Mesenchymal stem cell exosome in-vitro dressing as well as preparation method and application thereof

Abstract

The invention discloses a mesenchymal stem cell exosome in-vitro dressing as well as a preparation method and application thereof, and relates to the technical field of medical dressings. In order to improve the healing performance of wounds, the polyurethane foam dressing is prepared, and castor oil polyol containing guanidyl is introduced in the preparation process, so that the biocompatibility and antibacterial performance of the dressing are improved, and the risk that the wounds are infected by external bacteria is effectively reduced; and in order to further promote wound healing, mesenchymal stem cell exosomes are also added, so that cell proliferation can be effectively promoted, inflammation can be reduced, tissue regeneration can be promoted, wound healing is further promoted, and pain of patients is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of medical dressings, and in particular to an external dressing for mesenchymal stem cell exosomes, and a preparation method and application thereof. Background Art

[0002] As a natural barrier covering the human body, the skin plays an important protective role. Various superficial skin injuries suffered in life, such as knee abrasions and finger scratches, have a precise repair process for the healing of these wounds: from the initial coagulation to seal the wound, to the aggregation of immune cells to remove pathogens, to the filling of defects by new cells, and finally the reconstruction of tissue structure. The whole process requires the precise coordination of dozens of bioactive substances (such as coagulation factors released by platelets, antibacterial proteins secreted by leukocytes, and collagen fibers produced by fibroblasts), and needs to face the invasion of bacteria from the outside world after the skin barrier is damaged. In order to accelerate the healing of wounds, people often use Band-Aids, bandages and other methods to protect wounds; however, although the Band-Aids and bandages commonly used in traditional nursing can temporarily isolate external pollution, they will hinder the further healing of wounds, adhere to the wound or make the wound airtight, which will cause the wound to soak; therefore, new dressings with better performance are gradually replacing traditional dressings such as medical bandages. Summary of the invention

[0003] The purpose of the present invention is to provide a mesenchymal stem cell exosome dressing for external use and a preparation method and application thereof, so as to solve the problems raised in the prior art.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for preparing a mesenchymal stem cell exosome dressing for external use, comprising the following steps: S1. Preparation of modified castor oil polyol; S11. Castor oil is placed in a container, heated to 105-110° C. and kept warm for 15-30 min, ferric chloride and anhydrous ethanol are added thereto, stirred and mixed until uniform, sodium azide is added thereto, cooled to 0-5° C., irradiated with blue light, stirred and reacted for 12-24 h, and then the excess solvent is removed by rotary evaporation, and the reaction product is washed with deionized water for 2-3 times, and the remaining reaction product is heated to 105-110° C. again, and kept warm for 15-30 min to obtain azidized castor oil; S12. 1,3-di-BOC-2-(carboxymethyl)guanidine is dispersed in DMF, N,N-dicyclohexylcarbodiimide is added thereto, the mixture is stirred evenly, and then the mixture is added dropwise to a DMF solution containing butynediol, the mixture is heated to 75-80°C, the mixture is stirred for reaction for 3-6 hours, and then the excess solvent is removed by rotary evaporation to obtain an alkynol intermediate; S13. Dissolve azidized castor oil in DMF, add the alkynol intermediate thereto, maintain the temperature of the reaction system at 20 - 25 °C, stir and react for 12 - 24 h, then rotary evaporate to remove the excess solvent to obtain modified castor oil polyol; S2. Prepare the mesenchymal stem cell exosome topical dressing; S21. Mix polyethylene glycol and modified castor oil polyol, heat up to 105 - 110 °C, keep warm for 12 - 24 h, then cool down to room temperature, add toluene diisocyanate and glycerol, protect under a nitrogen atmosphere, stir and mix at 45 °C for 5 - 8 min to obtain a mixed solution for standby; S22. Add mesenchymal stem cell exosomes to ultrapure water, stir and mix evenly, then add the foaming agent and foam stabilizer, stir evenly, add the mixed solution, stir and mix at high speed, place it in a foaming mold, keep warm and foam, after the foaming is completed, cut to obtain the mesenchymal stem cell exosome topical dressing.

