Glycerol-plasticized bacterial nanocellulose-based composites with enhanced flexibility and liquid sorption capacity

Bacterial nanocellulose (BNC) and two BNC-based composites with carboxymethyl cellulose or hydroxyethyl cellulose (BNC-CMC or BNC-HEC, respectively), were produced in situ by Komagataeibacter xylinus E25 under stationary conditions and plasticized with glycerol (ex situ modification). The BNC-CMC composite had the loosest structure (visible in SEM images) and was less crystalline (CI of 88.6%) than BNC (CI of 92.9%) and BNC-HEC (CI of 90.4%). Cellulose fibers synthesized by K. xylinus E25 in the presence of HEC were thinner in comparison to the fibers of control BNC while there was no difference in the fibers width between the BNC-CMC and control BNC. The glycerol-plasticized BNC, BNC-CMC and BNC-HEC membranes were flexible after drying, and absorbed high amounts of artificial exudate and water after rehydration. BNC-CMC treated with 2.5% v/v aqueous glycerol was characterized by the greatest free swell absorptive capacity (up to 19g artificial exudate/g dry weight in 24h) while the highest rehydration capacity (around 96% of the initial water content) was observed in case of BNC-CMC plasticized with 10% v/v glycerol and dehydrated. The in situ and ex situ modifications of BNC affected also the tensile strength. The highest values of tensile strength at break (around 152.2N) and Young's modulus (around 290.3MPa) were observed in case of the BNC-CMC composite plasticized with 2.5% v/v glycerol. The impact of plasticized BNC, BNC-CMC and BNC-HEC on the viability of HaCaT keratinocytes was also studied and found to be positive at glycerol concentrations up to 2.5% (v/v) that suggests their potential utility as wound dressings.