Ethosomes for the delivery of anti-HSV-1 molecules: preparation, characterization and in vitro activity

This paper describes the production, characterization and in vitro activity of ethosomes containing two molecules with antiviral activity, such as acyclovir (ACY) and N1-beta-D-ribofuranosyl-pyrazole [3,4d]pyridazin-7(6p-chlorine-phenyl)-one nucleoside (N1CP). Ethosomes were prepared and morphologically characterized by Cryo-TEM. The encapsulation efficiency was 92.3 +/- 2.5% for ACY and 94.2 +/- 2.8% for N1CP. The release of the drug from vesicles, determined by a Franz cell method, indicated that both drugs were released in a controlled manner. In order to possibly guarantee the stability during long-term storage ethosome suspensions was freeze-dried. It was found that the freeze-dried ethosomes' cakes were compact, glassy characterized by low density and quick re-hydration. However, the storage time slightly influences the percentage of drug encapsulation within ethosomes showing a drug leakage after re-hydration around 10%. The antiviral activity against HSV-1 of both drugs was tested by plaque reduction assay in monolayer cultures of Vero cells. Data showed that ethosomes allowed a reduction of the ED50 of N1CP evidencing an increase of its antiviral activity. However, ACY remains more active than N1CP. No differences are appreciable between drug-containing ethosomes before and after freeze-drying. Taken together these results, ethosomal formulation could be possibly proposed as mean for topical administration of anti-herpetic molecules.