[0005] Further, by weight, in step S11, 10 parts of castor oil, 0.05 - 0.12 parts of ferric chloride and 1.1 - 2.1 parts of sodium azide need to be added.

[0006] Further, by weight, in step S12, 10 parts of 1,3 - bis - BOC - 2 - (carboxymethyl)guanidine, 0.03 - 0.07 parts of N,N - dicyclohexylcarbodiimide and 2.5 - 2.8 parts of butynediol need to be added.

[0007] Further, by weight, in step S13, 10 parts of azidized castor oil and 10 - 11.5 parts of alkynol intermediate need to be added.

[0008] Further, in step S2, the mesenchymal stem cell exosome topical dressing is composed of 24 - 32 parts of polyethylene glycol, 6 - 10 parts of modified castor oil polyol, 28 - 32 parts of toluene diisocyanate, 1.5 - 2.8 parts of glycerol, 2 - 8 parts of ultrapure water, 0.3 - 0.5 parts of mesenchymal stem cell exosomes, 0.5 - 0.8 parts of foaming agent and 1 - 1.2 parts of foam stabilizer.

[0009] Further, the foaming agent is alkyl polyglycoside; the foam stabilizer is any one of silicone - based surfactants.

[0010] Further, a mesenchymal stem cell exosome topical dressing is prepared by the above method.

[0011] Further, the mesenchymal stem cell exosome topical dressing can be used as a wound dressing.

[0012] Compared with the prior art, the beneficial effects of the present invention are: In order to improve the wound healing performance, the present invention prepares a polyurethane foam dressing. Compared with traditional bandages, the polyurethane foam dressing has better skin affinity, can effectively absorb wound exudate, avoid adhesion to the wound surface, reduce the risk of skin maceration around the wound, and the porous structure of the foam dressing also has a better stress dispersion effect compared with traditional bandages, which can effectively reduce the friction on the wound, reduce the pain of patients and facilitate the healing of wounds in movable parts; And in order to further improve the biocompatibility and accelerate the wound healing of the polyurethane foam dressing, when preparing the dressing, the present invention uses castor oil as a raw material. Castor oil is rich in olefins. When it is mixed with sodium azide and under the irradiation of ferrous ions and blue light, the unactivated olefins will react with sodium azide to form alkyl azide products, thereby introducing azide groups into the castor oil molecules; On this basis, the present invention further uses 1,3 - di - BOC - 2 - (carboxymethyl)guanidine containing carboxyl and guanidine groups as a raw material, reacts it with butynediol containing alkynyl groups, thereby generating an alkynol intermediate containing hydroxyl and guanidine groups. The guanidine group therein has broad - spectrum antibacterial activity, can effectively affect the cell membrane activity of bacteria and other microorganisms, thereby inhibiting bacterial activity and playing an antibacterial role; then the alkynol intermediate is mixed with azidated castor oil, and using the reaction between azide and alkynyl groups, a castor oil polyol containing guanidine groups is generated. Then, as a polyol raw material, it is further mixed with isocyanate for foaming reaction, thereby finally preparing a foam dressing with biocompatibility and antibacterial activity; At the same time, in order to further accelerate wound healing, the present invention also adds mesenchymal stem cell exosomes during the preparation of the foam dressing. Mesenchymal stem cell exosomes are nanoscale vesicles released by mesenchymal stem cells (MSCs) through paracrine action, which contain various bioactive substances such as proteins and mRNAs, can effectively promote cell proliferation, reduce inflammation and promote tissue regeneration. Adding them to the dressing can effectively promote wound healing. Detailed implementation methods

