Bacterial synthesized cellulose — artificial blood vessels for microsurgery

Measurement of the elastic modulus of single bacterial cellulose fibers using atomic force microscopy

The ability of the atomic force microscope to measure forces with subnanonewton sensitivity at nanometer-scale lateral resolutions has led to its use in the mechanical characterization of nanomaterials. Recent studies have shown that the atomic force microscope can be used to measure the elastic moduli of suspended fibers by performing a nanoscale three-point bending test, in which the center of the fiber is deflected by a known force. We extend this technique by modeling the deflection measured at several points along a suspended fiber, allowing us to obtain more accurate data, as well as to justify the mechanical model used. As a demonstration, we have measured a value of 78 +/- 17 GPa for Young's modulus of bacterial cellulose fibers with diameters ranging from 35 to 90 nm. This value is considerably higher than previous estimates, obtained by less direct means, of the mechanical strength of individual cellulose fibers.

Bacterial cellulose as a potential scaffold for tissue engineering of cartilage

Tissue constructs for cartilage with native mechanical properties have not been described to date. To address this need the bacterial cellulose (BC) secreted by Gluconacetobacter xylinus (= Acetobacter xylinum) was explored as a novel scaffold material due to its unusual material properties and degradability. Native and chemically modified BC materials were evaluated using bovine chondrocytes. The results indicate that unmodified BC supports chondrocyte proliferation at levels of approximately 50% of the collagen type II substrate while providing significant advantages in terms of mechanical properties. Compared to tissue culture plastic and calcium alginate, unmodified BC showed significantly higher levels of chondrocyte growth. Chemical sulfation and phosphorylation of the BC, performed to mimic the glucosaminoglycans of native cartilage, did not enhance chondrocyte growth while the porosity of the material did affect chondrocyte viability. The BC did not induce significant activation of proinflammatory cytokine production during in vitro macrophage screening. Hence, unmodified BC was further explored using human chondrocytes. TEM analysis and RNA expression of the collagen II from human chondrocytes indicated that unmodified BC supports proliferation of chondrocytes. In addition, ingrowth of chondrocytes into the scaffold was verified by TEM. The results suggest the potential for this biomaterial as a scaffold for tissue engineering of cartilage.

Synthesis of mesoporous titania networks consisting of anatase nanowires by templating of bacterial cellulose membranes

Mesoporous titania networks consisting of interconnected anatase nanowires have been synthesized by using unique bacterial cellulose membranes as natural biotemplates; the titania networks exhibit enhanced photocatalytic activity compared with titania microfiber networks.

In vivo biocompatibility of bacterial cellulose

The biocompatibility of a scaffold for tissue engineered constructs is essential for the outcome. Bacterial cellulose (BC) consists of completely pure cellulose nanofibrils synthesized by Acetobacter xylinum. BC has high mechanical strength and can be shaped into three-dimensional structures. Cellulose-based materials induce negligible foreign body and inflammatory responses and are considered as biocompatible. The in vivo biocompatibility of BC has never been evaluated systematically. Thus, in the development of tissue engineered constructs with a BC scaffold, it is necessary to evaluate the in vivo biocompatibility. BC was implanted subcutaneously in rats for 1, 4, and 12 weeks. The implants were evaluated in aspects of chronic inflammation, foreign body responses, cell ingrowth, and angiogenesis, using histology, immunohistochemistry, and electron microscopy. There were no macroscopic signs of inflammation around the implants. There were no microscopic signs of inflammation either (i.e., a high number of small cells around the implants or the blood vessels). No fibrotic capsule or giant cells were present. Fibroblasts infiltrated BC, which was well integrated into the host tissue, and did not elicit any chronic inflammatory reactions. The biocompatibility of BC is good and the material has potential to be used as a scaffold in tissue engineering.

Engineering a bifunctional starch–cellulose cross-bridge protein

Biodegradable starch- and cellulose-based polymers have a range of properties which make them suitable for use in a wide array of biomedical applications ranging from bone replacement to engineering of tissue scaffolds and drug delivery systems. A novel polysaccharide cross-bridging protein was designed which was comprised of a cellulose-binding domain from Clostridium cellulovorans (CBD(clos)) and a starch-binding domain from Aspergillus niger B1 (SBD(Asp)). The two genes were fused in-frame via a synthetic elastin gene to construct a Cellulose/Starch Cross bridging Protein (CSCP). Recombinant CSCP was expressed in Escherichia coli, and successfully refolded from inclusion bodies. CSCP demonstrated cross-bridging ability in different model systems composed of insoluble or soluble starch and cellulose. The aspect that different carbohydrate-binding module maintain their binding capacity over a wide range of conditions, without the need for chemical reactions, makes them attractive domains for designing new classes of chimeric polysaccharide-binding domains which demonstrate potential for use in a wide range of biomaterials.