Ultrasonic Emulsification and Characterizations of Bio-based Nanoemulsion Formulations Containing Citral with Their Antimicrobial Activity

Document Type : Original Article

Authors

1 Department of Plant Protection, Faculty of Agriculture, Damanhour University, Damanhour 22516, Egypt

2 Department of Pesticide Chemistry and Technology, Faculty of Agriculture, 21545 El -Shatby, Alexandria University, Alexandria, Egypt

Abstract

Natural antimicrobial agents, particularly
essential oils existing broad-spectrum antimicrobial activity, unique
mechanisms of action and low tendency to induce resistance. However, their
potential as a viable antimicrobial alternative greatly compromised due to
their hydrophobic and volatile nature. The current study deals with the
formulation and characterization of bio-based oil in water (O/W) nanoemulsions
and their potential antimicrobial activity against some plant pathogens.
Nanoemulsion was prepared using citral as the oil phase, chitosan as a
biopolymer carrier, tween 80 as a surfactant, and sodium tripolyphosphate (TPP)
as a polyanioncrosslinker by ultrasonication method. The success of formulation
was confirmed by dynamic light scattering (DLS) and scanning electron microscopy
(SEM) techniques. Physical stability and viscosity were investigated in
details. The antibacterial activity of formulations were evaluated against Erwinia
carotovora
using ELISA technique by measuring the minimum inhibitory
concentration (MIC). The results of DLS and SEM measurements showed that the
nanoemulsions had a nearly polydispersity index(PDI) ranged from 0.508 to 0.614
and these values decrease when the concentration of the citral increase.
Particle size analysis showed that the mean particle sizes of these
formulations ranged from 27 to 1283 nm. Stability studies showed that the
formulations were stable under centrifugation test at 5000 rpm for 30 min. Stability
under different storage temperature showed that the five formulations were
stable with no phase separation for the duration of 1 month at 25°C and 4°C.
The antibacterial activity of the essential oil against E.carotovora was
enhanced considerably when it was converted into a nanoemulsion, which was
attributed to easier access of the essential oils to the bacterial cells. The
highest antibacterial activity (MIC= 23 mg/L) was observed with the low
concentration of citral, which had the lowest Particle size value (27 nm).

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