Directional network structured aerogel wound dressing as well as preparation method and application thereof

Abstract

The invention discloses a directional network structured aerogel wound dressing as well as a preparation method and application thereof, and belongs to the technical field of biomedical materials. The preparation method disclosed by the invention comprises the following steps: mixing silk fibroin, polyvinyl alcohol, xanthan gum and glycerol, heating and stirring to obtain an aerogel precursor solution containing the silk fibroin; the aerogel precursor solution containing the silk fibroin is subjected to directional freezing, and the directional network structured aerogel wound dressing is obtained after freeze drying. According to the method, the microstructure of the SF / XG / PVA aerogel (directional network structured aerogel wound dressing) is regularized through a directional freezing technology, the porosity is remarkably improved, the aerogel is endowed with an aligned structure and rapid liquid absorption capacity, and the technical problems that an existing aerogel wound dressing is difficult to control and cannot meet application requirements can be solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical materials, and particularly relates to an oriented network structured aerogel wound dressing, a preparation method thereof and an application thereof. Background Art

[0002] Severe bleeding and wound infection are two major global problems that urgently need to be solved in trauma treatment and surgery. As the core medium of the body's internal environment homeostasis, blood undertakes key physiological functions such as oxygen transportation, immune defense, blood coagulation regulation and metabolic waste clearance. Acute massive blood loss can quickly trigger hypovolemic shock, leading to tissue perfusion insufficiency, multiple organ dysfunction syndrome (MODS), and even death. According to statistics, traumatic bleeding accounts for more than 10% of the global causes of death, and in war injuries and disaster medicine, uncontrollable bleeding is the leading factor leading to preventable death. At the same time, wound infection is a common complication in the process of wound healing. The colonization and biofilm formation of pathogenic microorganisms (such as Staphylococcus aureus, Pseudomonas aeruginosa, etc.) can induce a persistent inflammatory response, hinder cell migration and angiogenesis, prolong the healing cycle, and may cause serious consequences such as sepsis and implant failure. In chronic wounds (such as diabetic foot ulcers), the infection rate is as high as 60%, significantly increasing the risk of amputation and the medical burden. Therefore, the development of advanced dressings with both high-efficiency hemostasis and anti-infection functions has great clinical significance.

[0003] The porosity of aerogel enables it to absorb more secretions at the wound, which will reduce inflammation and prevent the development of bacterial infection in the wound. Aerogels represented by food-derived macromolecules such as proteins and polysaccharides have good biological activity, biocompatibility and biodegradability. Their wide availability and flexible preparation methods make their research in the field of wound dressings more and more attractive. However, controlling the microstructure of aerogel remains an academic challenge. Defects such as irregular structure, low porosity and easy deformation limit its application in wound dressings. Summary of the Invention

[0004] The purpose of the present invention is to provide an oriented network structured aerogel wound dressing, a preparation method thereof and an application thereof, so as to solve the technical problem that the existing aerogel wound dressing is difficult to control and difficult to meet the application requirements.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions to implement:

[0006] The present invention discloses a preparation method of an oriented network structured aerogel wound dressing, comprising the following steps:

[0007] Mix silk fibroin, polyvinyl alcohol, xanthan gum and glycerol, and then heat and stir to obtain an aerogel precursor solution containing silk fibroin;

[0008] The aerogel precursor solution containing silk fibroin is directionally frozen, and a directionally network-structured aerogel wound dressing is obtained after freeze-drying.

[0009] Furthermore, the preparation method of the silk fibroin is as follows:

[0010] Sodium bicarbonate anhydrous is added to boiling deionized water to obtain a sodium bicarbonate solution; subsequently, silk is added to the sodium bicarbonate solution and dried to obtain degummed dry silk.

[0011] The degummed dry silk is added to a lithium bromide solution, heated and stirred to dissolve, obtaining a solution.

[0012] The solution is successively dialyzed and centrifuged to obtain silk fibroin.

[0013] Furthermore, the mass concentration of the sodium bicarbonate solution is 0.5%; the concentration of the lithium bromide solution is 9.3 mol / L; the mixing ratio of the silk and the sodium bicarbonate solution is 5 g / L; the mixing ratio of the degummed dry silk and the lithium bromide solution is 0.08 - 0.11 g / mL.

