Preparation And Properties Of Porous Keratin Composite Bone Scaffolds

Human hair fiber contains a large number of keratin.The keratin has many unique properties such as biocompatibility, biodegradability and low immunity. Bone repair scaffold with a certain degree of hardness and porosity is an important medium for bone tissue repair. The pure keratin regenerated material is too fragile to meet the requirements of basic mechanical properties of artificial aggregate. In this paper, a new type of composite scaffold with high porosity and good mechanical properties can be prepared by compositing different micron size of reinforcement and keratin.This is a useful exploration for the development of new keratin composite artificial bone repair materials.In this thesis, the keratin was obtained from human hair by reduction method, while its molecular weight and extraction rate were tested. The experimental results show that the method can obtain a relatively complete keratin macromolecule and extraction rate of keratin reached as high as 66.34%. According to the multi-level fibril structure of human hair, it can be gradually separated into tiny "fibers". Finally, the giant fibril whisker was obtained, of which the length is 20μm—40μm and the diameter between 0.5μm and 2μm. The hair whisker kept the aggregation structure and the complete structure of keratin macromolecules, which has good mechanical properties and anisotropic structure. In order to improve the protein content of sponge, hair whisker was treated as an enhancement which was mixed with keratin solution and fabricated in hair whisker/keratin sponge.Meanwhile, K2Ti6O13 whisker and hydroxyapatite (HA) were chosen as enhancement. The former has the similar size with hair whisker and the latter has good biocompatibility. The K2Ti6O13/keratin sponge and HA/keratin layer porous sponge were prepared by using quick freezing.With the purpose of improving the mechanical properties of HA/keratin layer porous sponge, the sponge was placed in PBS solution and secondarily freeze-dried to obtain HA/keratin enhanced porous sponge.The research of the above three sponges include the morphology, porosity, mechanical properties, FTIR and XRD. The result of experiments showed that the porosity of the composite sponges was decreased with the increase of the concentration of the keratin solution. All of composite sponges have better mechanical properties than the pure keratin sponge. Especially the compression strength ofHA/keratin enhanced porous sponge was high to757KPa, which basically met the requirements of the 0.8MPa of cancellous bone compression modulus. The results of FTIR indicated that the peak strength of phosphate (PO4)functional groups was more obvious in the spectrum of HA/keratin enhanced porous sponge, which is owing to the fact that the sponge was absorbed and deposited more phosphate ions in the process of immersion to promote the growth of phosphate.Finally, the biological properties of HA/keratin enhanced porous sponge was investigated by water absorption, swelling, degradation and cell culture. The result suggested that the sponge has good hydrophilic property, and the maximum swelling ratio was 32%. The degradation rate of it was 31.4% after immersed in trypsin solution 7 days.The 3T3 cells were cultured in vitro, the results showed that the sponge has good biocompatibility.To sum up, the different properties of keratin composite scaffolds were produced by adding different types of enhancement into the keratin solution.With the changing of the concentration of keratin and the content of enhancement, the microstructure, porosity and mechanical properties of the composite sponges can be controlled, which leads to achieve the minimum requirements that bone porosity reached more than 70%, and compression strength is 0.8Mpa.