Solid lipid nanoparticles carrying Eugenia caryophyllata essential oil: the novel nanoparticulate systems with broad-spectrum antimicrobial activity

In this study, solid lipid nanoparticles containing Eugenia caryophyllata essential oil (SLN-EO) were prepared by high-shear homogenization and ultrasound methods, and used to eradicate pathogens. SLN formulations were evaluated for their size, zeta potential and encapsulation efficacy (EE). The morphological and thermal properties of the formulations were analysed by transmission electron microscopy (TEM) and differential scanning calorimetry methods. The lead formulations were chosen and tested with minimum inhibitory concentration (MIC), MBC and time-kill methods to investigate the antimicrobial activity against Salmonella typhi, Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. The particle size of three final formulations were 397 ± 10·1, 786·9 ± 11 and 506·4 ± 22 nm respectively. The zeta potential of all formulations was negative values. The size of the formulations was slightly increased during 3 months storage at 25°C. The TEM imaging showed that formulation had spherical shape. The EE of EO was estimated approximately 70%. MIC and MCC values of SLN-EO were lower than those of the oil alone. The time-kill studies showed that SLN-EO was either equivalent to or better than EO (P-value <0·05). The results of this study highlighted the effectiveness of SLN formulations against human pathogens.

Significance and impact of the study: Microbial resistance to antibiotics is a major problem in the treatment of diseases. Therefore, overcoming antimicrobial resistance is an urgent need. Drug delivery via nanoparticles and applying natural products are promising approaches to reduce microbial resistance. This study is designed to evaluate the antimicrobial activity of solid lipid nanoparticles (SLN) containing Eugenia caryophyllata essential oil (EO) against human pathogens. The results indicated that the antimicrobial activity of EO was remarkably enhanced when encapsulated in SLN.