Dissertation > Biological Sciences > Microbiology

Ordered Micro/nano Assembly of Bacterial Cellulose

Author LiuKun
Tutor YangGuang
School Huazhong University of Science and Technology
Course Biochemistry and Molecular Biology
Keywords Acetobacter xylinum microfluidics micro-groove hydrogen bone micro/nano assembling bacterial cellulose
Type Master's thesis
Year 2010
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Bacterial cellulose (BC) is one of the best nano-sized fibrous materials produced by Acetobacter xylinum in nature. Every bacterial secretes one cellulose fibril, which pushes bacterial forward and leads to cellulose aggradation and bacterial movement in a straight line. Usually, A. xylinum moves randomly in all directions and bacterial cellulose film of irregular network is formed when it is cultured in static liquid medium. In this paper, we applied micro and nano manufacturing technologies for micro-organism studies.Concretely, we exploited methods of laminar flow, micro-groove and hydrogen bond to control the directional movement of A. xylinum and regular aggradation of bacterium cellulose to obtain one novel multi-functional ordered nano-material.In the microfluidic chips prepared with PDMS and glass slide, A. xylinum can grow well and secrete cellulose because of the ventilation property and low toxicity of PDMS. We dyed A. xylinum with coriphosphine O and traced its movement in micro channel at different flow rates. We found that A. xylinum could move in a straight line when the flow rate was 5μL/h. The high activity in situation above was ideal for the ordered assembly of bacterium cellulose.PDMS and agarose gel micro-grooves were prepared. Movement of A. xylinum in micro-groove was restricted by oxygen and groove size. The results of real-time observation through fluorescence confirmed the directional movement of A. xylinum along the groove. Cellulose of grid structure and parallel arrangement can be obtained after precise control of culture. We could also vary the culture scaffold pattern to assemble other kinds of cellulose structure.As there are many hydroxide radical in bacterial cellulose fibrils, molecular chain Nematic Ordered Cellulose and thiol self-assembly monolayer were used to control the cellulose fibrils aggradation. The ordered hydroxide radical in template induced sequent assembly of new fibrils under the action of intermolecular hydrogen bond. Our result showed the cellulose structure on molecular template was more ordered than that of natural cellulose, the order degree of which remained to be improved. In summary, we established a method to ensure the directional movement of A. xylinum and realized ordered assembly of bacterial cellulose. This work can set the foundation for bacterial cellulose to be used as tissue engineering scaffold material in fast repair of nerve, skeleton and hamstring.

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