CN114933738B - High-strength high-toughness bacterial cellulose/polyurethane compound and preparation and application thereof - Google Patents

Abstract

The invention relates to a high-strength and high-toughness bacterial cellulose/polyurethane composite and its preparation and application, belonging to the field of biomedical composite materials. The method of the invention can enhance the reswellability of the bacterial cellulose by adding organic alcohol as a plasticizer, improve the compatibility of the bacterial cellulose and polyurethane, and further prepare a high-strength and high-toughness bacterial cellulose/polyurethane composite material. The preparation method of the present invention comprises: soaking the bacterial cellulose film in an aqueous solution of organic alcohol for plasticizing treatment; after the bacterial cellulose is fully absorbed, taking it out and drying to remove water; then, immersing the plasticized bacterial cellulose in fully soaked in the polyurethane solution, and then dried until the solvent evaporated completely to form a solidified bacterial cellulose/polyurethane composite. The complex of the present invention has good mechanical properties, and its mechanical properties can be adjusted in a large range according to the concentration of glycerol. In vivo subcutaneous implantation test showed that the composite material has good tissue compatibility.

Description

High-strength and high-toughness bacterial cellulose/polyurethane composite and its preparation and application

technical field

The invention belongs to the field of biological composite materials, and more specifically relates to a high-strength and high-toughness bacterial cellulose/polyurethane composite and its preparation and application.

Background technique

Bacterial cellulose (BC) is a kind of cellulose secreted by bacterial fermentation to the air-liquid interface of the medium. BC has the advantages of high purity, high crystallinity, high degree of polymerization, hydrophilicity, good chemical stability, and fine three-dimensional porous network structure. In addition, BC also has good biocompatibility and low immunogenicity, and has attracted extensive attention in various fields such as food, textiles, materials, cosmetics, biopharmaceuticals, and biomedical engineering. However, the poor mechanical properties of bacterial cellulose limit its application.

To address the above issues, BC can be compounded to enhance its mechanical properties. Through the impregnation method, the polymer solution/monomer/prepolymer can be incorporated into the three-dimensional porous network of BC, which is then cured or polymerized to form a composite material. BC-based composites prepared by this method, such as BC/polyurethane (Polyurethane, PU), BC/polyvinyl alcohol, BC/gelatin double network hydrogel, etc., usually have better Young's modulus and tensile strength than pure BC. strength. However, BC is a hydrophilic hydrogel, and PU is a hydrophobic polymer. Therefore, dehydration pretreatment of BC is required before the complex reaction. This leads to poor compatibility between BC and PU, and the obtained composite has the problem of low elongation at break.

Contents of the invention

In order to overcome the above-mentioned problems, the purpose of the present invention is to provide a kind of preparation method of bacterial cellulose/polyurethane composite of high strength and high toughness, first adopt organic alcohol to plasticize bacterial cellulose, then compound with polyurethane, this method improves The compatibility of bacterial cellulose and polyurethane, the prepared composite material has high Young's modulus and elongation at break. In addition, the composite material has good biocompatibility.

According to the first aspect of the present invention, a kind of preparation method of bacterial cellulose/polyurethane composite material is provided, comprising the following steps:

(1) soaking the bacterial cellulose film in an aqueous organic alcohol solution to swell the bacterial cellulose film; the organic alcohol is used to plasticize the bacterial cellulose film;

(2) The bacterial cellulose membrane obtained in step (1) is taken out and dried, then soaked in a polyurethane solution to re-swell the bacterial cellulose membrane, and the polyurethane is incorporated into the three-dimensional porous network of cellulose in the bacterial cellulose membrane and then drying to solidify the bacterial cellulose film to obtain a bacterial cellulose/polyurethane composite material.

Preferably, the organic alcohol is at least one of glycerol, ethylene glycol, polyethylene glycol, sorbitol and xylitol.

Preferably, the volume concentration of the organic alcohol in the organic alcohol aqueous solution is 2%-3%.

