Preparation And Evaluation Of Materials For Skin Tissue Repair From Bacterial Cellulose

Bacterial cellulose (BC) is a promising polymer with unique structure and exhibits excellent properties. Because of its good biocompatibility, BC preserves great potential to be developed as a series of biomedical materials for tissue regeneration and repair. The application and industrialization of BC are determined by its production and cost, as well as the safety and the efficacy of skin tissue repair. In this thesis, to generate and characterize their structure, several experimental methods were performed, such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis and Barrett-Joyner-Halenda (BJH) pore size and volume analysis, contact angle analysis, X-ray diffraction, differential scanning calorimetry (DSC) and UV-visible spectrophotometer. The toxicity, biocompatibility and histocompatibility of BC were evaluated in vitro through cell viability analysis of fibroblasts and stem cells and in vivo by using mouse full-thickness skin surgery mode.Acetobacter xylinum Y05 (CCTCC M207163) and Gluconacetobacter xylinus (ATCC 53582) were two strains used to produce BC. By optimizing the culture condition, we developed an efficient method to produce small BC films with uniform size in cell culture plate. The production of BC and the behavior of bacteria can be controlled by the shape and size of the container. The pore distribution and surface area of BC can also be strictly controlled by another important factor, the growth space. In addition, by using an improved method-the multilayer fermentation, multilayer BC can be produced by combining static and shaken-flask fermentation methods. The method is simple and efficient to control the reproducible thickness and homogeneity of BC, which might promote the development of industrialization of materials from BC.The antimicrobial ability of BC can be improved by adding chitosan at different concentrations in the culture medium. The BC/chitosan/sodium alginate in situ composites were also produced. Chitosan and sodium alginate could be wrapped in the network of BC during its biosynthesis. With the increase in the concentration of chitosan and sodium alginate, the production of BC was decreased generally. The BC/chitosan in situ composite sample with the highest degree of crystalinity occurred when the biosynthesis took place in the medium containing 2% chitosan. For sodium alginate, the highest condition for crystallization was in the medium with 0.5% sodium alginate.Just as the normal BC, the innovative multilayer BC also presents the nano-structured network, as well as good biocompatibility. Swiss mouse embryo fibroblast NIH/3T3 cells and human adipose-derived stem cells (hASCs) were used to evaluate the biocompatibility of the multilayer BC. Results suggest that the BC films can promote the proliferation and adhesion of NIH/3T3 cells and hASCs. By using the BALB/c mouse surgery model, the wound healing effects were thoroughly analyzed and compared among wound mice treated with BC films, wound dressings, xeno-skins and allo-skins respectively. The mechanism of wound healing effect was studied by enzyme linked immunosorbent assay (ELISA). Animal studies showed faster and better healing effect and less inflammatory response in the BC group. Furthermore, the thick BC film group showed a better and faster healing effect than the gauzes, the xeno-skin and allo-skin transplant groups.In conclusion, BC-based materials for skin tissue repair demonstrate huge advantages due to their unique characteristics such as controllable fermentation, reproducible production, high water content, air permeability, conformability and suitable elastic properties. The evaluations on molecular, cellular and individual levels and of BC have all suggested good biocompatibility, such as cytobiocompatibility and histocompatibility preserved by this kind of materials. Taken together, the skin tissue repair materials from BC exhibit better integrated properties that are promising for the application in the skin tissue regenerative field and wound dressing field.