[0014] Furthermore, the temperature for heating and stirring to dissolve is 60 °C, and the time is 2 - 5 h.

[0015] The dialysis time is 48 - 72 h.

[0016] The centrifugation conditions are 9000 - 10000 rpm, 4 °C, and 10 - 20 min.

[0017] Furthermore, in the aerogel precursor solution containing silk fibroin, the mass concentrations of silk fibroin, polyvinyl alcohol, and xanthan gum are 3 - 4 wt%, 1.5%, and 0.75 wt% respectively.

[0018] In the aerogel precursor solution containing silk fibroin, glycerol accounts for 30 wt% of the total solid content.

[0019] Furthermore, the temperature for heating and stirring is 90 - 95 °C, the time is 1 - 2 h, and the stirring speed is 300 - 500 rpm.

[0020] Furthermore, the directional freezing is to perform unidirectional freezing and bidirectional freezing on the aerogel precursor solution containing silk fibroin at -20 °C to -80 °C respectively.

[0021] Furthermore, the unidirectional freezing and bidirectional freezing use liquid nitrogen as the cold source and a copper column as the low-temperature substrate to enable the directional growth of ice crystals.

[0022] The present invention also discloses a directionally network-structured aerogel wound dressing prepared by the above preparation method.

[0023] The present invention also discloses the application of the above-mentioned directionally network-structured aerogel wound dressing in wound protection.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention discloses a preparation method of a directionally network-structured aerogel wound dressing, using silk fibroin (SF) as the matrix raw material, supplemented with polyvinyl alcohol (PVA) and xanthan gum (XG) to improve its structural and mechanical properties. SF has certain water retention properties, and the porous SF / XG / PVA aerogel obtained by drying has good air permeability and can release excessive exudate from the wound. Secondly, through the directional freezing technology, the microstructure of the SF / XG / PVA aerogel (directionally network-structured aerogel wound dressing) is regularized, and the porosity is significantly increased, endowing the aerogel with an aligned structure and rapid liquid absorption ability, which can solve the technical problems that the existing aerogel wound dressings are difficult to control and difficult to meet the application requirements.

[0026] The present invention also discloses a directionally network-structured aerogel wound dressing prepared by the above method, which has a directionally network structure, and the silk fibroin-based aerogel has good biocompatibility, wound healing promotion ability and hemostatic effect, and has the potential for application in wound healing. Description of the Drawings

[0027] Figure 1 It is a flexibility test diagram of the directionally network-structured aerogel wound dressing prepared by the present invention;

[0028] Figure 2 It is a scanning electron microscope (SEM) diagram of the directionally network-structured aerogel wound dressing prepared by the present invention;

[0029] Wherein: a - the radial SEM microstructure of the aerogel under unidirectional freezing at 20°C; b - the axial SEM microstructure of the aerogel under unidirectional freezing at 20°C.

[0030] Figure 3 It is a water absorption rate diagram of the directionally network-structured aerogel wound dressing prepared by the present invention;

[0031] Figure 4 It is a porosity result diagram of the directionally network-structured aerogel wound dressing prepared by the present invention;

[0032] Figure 5 It is a cell survival rate result diagram of L929 cells cultured in the extract of the directionally network-structured aerogel wound dressing prepared by the present invention for 24 h and 48 h;

[0033] Figure 6Hemostasis effect diagrams of the oriented network structured aerogel wound dressing prepared according to the present invention and medical gauze;

[0034] Among them: a - blank group (without treatment), in - situ hemostasis photos of the gauze group and the aerogel group after treating mouse liver injury; b - blank group (without treatment), blood loss of the gauze group and the aerogel group after treating mouse liver injury.

[0035] Figure 7 Photos taken at different time points within two weeks of wound closure using the oriented network structured aerogel wound dressing and medical gauze prepared according to the present invention. Detailed implementation manners

[0036] To enable those skilled in the art to understand the characteristics and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0037] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall in no way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0038] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub - ranges and individual values within the range (including integers and fractions).

[0039] In this article, unless otherwise specified, terms such as "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A only comprises a".

[0040] In this article, for the sake of brevity of description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as the scope described in this specification.

