Our last article on nanocellulose in environmental cleanup looked at the use of cellulose nanocrystals (CNCs) as adsorbents in the removal of dyes and heavy metals from water.
Do CNCs also have potential applications in tackling illness-causing bacteria? Cellulose nanocrystals were used as a gelling agent in hydroalcoholic hand sanitizer during the COVID-19 pandemic, and they can be used more directly to address bacterial contamination in water: Cellulose nanomaterials are widely investigated as supports for immobilizing various bactericidal inorganic nanoparticles, effectively preventing their agglomeration, which can otherwise hinder their antibacterial activity.
Ye et al. from South China University of Technology and the State Key Laboratory of NBC Protection for Civilian prepared antibacterial nanocomposites by growing Cu9S5 in-situ on rod-shaped cellulose nanocrystals and depositing them onto a glass fiber microfiltration membrane, as in the figure above. The Cu9S5 nanoparticles decreased in size by a factor of 11 (from 44 nm to 4 nm) when compounded with the CNCs, leading to more efficient copper ion release. Moreover, the cellulose nanocrystals themselves physically punctured the bacteria due to their unique shape, further enhancing the antibacterial effect.
Silver is another widely recognized bactericidal material; Xu et al. at Georgia Institute of Technology developed cellulose nanocrystal/silver thin film (CNC/Ag) nanocomposite nanofiltration membranes. Simultaneously addressing the issues of membrane permeability/selectivity and membrane fouling, they embedded CNC/Ag nanocomposites into a polyamide layer. With incorporation of only 0.01% w/w CNC/Ag, the membranes achieved high pure water permeability (25.4 L m-2 h-1 bar-1) along with exceptional antifouling and antibacterial performance, showing 99.4% E. coli inhibition. The silver nanoparticles also demonstrated good stability within the active thin-film layer.
These works exemplify the powerful synergy often achieved when cellulose nanocrystals are partnered with other materials.
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For more information, please consult the full articles:
Rod-shaped cellulose nanocrystal/Cu9S5 antibacterial nanocomposites for microfiltration.
Read more about CNCs for environmental cleanup:
Cellulose nanocrystals for efficient removal of environmental contaminants (part 1)
