Synthesis and Characterization of Antimicrobial Bacterial Cellulose Crosslinked with Branched Polyethylenimine

This study examines the development of composite bacterial cellulose (BC) sheets with antimicrobial properties for potential application in face masks. Branched polyethylenimine (PEI) is employed as the antimicrobial agent, effective against both gram-positive and gram-negative bacteria. Various concentrations of PEI are crosslinked into BC via epichlorohydrin under moderate conditions. The thermal and morphological properties of dried BC-PEI samples are comprehensively characterized. Results reveal that introducing PEI via crosslinking minimally impacts the thermal stability of BC, without any discernible physical disruption. Nevertheless, BC-PEI matrices present lower water evaporation enthalpies than BC, based on dynamic scanning calorimetry, caused by alteration of hydrogen bonding interactions (amine groups versus hydroxyl groups). Moreover, dried BC-PEI samples exhibit an improved efficacy against gram-positive bacteria as compared to gram-negative bacteria; S. aureus and P. aeruginosa, respectively. Indeed, a 2.5% (wt/v% of Milli-Q water) PEI concentration completely inhibits the growth of S. aureus after 6 h, while a 7.5% PEI concentration achieves similar effects on P. aeruginosa. Despite the notable antibacterial efficacy of BC-PEI matrices, their antiviral efficacy is less pronounced. This difference in antibacterial and antiviral efficacies could be attributed to variations in microorganism characteristics, mechanisms of action, and structures of PEI.