CN108992712A - A kind of cerium oxide nano nerve trachea composition, nerve trachea and its preparation method and application - Google Patents

Abstract

The invention provides a cerium oxide nano nerve guide composition, a nerve guide and its preparation method and application, the composition is composed of biodegradable and metabolized materials, cerium oxide nanometers, and biocompatible adhesive materials; using 3D printing Or electrospin biodegradable materials and cerium oxide nanocomposites or organic solvents to form catheters for various biomedical applications. After molding, print or spray a layer of bioadhesive substances on the inner wall according to needs to induce cell differentiation and growth in the catheter . The invention provides a catheter bracket required by biology, which has the advantages of ideal biomedical functional material, simple preparation, low cost, easy quality control, wide application and the like. Rat sciatic nerve defect repair experiments show that the cerium oxide nano-nerve guide of the present invention promotes nerve regeneration, increases the maturity of regenerated nerves and the number of functioning nerve fibers, and promotes the return of sciatic nerve function to normal, and the effect is better than that of autologous nerve transplantation. Good application prospects.

Description

A kind of cerium oxide nano nerve guide composition, nerve guide and its preparation method and application

technical field

The invention relates to the technical field of biomaterials, in particular to a cerium oxide nanometer nerve guide composition, a nerve guide and a preparation method and application thereof.

Background technique

Various biomedical catheters currently include degradable and non-degradable catheters. For example, polyethylene tubes have been used as nerve catheters to study nerve regeneration. Due to the non-degradable catheters, after the completion of nerve regeneration, if the catheters are not treated, it may cause Tissue fibrosis causes toxic and side effects such as inflammation, and the clinical application effect is not very satisfactory. At present, various biodegradable materials have been developed to prepare various biomedical catheters, such as collagen, polylactic acid, etc., but because these materials are used alone, there are some problems such as strength, nerve regeneration speed, and toxic side effects. Recently, it has been developed to further research on these catheters, such as performing various regenerations on the surface or inside of the catheter that are beneficial to the regeneration of various lumen injuries in the body, such as performing cell modification on the surface of the catheter, and carrying various active substances that promote the growth of the lumen. , such as nerve growth factor of the nerve conduit, blood cells, etc.

Electrospinning is to apply a high-voltage DC power supply to the capillary containing the polymer solution. Under the action of the electric field, the droplets suspended at the end of the capillary are deformed to form a Taylor cone. When the applied electric field exceeds a certain critical value, the electric field force Overcoming the surface tension of the solution, a finer surface-charged jet is formed. Under the action of the electric field, the jet moves to the grounded collector. During the movement, the jet is continuously stretched, and in some cases the jet will split and split into Finer jets, while the solvent continues to volatilize, and finally fibers with a diameter of several microns to tens of nanometers, or even several nanometers, are obtained on the collector. The nerve conduit scaffold material prepared by electrospinning can not only mimic the collagen fiber structure in the extracellular matrix, but also has high porosity and specific surface area, which is conducive to cell adhesion, growth and proliferation.

Although some research progress has been made on nerve guides, for example, the Chinese invention patent CN100479785C discloses a method for preparing nerve guides, but there is still a certain distance from autologous nerve repair. In addition, there are many patents disclosing different preparation methods (such as Chinese invention patent CN101439205A, open date 2009.5.27; CN101507842A, open date 2009.8.19, CN106668938A, open date 2017.05.17; CN106924820A, open date 2017.07.07), But these catheters have issues with either strength, toxicity, quality control, or cost. None of the nerve guides disclosed in the prior art are ideal biomedical guides. An ideal catheter should have: sufficient strength, elasticity, hardness, etc.; degradability and complete degradation in the body until the damaged tissue regenerates completely, and no need to be removed by surgery again; materials should be as non-toxic and side effects as possible; suitable degradation cycle ; It can guide the growth of tissue in the right direction; it can prevent unwanted tissue regeneration, etc.

Contents of the invention

The first purpose of the present invention is to provide a cerium oxide nano nerve guide for the deficiencies in the prior art.

The second purpose of the present invention is to provide a composition for preparing cerium oxide nano nerve guides to address the deficiencies in the prior art.

