation method of the sPL solution in the second step and the third step comprises the following steps:

transferring the anticoagulated blood into a centrifuge tube, centrifuging for 10-15 min at room temperature under the condition of 1000r/min, slowly increasing and decreasing the speed in the process, transferring the upper layer of platelet-rich plasma into an ultrafiltration centrifuge tube after centrifugation, centrifuging for 15-20 min at room temperature under the condition of 4000r/min, and taking the lower layer to obtain the hyperconcentrated PRP; adding 15-20 mmol/L CaCl into the super-concentrated PRP obtained by separation₂And 2U/ml of low-molecular-weight heparin sodium to obtain a solution X, incubating the solution X at 37 ℃ for 1-2 hours to fully activate platelets to release platelet-derived factors, then transferring the solution to a temperature of-80 ℃ for freezing for 1-2 hours, thawing at 37 ℃, cooling at 4 ℃ for 1-1.5 hours to coagulate fibrin, centrifuging at 1200r/min and 4 ℃ for 10-15 minutes, taking supernatant, and filtering by using a 0.22 mu m filter to obtain the sPL solution. Wherein CaCl in the solution X₂Is 15 to20mmol/L, and the concentration of the low molecular weight heparin sodium is 2U/ml.

Further, in the fourth step, the crosslinking temperature is room temperature, and the crosslinking time is 1-2 h.

The invention also provides application of the hydrogel dressing in preparing a medicament for promoting wound repair.

Further, the hydrogel dressing has the specific application method that: when in use, the first gel layer of the hydrogel dressing is directly contacted with the wound surface.

The invention has the beneficial effects that:

the invention adopts 3 kinds of cross-linking modes to combine, namely the ionic cross-linking of sodium alginate and calcium chloride; ultraviolet physical crosslinking of polyvinyl alcohol and a photoinitiator; chemically crosslinking the methacrylated carboxymethyl chitosan and glutaraldehyde, and combining the three crosslinking modes to form the multilayer gel. The sPL is added into the gel layer, and has stronger activity, more types and more quantity of nutritional factors, so that the biological effect of the sPL has the function of PL, and the sPL can activate endogenous stem cells of a direct acting part or a tissue to differentiate the endogenous stem cells into cells of an injured tissue part, thereby achieving the purposes of tissue regeneration and function recovery.

The first and second gel layers each contain sPL to be released, with the addition of sPL depot release, layered release, gradually promoting wound healing. The sPL contains various growth factors to promote wound healing, provide the growth factors required by wound healing, accelerate wound scabbing, and reduce scar generation by close application.

The first gel layer, which is in direct contact with skin, is composed of Ca²⁺Forming calcium alginate gel, Ca, with sodium alginate by ion exchange²⁺And Na on the wound⁺Exchange is carried out, the blood coagulation reaction is promoted, the bleeding is quickly stopped, and simultaneously the added sPL promotes the primary healing of the wound;

the second gel layer is formed by covalent bond connection of carboxymethyl chitosan and polyvinyl alcohol through glutaraldehyde serving as a cross-linking agent; the bacteriostasis is promoted, a large amount of sPL is slowly released, and the wound is promoted to be quickly recovered;

the third gel layer is formed by monomer photo-crosslinking of methacrylic acid carboxymethyl chitosan through a photo-crosslinking initiator 2549 to form a gel layer, and the gel layer is compact in structure, contains more sPL binding sites, contains a large amount of sPL to be released, promotes inflammatory reaction of wounds and accelerates wound healing. In order to prevent the first gel layer and the second gel layer from separating, the third gel layer wraps the upper layer of gel and the lower layer of gel to integrate and reinforce, and meanwhile, boric acid is added into the first gel layer to inhibit bacteria.

The three layers of gel of the hydrogel dressing are matched, so that the structure is easier to maintain, and the physical properties are stable before and after use. Provides growth factors required by wound recovery, accelerates wound healing, has long-acting and slow-release effects, and has an effective period of 20 days.

Drawings

FIG. 1 is a schematic diagram of a gel structure, wherein 1 is a first gel layer, 2 is a second gel layer, and 3 is a third gel layer;

FIG. 2 is a graph of modulus measurements of the gel before use;

FIG. 3 is a post-gel modulus measurement view;

figure 4 is a statistical plot of wound area versus number of days of recovery.

