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Abstract
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This study investigates the preparation, characterization, and evaluation of nanoemulsions (NEs) derived from cinnamon
essential oil (EO) and its main component, trans-cinnamaldehyde (TC), for antibacterial and antibiofilm effects against
Pseudomonas aeruginosa PAO1. NEs were prepared by high-energy ultrasonication using span 80, tween 80 as surfactants,
and lecithin as a ripening inhibitor. Dynamic light scattering analysis indicated that the system remained stable
for a period of 8 weeks. Antibacterial activity evaluated by the microdilution assay revealed that NEs showed enhanced
antibacterial activity compared to bulk oils. Biofilm inhibition assay using crystal violet staining at sub-MIC concentrations
demonstrated that NEs reduced biofilm formation by more than 50%, even at the lowest concentration (1/8 ×
MIC). Scanning electron microscopy images confirmed decreased bacterial attachment and extracellular matrix in treated
samples. Established biofilms were effectively eradicated by both NEs and bulk oils, with the best results achieved by
TC nanoemulsion (TC NE) at 1/2 × MIC, resulting in 79.86 ± 1.46% biofilm eradication. The impact of TC NE on pyocyanin
production, a virulence factor in P. aeruginosa, was also investigated. The NE inhibited pyocyanin production in
a concentration-dependent manner, showing the greatest inhibition (94.76 ± 0.38%) at 1/2 × MIC after 24 h. Finally, the
degradation of TC by PAO1 was assessed. The results showed that cinnamaldehyde was converted into the less toxic cinnamic alcohol, with a slower conversion rate in NE-treated samples. These findings suggest that cinnamon and TC NEs
may be effective antibacterial and antibiofilm agents.
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