Comparative antibacterial effects of cellulose nanofiber, chitosan nanofiber, chitosan/cellulose combination and chitosan alone against bacterial contamination of Iranian banknotes.

The aims of the current study were to evaluate the antibacterial effects of cellulose nanofiber (CNF), chitosan nanofiber (ChNF), CNF/ChNF combination and chitosan alone (Ch) against the isolated bacterial contaminations from the surface of Iranian banknotes using biochemical, disc diffusion and molecular analyses. The results unveiled that the CNF did not show the significant antibacterial effect against isolated bacterial strains, whereas the combination of CNF/ChNF (at concentration 100 μg/disc 1:1) exhibited the synergistic effects against Stenotrophomonas maltophilia. Also, ChNF (100 μg/disc) and Ch (100 and 200 μg/disc) displayed dose-dependent antibacterial effects against the sensitive bacteria including Bacillus subtilis, Bacillus pumilus, Micrococcus sp. Kosakonia cowanii, Brevibacterium frigoritolerans, Escherichia coli standard ATCC 25922, Staphylococcus aureus standard ATCC 25923. On the other hand, chitosan displayed the highest inhibitory effects against Gram-positive bacteria. Our results showed that the coating of banknotes with these compounds is a novel strategy to reduce the bacterial contaminations and increase the durability (or quality) of banknotes, without being toxic to the surrounding environment.