[0041] The present invention provides a method for preparing a directional network-structured aerogel wound dressing. A directional network-structured aerogel is successfully prepared by the ice-template method. Meanwhile, the porous structure generated by the volatilization of water during the drying process of the aerogel endows it with good breathability. The finally prepared aerogel wound dressing has good liquid absorption capacity, hemostatic properties and wound healing effect, and specifically includes the following steps:

[0042] Step 1: Add anhydrous sodium bicarbonate into boiling deionized water, stir and mix evenly to obtain a sodium bicarbonate solution. Then add silk, let it degum fully and wash it, and put it in an oven to dry to obtain degummed dry silk. Then add the degummed dry silk into a lithium bromide solution, heat and stir to dissolve it to obtain a solution. Dialyze the solution in deionized water, and after dialysis, perform centrifugation to remove the precipitate to obtain silk fibroin (SF);

[0043] Step 2: Add glycerol to the mixed solution of SF, polyvinyl alcohol (PVA) and xanthan gum (XG), and then heat and stir the mixed solution evenly, and cool it to room temperature to obtain an aerogel precursor solution containing silk fibroin;

[0044] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold, perform directional freezing under different freezing conditions, and obtain a directional network-structured aerogel wound dressing after freeze-drying.

[0045] Preferably, in Step 1, the mass concentration of the sodium bicarbonate solution is 0.5%, the mixing ratio of silk and the sodium bicarbonate solution is 5 g / L, the concentration of the lithium bromide solution is 9.3 mol / L, the mixing ratio of dry silk and the lithium bromide solution is 0.08 - 0.11 g / mL, the stirring time is 2 - 5 h, the heating temperature is 60 °C, the dialysis time is 48 to 72 h, and the centrifugation conditions are 9000 rpm, 4 °C, 20 min.

[0046] Preferably, in Step 2, the final mass concentration of SF in the aerogel precursor solution containing silk fibroin is 3 - 4 wt%, the final mass concentration of PVA is 1.5%, the final mass concentration of XG is 0.75 wt%, glycerol accounts for 30 wt% of the total solid content, the heating temperature is 90 °C, the time is 1 - 2 h, and the stirring speed is 300 rpm - 500 rpm.

[0047] Preferably, in Step 3, the different freezing conditions are unidirectional freezing and bidirectional freezing at -20 °C, -40 °C, and -80 °C respectively.

[0048] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0049] In the following embodiments, conventional instruments and equipment in the art are used. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. In the following embodiments, various raw materials are used. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0050] Example 1

[0051] A preparation method of a directional network structured aerogel wound dressing, comprising the following steps:

[0052] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix evenly to obtain a sodium bicarbonate solution with a mass concentration of 0.5%. Add silk and let it degum fully, then wash and put it into an oven to dry to obtain degummed dry silk. Add 3 g of degummed dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60 °C for 2 h until dissolved to obtain a dissolved solution. Dialyze the dissolved solution in deionized water for 72 h. After dialysis, centrifuge at 9000 rpm, 4 °C for 20 min to remove the precipitate, and obtain silk fibroin (SF);

[0053] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), and then heat and stir the mixed solution at 90 °C for 2 h until uniform, and cool to room temperature to obtain an aerogel precursor solution containing silk fibroin;

[0054] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold and freeze it under unidirectional freezing conditions: liquid nitrogen is used as the cold source, and a copper column is used as the low-temperature substrate, and the temperature is set at -20 °C. After freeze-drying, a directional network structured aerogel wound dressing is obtained.

[0055] Example 2

[0056] A preparation method of a directional network structured aerogel wound dressing, comprising the following steps:

[0057] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix well to obtain a sodium bicarbonate solution with a mass concentration of 0.5%. Add silk, let it degum fully, wash it, put it in an oven to dry, and obtain degummed dry silk; Add 3 g of degummed dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60 °C for 2 h until dissolved to obtain a dissolved solution; Dialyze the dissolved solution in deionized water for 72 h. After dialysis, centrifuge at 9000 rpm, 4 °C for 20 min to remove the precipitate and obtain silk fibroin (SF).

[0058] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), and then heat and stir the mixed solution at 90 °C for 2 h until uniform, and cool to room temperature to obtain an aerogel precursor solution containing silk fibroin.

