HIGHLIGHTS • The most common chemical treatments of cellulose to synthesize nanostructured cellulose are highlighted. • Various surface modifications of cellulose to develop non-leaching and durable antibacterial materials are discussed. • Biocompatibility and antibacterial performance of non-leaching surface-modified cellulosic materials along with their current challenges are discussed.

We used hairy nanocrystalline cellulose functionalized with aldehyde groups, otherwise known as sterically stabilized nanocrystalline cellulose (SNCC), to facilitate the attachment of the antibacterial agents lysozyme and nisin. Immobilization was achieved using a simple, green process that does not require any linker or activator. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses showed successful attachment of both nisin and lysozyme onto the SNCC. The efficacy of the conjugated nanocellulose against the model bacteria Bacillus subtilis and Staphylococcus aureus was tested in terms of bacterial growth, cell viability, and biofilm formation/removal. The results show that the minimum inhibitory concentration of the conjugated nanocellulose is higher than that of lysozyme and nisin in free form, which was expected given that immobilization reduces the possible spatial orientations of these proteins. We observed that free nisin is not active against S. aureus after 24 h of exposure due to either deactivation of free nisin or development of resistance in S. aureus against free nisin. Interestingly, we did not observe this phenomenon when the bacteria were exposed to antibacterials immobilized on nanocellulose, suggesting that immobilization of antibacterial agents onto SNCC effectively retains their activity over long time periods. We suggest that antibacterial SNCC is a promising candidate for the development of antibacterial wound dressings.

In this study, a carboxyl-modified cellulosic hydrogel was developed as the base material for wound dressings. ε-poly-l-lysine, a natural polyamide, was then covalently linked to the hydrogel through a bioconjugation reaction, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). The antibacterial efficacy of the hydrogel was tested against two model bacteria, Staphylococcus aureus and Pseudomonas aeruginosa, two of the most commonly found bacteria in wound infections. Bacterial viability and biofilm formation after exposure of bacteria to the hydrogels were used as efficacy indicators. Live/Dead assay was used to measure the number of compromised bacteria using a confocal laser scanning microscope. The results show that the antibacterial hydrogel was able to kill approximately 99% of the exposed bacteria after 3 h of exposure. In addition, NIH/3T3 fibroblasts were used to study the biocompatibility of the developed hydrogels. Water-soluble tetrazolium salt (WST)-1 assay was used to measure the metabolic activity of the cells and Live/Dead assay was used to measure the viability of the cells after 24, 48, and 72 h. The developed antibacterial hydrogels are light weight, have a high water-uptake capacity, and show high biocompatibility with the model mammalian cells, which make them a promising candidate to be used for wound dressing applications.

No abstract

Adsorption is a common technique for the treatment of dye-contaminated wastewater. Achieving a high dye removal capacity is a common challenge with sustainable, low-cost adsorbents. Recently, a class of easily functionalized, biorenewable cellulose nanoparticles called hairy nanocellulose has been developed. Electrosterically stabilized nanocrystalline cellulose (ENCC), which can be synthesized from wood pulp through a two-step oxidation by periodate and chlorite, is a form of hairy nanocellulose with a high negative charge density, and thus has the potential for a high adsorption capacity. In this work, the adsorption of methylene blue, a cationic dye, by ENCC was shown to occur up to charge stoichiometry (1400 mg dye/g adsorbent), at which point aggregation of ENCC–dye complexes is observed. A model is developed to show that the adsorption can be described by an ion-exchange mechanism and is influenced by the presence of other ions. Equilibrium dye removal is reduced at both high ionic strengths and low pH. To facilitate handling, composite hydrogel beads of sodium alginate and ENCC (ALG–ENCC beads) are developed, and their methylene blue removal capacity is shown to maintain a high removal capacity (1250 mg/g). ALG–ENCC beads provide a facile way to employ these nanoparticles on a larger scale, providing a potential means for the removal of dyes and other contaminants at larger wastewater volumes.