[0013] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0014] In the examples and comparative examples of the present invention, the polyethylene glycol has a weight - average molecular weight of 2000, and the mesenchymal stem cell exosomes used are human umbilical cord mesenchymal stem cell exosomes of model FRE - 08; Example 1. A preparation method of an external dressing of mesenchymal stem cell exosomes, comprising the following steps: S1. Prepare modified castor oil polyol; S11. Place 10 parts of castor oil by weight in a container, heat it up to 105 °C and keep it warm for 15 min. Then add 0.05 part of ferric chloride and absolute ethanol to it. After stirring and mixing until uniform, add 1.1 parts of sodium azide to it, cool it down to 0 °C, irradiate it with blue light, stir and react for 12 h. Then rotary evaporate to remove the excess solvent, and wash the reaction product with deionized water twice. Then heat the remaining reaction product to 105 °C again and keep it warm for 15 min to obtain azido castor oil; S12. Disperse 10 parts of 1,3 - di - BOC - 2 - (carboxymethyl)guanidine by weight in DMF, add 0.03 part of N,N - dicyclohexylcarbodiimide to it, continue to mix and stir until uniform, then drop it into the DMF solution containing 2.5 parts of butynediol. Heat it up to 75 °C, stir and react for 3 h. Then rotary evaporate to remove the excess solvent to obtain an alkynol intermediate; S13. Dissolve 10 parts of azido castor oil by weight in DMF, add 10 parts of the alkynol intermediate to it, maintain the temperature of the reaction system at 20 °C, stir and react for 12 h. Then rotary evaporate to remove the excess solvent to obtain a modified castor oil polyol; S2. Prepare a mesenchymal stem cell exosome topical dressing; S21. Mix 24 parts of polyethylene glycol and 6 parts of modified castor oil polyol by weight, heat it up to 105 °C and keep it warm for 12 h. Then cool it down to room temperature, add 28 parts of toluene diisocyanate and 1.5 parts of glycerol. Under the protection of a nitrogen atmosphere, stir and mix and react at 45 °C for 5 min to obtain a mixed solution for standby; S22. Add 0.3 part of mesenchymal stem cell exosomes to 2 parts of ultrapure water by weight, stir and mix until uniform. Then add 0.5 part of a foaming agent and 1 part of a foam stabilizer, stir evenly, add the mixed solution, stir and mix at high speed, then place it in a foaming mold, keep it warm and foam. After foaming is completed, cut it to obtain a mesenchymal stem cell exosome topical dressing.

[0015] Example 2. A preparation method of a mesenchymal stem cell exosome topical dressing, comprising the following steps: S1. Prepare a modified castor oil polyol; S11. Place 10 parts of castor oil by weight in a container, heat it up to 110 °C and keep it warm for 30 min. Then add 0.12 part of ferric chloride and absolute ethanol to it. After stirring and mixing until uniform, add 1.1 parts of sodium azide to it, cool it down to 5 °C, irradiate it with blue light, stir and react for 24 h. Then rotary evaporate to remove the excess solvent, and wash the reaction product with deionized water three times. Then heat the remaining reaction product to 110 °C again and keep it warm for 30 min to obtain azido castor oil; S12. Disperse 10 parts of 1,3 - bis - BOC - 2 - (carboxymethyl)guanidine by weight into DMF, add 0.07 part of N,N - dicyclohexylcarbodiimide thereto, continue to mix and stir evenly, then drop it into the DMF solution containing 2.5 parts of butynediol, raise the temperature to 80 °C, stir and react for 6 h, then rotary evaporate to remove the excess solvent to obtain an alkynol intermediate; S13. Dissolve 10 parts of azidized castor oil by weight in DMF, add 10 parts of the alkynol intermediate thereto, maintain the temperature of the reaction system at 25 °C, stir and react for 24 h, then rotary evaporate to remove the excess solvent to obtain a modified castor oil polyol; S2. Prepare a mesenchymal stem cell exosome topical dressing; S21. Mix 24 parts of polyethylene glycol and 6 parts of the modified castor oil polyol by weight, raise the temperature to 110 °C, keep warm for 24 h, then cool down to room temperature, add 28 parts of toluene diisocyanate and 1.5 parts of glycerol, under the protection of a nitrogen atmosphere, stir and mix at 45 °C for 8 min to obtain a mixed solution for standby; S22. Add 0.3 part of mesenchymal stem cell exosomes to 2 parts of ultrapure water by weight, stir and mix evenly, then add 0.5 part of a foaming agent and 1 part of a foam stabilizer thereto, stir evenly, add the mixed solution, stir and mix at high speed, then place it in a foaming mold, keep warm and foam, after the foaming is completed, cut it to obtain the mesenchymal stem cell exosome topical dressing.