Preferably, the soaking temperature in step (1) is 16°C-40°C, and the soaking time is 8h-24h.

Preferably, in step (2), the mass ratio of the cellulose in the bacterial cellulose film to the polyurethane in the polyurethane solution is 1:5-1:10.

Preferably, the soaking temperature in step (2) is 25°C-80°C, and the time is 4h-12h.

According to another aspect of the present invention, the bacterial cellulose/polyurethane composite material prepared by any one of the methods is provided.

According to another aspect of the present invention, an application of the bacterial cellulose/polyurethane composite material for preparing implant materials is provided.

Generally speaking, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

(1) The present invention adds organic alcohol as plasticizer in bacterial cellulose. Organic alcohols are rich in hydroxyl groups, which can form hydrogen bonds with the hydroxyl groups on bacterial cellulose, avoiding the irreversible intramolecular hydrogen bonds formed during the dehydration process of bacterial cellulose. The plasticized dehydrated bacterial cellulose is immersed in the polyurethane solution, part of the organic alcohol molecules on the cellulose molecular chain falls off, and the free hydroxyl groups form hydrogen bonds with the ester groups on the polyurethane and the amide groups in the solvent. Bacterial cellulose re-swells and fully contacts with polyurethane, which improves the compatibility of bacterial cellulose and polyurethane, and obtains high-strength and high-toughness bacterial cellulose/polyurethane composite materials, and the Young's modulus and elongation at break are adjustable .

(2) The high-strength and high-toughness bacterial cellulose/polyurethane composite material prepared by the method of the present invention does not cause histopathological changes and has good biocompatibility.

(3) The preparation process of the present invention is simple, easy to control, and can be produced on a large scale.

Description of drawings

Figure 1 is (A) the mass change of BC-G, and (B) the effect of glycerol concentration on the reswelling behavior of BC-G.

Figure 2 is a cross-sectional SEM image of the BC/PU composite film; among them, (a1, a2) PU, (b1, b2) BC/PU-0, (c1, c2) BC/PU-0.5, (d1, d2) BC /PU-1, (e1,e2)BC/PU-2, and (f1,f2)BC/PU-3.

Fig. 3 is the mechanical property of BC/PU composite film; (A) tensile stress-strain curve, (B) Young's modulus, (C) elongation at break, and (D) break strength (n=5, * P<0.05, **P<0.01).

Figure 4 is the HE staining and Masson staining of the surrounding skin tissue after 7 days and 14 days of subcutaneous implantation of the BC/PU complex.

Fig. 5 is a schematic diagram of the preparation mechanism of the bacterial cellulose/polyurethane composite material of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

The main source of experimental materials

Bacterial cellulose (BC) was purchased from Hainan Coslight Biotechnology Co., Ltd. Polyurethane (PU) was purchased from Wuhan Janssen Biotechnology Co., Ltd.

The present invention is a high-strength and high-toughness bacterial cellulose/polyurethane composite material. The high-strength and high-toughness composite material is made of bacterial cellulose plasticized by organic alcohol and polyurethane. The Young's modulus is 20-450Mpa, The elongation at break can be controlled by the concentration of glycerol in the range of 1-35%.

A kind of preparation method of bacterial cellulose/polyurethane compound of high strength and high toughness provided by the invention comprises the following steps:

(1) cutting the purified bacterial cellulose membrane into required size;

(2) Soak the BC prepared in step (1) in an aqueous glycerin solution with a suitable concentration, soak for a period of time at a suitable temperature, and allow it to fully absorb glycerol molecules;

(3) Take out the BC film and put it into an oven, and fully dry it at a suitable temperature;

(4) Soak the BC film in a certain mass ratio (w/w) of PU solution, seal it and let it stand for a period of time to fully re-swell the BC. Then place it in an oven to dry and solidify to form bacterial cellulose/polyurethane composite.