Detailed Description

The technical solution of the present invention is not limited to the following specific embodiments, but includes any combination of the specific embodiments.

The first embodiment is as follows: the hydrogel dressing for wound repair of the present embodiment includes a first gel layer, a second gel layer, and a third gel layer; wherein the first gel layer is a calcium alginate gel layer, the second gel layer is a carboxymethyl chitosan gel layer, and the third gel layer is a methacrylated carboxymethyl chitosan gel layer; the second gel layer is located above the first gel layer, and a third gel layer is covered on the second gel layer and the side surfaces of the first gel layer and the second gel layer.

The second embodiment is as follows: the preparation method of the hydrogel dressing of the embodiment comprises the following steps:

The recovery promoting effect is different due to different addition amounts of sPL, the wound recovery time is 1-5 days under the condition that the addition amount of the sPL in the second gel layer is 20% and the addition amount of the sPL in the first gel layer is 10%; the wound recovery time is 5-15 days under the condition that the addition amount of sPL of the second gel layer is 30% and the addition amount of sPL of the first gel layer is 15%; the wound recovery time was 15-30 days with the second gel layer sPL added at 40% and the first gel layer at 20%. The amount of sPL added can therefore be selected according to the wound recovery time.

The third concrete implementation mode: the second embodiment is different from the first embodiment in that: in the first step, the volume ratio of the carboxymethyl chitosan aqueous solution to the methacrylic anhydride aqueous solution is 1 (1.2-1.3). The rest is the same as the second embodiment.

The fourth concrete implementation mode: the second embodiment is different from the first embodiment in that: step one the pH of the alkaline conditions is 8-10. The rest is the same as the second embodiment.

The fifth concrete implementation mode: the second embodiment is different from the first embodiment in that: in the second step, the mass concentration of the sodium alginate aqueous solution is 1.8-2.2%, and the concentration of the calcium chloride aqueous solution is 190-210 mmol/L. The rest is the same as the second embodiment.

The sixth specific implementation mode: the second embodiment is different from the first embodiment in that: in the second step, the volume of the sPL solution in the mixed solution A is 2.5-10% of the total volume of the mixed solution A. The rest is the same as the second embodiment.

The seventh embodiment: the second embodiment is different from the first embodiment in that: in the third step, the mass concentration of the carboxymethyl chitosan aqueous solution is 1.4-1.6%. The rest is the same as the second embodiment.

The specific implementation mode is eight: the second embodiment is different from the first embodiment in that: and in the third step, the volume of the sPL solution in the mixed solution B is 5-25 percent of the total volume of the mixed solution B. The rest is the same as the second embodiment.

The specific implementation method nine: the second embodiment is different from the first embodiment in that: in the third step, the mass concentration of the glutaraldehyde aqueous solution is 2-2.1%. The rest is the same as the second embodiment.

The detailed implementation mode is ten: the second embodiment is different from the first embodiment in that: the preparation method of the sPL solution in the second step and the third step comprises the following steps:

transferring the anticoagulated blood into a centrifuge tube, centrifuging for 10-15 min at room temperature under the condition of 1000r/min, slowly increasing and decreasing the speed in the process, transferring the upper layer of platelet-rich plasma into an ultrafiltration centrifuge tube after centrifugation, centrifuging for 15-20 min at room temperature under the condition of 4000r/min, and taking the lower layer to obtain the hyperconcentrated PRP; adding 15-20 mmol/L CaCl into the super-concentrated PRP obtained by separation₂And 2U/ml of low-molecular-weight heparin sodium to obtain a solution X, incubating the solution X at 37 ℃ for 1-2 hours to fully activate platelets to release platelet-derived factors, then transferring the solution to a temperature of-80 ℃ for freezing for 1-2 hours, thawing at 37 ℃, cooling at 4 ℃ for 1-1.5 hours to coagulate fibrin, centrifuging at 1200r/min and 4 ℃ for 10-15 minutes, taking supernatant, and filtering by using a 0.22 mu m filter to obtain the sPL solution. Wherein CaCl in the solution X₂The concentration of the low molecular weight heparin sodium is 15-20 mmol/L, and the concentration of the low molecular weight heparin sodium is 2U/ml. The rest is the same as the second embodiment.