[0016] Example 3. A preparation method of a mesenchymal stem cell exosome topical dressing, comprising the following steps: Compared with Example 2, the addition amount of sodium azide in step S11 is increased in this example; S1. Prepare a modified castor oil polyol; S11. Place 10 parts of castor oil in a container by weight, heat and raise the temperature to 110 °C and keep warm for 30 min, then add 0.12 part of ferric chloride and anhydrous ethanol thereto, stir and mix until uniform, then add 2.1 parts of sodium azide thereto, cool down to 5 °C, irradiate with blue light, stir and react for 24 h, then rotary evaporate to remove the excess solvent, and wash the reaction product 3 times with deionized water, then raise the remaining reaction product to 110 °C again and keep warm for 30 min to obtain azidized castor oil; S12. Disperse 10 parts of 1,3 - bis - BOC - 2 - (carboxymethyl)guanidine by weight into DMF, add 0.07 part of N,N - dicyclohexylcarbodiimide thereto, continue to mix and stir evenly, then drop it into the DMF solution containing 2.5 parts of butynediol, raise the temperature to 80 °C, stir and react for 6 h, then rotary evaporate to remove the excess solvent to obtain an alkynol intermediate; S13. Dissolve 10 parts of azidized castor oil by weight in DMF, add 10 parts of alkynol intermediate thereto, maintain the temperature of the reaction system at 25 °C, stir and react for 24 h, then rotary evaporate to remove the excess solvent to obtain modified castor oil polyol; S2. Prepare a mesenchymal stem cell exosome topical dressing; S21. Mix 24 parts of polyethylene glycol and 6 parts of modified castor oil polyol by weight, heat up to 110 °C, keep warm for 24 h, then cool down to room temperature, add 28 parts of toluene diisocyanate and 1.5 parts of glycerol, protect under a nitrogen atmosphere, stir and mix at 45 °C for 8 min to obtain a mixed solution for standby; S22. Add 0.3 part of mesenchymal stem cell exosomes to 2 parts of ultrapure water by weight, stir and mix evenly, then add 0.5 part of foaming agent and 1 part of foam stabilizer thereto, stir evenly, add the mixed solution, stir and mix at high speed, then place it in a foaming mold, keep warm and foam, after foaming is completed, cut to obtain the mesenchymal stem cell exosome topical dressing.

[0017] Example 4. A preparation method of a mesenchymal stem cell exosome topical dressing, comprising the following steps: Compared with Example 3, the addition amount of butynediol in step S12 is increased in this example, and the other steps remain unchanged; S1. Prepare modified castor oil polyol; S11. Place 10 parts of castor oil in a container by weight, heat up to 110 °C and keep warm for 30 min, then add 0.12 part of ferric chloride and absolute ethanol thereto, stir and mix until uniform, then add 2.1 parts of sodium azide thereto, cool down to 5 °C, irradiate with blue light, stir and react for 24 h, then rotary evaporate to remove the excess solvent, and wash the reaction product 3 times with deionized water, then heat the remaining reaction product to 110 °C again and keep warm for 30 min to obtain azidized castor oil; S12. Disperse 10 parts of 1,3 - bis - BOC - 2 - (carboxymethyl)guanidine by weight in DMF, add 0.07 part of N,N - dicyclohexylcarbodiimide thereto, continue to mix and stir evenly, then drop it into the DMF solution containing 2.8 parts of butynediol, heat up to 80 °C, stir and react for 6 h, then rotary evaporate to remove the excess solvent to obtain the alkynol intermediate; S13. Dissolve 10 parts of azidized castor oil by weight in DMF, add 10 parts of alkynol intermediate thereto, maintain the temperature of the reaction system at 25 °C, stir and react for 24 h, then rotary evaporate to remove the excess solvent to obtain modified castor oil polyol.