In some embodiments of the above-mentioned preparation method of the present invention, the BC film in the step (1) can be cut into any shape, preferably a square with a length of 10 cm and a width of 10 cm.

In some embodiments of the above-mentioned preparation method of the present invention, the volume fraction of the aqueous glycerol solution in step (2) is 2-3%, preferably 2%; BC soaks in the glycerol solution for 8-24h, preferably 12h; the temperature is 16-40°C, preferably 25°C; the shaking speed is 50-200rpm, preferably 100rpm.

In some embodiments of the above-mentioned preparation method of the present invention, the drying temperature in the step (3) is 60-80° C., preferably 65° C.; the drying time is more than 8 hours, preferably 12 hours.

In some embodiments of the above-mentioned preparation method of the present invention, the shape and size of the reaction vessel in step (4) need to match the BC membrane.

In some embodiments of the above-mentioned preparation method of the present invention, in the PU solution and BC film in the step (4), the mass ratio of PU to BC is preferably 10:1.

In some embodiments of the above-mentioned preparation method of the present invention, in the step (4), the time for mixing BC and PU into the container and sealing it for standing is 4-12h, preferably 8h; the standing temperature is 25-80°C, preferably is 65°C.

In some embodiments of the above-mentioned preparation method of the present invention, the curing temperature of the BC/PU composite in the step (4) is 60-80°C, preferably 65°C; the curing time is more than 8 hours, preferably 12 hours.

Embodiment 1: the plasticizing pretreatment of bacterial cellulose

Cut the BC film into a square with a length of 10 cm and a width of 10 cm, and use an analytical balance to measure its wet weight, and then soak the film in aqueous solutions of 0%, 0.5%, 1%, 2%, and 3% glycerol (G) , under the conditions of 25°C and 100rpm, fully shaken for 12h to form glycerol-plasticized BC-G films, which were named BC-G0, BC-G0.5, BC-G1, BC-G2 and BC-G3. The BC-G film was dried and dehydrated in an oven at 65°C until the mass remained constant, and then its dry weight was measured with an analytical balance.

Example 2: Detection of reswellability of BC-G

The dried BC-G membrane was immersed in excess ultrapure water at 25 °C, and reswelled after absorbing water. They were taken out at 1, 2, 3, 5, 10, 15 and 25 days respectively, and their wet weights were weighed and recorded. The results are shown in Fig. 1, as the glycerol concentration increased, the dried BC-G exhibited better reswellability. BC-G0 could only reswell to the original 3.3±0.3%, however, as the glycerol concentration increased to 0.5%, 1%, 2% and 3%, the water resorption of BC-G gradually increased to 46.4±8.9%, 72.1 ±14.3%, 102.0±5.9%, and 109.2±3.6%. Furthermore, the higher the concentration of glycerol, the faster the reswelling rate of BC-G. The experimental results showed that the addition of glycerol successfully enhanced the reswellability of BC.

Embodiment 3: the preparation of bacterial cellulose/polyurethane composite membrane

The preparation method of described bacterial cellulose/polyurethane composite film comprises the following steps:

(1) Put the dried BC-G described in reference to Example 1 into a 10cm square mold with a width of 10cm. Weigh an appropriate amount of PU solution at a ratio of PU:BC=10:1 (W/W), and add it to the mold.

(2) Seal the BC/PU mixture in step (1), place it in an oven at 65° C., and seal it for 8 hours to allow BC-G to re-swell in the PU solution.

(3) The container in step (2) was opened, and the BC/PU was dried and solidified to form a BC/PU composite film at a drying temperature of 65° C. and a drying time of 12 hours.

