Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.

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Bacterial nanocellulose (BNC) is chemically identical with plant cellulose but free of byproducts like lignin, pectin, and hemicelluloses, featuring a unique reticulate network of fine fibers. BNC sheets are mostly obtained by static cultivation. Now, a Horizontal Lift Reactor may provide a cost efficient method for mass production. This is of particular interest as BNC features several properties of an ideal wound dressing although it exhibits no bactericidal activity. Therefore, BNC was functionalized with the antiseptics povidone-iodine (PI) and polihexanide (PHMB). Drug loading and release, mechanical characteristics, biocompatibility, and antimicrobial efficacy were investigated. Antiseptics release was based on diffusion and swelling according to Ritger-Peppas equation. PI-loaded BNC demonstrated a delayed release compared to PHMB due to a high molar drug mass and structural changes induced by PI insertion into BNC that also increased the compressive strength of BNC samples. Biological assays demonstrated high biocompatibility of PI-loaded BNC in human keratinocytes but a distinctly lower antimicrobial activity against Staphylococcus aureus compared to PHMB-loaded BNC. Overall, BNC loaded with PHMB demonstrated a better therapeutic window. Moreover, compressive and tensile strength were not changed by incorporation of PHMB into BNC, and solidity during loading and release could be confirmed.

Cellulosefibrillen und ‐kristalle mit einem Durchmesser im Nanometerbereich sind naturbasierte Materialien mit einzigartigen und potenziell wertvollen Eigenschaften. Vor allem eröffnen diese neuartigen Nanocellulosen dem natürlichen Polymer Cellulose die stark expandierenden Einsatzgebiete nachhaltige Materialien, Nanokomposite sowie Produkte für die Medizin und die Lebenswissenschaften. Die Nanodimensionen der Strukturelemente führen zu großen Oberflächen und damit zu starken Wechselwirkungen dieser Cellulosen mit umgebenden Stoffen wie Wasser, anorganischen, organischen und polymeren Verbindungen, Nanopartikeln und lebenden Zellen. Diese Übersicht bietet das aktuelle Wissen über die Isolierung mikrofibrillierter Cellulose aus Holz und ihre Anwendung in Nanokompositen, die Herstellung nanokristalliner Cellulose und ihren Einsatz als Verstärkungsmaterial sowie die biotechnologische Erzeugung bakterieller Nanocellulose einschließlich ihrer Eignung als Biomaterial für medizinische Implantate.