Ensuring microbial safety in pharmaceutical applications remains a critical public health priority, motivating the development of novel antimicrobial delivery systems targeting pathogenic microorganisms. The antibacterial activity of a nanoemulsion formulated with Pelargonium graveolens essential oil (P. graveolens EO) was evaluated against two bacterial species, E. coli (ATCC 25922) and B. subtilis (ATCC 23857), using both conventional and microfluidic techniques. The optimized P. graveolens essential oil nanoemulsion exhibited a mean droplet size of 68.94± 3.1 nm, with surfactant, essential oil, and HLB values optimized at 5.29% w/w, 2.60% w/w, and 11.82, respectively. The effects of the nanoemulsion on bacterial cells were assessed by monitoring the release of intracellular proteins, nucleic acids, and potassium ions, as well as by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and conducting time-kill assays. The use of microfluidic technology significantly enhanced bacterial exposure to the nanoemulsion due to increased contact areas between bacterial membranes and nanodroplets. With microfluidic methods, the MIC values for B. subtilis and E. coli were determined within 15 min, compared to 3.12 and 6.25 µg/mL over 24 h by conventional means. Notably, B. subtilis exhibited greater resistance to the nanoemulsion than E. coli, likely due to differences in their cell wall structures. Further analysis using desorption electrospray ionization mass spectrometry revealed changes in the bacterial cell membrane, particularly through the detection of released phosphatidylglycerol and phosphatidylethanolamine. These results indicate that the nanoemulsion prompted more pronounced structural alterations in Gram-negative E. coli cells. These results highlight the potential of P. graveolens EO nanoemulsions as innovative antimicrobial agents for pharmaceutical use.
Alvand et al. (Thu,) studied this question.