[0018] Example 5. A preparation method of a mesenchymal stem cell exosome topical dressing, comprising the following steps: Compared with Example 4, the amount of alkynol intermediate added in step S13 is increased in this example, and the remaining steps remain unchanged; S1. Prepare modified castor oil polyol; S11. By weight, place 10 parts of castor oil in a container, heat it up to 110 °C and keep it warm for 30 min, then add 0.12 part of ferric chloride and absolute ethanol to it. After stirring and mixing evenly, add 2.1 parts of sodium azide to it, cool it down to 5 °C, irradiate it with blue light, stir and react for 24 h, then rotary evaporate to remove the excess solvent, and wash the reaction product 3 times with deionized water. Then heat the remaining reaction product to 110 °C again and keep it warm for 30 min to obtain azido castor oil; S12. By weight, disperse 10 parts of 1,3-di-BOC-2-(carboxymethyl)guanidine in DMF, add 0.07 part of N,N-dicyclohexylcarbodiimide to it, continue to mix and stir evenly, then drop it into the DMF solution containing 2.8 parts of butynediol, heat it up to 80 °C, stir and react for 6 h, then rotary evaporate to remove the excess solvent to obtain an alkynol intermediate; S13. By weight, dissolve 10 parts of azido castor oil in DMF, add 11.5 parts of alkynol intermediate to it, maintain the temperature of the reaction system at 25 °C, stir and react for 24 h, then rotary evaporate to remove the excess solvent to obtain modified castor oil polyol.

[0019] Example 6. A preparation method of a mesenchymal stem cell exosome topical dressing, comprising the following steps: Compared with Example 1, the addition amounts of the component raw materials in step S2 are changed in this example; S1. Prepare modified castor oil polyol; S11. By weight, place 10 parts of castor oil in a container, heat it up to 105 °C and keep it warm for 15 min, then add 0.05 part of ferric chloride and absolute ethanol to it. After stirring and mixing evenly, add 1.1 parts of sodium azide to it, cool it down to 0 °C, irradiate it with blue light, stir and react for 12 h, then rotary evaporate to remove the excess solvent, and wash the reaction product 2 times with deionized water. Then heat the remaining reaction product to 105 °C again and keep it warm for 15 min to obtain azido castor oil; S12. By weight, disperse 10 parts of 1,3-di-BOC-2-(carboxymethyl)guanidine in DMF, add 0.03 part of N,N-dicyclohexylcarbodiimide to it, continue to mix and stir evenly, then drop it into the DMF solution containing 2.5 parts of butynediol, heat it up to 75 °C, stir and react for 3 h, then rotary evaporate to remove the excess solvent to obtain an alkynol intermediate; S13. Dissolve 10 parts of azidized castor oil by weight in DMF, add 10 parts of alkynol intermediate thereto, maintain the temperature of the reaction system at 20 °C, stir and react for 12 h, then rotary evaporate to remove the excess solvent to obtain modified castor oil polyol; S2. Prepare the mesenchymal stem cell exosome topical dressing; S21. Mix 32 parts of polyethylene glycol and 10 parts of modified castor oil polyol by weight, heat up to 105 °C, keep warm for 12 h, then cool down to room temperature, add 32 parts of toluene diisocyanate and 2.8 parts of glycerol, protect under nitrogen atmosphere, stir and mix at 45 °C for 5 min to obtain a mixed solution for standby; S22. Add 0.5 part of mesenchymal stem cell exosomes to 8 parts of ultrapure water by weight, stir and mix evenly, then add 0.8 part of foaming agent and 1.2 parts of foam stabilizer thereto, stir evenly, add the mixed solution, stir and mix at high speed, then place it in a foaming mold, keep warm and foam, after foaming is completed, cut to obtain the mesenchymal stem cell exosome topical dressing.

