Abstract
Bacterial nano-cellulose (BNC) is considered to possess incredible potential in biomedical applications due to its innate unrivaled nano-fibrillar structure and versatile properties. However, its use is largely restricted by inefficient production and by insufficient strength when it is in a highly swollen state. In this study, a fabric skeleton reinforced chitosan (CS)/BNC hydrogel with high mechanical reliability and antibacterial activity was fabricated by using an efficient dynamic culture that could reserve the nano-fibrillar structure. By adding CS in culture media to 0.25–0.75% (w/v) during bacterial cultivation, the CS/BNC composite hydrogel was biosynthesized in situ on a rotating drum composed of fabrics. With the proposed method, BNC biosynthesis became less sensitive to the adverse antibacterial effects of CS and the production time of the composite hydrogel with desirable thickness could be halved from 10 to 5 days as compared to the conventional static cultures. Although, its concentration was low in the medium, CS accounted for more than 38% of the CS/BNC dry weight. FE-SEM observation confirmed conservation of the nano-fibrillar networks and covering of CS on BNC. ATR-FTIR showed a decrease in the degree of intra-molecular hydrogen bonding and water absorption capacity was improved after compositing with CS. The fabric-reinforced CS/BNC composite exhibited bacteriostatic properties against Escherichia coli and Staphylococcus aureus and significantly improved mechanical properties as compared to the BNC sheets from static culture. In summary, the fabric-reinforced CS/BNC composite constitutes a desired candidate for advanced wound dressings. From another perspective, coating of BNC or CS/BNC could upgrade the conventional wound dressings made of cotton gauze to reduce pain during wound healing, especially for burn patients.
Highlights
Bacterial nano-cellulose (BNC) is a natural cellulosic material, which is mainly secreted by acetic acid bacteria
The composite sheets floated on the surface of culture broth, while in the rotating culture the fabric-reinforced composite sheets formed via rotation coating and in situ biosynthesis of BNC on the fabric skeleton
A longer cultivation period of 10 d was required for static culture to obtain the thickness of pristine BNC sheet of 2.50 ± 0.35 mm, while only 5 d rotating cultivation was needed for the fabric-reinforced BNC sheet to achieve similar thickness (2.49 ± 0.32 mm)
Summary
Bacterial nano-cellulose (BNC) is a natural cellulosic material, which is mainly secreted by acetic acid bacteria. BNC has more value other than a simple raw material because it is not just used as a new alternative cellulosic source, and is an unparalleled functional material for its decent biocompatibility, nano-fibrillar supramolecular structure, hydrogel property, and super-high specific surface area, which is distinct from plant cellulose (Gatenholm and Klemm, 2010). The nano-fibrillar reticulate structure of microbially manufactured BNC is beyond what can currently be achieved artificially, and it looks like natural collagen in terms of its nanostructure and morphology, which is attractive for cell immobilization and because it mimics extracellular matrix (ECM) support (Petersen and Gatenholm, 2011). The added materials may include soluble polymers (Phisalaphong and Jatupaiboon, 2008), particles (Yan et al, 2008), fibers (Pommet et al, 2008), and even some block fabrics (Meftahi et al, 2010)
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