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.

Evaluation of liposomal and conventional formulations of octyl methoxycinnamate on human percutaneous absorption using the stripping method.

The objective of this study was to determine the influence of vehicles on the penetration of octyl methoxycinnamate (OMC), as a UV absorber, to the stratum corneum by the stripping method. The experimental formulations consisted of a conventional o/w emulsion and multilamellar and small unilamellar liposomes (MLVs and SUVs) containing OMC. MLVs containing OMC were prepared by the fusion method and then converted to SUVs by probe sonication. Various formulations were then applied onto the midvolar forearms of six volunteers at a dose of 2 mg/cm2. After determined timepoints, the stripping method was conducted whereby 22 tape strips were applied and subsequently divided into different stripping groups. The sunscreen agent was assessed by HPLC while the SPF (sun protection factor) of the formulations was determined in human volunteers in accordance with the Australian standard. Overall the results indicate that skin accumulation of OMC in MLVs was significantly greater than in the o/w emulsion and SUVs. Furthermore, SUV's penetration into the deeper skin layers was significantly greater than MLV's and that of a conventional o/w emulsion. Also, higher amounts of OMC were recovered from the upper layers of the stratum corneum than from the deeper layers in all the formulations tested. Finally, the SPF of the liposomes containing OMC was slightly greater than that of the control lotions at a similar concentration of OMC. In conclusion, the result of this study indicates that an MLV prepared by the fusion method could be a better vehicle for OMC as a sunscreen since it has a slightly better SPF compared to a conventional formulation and more remains in the stratum corneum, reducing its penetration to the deeper layers.