Embodiment 4: Morphological characterization of bacterial cellulose/polyurethane

With reference to the operation steps and methods described in Example 1 and Example 3, the BC/PU samples with a glycerin concentration of 0%, 0.5%, 1%, 2% and 3% were cut into appropriate sizes and placed in liquid nitrogen Cut in the middle to obtain a section. Fix the cross-section upward on the side of the stage with carbon conductive glue, spray gold on the surface of the sample by vacuum sputtering for 300s, and then observe the microscopic morphology of the sample by field emission scanning electron microscope (FESEM) (Figure 2). It can be seen that the pure PU has a uniform cross-section and is a dense homogeneous material. When not plasticized by glycerol, the BC/PU-0 composite film showed serious delamination, with a dense BC layer in the middle, with a thickness of about 15 μm, and the fibers were arranged in layers, and the upper and lower surfaces were covered by PU layers, indicating that BC and PU The compatibility is poor. This is due to the aggregation of fibers during the drying process of pure BC, the formation of a large number of hydrogen bonds between cellulose molecules, the decrease of swelling property, the decrease of specific surface area, and the lack of hydroxyl groups that can hydrogen bond with DMAC and PU after being immersed in PU solution. After adding glycerol, the interaction between BC fibers decreased, and they could re-swell after being immersed in PU solution, and formed hydrogen bonds with carbamate groups in PU molecules, and the compatibility between BC and PU was effectively improved.

Embodiment 5: the mechanical performance test of bacterial cellulose/polyurethane composite film

The BC/PU composite film was obtained by the preparation method in Example 3, and a uniaxial tensile test was performed to test the mechanical properties of the sample. Cut the sample into a strip sample with a length of 80 mm and a width of 20 mm, and measure its thickness with a vernier caliper for uniaxial tensile test. The sample is stretched at a speed of 5 mm/min until it breaks. The Young's modulus, maximum stress, and elongation at break of the samples were determined from the strain-stress curves (Fig. 3). It can be seen from Figure 3 that the mechanical properties of BC after drying and rewetting are poor, the Young's modulus is 19.2±6.0MPa, the elongation at break is only 8.2±1.5%, and the tensile strength at break is 2.2±0.6MPa. The Young's modulus of pure PU is 2.3±0.2MPa, but the elongation at break is as high as 490.1±31.4%, and the tensile strength at break is 14.2±2.6MPa. After compounding BC and PU, the Young's modulus of BC/PU-0 increased to 451.5±20.9MPa, but due to the poor compatibility of BC and PU, the elongation at break was only 1.2±0.2%, and the tensile strength at break It is 4.6±0.3MPa. With the addition of glycerol, the Young's modulus of BC/PU-0.5, BC/PU-1, BC/PU-2 and BC/PU-3 gradually decreased to 367.5±16.9, 163.9±9.7, 120.9±5.3 and 79.3 ±7.0MPa; elongation at break increased to 15.6±1.5%, 17.1±1.1%, 33.2±4.1% and 34.4±1.6%; tensile strength at break were 26.7±0.5, 13.6±0.7, 16.2±0.5 and 13.8± 0.3 MPa. There is no significant difference in elongation at break between BC/PU-2 and BC/PU-3, because the elongation at break of pure BC films synthesized by fermentation is usually 30%-40%. In general, the addition of glycerol reduces the composite Young's modulus, but increases its elongation at break to about 30%, and the stress at break to more than 10MPa. In this study, the problems of low tensile strength at break of BC and poor toughness of BC/PU-0 were solved, and strong and tough BC/PU composites were successfully prepared, and the mechanical properties of the prepared samples were adjustable.

Embodiment 6: the biocompatibility test of bacterial cellulose/polyurethane composite film

