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.
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.
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