[0020] Comparative Example 1. A preparation method of a mesenchymal stem cell exosome topical dressing, comprising the following steps: Compared with Example 2, this comparative example did not add mesenchymal stem cell exosomes, and the other steps remained unchanged; S1. Prepare modified castor oil polyol; S11. Place 10 parts of castor oil in a container by weight, heat up to 110 °C and keep warm for 30 min, then add 0.12 part of ferric chloride and absolute ethanol thereto, stir and mix until uniform, then add 1.1 parts of sodium azide, cool down to 5 °C, irradiate with blue light, stir and react for 24 h, rotary evaporate to remove the excess solvent, and wash the reaction product 3 times with deionized water, then heat the remaining reaction product to 110 °C again and keep warm for 30 min to obtain azidized castor oil; S12. Disperse 10 parts of 1,3 - bis - BOC - 2 - (carboxymethyl) guanidine by weight in DMF, add 0.07 part of N,N - dicyclohexylcarbodiimide thereto, continue to mix and stir evenly, then drop it into the DMF solution containing 2.5 parts of butynediol, heat up to 80 °C, stir and react for 6 h, rotary evaporate to remove the excess solvent to obtain alkynol intermediate; S13. Dissolve 10 parts of azidized castor oil by weight in DMF, add 10 parts of alkynol intermediate thereto, maintain the temperature of the reaction system at 25 °C, stir and react for 24 h, then rotary evaporate to remove the excess solvent to obtain modified castor oil polyol; S2. Prepare the mesenchymal stem cell exosome topical dressing; S21. Mix 24 parts by weight of polyethylene glycol and 6 parts of modified castor oil polyol, heat up to 110 °C, keep warm for 24 h, then cool down to room temperature. Add 28 parts of toluene diisocyanate and 1.5 parts of glycerol, and under the protection of nitrogen atmosphere, stir and mix for reaction at 45 °C for 8 min to obtain a mixed solution for standby; S22. Add 0.5 part of foaming agent and 1 part of foam stabilizer to 2 parts of ultrapure water by weight, stir evenly, add the mixed solution, stir and mix at high speed, then place it in a foaming mold, keep warm and foam. After the foaming is completed, cut it to obtain an external dressing for mesenchymal stem cell exosomes.

[0021] Comparative Example 2. A preparation method of an external dressing for mesenchymal stem cell exosomes, comprising the following steps: Compared with Example 2, in this comparative example, modified castor oil polyol was not prepared and added, but polyethylene glycol of equal mass was directly used instead; S1. Prepare an external dressing for mesenchymal stem cell exosomes; S11. Heat 30 parts of polyethylene glycol to 110 °C by weight, keep warm for 24 h, then cool down to room temperature. Add 28 parts of toluene diisocyanate and 1.5 parts of glycerol, and under the protection of nitrogen atmosphere, stir and mix for reaction at 45 °C for 8 min to obtain a mixed solution for standby; S12. Add 0.3 part of mesenchymal stem cell exosomes to 2 parts of ultrapure water by weight, stir and mix evenly, then add 0.5 part of foaming agent and 1 part of foam stabilizer thereto, stir evenly, add the mixed solution, stir and mix at high speed, then place it in a foaming mold, keep warm and foam. After the foaming is completed, cut it to obtain an external dressing for mesenchymal stem cell exosomes.

[0022] Detection: Calculate the antibacterial activities of the external dressings for mesenchymal stem cell exosomes prepared in Examples 1-6 and Comparative Examples 1-2 against Staphylococcus aureus, Escherichia coli, and Candida albicans by the plate counting method; Select 100 SPF-grade male SD rats with similar body weights and ages, with an average weight of 250 ± 10 g. After feeding them in the same environment and under the same conditions for 2 weeks, remove the hair on their backs, create 2×10 mm wounds on their backs, place the external dressings for mesenchymal stem cell exosomes prepared in Examples 1-6 and Comparative Examples 1-2 on the wound sites of the rats in sequence, observe their hemostasis conditions, and calculate the wound closure degree by comparing the wound areas on the first day and the seventh day. The test results are shown in the following table;