The histocompatibility of BC, PU and BC/PU artificial blood vessels was investigated by subcutaneous implantation experiment in rats. Rats were anesthetized by intraperitoneal injection of 3% pentobarbital sodium at a ratio of 1 mL/100 g. When the depth of anesthesia was appropriate, the rats were fixed in a prone position, and the rat hair on the back was depilated. After being wiped and disinfected by iodophor, three subcutaneous wounds were made at about 1 cm on both sides of the spine, and tubular stents were implanted in them respectively. Each group of samples had six parallels, and no wound treatment was performed on the blank control. The wound was sutured with 6-0 suture thread with a needle, wiped with povidone iodine for disinfection, and returned to the cage for rearing. At 7 days and 14 days after the operation, the rats were re-anesthetized, and the skin tissue near the implanted sample site was removed. Tissues were soaked in 4% tissue fixative solution and routinely paraffin-embedded for sectioning. Regular hematoxylin-eosin (Hematoxylin-Eosin, HE) staining and Masson (Masson) staining were performed on the tissue sections to examine the histocompatibility of the material. As shown in Figure 4, the experimental results of BC, PU, BC/PU-0 and BC/PU-3 were analyzed using the normal skin on the back of normal rats as a control. The HE staining results of BC, PU, BC/PU-0 and BC/PU-3 at 7 days and 14 days after implantation showed that the skin tissue after contact with the material had a complete epidermis, dermis and subcutaneous tissue, each layer The morphology is not significantly different from normal skin tissue. The results of Masson staining showed that the skin tissues that had been in contact with the material for 7 days and 14 days had normal collagen distribution. Therefore, it can be judged that the implantation of BC/PU will not cause pathological changes in the surrounding skin tissue, has good histocompatibility, and can be used as an implant material.

Fig. 5 is a diagram of the preparation mechanism of the present invention. The present invention adds organic alcohol as a plasticizer to bacterial cellulose. Organic alcohols are rich in hydroxyl groups, which can form hydrogen bonds with the hydroxyl groups on bacterial cellulose, avoiding the irreversible intramolecular hydrogen bonds formed during the dehydration process of bacterial cellulose. The plasticized dehydrated bacterial cellulose is immersed in the polyurethane solution, part of the organic alcohol molecules on the cellulose molecular chain falls off, and the free hydroxyl groups form hydrogen bonds with the ester groups on the polyurethane and the amide groups in the solvent. Bacterial cellulose re-swells and fully contacts with polyurethane, which improves the compatibility of bacterial cellulose and polyurethane, and obtains high-strength and high-toughness bacterial cellulose/polyurethane composite materials, and the Young's modulus and elongation at break are adjustable .

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (8)

1. A method of preparing a bacterial cellulose/polyurethane composite, the method comprising the steps of:

(1) Soaking a bacterial cellulose membrane in an organic alcohol aqueous solution to swell the bacterial cellulose membrane; the organic alcohol is used for plasticizing the bacterial cellulose membrane;

(2) Taking out and drying the bacterial cellulose membrane obtained in the step (1), soaking the bacterial cellulose membrane in polyurethane solution to enable part of organic alcohol molecules on bacterial cellulose molecular chains to fall off, re-expanding the bacterial cellulose membrane, fully contacting with polyurethane, and improving the compatibility of bacterial cellulose and polyurethane, wherein the polyurethane is doped into a cellulose three-dimensional porous network in the bacterial cellulose membrane; and then drying to solidify the bacterial cellulose membrane to obtain the bacterial cellulose/polyurethane composite material.

2. The method of claim 1, wherein the organic alcohol is at least one of glycerol, ethylene glycol, polyethylene glycol, sorbitol, and xylitol.

3. The method of claim 1 or 2, wherein the volume concentration of the organic alcohol in the aqueous organic alcohol solution is 2% to 3%.

4. The method of claim 1, wherein the soaking temperature in step (1) is 16 ℃ to 40 ℃ and the soaking time is 8h to 24h.

5. The method of claim 1, wherein in step (2), the mass ratio of cellulose in the bacterial cellulose film to polyurethane in the polyurethane solution is 1:5 to 1:10.

6. The method of claim 1, wherein the soaking in step (2) is performed at a temperature of 25 ℃ to 80 ℃ for a time of 4h to 12h.

7. Bacterial cellulose/polyurethane composite obtainable by the process according to any one of claims 1 to 6.

8. Use of the bacterial cellulose/polyurethane composite material according to claim 7 for the preparation of an implant material.