Antibacterial paper based on composite coatings of nanofibrillated cellulose and ZnO

New composites of nanofibrillated cellulose (NFC) and ZnO nanoparticles (NP) have been prepared by electrostatic assembly in aqueous medium and using polyelectrolytes as macromolecular linkers. Selected NFC/ZnO systems were employed as fillers in starch based coating formulations for Eucalyptus globulus-based paper sheets. Using this method, antibacterial paper with low content of ZnO (<0.03%) and slight improvements in air permeability and mechanical properties were obtained. The antibacterial activity of the ZnO/NFC coatings was investigated namely by submitting paper samples to solar light exposure and dark conditions. In both conditions, the paper samples have shown bacteriostatic and/or bactericidal activity against Gram positive (Staphylococcus aureus and Bacillus cereus) and Gram negative (Klebsiella pneumoniae) bacteria. These results seem to support that the mechanism for ZnO antimicrobial activity is not mediated only by the photoactivity of the semiconductor but also by oxidizing species formed at the particles surfaces.