Chemical modification of bacterial cellulose for the development of an antibacterial wound dressing

Bacterial cellulose is a bacterially derived polymer with great potential for application in wound healing due to its innate properties such as high biocompatibility and biodegradability. In addition to this, it is naturally biosynthesized by bacteria as a hydrogel, which makes it an optimal substrate for the treatment of dry wounds, where additional moisture is required to facilitate the healing process. However, this polymer lacks antibacterial properties. As bacterial infections are becoming increasingly common and difficult to treat due to antimicrobial resistance, it is of crucial importance to develop strategies for the modification of cellulose to ensure protection against bacterial contamination. In this study, a green-chemistry approach was proposed for the functionalization of cellulose to introduce antibacterial functional groups. Two different active agents, namely glycidyl trimethylammonium chloride and glycidyl hexadecyl ether, were used for the covalent derivatization of the hydroxyl groups of glucose through a heterogeneous reaction in basic aqueous conditions. The modified material was chemically and mechanically characterized by solid-state techniques and rheological measurements. A biological assessment was then carried out both using bacterial cells and human keratinocytes. It was observed that the functionalization performed induced a reduction of approximately half of the bacterial population within 24 h of direct contact with Staphylococcus aureus subsp. aureus Rosenbach 6538PTM and Escherichia coli (Migula) Castellani and Chalmers ATCC® 8739TM (respectively, a reduction of 53% and 43% in the cell number was registered for the two strains). In parallel, cytotoxicity studies performed on keratinocytes (HaCaT cell line) showed cell viability in the range of 90 to 100% for up to 6 days of direct contact with both unmodified and modified samples. The morphology of the cells was also visually evaluated, and no significant difference was noted as compared to the control. Finally, the in vitro scratch assay evidenced good wound closure rates in the presence of the samples, with complete coverage of the scratched area after 5 days for both the modified cellulose and the positive control (i.e., keratinocytes growth medium). Overall, the modified hydrogel showed promising features, confirming its potential as an alternative substrate to develop a sustainable, antibacterial and biocompatible wound dressing.