[0059] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold and freeze it under bidirectional freezing conditions: Use liquid nitrogen as the cold source and a copper column as the low-temperature substrate. Place a PDMS wedge with an inclination angle of 20° between the copper column and the precursor solution, set the temperature to -20 °C, and obtain a directionally network-structured aerogel wound dressing after freeze-drying.

[0060] Example 3

[0061] A preparation method of a directionally network-structured aerogel wound dressing, comprising the following steps:

[0062] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix well to obtain a sodium bicarbonate solution with a mass concentration of 0.5%. Add silk, let it degum fully, wash it, put it in an oven to dry, and obtain degummed dry silk; Add 3 g of degummed dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60 °C for 2 h until dissolved to obtain a dissolved solution; Dialyze the dissolved solution in deionized water for 72 h. After dialysis, centrifuge at 9000 rpm, 4 °C for 20 min to remove the precipitate and obtain silk fibroin (SF).

[0063] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), and then heat and stir the mixed solution at 90 °C for 2 h until uniform, and cool to room temperature to obtain an aerogel precursor solution containing silk fibroin.

[0064] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold and freeze it under unidirectional freezing conditions: liquid nitrogen is used as the cold source, a copper column is used as the low-temperature substrate, the temperature is set at -40°C, and a directionally network-structured aerogel wound dressing is obtained after freeze-drying.

[0065] Example 4

[0066] A method for preparing a directionally network-structured aerogel wound dressing, comprising the following steps:

[0067] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix evenly to obtain a sodium bicarbonate solution with a mass concentration of 0.5%, add silk, let it be fully degummed, wash it, put it in an oven to dry, and obtain degummed dry silk; add 3 g of degummed dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60°C for 2 h until dissolved to obtain a solution; dialyze the solution in deionized water for 72 h, and after dialysis, perform centrifugation at 9000 rpm, 4°C for 20 min to remove the precipitate, and obtain silk fibroin (SF);

[0068] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), and then heat and stir the mixed solution at 90°C for 2 h until uniform, and cool to room temperature to obtain an aerogel precursor solution containing silk fibroin;

[0069] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold and freeze it under bidirectional freezing conditions: liquid nitrogen is used as the cold source, a copper column is used as the low-temperature substrate, a PDMS wedge with an inclination angle of 20° is placed between the copper column and the precursor solution, the temperature is set at -40°C, and a directionally network-structured aerogel wound dressing is obtained after freeze-drying.

[0070] Example 5

[0071] A method for preparing a directionally network-structured aerogel wound dressing, comprising the following steps:

[0072] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix evenly to obtain a sodium bicarbonate solution with a mass concentration of 0.5%, add silk, let it be fully degummed, wash it, put it in an oven to dry, and obtain degummed dry silk; add 3 g of degummed dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60°C for 2 h until dissolved to obtain a solution; dialyze the solution in deionized water for 72 h, and after dialysis, perform centrifugation at 9000 rpm, 4°C for 20 min to remove the precipitate, and obtain silk fibroin (SF);

[0073] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), and then heat and stir the mixed solution at 90 °C for 2 h until it is uniform, and cool it to room temperature to obtain an aerogel precursor solution containing silk fibroin;

[0074] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold and freeze it under unidirectional freezing conditions: liquid nitrogen is used as the cold source, a copper column is used as the low-temperature substrate, the temperature is set at -80 °C, and a directional network-structured aerogel wound dressing is obtained after freeze-drying.

[0075] Example 6

[0076] A preparation method of a directional network-structured aerogel wound dressing, comprising the following steps:

[0077] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix evenly to obtain a sodium bicarbonate solution with a mass concentration of 0.5%, add silk, let it be fully degummed and then washed, and put it in an oven to dry to obtain degummed dry silk; add 3 g of degummed dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60 °C for 2 h until it dissolves to obtain a solution; dialyze the solution in deionized water for 72 h, and after dialysis, perform centrifugation at 9000 rpm, 4 °C for 20 min to remove the precipitate, and obtain silk fibroin (SF);

[0078] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), and then heat and stir the mixed solution at 90 °C for 2 h until it is uniform, and cool it to room temperature to obtain an aerogel precursor solution containing silk fibroin;

[0079] Step 3: Transfer the aerogel precursor solution containing silk fibroin obtained in Step 2 to a polytetrafluoroethylene mold and freeze it under bidirectional freezing conditions: liquid nitrogen is used as the cold source, a copper column is used as the low-temperature substrate, a PDMS wedge with an inclination angle of 20° is placed between the copper column and the precursor solution, the temperature is set at -80 °C, and a directional network-structured aerogel wound dressing is obtained after freeze-drying.