The third object of the present invention is to provide the application of the above-mentioned composition in the preparation of biological materials to address the deficiencies in the prior art.

The fourth object of the present invention is to provide the application of cerium oxide nanometers in the preparation of biological materials to address the deficiencies in the prior art.

For realizing above-mentioned first object, the technical scheme that the present invention takes is:

A cerium oxide nano nerve guide, which is prepared by the following method: take 90-99.5% by weight of biodegradable materials, 0.5-10% by weight of cerium oxide nanometers, and use 3-6 times the weight of biodegradable materials The weight of the organic solvent is dissolved, then the cerium oxide nanometer is added and mixed thoroughly, injected into the injector, and the tube is formed by the electrospinning process, and sprayed onto the continuously rotating rod-shaped mold by direct current voltage. After the tube is formed, the nerve guide is taken off from the mold. Dry the volatile solvent, cut into cerium oxide nano nerve conduits of different lengths and specifications; the biodegradable materials are polylactic acid, polylactic acid-polyglycolic acid, polycaprolactone, silk protein, collagen, gelatin, hyaluronic acid, shell One or more combinations of polysaccharides; the organic solvent is dichloromethane or ethyl acetate.

For realizing above-mentioned second purpose, the technical scheme that the present invention takes is:

A composition for preparing a cerium oxide nano nerve guide, which is composed of biodegradable materials and cerium oxide nanometers, and the weight percentage is: 90-99.5% of biodegradable materials, 0.5-10% of cerium oxide nanometers; the biodegradable material is polylactic acid , polylactic acid-polyglycolic acid, polycaprolactone, silk protein, collagen, gelatin, hyaluronic acid, chitosan or a combination of one or more.

In the above composition for preparing cerium oxide nanometer nerve guide, as a preferred solution, the weight percentage is: biodegradable material 95-99%, cerium oxide nanometer 1-5%.

For realizing above-mentioned 3rd purpose, the technical scheme that the present invention takes is:

The application of the composition as described above in the preparation of biomaterials for promoting peripheral nerve regeneration after nerve injury.

In the above specific application, as a preferred solution, the biological material specifically refers to a nerve guide.

The present invention also provides a cerium oxide nano nerve guide, which is prepared by 3D printing or electrospinning using any of the compositions described above to prepare a cerium oxide nano nerve guide, including the following steps: preparing a biodegradable material and a cerium oxide nanosuspension Or add cerium oxide nanoparticles into the molten biodegradable material and mix to obtain a mixture; add the above suspension or mixture into 3D printing or electrospinning equipment, and print or electrospin to prepare the required catheter.

In the above-mentioned cerium oxide nano-guide, as a preferred solution, it also includes the following steps: internally print or electrospin a layer of bioadhesive substance on the prepared catheter, and perform cross-linking and curing; the bioadhesive substance is Refers to any one of dopamine, bioadhesive peptides, extracellular matrix or any mixture thereof.

In the above-mentioned cerium oxide nano-guide, as a preferred solution, the average pore diameter of the outer surface of the catheter is 0.01 to 10 μm, and the average pore diameter of the bioadhesive layer inside the catheter is 10-1000 μm.

For realizing above-mentioned 4th object, the technical scheme that the present invention takes is:

Application of nano cerium oxide in preparation of biomaterial for promoting peripheral nerve regeneration after nerve injury.

In the above specific application, as a preferred solution, the biological material specifically refers to a nerve guide.

The present invention has the advantage that:

1. Provide a catheter stent that meets biological needs and has ideal biomedical functional materials.

2. It has sufficient strength, elasticity, hardness, and degradability, and the damaged tissue in the body after transplantation is completely regenerated, and the nerve guide is completely degraded, and no further surgery is required to remove it;

3. The rat sciatic nerve defect repair experiment shows that the cerium oxide nano-nerve guide of the present invention can promote nerve regeneration, improve the maturity of the regenerative nerve and the number of nerve fibers that play a role, improve the rat sciatic nerve function index, and promote the return of sciatic nerve function to normal, and The effect is better than that of autologous nerve transplantation, and it has a good application prospect.

