Development of Topical Formulations Containing 20% Zinc Oxide Nanoparticles: Stability Assessment and Penetration Evaluation

The study developed a simple stable formulation containing 20% of coated and uncoated Zinc Oxide Nanoparticles (ZnOn), characterized the formulations and the nanoparticles, and assessed the skin penetration. The Feret's diameter for the uncoated and coated ZnOn was 137 nm and 134 nm, respectively. The incorporation of ZnOn led to formulations that were more consistent and easier to spread. The stability assessment at 45ºC suggested that the formulations containing the ZnOn were stable for 30 days and the vehicle was stable for 90 days. The skin penetration assessment indicated that the formulations did not permeate into the deepest layers of the skin, but accumulated on the skin furrows, hair, and hair follicle.