The concrete implementation mode eleven: the second embodiment is different from the first embodiment in that: and in the fourth step, the crosslinking temperature is room temperature, and the crosslinking time is 1-2 h. The rest is the same as the second embodiment.

The specific implementation mode twelve: the hydrogel dressing of the embodiment is applied to preparation of a medicine for promoting wound repair.

The specific implementation mode is thirteen: the present embodiment is twelve different from the specific embodiment: the hydrogel dressing has the specific application method that: when in use, the first gel layer of the hydrogel dressing is directly contacted with the wound surface. The rest is the same as the embodiment twelve.

The following examples are given to illustrate the present invention in detail, and the following experiments are carried out on the premise of the technical scheme of the present invention, and detailed embodiments and specific operation procedures are given, but the scope of the present invention is not limited to the following experiments.

Experimental group 1:

the preparation method of the hydrogel dressing comprises the following steps:

firstly, continuously stirring and reacting a 1.2 mass percent carboxymethyl chitosan aqueous solution and a 2 mass percent methacrylic anhydride aqueous solution for 24 hours under the conditions of alkalinity (pH 8-10) and ice bath, then carrying out vacuum drying to obtain methacrylated carboxymethyl chitosan, and storing at-80 ℃; wherein the volume ratio of the carboxymethyl chitosan aqueous solution to the methacrylic anhydride aqueous solution is 1: 1.2;

mixing a sodium alginate aqueous solution with the mass concentration of 2% with an sPL solution to obtain a mixed solution A, pouring the mixed solution A into a mold, freezing for 30-60 min, adding a pre-cooled 200mmol/L calcium chloride aqueous solution into the frozen mold, continuously crosslinking at 4 ℃ for 20-40min to obtain a first gel layer, namely a calcium alginate gel layer; the volume of the sPL solution in the mixed solution A is 5 percent of the total volume of the mixed solution A;

mixing a 1.5% carboxymethyl chitosan aqueous solution with an sPL solution to obtain a mixed solution B, pouring the mixed solution B into a mold above a first gel layer, adding a 2% glutaraldehyde aqueous solution into the mold with the mixed solution B being higher than the mixed solution B, and crosslinking for 15-20 min at 65-70 ℃ to form a second gel layer above the first gel layer; wherein the first gel layer is the same size as the second gel layer; the volume of the sPL solution in the mixed solution B is 5 percent of the total volume of the mixed solution B;

taking out the first gel layer and the second gel layer together, putting the two layers of gel into a new mold with the size larger than that of the first gel layer and enabling the first gel layer to face downwards, adding the mixed solution C into the new mold, enabling the height of the mixed solution C to be 2mm higher than that of the second gel layer, and performing crosslinking under a 100W ultraviolet lamp to form a third gel layer; namely, a third gel layer is covered on the second gel layer and the side surfaces of the first gel layer and the second gel layer; the temperature of crosslinking is room temperature, and the time of crosslinking is 2 h.

The mixed solution C is a mixed solution composed of methacrylic acid carboxymethyl chitosan, polyvinyl alcohol (PVA), an initiator 2549, boric acid and glycerol according to a mass ratio of 10:2.5:0.01:1: 1. The layer containing boric acid has bactericidal effect, surrounds the gel, and maintains the aseptic state of the gel.

The preparation method of the sPL solution in the second step and the third step comprises the following steps:

transferring the anticoagulated blood into a centrifuge tube, centrifuging for 10-15 min at room temperature under the condition of 1000r/min, slowly increasing and decreasing the speed in the process, transferring the upper layer of platelet-rich plasma into an ultrafiltration centrifuge tube after centrifugation, centrifuging for 15-20 min at room temperature under the condition of 4000r/min, and taking the lower layer to obtain the hyperconcentrated PRP; adding 1 to the separated super concentrated PRP5-20 mmol/L CaCl₂And 2U/ml of low-molecular-weight heparin sodium to obtain a solution X, incubating the solution X at 37 ℃ for 1-2 hours to fully activate platelets to release platelet-derived factors, then transferring the solution to a temperature of-80 ℃ for freezing for 1-2 hours, thawing at 37 ℃, cooling at 4 ℃ for 1-1.5 hours to coagulate fibrin, centrifuging at 1200r/min and 4 ℃ for 10-15 minutes, taking supernatant, and filtering by using a 0.22 mu m filter to obtain the sPL solution. Wherein CaCl in the solution X₂The concentration of the low molecular weight heparin sodium is 15-20 mmol/L, and the concentration of the low molecular weight heparin sodium is 2U/ml.

