Antibacterial Pickering emulsions stabilized by bifunctional hairy nanocellulose

Hypothesis: Pickering emulsions, defined as emulsions that are stabilized by colloidal particles, provide dispersion stability by preventing coalescence of the dispersed phase. In this study, we used a bifunctional hairy nano-cellulose (BHNC) bearing both aldehyde and carboxylic acid groups as an stabilizer. We hypothesize that these particles as Pickering stabilizers can effectively reside at the oil-water interface, better than hairy nanocelluloses containing only carboxyl groups or aldehyde groups, and provide long-term stability without the need of any surfactants.Experiments: Varying concentrations of BHNC were tested to explore the optimal concentration that provides emulsion stability. The effects of various preparation conditions such as salt and pH were also studied. Finally, carvacrol, an antibacterial essential oil, was loaded in the oil phase to develop antibacterial emulsions.Findings: It was shown that a 1% BHNC suspension provides 90% and 80% stability for a duration of 30 and 60 days, respectively. A theoretical model using nuclear magnetic resonance relaxometry data is developed to prove that only a monolayer of BHNC covers oil droplets. Increasing the concentration of BHNC decreased the size of oil droplets, which as a result increases the surface area available for monolayer coverage. It was also shown that the antibacterial emulsions are highly effective against Gram-negative (i.e. E. coli) and Gram-positive (i.e. S. aureus) bacteria. Accordingly, BHNC as a highly functionalized bio-derived colloidal particle opens new opportunities for engineering highly stable Pickering emulsions.

Automated summary

In this study, a bifunctional hairy nano-cellulose (BHNC) bearing both aldehyde and carboxylic acid groups was used as a stabilizer in Pickering emulsions. It was found that a 1% BHNC suspension provided 90% and 80% stability for 30 and 60 days, respectively. Theoretical modeling and antibacterial tests showed that BHNC can effectively cover oil droplets and produce highly stable and antibacterial emulsions.