[0080] Comparative Example 1

[0081] Step 1: Add 20g of anhydrous sodium bicarbonate to 4L of boiling deionized water and stir to obtain a 0.5% sodium bicarbonate solution. Add the silk to allow it to be fully degummed, then wash it and dry it in an oven to obtain degummed dry silk. Then, add 3g of dry silk to 30mL of lithium bromide solution (9.3mol / L) and heat and stir at 60°C for 2h until dissolved. The solution is dialyzed in deionized water for 72h. After the dialysis is completed, centrifuge it at 9000rpm, 4°C, and 20min to remove the precipitate to obtain SF;

[0082] Step 2: Prepare a mixture containing 3 wt% SF, 1.5 wt% PVA, and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), heat and stir the mixture at 90°C for 2 h until uniform, and cool it to room temperature to obtain an aerogel precursor solution;

[0083] Step 3: The aerogel precursor solution obtained in step 2 is transferred to a polytetrafluoroethylene mold, frozen under multi-directional freezing conditions (refrigerator freezing) at a temperature set to -20°C, and freeze-dried to obtain an aerogel.

[0084] Comparative Example 2

[0085] Step 1: Add 20g of anhydrous sodium bicarbonate to 4L of boiling deionized water and stir to obtain a 0.5% sodium bicarbonate solution. Add the silk to allow it to be fully degummed, then wash it and dry it in an oven to obtain degummed dry silk. Then, add 3g of dry silk to 30mL of lithium bromide solution (9.3mol / L) and heat and stir at 60°C for 2h until dissolved. The solution is dialyzed in deionized water for 72h. After the dialysis is completed, centrifuge it at 9000rpm, 4°C, and 20min to remove the precipitate to obtain SF;

[0086] Step 2: Prepare a mixture containing 3 wt% SF, 1.5 wt% PVA, and 0.75 wt% XG, add glycerol (accounting for 30% of the solid content), heat and stir the mixture at 90°C for 2 h until uniform, and cool it to room temperature to obtain an aerogel precursor solution;

[0087] Step 3: The aerogel precursor solution obtained in step 2 is transferred to a polytetrafluoroethylene mold, frozen under multi-directional freezing conditions (refrigerator freezing) at a temperature set to -40°C, and freeze-dried to obtain an aerogel.

[0088] Comparative Example 3

[0089] Step 1: Add 20 g of anhydrous sodium bicarbonate to 4 L of boiling deionized water, stir and mix evenly to obtain a 0.5% sodium bicarbonate solution. Add silk and let it degum fully, then wash and put it into an oven to dry, obtaining degummed dry silk. Then add 3 g of dry silk to 30 mL of lithium bromide solution (9.3 mol / L), heat and stir at 60 °C for 2 h until dissolved. The dissolved solution is dialyzed in deionized water for 72 h. After dialysis, centrifuge at 9000 rpm, 4 °C for 20 min to remove the precipitate, obtaining SF;

[0090] Step 2: Prepare a mixed solution containing 3 wt% SF, 1.5 wt% PVA and 0.75 wt% XG, add glycerol (30% of the solid content), and then heat and stir the mixed solution at 90 °C for 2 h until uniform, and cool to room temperature to obtain the aerogel precursor solution;

[0091] Step 3: Transfer the aerogel precursor solution obtained in Step 2 to a polytetrafluoroethylene mold, freeze it under multi-directional freezing (freezing in a refrigerator) conditions, set the temperature to -80 °C, and freeze-dry to obtain the aerogel.

[0092] Macroscopically observe the macroscopic morphology and flexibility of the directionally network-structured aerogel wound dressing prepared in the above examples. Fold and unfold the aerogel, observe whether the aerogel breaks, and take pictures for recording. The results are as Figure 1 shown. It can be seen from the figure that the prepared aerogel has a flat surface, good flexibility, and is not damaged after bending.