Description of drawings

Accompanying drawing 1 is the appearance diagram of the nerve guide prepared by the embodiment of the present invention.

Accompanying drawing 2 is the graph of transmission electron microscope detection result of pure PLA catheter regenerative nerve.

Accompanying drawing 3 is the transmission electron microscope detection result diagram of the regenerated nerve of autologous nerve transplantation.

Accompanying drawing 4 is the transmission electron microscope detection result of nerve conduit group regeneration nerve prepared by 1% cerium oxide nanometer and PCL composition prepared in the embodiment of the present invention.

Detailed ways

The present invention will be further described below in combination with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the contents of 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 the present application.

Embodiment 1 nerve guide biodegradable material composition

The weight ratio of polylactic acid is 99%, the weight ratio of cerium oxide nanometer (10-1000nm) is 1%, the polylactic acid is dissolved with 3-6 times the weight of methylene chloride, and then the cerium oxide nanometer is added and mixed well to prepare the biodegradable nerve guide material composition.

Embodiment 2 nerve guide biodegradable material composition

The weight ratio of polylactic acid-polyglycolic acid is 99.5%, and the weight ratio of cerium oxide nanometer is 0.5%. Dissolve polylactic acid-polyglycolic acid with 3-6 times the weight of ethyl acetate, then add cerium oxide nanometer and mix well to prepare nerve Catheter biodegradable material composition.

Embodiment 3 nerve guide biodegradable material composition

The weight ratio of polycaprolactone is 98%, the weight ratio of cerium oxide nanometer is 2%, the polycaprolactone is dissolved with 3-6 times the weight of methylene chloride, and then the cerium oxide nanometer is added to mix well to prepare the nerve guide biodegradable material combination.

Embodiment 4 nerve guide biodegradable material composition

The weight ratio of the polylactic acid is 95%, and the weight ratio of the cerium oxide nanometer is 5%, and the cerium oxide nanometer is added into the melted polylactic acid and mixed thoroughly to prepare a nerve guide biodegradable material composition.

Embodiment 5 nerve guide biodegradable material composition

The weight ratio of polylactic acid-polyglycolic acid is 90%, and the weight ratio of cerium oxide nanometer is 10%, and the cerium oxide nanometer is added to the molten polylactic acid-polyglycolic acid and mixed well to prepare the nerve guide biodegradable material composition.

The preparation of embodiment 6 nerve guide

Take the biodegradable material composition described in any one of Examples 1-5 to prepare catheters, and use conventional electrospinning technology to prepare various required catheters; or use 3D printing technology to print various catheters; or use catheter molds to prepare various catheters. the required catheter. For example, 3D printed and 1% cerium oxide nano-PCL nerve guides have good nerve regeneration properties, such as elastic modulus better than pure PCL printing (48.32 and 31.77 MPa, respectively).

The preparation of embodiment 7 nerve guide

On the basis of the nerve guide in Example 6, a layer of bioadhesive substance is internally printed or electrospun, and then cross-linked and cured. The bioadhesive substance can be any one of dopamine, bioadhesive peptide or extracellular matrix, or a mixture of them in any proportion.

The preparation of embodiment 8 nerve guide

Utilize the biodegradable material composition of Example 1 to prepare the catheter, the specific steps are as follows: take the nerve catheter biodegradable material composition, take 100ml after defoaming, inject it into the injector and output it at a flow rate of 15ml/h, and use the electrospinning process to form the catheter. The tube is sprayed onto a rod-shaped mold with a rotating speed of 600rpm and a diameter of 3mm through a DC voltage, a voltage of 20KV, and a receiving distance of 20cm. The electrospinning nozzle moves back and forth at a speed of 10cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod-shaped mold continues to rotate for 5-10 hours to evaporate the solvent. The nerve guide is taken off from the mold, dried to completely evaporate the solvent, and the nerve guide is cut into different length specifications.

