| Biomedical materials are related to human survival and health,which have been increasingly conspicuous.As is well-known,bilirubin from the blood of patients suffering from liver failure often increases rapidly and then evokes clinical syndrome with multiple organ failure,leading to the threat of patient’s life.Therefore,it is urgent to find a bilirubin adsorbent which had highly efficient bilirubin adsorption and no influence on protein and coagulation function systems.Moreover,the treatment of peripheral nerve injuries arisen from various kinds of trauma is a considerable clinical challenge.Synthetic nerve conduit is a promising approach to encourage new nerve axons regeneration and some degree of functional recovery of peripheral nerve.Therefore,looking for nerve scaffold materials with biocompatibility for nerve regeneration is of great significance.Natural polymer from the renewable biomass resources is not only inexhaustible,but also biocompatible and biodegradable,thus it is an ideal biomedical material.Chitin,as the second most abundant natural polymer,exists mainly in the shell of arthropods,possesses the common properties of biopolymer including biocompatibility,biodegradability and biological activity.On the other hand,carbon nanotubes(CNTs)have several excellent properties,such as excellent adsorption for many substances and gwoth-promoting for neuronal cells,mainly due to their special nanoscale tubular structure and the graphene sheets on the surface wall.However,the potential toxicity of CNTs to both the environment and human health limit their application.Therefore,combining CNTs with chitin can improve the biological function of chitin and the biocompatibility of CNTs.Thus,constructing chitin/carbon nanotube(Ch/CNT)composite materials will have academic value and application prospect in blood perfusion,neuroscience and tissue engineering.In this work,based on the chitin dissolved in NaOH/urea aqueous solution at low temperature,we prepared biocompatible and biodegradable chitin/carbon nanotube(Ch/CNT)composite materials(such as hydrogel and nanofibrous microspheres)from chitin/NaOH/urea aqueous solution by blending with modified CNTs.The structure and properties of these composite materials were characterized by atomic force microscopy(AFM),transmission electron microscope(TEM),scanning electron microscope(SEM),wide angle X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),laser confocal Raman spectroscopy(Raman),nitrogen adsorption and mechanical testing.The correlation between structure and properties was also studied.Meanwhile,the potential application prospect of Ch/CNT composite hydrogel in neural regeneration was evaluated by cell culture experiments and the application prospect in blood perfusion was evaluated by a serial of adsorption,plasma perfusion,blood compatibility and cell culture experiments.The innovative points of this work are as follows.(1)chitin/carbon nanotube composite hydrogel was successfully constructed and demonstrated to be biocompatible,biodegradable has excellent mechanical properties,and could obviously promote the adhesion and growth of nerve cells.(2)chitin/carbon nanotube composite nanofiberous microspheres were firstly prepared by emulsification and thermal induction method.Meanwhile,lysine has been immobilized into the Ch/CNT microspheres to obtain lysine-immobilized chitin/carbon nano tube(Ch/CNT/Lys)microspheres,which exhibited excellent selective bilirubin adsorption properties in hyperbilirubinemia plasma,and they could be used as bilirubin adsorbents for blood perfusion.(3)Revealing the biocompatibility and blood compatibility of Ch/CNT/Lys microspheres for the first time and pointing out the application prospect as the whole blood perfusion adsorbents.The main contents and conclusions in this project are divided into the following parts.Chitin could be dissolved completely in NaOH/urea aqueous solution via the freezing/thawing method,then,the Ch/CNT composite hydrogel was constructed from chitin/NaOH/urea aqueous solution by blending with modified CNTs.The structure of them was investigated by SEM,TEM,XRD,FT-IR and Raman,indicating that CNTs and chitin nanofibers combined with each other to form a close crosslinked network structure through electrostatic interaction,hydrogen bonding interaction and amphiphilic interaction.The composite hydrogel displayed excellent biocompatibility,blood compatibility and biodegradability,as a result of the inherent biocompatibility of chitin.In addition,the introduction of CNTs could enhance the mechanical properties of the Ch/CNT composite hydrogel,and had decreased swelling degree and slow in vitro degradation rate.The results of cell culture indicated that the Ch/CNT composite hydrogel enhanced induction for neuronal PC 12 cells and RSC96 cells adhesion,proliferation and neurite outgrowth of neuronal cells with a great increase in both the percentage and the length of neurites,which were beneficial to the transmission of nerve signal and nerve regeneration.In addition,the Ch/CNT composite hydrogel could also promote the adhesion and proliferation of MC-3T3 and L-02 cells.Therefore,this work provides a new avenue and valuable informations for the design of the nerve repairing scaffold and tissue engineering scaffold.As mentioned above,chitin/carbon nanotube composite nanofibrous microspheres were constructed from chitin/NaOH/urea aqueous solution by blending with modified CNTs through emulsification and thermal induction method.Then,lysine has been immobilized into the microspheres to obtain lysine-immobilized chitin/carbon nanotubes(Ch/CNT/Lys)microspheres.The results of SEM and nitrogen adsorption indicated that the Ch/CNT microspheres exhibited multilevel pore structure and interconnected 3D network architecture composed from CNTs and chitin nanofibers with compared diameter.Such multilevel pore structure is beneficial to the diffusion and adsorption of bilirubin and obviously improve the bilirubin adsorption.In particular,the Ch/CNT/Lys microspheres exhibited highly efficient and selective bilirubin adsorption properties in hyperbilirubinemia.Therefore,they can be used for blood perfusion to remove the excess bilirubin for the effective treatment of liver disease.It’s difficult of the present blood perfusion adsorbents to achieve the perfect integration of high bilirubin adsorption and blood compatibility.In view of this,the biocompatibility and blood compatibility of Ch/CNT/Lys microspheres were herein evaluated in details.The results indicated that there were few adverse effects on the protein,clotting factors,erythrocyte and other cells in blood after the composite microspheres direct contacted with blood,showing the blood compatibility of the composite microspheres.Based on the blood compatibility and high bilirubin adsorption capacity,the composite microspheres could be used in whole blood perfusion,which could avoid blood separation process,reduce the cost and improve the security and maneuverability.Therefore it could be an excellent alternative bilirubin adsorbent.Furthermore,it’s finding out that the normal liver cells(L-02)adhere and proliferate well on the Ch/CNT/Lys microspheres,thus the the Ch/CNT/Lys microspheres can be applied in suspension culture systems for bio-artificial liver system,showing the great promising potential in blood purification field for liver disease treatment.This thesis developed a series of chitin/carbon nanotube composite functional materials and investigated the structure,intermolecular interaction and biological function relationship of structure-property by a series experiments.These studies provide novel valuable biomedical materials for blood perfusion,neural biological engineering and tissue engineering.This work involves interdisciplinary fields of chemistry,biology and medicine,and also has important academic value and application prospect. |
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