| Nerve injury is very common clinically. The reparation of the impaired never goes very adagio, and when nerve injury is severe and the nerve function is lost, a series of functional disturbance of other parts of the organism will be initiated, so the regenerate and reestablish the injured nerve still be a hang-up puzzled the clinicians, which is paid close attention by the medical profession. There are tissue engineering method which can promote the regeneration and reestablishment of the impaired nerve. The key of the tissue engineering method is how to find stuff with perfect biological efficiency and great biodegradability. The material should not only possess great structure and biocompability, but also have perfect contribution as scaffold, which can provide satisfactory microenvironment for the damaged nerve, providing effects of targeting. At the present time, there are many kinds of biodegradabal materials to restore the damaged nerve, such as polylactic acid, poly-hydroxy buterate, PLGA, chitosan, collagen protein and so on. Among the above, chitosan is one kind of polysaccharide with great biocompability and biodegradability. Its degradation products have no adverse reaction and immunogenicity to the organism. Chitosan and its degradation product possess such biological activities as antibiosis, disinfection, antiambury, facilitation of tissue reestablishment, etc., so chitosan can be used as the cellular carrying agent to regenerate many kinds of injured tissues. Collagen type I is the most abundant collangen which can provide scaffold for the creature cells to maintain their structure. Gelatin, a kind of polypeptide mixture which is degradated from collagen, can be degenerated by the organism, also with excellent pasticity. Chitosan, collagen type I and gelatin, all belong to natural extracellular matrix, are considered as high-qualified materials to repair injured nerve. The prospects is for a very wide range, of which the compound material to repair injured nerve made from these three kinds of material through a certain preparation technology applied to the medicine profession. In this research, chitosan, collagen type I and gelatin are mixed with a certain propotion through a specific technology, making a new type of nerve repair material. Testing the bio- compability by animal experiments, the whole study not only provides the experimental basis for testing the role of this new kind of compound material to repair the damaged nerve, but also lays the foundation for this material using in clinical to solve the medical tough problems.Objective:Compound nerve-repair material was made from chitosan, collagen type I and gelatin. The external appearance and internal ultramicro-structure was observed and the bio- compablity was detected in Wista rats, through which to determin the prospective of this new nerve-repair material's clinical application.Methods:The preparation of the chitosan nerve-repair material Weight 200 mg collagen type I, dissolved in 10 ml 1% acetic acid solution, agitating in super speed for 6 h with stirring apparatus at 4℃. Weight 1 g chitosan, dissolved in 100 ml 1% acetic acid solution, agitating in super speed for 6 h with stirring apparatus at 4℃. Mixed the two kinds of solution, add in 3.33 g gelatin, stirring overnight with stirring apparatus at 4℃. After suction filtration with 200 m carbasus, the insoluble substance was eliminated. Then infunded the filtering solution to silicone tube 12cm long and inter diameter 3 mm. Afer freeze dry the tube material, the lyophilized tubes were exposed to 60Co for 24 h. Sliced the transverse section, longitudinal section, diagonal section and usface of the sterilized material, observe the ultramicro-structure under scanning electron microscope.The biocompability of the chitosan nerve-repair material 120 Wistar rats weighed 200±20 were stochastically divided into three groups, material group, surgery group and normal group. The paralysed rats were held on the surgery board in prone positon, cut the skin to reach the musle tissue, expose the musle clearance. Cut the sterilized material into 2 cm long, heeled the material in the muscle along the muscle fiber. Sew up the muscle and skin at the operative site layer by layer. Treated the surgery group the same way except heeling in the material. No treating with the normal group. Breeded the three groups under similarity condition, abserve the general condition and the intention.On day 3, day 7, day 14, and day 21 after the surgery, ten rats of each group were treated as the following step, weighed, took blood 4 to 6 ml, then sacrificeed and dissected, weighed the liver, kidney and the operative-site musle, put into 10% formalin solution to fix. Made slice of the tissue and observed the slice under hematoxylin and eosin stain to detect the effects of the material over the liver, kidney and musle. The blood should be stored in low temperature for 1 h, then centrifuged 10 min under 2 500 rpm, took the supernatant and evaluated the biochemical indicator of the blood serum.The data was analysed by SPSS statistics software 13.0, the variable was expresssed as x±S, the difference of data among different groups was done by variance analysis.Results:The preparation of the chitosan nerve-repair material Under ratio of 1:200μm, 1:100μm and 1:50μm, the microstructure of the transverse section, longitudinal section and diagonal section of the sterilized material under scanning electron microscope showed that the inter structure