Experimental group 2:

the experimental group only differs from the experimental group 1 in that the volume of the sPL solution in the mixed solution B in the step three is 10% of the total volume of the mixed solution B.

Experimental group 3:

the experimental group differs from the experimental group 1 only in that the volume of the sPL solution in the mixed solution B in the step three is 15% of the total volume of the mixed solution B.

Experimental group 4:

the experimental group only differs from the experimental group 1 in that the volume of the sPL solution in the mixed solution B in the step three is 20% of the total volume of the mixed solution B.

Experimental group 5:

the experimental group only differs from the experimental group 1 in that the volume of the sPL solution in the mixed solution B in the step three is 40% of the total volume of the mixed solution B.

(1) 24 SD rats were taken and weighed 180-. The dressing of the invention was applied to wounds of different depths on the skin of the rat back, divided into 5 groups, and after the corresponding recovery time, the gel was removed for observation, the results are shown in table 1.

TABLE 1

As shown in table 1, fig. 2 and fig. 3 (● shows viscous modulus, ■ shows elastic modulus), wounds with different amounts of sPL added were applied to the skin wounds on the backs of rats to form a model, and after the wounds were healed, the gel was removed; through microscope observation and rheometer detection (viscous modulus and elastic modulus), the difference between the elastic modulus and the viscous modulus is small in comparison of FIGS. 2 and 3; the physical properties (hardness, viscoelasticity, adhesion and water solubility) of the hydrogel are proved; this shows that the addition of sPL will not affect the gel morphology, and can maintain water for a long time, and the gel has stable physical properties, and can maintain normal morphology within 22 days, and has little difference from the initial gel preparation.

(2) SD rats 24, body weight 180-. The dressing prepared by each experimental group is applied to wounds with different sizes and depths on the back skin of the rat.

1. Blank group: blank 1 is subjected to damage molding without repairing, blank 2 is added with sPL without applying, and blank 3 is subjected to mold molding without adding sPL.

2. Experimental groups: the rats were subjected to wound modeling, dressings containing different amounts of sPL were applied, wounds were photographed every 3 days, and the results were recorded for wound recovery time. The specific groupings are as follows.

TABLE 2

Table 2 blank 1 shows the group that recovers solely on its healing capacity without treating the wound at all, and blank 2 can explore the recovery capacity of the wound under the influence of sPL when injected into the wound only; blank group 3 illustrates the effect of single-factor hydrogels on wound recovery; the results of comparing the experimental groups with the blank group show that the difference between the wound recovery ability of the gel and the sPL in the presence of both factors alone is different.

The specific hemostasis, anti-inflammation and recovery time are shown in the following table.

TABLE 3

Group of	Wound size of model	Time of hemostasis	Time to relieve red swelling	Time to scab
					Blank group 1	1cm×1cm×1.5mm	30min	5d	25d
Blank group
	2	1cm×1cm×1.5mm	25min	4.5d	23d
Blank group
	3	1cm×1cm×1.5mm	20miin	4d	24d
Experimental group 1						1cm×1cm×1.5mm	20min	4d	22d
	Experimental group 2	1cm×1cm×1.5mm	18min	3d	20d
Experimental group 3						1cm×1cm×1.5mm	15min	2d	15d
	Experimental group 4	1cm×1cm×1.5mm	5min	2d	7d
Experimental group 5						1cm×1cm×1.5mm	2min	2d		5d

Table 3 shows the differences in the hemostasis time, red swelling disappearance time, and wound scab recovery time between the blank and experimental groups under the same size of wound creation conditions directly reflect the time for wound hemostasis, inflammation reduction, and complete recovery under different conditions, reflecting the effects of different hydrogels.