The preparation of embodiment 9 nerve guide

Utilize the biodegradable material composition of embodiment 1 to prepare catheter, concrete steps are as follows: take polylactic acid weight ratio 99%, dopamine weight ratio 1%, polylactic acid is dissolved with the dichloromethane of 3-6 times weight, then add dopamine fully Mix well to obtain a mixture. Take 10ml of the mixture after defoaming and inject it into the injector at a flow rate of 10ml/h, and use the electrospinning process to form a tube, and spray it onto a rod-shaped mold with a rotation speed of 800rpm and a diameter of 3mm through a DC voltage, the voltage is 20KV, and the receiving distance 20cm. The electrospinning nozzle moves back and forth at a speed of 15cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod-shaped mold continues to rotate for 5-10 hours to evaporate the solvent. Take the nerve conduit biodegradable material composition, after defoaming, take 100ml and inject it into the injection device at a flow rate of 10ml/h, and use the electrospinning process to form a tube, and spray it on the surface of the tube body of the rod-shaped mold with a rotation speed of 800rpm through a DC voltage. 20KV, the receiving distance is 20cm. The electrospinning nozzle moves back and forth at a speed of 15cm/min in the horizontal direction, and the length of the tube is 15-20cm. The nerve guide is taken off from the mold, dried to completely evaporate the solvent, and the nerve guide is cut into different length specifications.

The preparation of embodiment 10 nerve guide

Utilize the biodegradable material composition of Example 2 to prepare the catheter, the specific steps are as follows: take 100ml of the nerve catheter biodegradable material composition after defoaming, inject it into the injector and output it at a flow rate of 10ml/h, and use the electrospinning process to form a catheter , sprayed onto a rod-shaped mold with a rotational speed of 900rpm and a diameter of 5mm through a DC voltage, a voltage of 20KV, and a receiving distance of 20cm. The electrospinning nozzle moves back and forth at a speed of 15cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod mold continues to rotate to evaporate the solvent. The nerve guide is taken off from the mold, dried to completely evaporate the solvent, and the nerve guide is cut into different length specifications.

The preparation of embodiment 11 nerve guide

Utilize the biodegradable material composition of embodiment 2 to prepare catheter, specific steps are as follows: take polylactic acid-polyglycolic acid weight ratio 99.5%, bioadhesive peptide weight ratio 0.5%, polylactic acid-polyglycolic acid is used 3-6 times Weight of ethyl acetate was dissolved, and then the bioadhesive peptide was added and mixed thoroughly to obtain a mixture. Take 10ml of the mixture after defoaming and inject it into the injector at a flow rate of 10ml/h, and use the electrospinning process to form a tube, and spray it on a rod-shaped mold with a rotation speed of 1000rpm and a diameter of 5mm through a DC voltage, the voltage is 20KV, and the receiving distance 20cm. The electrospinning nozzle moves back and forth at a speed of 10cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod mold continues to rotate to evaporate the solvent. Take the nerve conduit biodegradable material composition, after defoaming, take 100ml and inject it into the injection device at a flow rate of 5ml/h, and use the electrospinning process to form a tube, and spray it on the surface of the tube body of the rod-shaped mold with a rotation speed of 1000rpm through a DC voltage. 20KV, the receiving distance is 20cm. The electrospinning nozzle moves back and forth at a speed of 10cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod mold continues to rotate to evaporate the solvent. The nerve guide is taken off from the mold, dried to completely evaporate the solvent, and the nerve guide is cut into different length specifications.

The preparation of embodiment 12 nerve guide

Utilize the biodegradable material composition of Example 3 to prepare the catheter, the specific steps are as follows: take the nerve catheter biodegradable material composition, take 100ml after defoaming and inject it into the injector at a flow rate of 15ml/h, and use the electrospinning process to form the catheter. The tube is sprayed onto a rod-shaped mold with a rotational speed of 1000rpm and a diameter of 5mm through a DC voltage, a voltage of 20KV, and a receiving distance of 20cm. The electrospinning nozzle moves back and forth at a speed of 15cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod mold continues to rotate to evaporate the solvent. The nerve guide is taken off from the mold, dried to completely evaporate the solvent, and the nerve guide is cut into different length specifications.

