A novel bioabsorbable bacterial cellulose.

摘要

Bacterial cellulose (BC), a polymer of glucose, is becoming one of the most effective candidates for medical uses due to its predominant ability of fluid exchange, benign degradation product and very good biocompatibility. Our current work is focused on altering non-bioabsorbable bacterial cellulose to in-body bioabsorbable bacterial cellulose (BBC).;To achieve in-body bioabsorption of BC, an enzymatic incorporating technique was used in studies to engineer a novel BC. The enzymatic incorporating technique was accomplished via a double lyophilizing process. Two methods, incorporating cellulases to BC without or along with buffer ingredients, were subsequently used to examine in-vitro biodegradability of BBC materials. The first method screened various single cellulases and their combination in terms of lifetime of cellulases in an environment presenting a suboptimal pH value (6.5--7.0). Results revealed that BBC samples containing acidic cellulases presented relatively good degradability in environments with different pH values from 4.5 to 7.4, while those BBC samples containing neutral/alkaline cellulases exhibited inverse results, suggesting that pure neutral/alkaline cellulases might not be able to work on pure BC because their substrates are usually alkali celluloses, such as carboxylmethylcellulose. The second method related to the use of buffer ingredients. Here, the incorporation of buffer ingredients to BBC material was expected to manipulate wound local pH preserving the optimal activity of cellulases. Results showed that incorporated buffer ingredients appeared to have helped form an optimal pH microenvironment for cellulases and the released glucose was accordingly increased from approximately 30% without incorporated buffer ingredients to 97% in the presence of buffer ingredients in an environment with a pH value of 7.4.;Results from subsequent in-vitro and in-vivo biocompatibility assays of BBC samples revealed a very good biocompatibility between cells examined (human fibroblast and human osteoblast) and both unmodified BC and BBC. The resulting BBC samples appeared to be more appropriate for facilitating the growth of human osteoblast, suggesting a future application of BC in bone-type tissue engineering or scaffolds.;Next, a unique spherelike structure of BC synthesized by specific cellulose producing bacterial strain (Gluconacetobacter xylinum JCM 9730) was evaluated and characterized. Cell assays of human osteoblast on these spheres exhibited good cell viability, which makes it being considered to use spherelike BC in developing specific biomedical materials, such as bone-type tissue scaffolds. These cellulose spheres varied in size from approximately 0.5 to 8 mm under different cultivation rotational speeds. The observation under field emission scanning electron microscope (FESEM) revealed that cellulose spheres obtained at 150 rpm orbitally rotational speed (ORS) were hollow with a layered outer shell, while cellulose spheres obtained at 125 rpm ORS showed a layered outer shell and an unlayered, cellulose fiber filled center. Many extraneous factors could affect the formation of spherelike BC other than the rotational speed. The results revealed that cellulose fibers left in the initial inoculu;Undoubtedly, the application of BC is always limited by its low yield and high cost. The last study, accordingly, focused on cellulose production. 1-Methylcyclopropene (1-MCP), a potent inhibitor of plant growth, was first used in this study to investigate its effect on the yield of Gluconacetobacter xylinum and its cellulose production. Results revealed that a higher biomass yield was achieved when using culture medium excluding 1-MCP while bacterial cellulose yield was low in this case. Cellulose with 15.6% more production (1-MCP added on day 1) and 25.4% more production (1-MCP added on each assigned day) was achieved when using culture medium containing 1-MCP while biomass yield was low in this case. This suggested that 1-MCP was able to impact cell activity probably because it can maintain vigorous growth of bacterial cells resulting in the enhancement of cellulose production up to 25.4% over controls. (Abstract shortened by UMI.)