of the material arranged crumbly, the porous structure arranged regularly, and the size of the pore was uniform; under ratio of 1:20μm and 1:10μm, the pore has uniform and slick inter paries and sized regularly. Under ratio of 1:200μm, 1:100μm and 1:50μm, the microstructure of the surface of the sterilized material under scanning electron microscope showed that the surface of the material arranged crumbly, the lines arranged regularly, there were no obvious salience or hollow; under ratio of 1:20μm and 1:10μm, the suface was uniform and slick, the revine sized regularly.The biocompability of the chitosan nerve-repair material After surgery, the rats of surgery group and material group reduced activities significantly, the operated-side's sole of foot dropsied and could not touch down and lame, but no notable inflammatory action and self-mutilation appeared. On day 3 after surgery, the muscle of the operative site cicatrized well when we dissected the rats, the material embedded had not changed obviously. On day 7 after surgery, the outside of the wound healed perfect, the oedema lightened. We could see the material become smaller and coalesce with the muscle when we dissected the rats. On day 14 after sugery, the outside of the wound completely healed, there were no oedema and the rats could behave freely, we could see that there are no outline between the material and the muscle. On day 21, there were no difference between normal group and the other two groups. When dissecting the animals, we could see the wound totally heal and did not see dividing line between the material and the muscle tissue around it.There were no significant difference in the the body rate of liver, kidney and musle tissue of the operation site and the BUN, CR, AST, ALT, IgA, IgG and IgM in the rats'blood serum between the three groups on day 3 after the surgery, the LDH, CK in the rats'blood on the material group was significantly higher than those on the other two groups but no difference between the other two groups; There were no significant difference in the the body rate of liver, kidney and musle tissue of the operation site and the BUN, CR, AST, ALT, LDH, IgA and IgG in the rats'blood serum between the three groups on day 7 after the surgery, compared with the normal, the CK and IgM contents of the rats'blood serum on the material and surgery groups were significantly higher, the CK content of the rats'blood serum on the surgery group is higher than that on the material group; On day 14 after the surgery, there were no significant difference in the the body rate of liver, kidney and the BUN, CR, ALT, IgA, IgG and IgM in the rats'blood serum between the three groups, the musle/body weight on surgery group was lower than that on the other two groups but no difference between the other two, the LDH, AST and CK content on the surgery group was absolutely higher than that on the other two groups but no difference between the other two, the CK concentration in the rats'blood serum on the material and surgery groups were higher than that on the normal group; On day 21 after the surgery, there were no significant difference in the the body rate of liver, kidney and musle tissue of the operation site and the CR, AST, ALT, IgA, and IgG in the rats'blood serum between the three groups, the BUN, LDH and CK contents on the material group was higher than that on the other two groups but no difference between the other two, the IgM contents in the surgery group was significantly higer than that on the other two groups but no difference between the other two.The pathology results showed that, from day 3 to day 21 after surgery, the liver and kidney of material group and surgery group had no difference compared with normal group. On day 3 after surgery, there were inflammatory cell infiltration on the material region, in sugery group, there were also inflammatory infiltration on the sugery region, and there were diapedesis can be seen. On day 7 after surgery, the inflammatory cells on both surgery and material groups decrease and the material became more porous than that on day 3, but the wounds were not heal. On day 14 after surgery, the inflammatory cell infiltration further weakened, the material in the muscle shrinked more and became more porous than before. There were some rats on the surgery group begain to heal, the regenerated muscle fibrocytes were of different sizes and arranged with no regulation, not like that on the normal group. On day 21 after sugery, the inflammatory cell infiltration almost fadeaway on the material group, the material became further smaller and more porous, regenerated muscle fiber could be seen in the lax ventage. The muscle fiber of the rats on surgery group almost totally healed, the size and the alinement were nearly indiscriminate compared with the normal group.Conclusion:1.The internal structure of the compound material to repair nerve which made of chitosan, type-I collagen and gelatin is of regulation, and the porous structure arranged uniformly, the compound material possess favourable biosimilarity, witch will be suitable to support of cell and tissue.2.The compound material to repair nerve which made of chitosan, type-I collagen and gelatin has great biocompatibility and favourable biodegradability.3.The compound material to repair nerve which made of chitosan, type-I collagen and gelatin may provide great opportunity for injured nerve repair and can be used in further study.
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