The preparation of embodiment 13 nerve guide

Utilizing the biodegradable material composition of Example 3 to prepare a catheter, the specific steps are as follows: take polycaprolactone with a weight ratio of 98%, and dopamine with a weight ratio of 2%, and dissolve polycaprolactone with 3-6 times the weight of dichloromethane, Then add dopamine and mix thoroughly to obtain a mixture. After defoaming the mixture, take 10ml and inject it into the injector at a flow rate of 15ml/h, and use the electrospinning process to form a tube, and spray it on a rod-shaped mold with a rotation speed of 1000rpm and a diameter of 5mm through a DC voltage, the voltage is 20KV, and the receiving distance 20cm. The electrospinning nozzle moves back and forth at a speed of 15cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod mold continues to rotate to evaporate the solvent. Take the nerve conduit biodegradable material composition, after defoaming, take 100ml and inject it into the injector at a flow rate of 15ml/h, and use the electrospinning process to form a tube, and spray it on the surface of the tube body of the rod-shaped mold with a rotation speed of 1000rpm through a DC voltage. 20KV, the receiving distance is 20cm. The electrospinning nozzle moves back and forth at a speed of 15cm/min in the horizontal direction, and the length of the tube is 15-20cm. After the solution is sprayed, the rod mold continues to rotate to evaporate the solvent. The nerve guide is taken off from the mold, dried to completely evaporate the solvent, and the nerve guide is cut into different length specifications.

Embodiment 14 Animal experiments

The nerve guide prepared in the above-mentioned Example 8 was implanted into the sciatic nerve of the rat (to repair the damage of 15 mm), and the guide tube made of 1% cerium oxide nanometer PCL material was selected as shown in FIG. 1 . As shown in Figures 2-4, the thickness of myelin sheath is an important indicator reflecting the maturation of regenerative nerves. The results in the figure show that at the 12th week after operation, the thickness of myelin sheath of the nerve conduit prepared by 1% cerium oxide nanometer and PCL composition is greater than that of pure The PLA conduit group and the autologous nerve transplantation group show that the nerve conduit of the present invention has a remarkable effect of promoting nerve regeneration, and the effect is better than that of the autologous nerve and pure PCL conduit.

Embodiment 15 Animal experiments

Thirty healthy adult male SD rats were divided into two groups A and B according to the random number table method, with 15 rats in each group. The right side of all rats is the experimental side, and the left side is the normal control side. Under anesthesia by intraperitoneal injection of ketamine, a longitudinal incision was made on the posterolateral aspect of the right femur, and the sciatic nerve was exposed from the intermuscular space. A 10 mm trunk of the sciatic nerve was excised from the middle part of the thigh, and group A used autologous nerves for in situ nerve transplantation; group B used the nerve conduit prepared in Example 9 to bridge and repair, and the two nerve stumps were respectively inserted into the conduit 1 mm, and a gap of 10 mm was reserved for the nerve defect. -0 silk sutures the wall and the epineurium with 3-4 stitches at each end. After operation, they were housed in separate cages. The sciatic nerve function index (SFI) values of the rats in each group were detected at the 4th, 6th, 8th, and 10th weeks. When the SFI was close to 0, it indicated that the sciatic nerve function was normal. When the SFI value was -100, it indicated that the sciatic nerve function was completely lost. Calculated according to the SFI formula: SFI＝-38.3(EPL-NPL)/NPL+109.5(ETS–NTS)/NTS+13.3(EIT-NIT)/NIT-8.8 (E: Experimental side foot; N: Normal side foot). The results are shown in the table below. In the second week after the operation, the SFI values of the two groups had no significant difference (P>0.05). From the 8th week, the SFI values of the two groups showed significant differences. The nerve guide can significantly promote the normal function of the sciatic nerve.

Table 1 Comparison of sciatic nerve functional index SFI between the two groups after operation

postoperative time Group A Group B Two weeks -87±2.90 -86±2.75 4 weeks -74±2.65 -71±2.55 6 weeks -65±2.40 -58±2.45 8 weeks -51±2.35 -42±2.30 10 weeks -48±2.25 -33±2.15

At the 12th week, regenerated nerves were cut at 2 mm from the anastomosis at the distal end of the sciatic nerve, fixed with 4% glutaraldehyde and 1% osmic acid, embedded, sectioned, and stained. In the lower right five unit fields of view, the number of myelinated nerve fibers was counted, and the diameter of the axon and the thickness of the myelin sheath were measured. The results are shown in the table below. Axon diameter and myelin sheath thickness are the main morphological markers of nerve maturation, and more mature myelinated nerve fibers in regenerated nerves are effective regeneration. As can be seen from the results in the table, group B is significantly higher than group A in the number of regenerated nerve fibers, axon diameter and myelin sheath thickness, indicating that the nerve guide of the present invention can promote nerve regeneration, improve the maturity of regenerated nerves and play a role number of nerve fibers.

