Synthesis of cationized nanofibrillated cellulose and its antimicrobial properties

Two types of cationized nanofibrillated cellulose (NFC) were prepared by redox initiated graft copolymerization and etherification with quaternary ammonium compounds (QAC). The QAC content and charge density of the products were measured. The NFC derivatives were tested for antimicrobial activity against Gram positive and negative bacteria, and yeast. Both NFC types exhibited broad spectrum antimicrobial activity. Etherification resulted in a higher degree of substitution and charge density, and the product also showed higher antimicrobial activity than the copolymerization product. Etherified NFC was more efficient against Gram negative than positive bacteria, whereas the polymer grafted NFC was equally active against both. This was attributed to the ability of the polymeric grafts to penetrate the thick cell wall of Gram positive bacteria, followed by the destabilization of the cellular membrane. Neither cationized NFC type showed cytotoxicity against human cells, providing means to manufacture safe, insoluble, and permanently antimicrobial materials via aqueous synthesis.