Biosynthesis Of Bacterial Cellulose And Research On Bacterial Cellulose/Apatite Nanocomposites

As new-fashioned biomaterial,bacterial cellulose（BC） has been widely investigated in wound dressing,nerves,cartilage and blood vessel, for the unique physical and chemical structure,such as high purity,excellent biocompatibility,biodegradability,mechanical properties,and ultrafine 3-dimensional microstructure.Meanwhile,hydroxyapatite（Hap） is the main inorganic component of bones from human-beings or animals,and Hap has also been proved to be a safe biomaterial according to the results from biomedical research.In the past decades,composites based on polymer and Hap has been widely investigated all over the world.However,few researches have been focused in polymer/Hap composites with a biomimetic bone-like microstructure.In this dissertation,BC was synthesized by Acetobacter xylinum,and then BC/Hap nanocompisites with a biomimetic bone-like structure was prepared based on the ultrafine 3-dimensional network of BC.The detailed researches are as follows.1.Based on the earlier research work in our lab（the optimization results of culture medium,pH and temperature of culture medium,etc）,the biosynthesis kinetic research of BC by acetobacter xylinum were studied by investigating the relationship of the concentration of glucose and protein, the output values of BC,pH of the medium versus synthetic time.The experimental results indicated that the spending rate of glucose and protein increase at a high speed during the 24 hour to 96 hour.So did the decrease rate of pH and the productive rate of BC.Besides,the productive rate of BC reaches the maximum values at about the synthetic time 70 hour. 2.The structures and properties of BC were characterized by FTIR, XRD,SEM,ICP-AES,etc.The analytical results show that BC could be purified by boiling in 4%NaOH aqueous solution and the percentage purity of BC is 98.5%.The viscometric degree of polymerization of BC is about 1000.SEM images show that the diameter of BC nanofibers ranges from 40 nm to 100 nm,and the existence of ultrafine 3-dimensional network structure of BC.The FTIR and XRD analytical results indicate the high contents of cellulose I_αand high crystalline indices.Besides,BC was proved to be a polymer with high mechanical property.3.BC/Hap composites were synthesized by three different ways,and the structure and properties of the novel composites were characterized by FTIR,SEM,XRD,ICP-AES etc.The analytical results indicate that the novel nanocomposites with a microstructure of the Hap deposition on BC nanofibers could be obtained by means of pretreatment of Ca²⁺ activated or phosphorylation modification of BC prior to biomimetic mineralization.4.Alkaline pretreatment of BC prior to Ca²⁺ activated treatment and biomimetic mineralization was introduced in the synthesis of BC/Hap nanocomposites.And nanocomposites,obtained by this new method,were characterized by FTIR,SEM,XRD,ICP-AES etc.The analytical results indicate that the novel nanocomposites with a microstructure of the Hap deposition on BC nanofibers could be obtained by this method.And the efficiency of the deposition of Hap on BC nanofibers was increased.5.The phase transition of Hap in BC/Hap composites synthesized by different methods was studied in the dissertation.The chemical composition of Hap in BC/Hap composite in different mineralization time was characterized by ICP-AES,FTIR,and XRD.The results of phase transition research indicated that the precursors of Hap in composites abide by the expression:Ca₈H_x（PO4）_y（X＞2,Y＞6,X=3Y-16）.