Table 2 Comparison of the number of regenerated nerve fibers, axon diameter and myelin sheath thickness between the two groups at 12 weeks after operation

number of nerve fibers Axon diameter (μm) Myelin thickness (μm) Group A 225.1±13.5 3.61±0.64 1.21±0.08 Group B 245.1±15.8 ^* 4.41±0.82 ^* 1.42±0.12 ^*

Note: * means compared with group A, P<0.05.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the method of the present invention, some improvements and supplements can also be made, and these improvements and supplements should also be considered Be the protection scope of the present invention.

Claims (10)

1. a kind of cerium oxide nano nerve trachea, which is characterized in that the cerium oxide nano nerve trachea is made with the following method It is standby: biodegradation material weight percent 90-99.5%, cerium oxide nano weight percent 0.5-10% are taken, it will be biodegradable The organic solvent of 3-6 times of weight of material dissolves, and cerium oxide nano is then added and mixes well, injects injection instrument, utilizes electrostatic Spinning technique is ejected on the bar molds constantly rotated at pipe by DC voltage, and Cheng Guanhou takes off nerve trachea from mold Under, solvent flashing is dried, the cerium oxide nano nerve trachea of different length specification is cut into；The biodegradation material is poly- cream One of acid, polyglycolic-polylactic acid, polycaprolactone, silk-fibroin, collagen, gelatin, hyaluronic acid, chitosan are a variety of Combination；The organic solvent is methylene chloride or ethyl acetate.

2. a kind of composition for preparing cerium oxide nano nerve trachea, which is characterized in that received by biodegradation material and cerium oxide Meter Zu Cheng, weight percent are as follows: biodegradation material 90-99.5%, cerium oxide nano 0.5-10%；The biodegradation material For one of polylactic acid, polyglycolic-polylactic acid, polycaprolactone, silk-fibroin, collagen, gelatin, hyaluronic acid, chitosan Or a variety of combination.

3. composition according to claim 2, which is characterized in that weight percent are as follows: biodegradation material 95-99%, Cerium oxide nano 1-5%.

4. any composition of claim 2-3 is preparing the application in biomaterial, the biomaterial is for nerve Promote peripheral nerve regeneration after damage.

5. application according to claim 4, which is characterized in that the biomaterial refers specifically to nerve trachea.

6. a kind of cerium oxide nano nerve trachea, which is characterized in that carried out using the composition any in claim 2-3 3D printing or electrostatic spinning prepare cerium oxide nano nerve trachea, include the following steps: to prepare biodegradation material and cerium oxide Nanosuspension or cerium oxide nano be added melting biodegradation material in mix to obtain mixture；By above-mentioned suspension or mix It is added in 3D printing or electrospinning device with object, carries out printing or electrostatic spinning is prepared into required conduit.

7. cerium oxide nano nerve trachea according to claim 6, which is characterized in that further include following steps: will prepare Conduit carry out one layer of bioadhesion substance of house print or electrostatic spinning, and carry out crosslinking curing；The bioadhesion substance Refer to dopamine, bioadhesion peptide, any one or their any mixtures in extracellular matrix.

8. cerium oxide nano nerve trachea according to claim 7, which is characterized in that the average hole of the catheter outer surface Diameter is 0.01 to 10 μm, and the average pore size of bioadhesive layer is 10-1000 μm in conduit.

9. nano-cerium oxide is preparing the application in biomaterial, which is characterized in that after the biomaterial is used for neurotrosis Promote peripheral nerve regeneration.

10. application according to claim 9, which is characterized in that the biomaterial refers specifically to nerve trachea.