Characterization of anionic and cationic functionalized bacterial cellulose nanofibres for controlled release applications

Bacterial cellulose (BC) is a biocompatible biopolymer synthesized by Gluconacetobacter xylinus. In this study, BC was oxidized and aminated to produce hydrogels for biomedical applications, and the products were characterized. A carboxyl (pK(a) of 3.9 +/- A 0.1) content of 1.13 +/- A 0.02 mmol/g was obtained with the TEMPO-catalyzed oxidation. Epichlorohydrin-mediated amination introduced amine groups (pK(a) of 11.0 +/- A 0.1) up to 1.74 +/- A 0.06 mmol/g. The oxidation of BC caused a decrease in its zeta-potential to -103 +/- A 6 mV, and amination increased the zeta-potential to -4 +/- A 6 mV. The fibre diameter decreased after both reactions. The high absolute value of the zeta-potential for oxidized BC led to superior colloidal stability in water, and a 390 % increase in water retention. The oxidized BC hydrogel was also found to increase in water retention fivefold from pH 1 to 7, making it a smart hydrogel. The cationic and anionic BC hydrogels described here could be used for several biomedical applications, including self-assembling drug delivery devices.