[0023] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an external dressing containing mesenchymal stem cell exosomes, characterized in that: The following steps are involved: S1. Preparation of modified castor oil polyol; S11. Castor oil is placed in a container, heated to 105-110° C. and kept warm for 15-30 min, ferric chloride and anhydrous ethanol are added thereto, stirred and mixed until uniform, sodium azide is added thereto, cooled to 0-5° C., irradiated with blue light, stirred and reacted for 12-24 h, and then the excess solvent is removed by rotary evaporation, and the reaction product is washed with deionized water for 2-3 times, and the remaining reaction product is heated to 105-110° C. again, and kept warm for 15-30 min to obtain azidized castor oil; S12. 1,3-di-BOC-2-(carboxymethyl)guanidine is dispersed in DMF, N,N-dicyclohexylcarbodiimide is added thereto, the mixture is stirred evenly, and then the mixture is added dropwise to a DMF solution containing butynediol, the mixture is heated to 75-80°C, the mixture is stirred for reaction for 3-6 hours, and then the excess solvent is removed by rotary evaporation to obtain an alkynol intermediate; S13. The azidized castor oil was dissolved in DMF, to which the alkynol intermediate was added, the reaction system temperature was maintained at 20-25 ° C, the reaction was stirred for 12-24h, and the excess solvent was removed by rotary evaporation to obtain a modified castor oil polyol; S2. Preparation of mesenchymal stem cell exosome dressing for external use; S21. The polyethylene glycol and modified castor oil polyol were mixed, heated to 105-110 ° C, kept warm for 12-24h, cooled to room temperature, toluene diisocyanate and propylene glycol were added, and the mixture was stirred and reacted at 45 ° C for 5-8min to obtain a mixed solution for standby use; S22. Add mesenchymal stem cell exosomes to ultrapure water, stir and mix evenly, add a foaming agent and a foam stabilizer thereto, stir evenly, add the mixed solution, stir and mix at high speed, place it in a foaming mold, keep it warm and foam it, cut it after the foaming is completed, and obtain a mesenchymal stem cell exosome external dressing.

2. The method for preparing an external dressing containing mesenchymal stem cell exosomes according to claim 1, characterized in that: In terms of weight, in step S11, 10 parts of castor oil, 0.05-0.12 parts of ferric chloride and 1.1-2.1 parts of sodium azide need to be added.

3. The method for preparing an external dressing containing mesenchymal stem cell exosomes according to claim 1, characterized in that: In terms of weight, in step S12, 10 parts of 1,3-di-BOC-2-(carboxymethyl)guanidine, 0.03-0.07 parts of N,N-dicyclohexylcarbodiimide and 2.5-2.8 parts of butynediol need to be added.

4. The method for preparing an external dressing containing mesenchymal stem cell exosomes according to claim 1, characterized in that: In terms of weight, in step S13, 10 parts of castor oil azidate and 10-11.5 parts of alkynol intermediate need to be added.

5. The method for preparing an external dressing containing mesenchymal stem cell exosomes according to claim 1, characterized in that: In step S2, the mesenchymal stem cell exosome external dressing is composed of 24-32 parts of polyethylene glycol, 6-10 parts of modified castor oil polyol, 28-32 parts of toluene diisocyanate, 1.5-2.8 parts of propylene glycol, 2-8 parts of ultrapure water, 0.3-0.5 parts of mesenchymal stem cell exosomes, 0.5-0.8 parts of foaming agent and 1-1.2 parts of foam stabilizer.

6. The method for preparing an in vitro dressing containing mesenchymal stem cell exosomes according to claim 1, characterized in that: The foaming agent is an alkyl polyglycoside; and the foam stabilizing agent is any one of the organosilicon surfactants.

7. A mesenchymal stem cell exosome dressing for external use, characterized in that: The mesenchymal stem cell exosome dressing for external use is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the mesenchymal stem cell exosome dressing as claimed in claim 7 as a wound dressing.

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