A new method for liposome preparation using a membrane contactor

In this article, we present a novel, scalable liposomal preparation technique suitable for the entrapment of pharmaceutical agents into liposomes. This new method is based on the ethanol-injection technique and uses a membrane contactor module, specifically designed for colloidal system preparation. In order to investigate the process, the influence of key parameters on liposome characteristics was studied. It has been established that vesicle-size distribution decreased with a decrease of the organic-phase pressure, an increase of the aqueous-phase flow rate, and a decrease of the phospholipid concentration. Additionally, special attention was paid on reproducibility and long-term stability of lipid vesicles, confirming the robustness of the membrane contactor-based technique. On the other hand, drug-loaded liposomes were prepared and filled with two hydrophobic drug models. High entrapment-efficiency values were successfully achieved for indomethacin (63%) and beclomethasone dipropionate (98%). Transmission electron microscopy images revealed nanometric quasispherical-shaped multilamellar vesicles (size ranging from 50 to 160?nm).     

Interstrains comparison of the antimicrobial effect and mode of action of a Vietnamese Cinnamomum cassia essential oil from leaves and its principal component against Listeria monocytogenes

The antibacterial activity of a Cinnamomum cassia essential oil (EO) and of its main component trans-cinnamaldehyde (90% w/w) was examined against five Listeria monocytogenes strains. The minimal inhibitory concentrations (MICs) of C. cassia EO against the five L. monocytogenes strains were identical (250 µg ml⁻¹), while the minimal bactericidal concentrations (MBCs) ranged between 800 and 1200 µg ml⁻¹. In order to study if this EO and trans-cinnamaldehyde altered the five strains at the membrane level, fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) was measured in presence of different concentrations (1/2MIC, MIC, 2MIC) of these antibacterial agents. A concentration-dependent increase of fluorescence anisotropy of DPH in their presence reflecting a rigidification of the membrane was observed for the five strains. This modification of the membrane fluidity was associated with a perturbation of the selective membrane permeability, as a perturbation of the gradient between intracellular and extracellular pH was also observed.