[0093] Select the SF / XG / PVA aerogel prepared under unidirectional freezing at -20 °C, and observe its internal radial and axial microstructures by scanning electron microscopy (SEM). The results are as Figure 2 shown. From the radial cross-section, the pore structure of the aerogel under unidirectional freezing is uniformly arranged. This is because in the unidirectional freezing direction, the ice crystals formed by the solvent form in a fixed direction, and the solute is repelled by the ice crystals and compressed and uniformly distributed between the ice crystals. From the axial cross-section, the unidirectional freezing aerogel has an oriented layered structure, that is, anisotropy. This is because during unidirectional freezing, the formed temperature gradient induces the growth of fine ice crystals, squeezing the gel network to form a layered assembly structure with aligned channels.

[0094] Make the dried aerogel samples into cylinders of the same size, weigh them, record the mass as M0, measure the diameter d and thickness h, and calculate the volume v. Immerse the samples in anhydrous ethanol until saturated (ρ = 0.7893 g / cm 3 ), take them out and weigh, record as M t . Use the following formula to calculate the porosity:

[0095]

[0096] The results are as follows Figure 3 As shown, it can be seen from Figure 3 that all aerogels are highly porous, with the porosity ranging from 60.85 ± 1.89% to 101.98 ± 1.84%. Under the same freezing direction, the porosity of the aerogel prepared by unidirectional freezing at -20°C is significantly higher than that of the aerogel prepared at -80°C. This result can be explained by the above microscopic morphology structure. The lower the freezing temperature, the denser the internal structure of the gel, so the lower the porosity. The porosity of the aerogel under unidirectional freezing is always higher than that of the aerogel under multi-directional freezing and bi-directional freezing. This is because multi-directional and bi-directional freezing make the internal microstructure of the aerogel more complex and the space occupancy ratio is higher, while the internal microstructure of the sample prepared by unidirectional freezing is relatively simple, so the space occupancy ratio of the microstructure is lower.

[0097] Weigh the aerogel (M0) at room temperature and soak it in 100 mL of PBS (pH = 7.4) solution. Take out the aerogel every 8 s, remove the excess unabsorbed water and weigh it, denoted as M t , and calculate the water absorption rate using the following formula:

[0098]

[0099] The results are as follows Figure 4 As shown, it can be seen from Figure 4 that the aerogel can reach the water absorption equilibrium within 112 s, showing a relatively fast water absorption rate. From the water absorption rate of the aerogel at 24 s, under the same freezing direction, the order of the water absorption rate of aerogels at different freezing temperatures is: -20°C > -40°C > -80°C. This is because the lower the freezing temperature, the smaller the pore size of the aerogel and the slower the water absorption; at the same freezing temperature, the order of the water absorption rate of aerogels in different freezing directions is: unidirectional freezing > bi-directional freezing > multi-directional freezing. This may be because the aerogel prepared by unidirectional freezing has a structure with through holes up and down. During the water absorption process, there are fewer "obstacle" structures encountered by water molecules during diffusion in the network structure, while the structure of the aerogel prepared by bi-directional and multi-directional freezing is relatively complex, thus slowing down the diffusion of water molecules.

[0100] Inoculate L929 cells (1×105 cells / well) into a 96-well plate. After culturing for 24 h, remove the culture medium, and treat the L929 cells with 200 μL of aerogel extract (25 mg / mL) or complete growth medium respectively, with untreated L929 cells as the control group; after co-incubating in a humidified incubator at 37°C with 5% CO2 for 24 h and 48 h, add 200 μL of MTT reagent with a concentration of 0.5 mg / mL to each well. After culturing for 4 h, aspirate the MTT reagent, add 200 μL of DMSO, place it on a constant temperature shaker at 37°C and shake at 100 rpm. After 10 min, read the absorbance at 490 nm, and calculate the cell survival rate according to the following formula:

[0101]

[0102] Wherein: A test refers to the absorbance value of the cells after sample treatment; A control refers to the absorbance value without sample treatment; A blank refers to the absorbance value without adding cell suspension and without sample treatment solution;

[0103] The results are as Figure 5 shown. It can be seen from Figure 5 that after the aerogel extract acts on L929 for different times (24 h, 48 h), the cell survival rate measured by the MTT method is above 80%, indicating that the aerogel wound dressing is non-toxic to cells and has good cell compatibility.

