Microfibrillated cellulose films have been gathering considerable attention due to their high mechanical properties and cheap cost. Additionally, it is possible to include compounds within the fibrillated structure in order to confer desirable properties. Ilex paraguariensis A. St.-Hil, yerba mate leaf extract has been reported to possess a high quantity of caffeoylquinic acids that may be beneficial for other applications instead of its conventional use as a hot beverage. Therefore, we investigate the effect of blending yerba mate extract during and after defibrillation of Eucalyptus sp. bleached kraft paper by ultrafine grinding. Blending the extract during defibrillation increased the mechanical and thermal properties, besides being able to use the whole extract. Afterwards, this material was also investigated with high content loadings of starch and glycerine. The results present that yerba mate extract increases film resistance, and the defibrillated cellulose is able to protect the bioactive compounds from the extract. Additionally, the films present antibacterial activity against two known pathogens S. aureus and E. coli, with high antioxidant activity and increased cell proliferation. This was attributed to the bioactive compounds that presented faster in vitro wound healing, suggesting that microfibrillated cellulose (MFC) films containing extract of yerba mate can be a potential alternative as wound healing bandages.

The effectiveness of tannic acid as antimicrobial and wound healing for burns have been shown for a century; however, uncontrolled target dosage may result in undesirable side-effects. Remarkably, tannic acid polyphenols compounds crosslinked with polymeric materials produce a strong composite containing the beneficial properties of this tannin. However, investigation of the crosslink structure and its antibacterial and regenerative properties are still unknown when using nanocellulose by mechanical defibrillation; additionally, due to the potential crosslink structure with chitosan, its structure can be complex. Therefore, this work uses bleach kraft nanocellulose in order to investigate the effect on the physical and regenerative properties when incorporated with chitosan and tannic acid. This film results in increased rigidity with a lamellar structure when incorporated with tannic acid due to its strong hydrogen bonding. The release of tannic acid varied depending on the structure it was synthesised with, whereas with chitosan it presented good release model compared to pure cellulose. In addition, exhibiting similar thermal stability as pure cellulose films with antibacterial properties tested against S. aureus and E. coli with good metabolic cellular viability while also inhibiting NF-κB activity, a characteristic of tannic acid.

The aim of this study was to assess the performance of graphene oxide nanoparticles in paper coating formulations in order to improve the antibacterial, physical and mechanical properties of paperboard. The paper was coated with graphene oxide nanoparticles at concentrations of 100 and 200 ppm together with 5% cationic starch (dry weight) as a retention aid and for better coverage and more homogeneous positioning of nanographene oxide particles on the surface of the paper. The paper surface coated with nanographene oxide particles and starch was characterised using ATR-FTIR and SEM. The antibacterial assay was performed according to the Turbidity Method. For the antibacterial tests of paper sheets, Escherichia coli and Staphylococcus aureus were used as Gram-negative and Gram-positive bacteria respectively. The results showed that UV adsorption was reduced, with the largest reduction obtained when using nanographene oxide particles at 200 ppm. Turbidity in the samples including S. aureus was also lower. The growth rates of S. aureus bacterium in the control and the paper specimens coated with 200 ppm nanographene oxide were 89% and 24%, respectively. The density and thickness of the paper sheets increased in the paper coated with cationic starch and nanoparticles in comparison with uncoated paper. The nanoparticles had no significant effect on the thickness of coated papers. The addition of nanographene oxide particles improved the resistance to air and barrier properties of paper sheets. The burst and tear indexes increased for the paper coated with starch and nanographene oxide particles.