Structural changes of bacterial cellulose due to incubation in conditions simulating human plasma in the presence of selected pathogens.

Bacterial nanocellulose (BNC) is a natural biomaterial with a wide range of medical applications. However, it cannot be used as a biological implant of the circulatory system without checking whether it is biodegradable under human plasma conditions. This work aimed to investigate the BNC biodegradation by selected pathogens under conditions simulating human plasma. The BNC was incubated in simulated biological fluids with or without Staphylococcus aureus, Candida albicans and Aspergillus fumigatus, and its physicochemical properties were studied. The results showed that the incubation of BNC in simulated body fluid with A. fumigatus contributes more to its degradation than that under other conditions tested. The rearrangement of the hydrogen-bond network in this case resulted in a more compact structure, with an increased crystallinity index, reduced thermal stability and looser cross-linking. Therefore, although BNC shows great potential as a cardiovascular implant material, before use for this purpose its biodegradability should be limited.

Enzymatic and Chemical Cross-Linking of Bacterial Cellulose/Fish Collagen Composites-A Comparative Study.

This article compares the properties of bacterial cellulose/fish collagen composites (BC/Col) after enzymatic and chemical cross-linking. In our methodology, two transglutaminases are used for enzymatic cross-linking-one recommended for the meat and the other proposed for the fish industry-and pre-oxidated BC (oxBC) is used for chemical cross-linking. The structure of the obtained composites is characterized by scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and Fourier transform infrared spectroscopy, and their functional properties by mechanical and water barrier tests. While polymer chains in uncross-linked BC/Col are intertwined by H-bonds, new covalent bonds in enzymatically cross-linked ones are formed-resulting in increased thermal stability and crystallinity of the material. The C2-C3 bonds cleavage in D-glucose units, due to BC oxidation, cause secondary alcohol groups to vanish in favor of the carbonyl groups' formation, thus reducing the number of H-bonded OHs. Thermal stability and crystallinity of oxBC/Col remain lower than those of BC/Col. The BC/Col formation did not affect tensile strength and water vapor permeability of BC, but enzymatic cross-linking with TGGS improved them significantly.