In fig. 4, ● indicates blank 1, ■ indicates blank 2, a-solidup indicates blank 3, a-x indicates experiment 1, diamond-solid indicates experiment 2, a-x indicates experiment 3, □ indicates experiment 4, and a-x indicates experiment 5. The line graph shown in fig. 4 shows that at 20% sPL addition, the wound recovered completely on day 20, followed by 40%, 10%, 5% addition, but the three groups did not recover completely. Blank group recovery case: blank 1 is worst and

blanks

2, 3 are not very different.

(3) Long-acting sustained release proves that key cytokines in sPL are gradually released

TABLE 4

TABLE 5

TABLE 6

The consumption degree of sPL is indirectly reflected according to the content of several important factors in sPL, and the residual content of each factor in gel can be directly detected by using the kit.

As shown in tables 4-6, several factors were released gradually for up to 20 days. Part of the factors with higher content are not released completely, which shows that the gel release sPL process meets the long-acting and slow-release requirements, can effectively provide sufficient nutrient substances for the wound in the wound recovery period and promotes the repair process.

Claims

1. A slow-release multi-crosslinked hydrogel dressing, which is characterized by comprising a first gel layer, a second gel layer and a third gel layer; wherein the first gel layer is a calcium alginate gel layer, the second gel layer is a carboxymethyl chitosan gel layer, and the third gel layer is a methacrylated carboxymethyl chitosan gel layer; the second gel layer is located above the first gel layer, and a third gel layer is covered on the second gel layer and the side surfaces of the first gel layer and the second gel layer.

2. The slow-release multi-crosslinked hydrogel dressing according to claim 1, wherein the hydrogel dressing is prepared by a method comprising the steps of:

3. The slow-release multi-crosslinked hydrogel dressing according to claim 2, wherein the volume ratio of the carboxymethyl chitosan aqueous solution to the methacrylic anhydride aqueous solution in the step one is 1 (1.2-1.3).

4. The slow-release multi-crosslinked hydrogel dressing according to claim 2, wherein the volume of sPL solution in the mixed solution A in the second step is 2.5% -10% of the total volume of the mixed solution A.

5. The slow-release multi-crosslinked hydrogel dressing according to claim 2, wherein the volume of sPL solution in the mixed solution B in the third step is 5% -25% of the total volume of the mixed solution B.

6. The sustained-release multi-crosslinked hydrogel dressing according to claim 2, wherein the mass concentration of the glutaraldehyde aqueous solution in step three is 2-2.1%.

7. The slow-release multi-crosslinked hydrogel dressing according to claim 2, wherein the sPL solution is prepared in the second step and the third step by:

transferring the anticoagulated blood into a centrifuge tube, centrifuging for 10-15 min at room temperature under the condition of 1000r/min, slowly increasing and decreasing the speed in the process, transferring the upper layer of platelet-rich plasma into an ultrafiltration centrifuge tube after centrifugation, centrifuging for 15-20 min at room temperature under the condition of 4000r/min, and taking the lower layer to obtain the hyperconcentrated PRP; adding 15-20 mmol/L CaCl into the super-concentrated PRP obtained by separation₂Mixing the solution X with 2U/ml low molecular weight heparin sodium to obtain a solution X, incubating the solution X at 37 ℃ for 1-2 hours to fully activate platelets to release platelet-derived factors, then transferring the solution X to a temperature of-80 ℃ for freezing for 1-2 hours, thawing at 37 ℃, cooling at 4 ℃ for 1-1.5 hours to coagulate fibrin, centrifuging at 1200r/min and 4 ℃ for 10-15 minutes, taking supernatant, and filtering by using a 0.22 mu m filter to obtain an sPL solution; wherein CaCl in the solution X₂The concentration of the low molecular weight heparin sodium is 15-20 mmol/L, and the concentration of the low molecular weight heparin sodium is 2U/ml.

8. The slow-release multi-crosslinked hydrogel dressing according to claim 2, wherein the crosslinking temperature in the fourth step is room temperature, and the crosslinking time is 1-2 h.

9. Use of a hydrogel dressing as claimed in claim 1 in the manufacture of a medicament for promoting wound repair.

10. The use according to claim 9, wherein the hydrogel dressing is applied by a method comprising: when in use, the first gel layer of the hydrogel dressing is directly contacted with the wound surface.