Optimisation of multiple W/O/W nanoemulsions for dermal delivery of acyclovir

In the present study multiple W/O/W nanoemulsions were optimised for the dermal application of the antiviral drug aciclovir. The phase inversion temperature method was employed to prepare the formulations without the input of high pressure. During formulation design the ethoxylated surfactants were varied and if possible partly replaced by natural sugar surfactants. Multiple nanoemulsions with mean droplet sizes around 100 nm and polydispersity indices below 0.1 were prepared. At room temperature, they exhibited excellent physicochemical stability over an observation period of 6 months. Furthermore, cryo electron microscopy gave an insight into the microstructure of the multiple nanoemulsions. Moreover, the formulations' interaction with skin was analysed by ATR-FTIR. In Franz-type diffusion cell and tape stripping experiments aciclovir showed satisfying skin permeation from the novel nanoemulsions.