[0104] The mice were anesthetized and fixed on the operating table. The abdominal cavity was opened to expose the liver of the mice. The weighed filter paper was placed on the paraffin film and placed under the liver to absorb blood. An acute bleeding wound was made on the liver with a scalpel, and the bleeding site was immediately covered with the aerogel sample. Medical gauze was used as the control group, and the untreated acute wound was used as the blank group. The results are as Figure 6 shown. It can be seen from Figure 6 that the blood stain area on the filter paper in the control group was larger, and the blood loss was about 200 mg. The blood loss in the aerogel group was less, about 79 mg, which was significantly lower than that in the control group and the gauze group (P < 0.05), indicating the good hemostatic effect of the aerogel.

[0105] After adopting the standard anesthesia procedure and injecting anesthetic (tribromoethanol) intraperitoneally, the dorsal skin of the rats was shaved, and a full-thickness skin incision with a diameter of 6 mm was made using a puncher. The control group covered the wound with medical gauze, and the sample group was treated with aerogel. The dressing was changed every day, and the wound was photographed. The results are as Figure 7 shown. It can be seen from the figure that by comparing the wound area on the 7th day, 10th day, and 14th day, it was found that the directional network-structured SF / XG / PVA aerogel wound dressing could more effectively promote wound healing and accelerate skin tissue regeneration compared with ordinary medical gauze.

[0106] The above content is only to illustrate the technical idea of the present invention and cannot limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a directional network-structured aerogel wound dressing, characterized in that, It includes the following steps: After mixing silk fibroin, polyvinyl alcohol, xanthan gum and glycerol, heat and stir to obtain an aerogel precursor solution containing silk fibroin; Subject the aerogel precursor solution containing silk fibroin to directional freezing, and obtain a directionally network-structured aerogel wound dressing after freeze-drying.

2. The preparation method of an oriented network-structured aerogel wound dressing according to claim 1, characterized in that, The preparation method of the silk fibroin is as follows: Add anhydrous sodium bicarbonate into boiling deionized water to obtain a sodium bicarbonate solution; Subsequently, add silk to the sodium bicarbonate solution and perform a drying treatment to obtain degummed dry silk; Add the degummed dry silk into a lithium bromide solution, heat and stir to dissolve to obtain a solution; Subject the solution to dialysis and centrifugation treatments in sequence to obtain silk fibroin.

3. The preparation method of an oriented network-structured aerogel wound dressing according to claim 2, characterized in that, The mass concentration of the sodium bicarbonate solution is 0.5%; the concentration of the lithium bromide solution is 9.3 mol / L; the mixing ratio of the silk and the sodium bicarbonate solution is 5 g / L; the mixing ratio of the degummed dry silk and the lithium bromide solution is 0.08 - 0.11 g / mL.

4. The preparation method of an oriented network-structured aerogel wound dressing according to claim 2, characterized in that, The temperature for the heat and stir to dissolve is 60 °C, and the time is 2 - 5 h; The time for the dialysis is 48 - 72 h; The conditions for the centrifugation are 9000 - 10000 rpm, 4 °C, and 10 - 20 min.

5. The preparation method of an oriented network structured aerogel wound dressing according to claim 1, characterized in that, In the aerogel precursor solution containing silk fibroin, the mass concentrations of silk fibroin, polyvinyl alcohol and xanthan gum are 3 - 4 wt%, 1.5% and 0.75 wt% respectively; In the aerogel precursor solution containing silk fibroin, glycerol accounts for 30 wt% of the total solid content.

6. The preparation method of an oriented network-structured aerogel wound dressing according to claim 1, characterized in that, The temperature for the heat and stir is 90 - 95 °C, the time is 1 - 2 h, and the rotation speed of the stir is 300 - 500 rpm.

7. The preparation method of an oriented network structured aerogel wound dressing according to claim 1, characterized in that, The directional freezing is to subject the aerogel precursor solution containing silk fibroin to unidirectional freezing and bidirectional freezing at -20 °C to -80 °C respectively.

8. The preparation method of an oriented network-structured aerogel wound dressing according to claim 7, characterized in that, The unidirectional freezing and bidirectional freezing use liquid nitrogen as the cold source and a copper column as the low-temperature substrate to enable the directional growth of ice crystals.

9. A directional network-structured aerogel wound dressing, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 8.

10. Application of the directionally network-structured aerogel wound dressing described in claim 9 in wound protection.

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