E.M. van Zyl, J.M. Coburn
Worcester Polytechnic Institute,
Keywords: biomaterials, bacterial cellulose, wound dressing, materials characterization
Summary:Bacterial-derived cellulose (BC) is synthesized as an exopolymer saccharide by several bacterial species and strains. Some bacterial species produced BC as a nanofibrous pellicle at the air-liquid interface of the bacteria culture. BC has been investigated for numerous biomedical applications, in part due to is nanofibrous nature mimicking the extracellular matrix of tissues. BC-based wound dressings have been found to provide immediate pain relief, reduced treatment time, improved development of granulation tissue, and accelerated re-epithelialization in the wound site.[1,2] Unmodified BC has been characterized and found to have favorable wound dressing properties such as liquid/gas permeability, and high wound exudate absorption capabilities.[1,2] Despite this, BC’s lack of transparent properties and incorporated antibacterial properties greatly limits its clinical application. Glucose is the commonly used carbon source for BC synthesis. Yet, alternative sugars, abundant in inexpensive biomass, can change host metabolism - impacting BC synthesis and properties. In this work, we explore the development and characterization of BC utilizing Gluconacetobacter hansenii (ATCC 53582) with clinically accepted optical clarity using arabitol as the primary carbon source in culture. G. hansenii was maintained Hestrin Schramm (HS) containing glucose as a sugar, or carbon, source. For alternative carbon source, arabitol was evaluated. Fresh HS medium without a carbon source was inoculated with 0.1% (v/v) G. hansenii culture. The media was supplemented to 1 mM of total carbon source with mixtures of either 100/0, 95/5, 85/15, 75/25, 50/50, or 0/100 arabitol/glucose. BC transparency, yield, and fiber width analysis were performed. With increased arabitol concentration, an increase in transparency was observed. Maximum transparency plateaued at arabitol concentrations between 80 and 95%. The BC produced with arabitol concentrations >75% produced optical transparency values comparable to that of commercially available transparent wound dressings. This altered optical property is believed to be due to arabitol’s metabolism through the pentose phosphate pathway, rather than through the conventional glucose metabolic pathway. To confirm that the changes in transparency were not attributed to BC thickness, BC yield was evaluated as a surrogate measurement (all samples had a fixed diameter). The BC yield for the 100% arabitol condition was significantly less than the 85%, 75%, 50%, and 0% arabitol conditions. No significant difference was observed amongst samples formed using mixtures of arabitol and glucose, suggesting that the change in transparency cannot be attributed to yield alone. Significant morphological differences in cellulose fiber width were observed between 100% arabitol and 0% arabitol samples. The difference in fiber width may also be attributed to the alternative metabolic pathway of arabitol as well. The development and characterization of this novel method for transparent BC production without the addition of composite materials allows for further research into BC’s use as a clinically effective wound dressing. Ongoing work will characterize the liquid absorption, crystallinity of the BC, and the incorporation of antibacterial activity with the long-term goal to develop novel antimicrobial wound dressing to reduce infection and promote wound healing.  Fontana, Appl Biochem Biotech, 1990;24:253-264;  Czaja, Biomaterials, 2006;27:145-151.  Chen, J Am Acad Dermatol, 2001;45:919-923.