Modification Of Bacterial Cellulose Nanofibrous Tissue Engineering Scaffolds And Its Composites

Bacterial cellulose (BC) is a kind of new nano-biomaterials, which has three dimensional nano-networks built from nano-fibrils. BC is pure and crystalline nano-celluose, which has high mechanical properties, hydrophilicity and biocompatibility. But there are some disadvantages such as lack of 50-200μm pores, hard to degrade in vivo without cellulase and limited physiological function. So BC nano-scaffolds need to be modified and composited.In this thesis, BC, modified BC and their nano-composites were studied as potential artificial skin materials and tissue engineering scaffolds. Hydrophilicity and biocompatibility of BC were examined as artificial skin. BC tissue engineering scaffolds with nano-micro structure were manufactured by biosynthesis control technique, pattern plate technique, sol-gel technique and chemical modification. BC nano-composites were acquired through bio-mimetic, culture medium modification and chemical grafting way. BC nano-whiskers and poly-(lactic acid) porous scaffolds were also made successfully. SEM and TEM were used to observe the nano structure of BC scaffolds. XRD, FTIR and XPS were used to analyze the crystalline and chemical structure of BC composites. Porosity, degradation and mechanical propersites of BC scaffolds were also studied. All these research proved that BC is competitive as potential biomedical scaffolds.Research indicated that BC hydrogel had high water uptaken, which could be degraded by cellulase. Freeze-dried BC in proper thickness could match the water vapour permeability of artificial skin in clinic. The cell compatibility was proved to be good by mouse embryo cell and osteoblast growing with mateirials.BC micro-nano porous materials could be made in many ways. Nano-porous scaffolds associated with micro pores could be achieved via template adding to static bacterial culture. NMMO could dissolve BC, microporous regenerated cellulose could be manufactured by gelating plus particle leaching method. Furthermore, carboxylic BC microporous scaffolds with nano structure could be acquired from freeze-dry after chemical modification.BC could be oxidized to 2,3-dialehyde BC (DABC) which was degradable without cellulase. DABC maintained the three dimensional nano-networks as original BC. It changed into microporous structure after degradation in simulated body fluid. The degrade rate of DABC was related to oxidized degree. Degradation happened at the oxidized parts firstly. After degradation, there were low-molecular weight organic matters dissolved into solution and some undegraded BC residues remained.Hydroxyapatie/DABC composites could be acquired by bio-mimetic route. Collagen/BC composites could be synthesized by adding collagen into static bacterial culture. Gelatin/DABC composites were produced by covering and grafting gelatin to DABC by Schiff's base reaction.BC nano-whiskers (BCNW) could be prepared from acid hydrolyse. When BCNW dispersed into poly-(lactic acid) (PLA), BCNW/PLA porous composites scaffold could manufactured, which will be more hydrophilic and porous than PLA scffold. It is good for tissue engineering applications.In this thesis, modification of BC tissue engineering scaffolds and its composites were studied. BC tissue engineering scaffolds with micro-nano structure were prepared for nano bio-effect research. DABC were achieved from modified BC, which could be biodegraded under control. Gelatin/DABC, collagen/BC and HAp/BC composites were made by biosynthesis, chemical modification and biomimics techniques. BC nano-scaffolds and its composites are new materials for nano tissue engineering research and become promising biomaterials for biomechical applications.