Bacterial cellulose (BC) is a biotechnologically derived nanostructured biopolymer with high potential in applications such as wound management or drug delivery systems [e.g. 1, 2]. It combines typical cellulose properties such as an excellent biocompatibility with the features of nanostructured materials, among them a high mechanical stability as well as a high liquid loading capacity.
In the InflammAging project, anti-inflammatory natural substances, such as triterpene acids from frankincense, are investigated as innovative active pharmaceutical ingredients. The most promising candidates are incorporated in BC-based wound dressings in order to treat local inflammatory wounds. However, the loading of BC with lipophilic substances is still challenging due to the hydrophilicity of the material. To overcome this challenge, achieving lipophilic drug incorporation and release, post- as well as in situ-modifications of the biopolymer during the bioprocess were investigated.
Native BC was synthesized by the bacteria strain Komagataeibacter xylinus at 28 °C in trays (20 x 20 cm) for seven days. For in situ-modification of the biopolymer BC during the cultivation in Hestrin-Schramm-medium different additives (e.g. with poly(ethylene glycol)) were tested. As a main result, pore sizes of the cellulose network could be varied in the range of 2-10 µm. Post-modification strategies focused on a hydrophobization of the nanostructured BC network in order to increase the uptake of lipophilic drugs. Results of the successful BC modification by acetylation or oxidation with 2,2,6,6-tetramethylpyperidine-1-oxyl (TEMPO) and subsequent conjugation with more hydrophobic compounds such as phenylalanine will be presented. An in-vitro toxicity test (MTT assay) proved preserved biocompatibility of the chemically modified biomaterial. In case of both, in-situ as well as post-modification, different loading capacities for anti-inflammatory model substances of varying lipophilicity (e.g. diclofenac & indomethacin) and release profiles could be observed. These findings are currently used for the incorporation of lipophilic frankincense extract, quantified by the lead substances 3-O-acetyl-11-keto-β-boswellic acid (AKBA) and 11-keto-β-boswellic acid (KBA) into BC for innovative product design based on highly promising natural compounds.
 Sulaeva, I., et al., Biotechnol. Adv., 2015, 33(8): 1547-71.
 Mueller, A., et al., J. Pharm. Sci., 2013, 102(2): 579-592.