Formulation and in vitro stability evaluation of ethosomal carbomer hydrogel for transdermal vaccine delivery

The primary objective of this study was to develop, evaluate and compare the effectiveness and stability of ethosomal carbomer gels in different solvents. The optimal ethosomal formulation was isolated to create ethosomal gels using carbomer in either pure water (water gel) or PBS containing 30% ethanol (PBS gel). In vitro release of the ethosomal gels were tested using Franz apparatus on hydrophilic and hydrophobic artificial membranes. In vitro stability of two ethosomal gels was systematically evaluated. Transdermal antigen delivery of ethosomal gel was finally performed on the skin of hair removal mice. Both solvent and concentration effects on the in vitro release performance of ethosomal gel of carbomer have been confirmed. Penetration depth has been found to be dependent on the nature of the membranes such that penetration rate is higher in the hydrophobic membrane than the hydrophilic ones. Furthermore, in vitro stability test indicated that ethosomal PBS gel was more stable than ethosomal water gel. In vivo immunoassay confirmed that the ethosomal PBS gel could deliver the antigenic molecules into the skin of mice and stimulate specific IgG secretion. Using the same solvent for lipid vesicular formulation when making polymeric hydrogel may help to provide a more conducive environment for lipid vesicles and hence enhance their roles in transdermal antigen delivery.