Sunflower Oil Based Nanoemulsion Loaded into Carbopol Gel: Semisolid State Characterization and Ex Vivo Skin Permeation

Abstract

Sunflower oil, a commonly available vegetable oil, is used as a lipid component in nanoemulsion. When a nanoemulsion is loaded into an aqueous gel platform for transdermal delivery, skin permeation of a drug depends on the release of nanosize droplets from the gel. Semisolid characteristics, such as viscosity, spreadability, rheological properties, can greatly affect the drug release and permeation. We have formulated a nanoemulsion using sunflower oil as lipid carrier and raloxifene as a model drug by cold emulsification method. The most suitable nanoemulsion was composed of lipid:mixture of surfactant-cosurfactant (Tween 20-Transcutol® P, 3:1 w/w) in a ratio of 12.5:87.5 %. This formulation was loaded into carbopol 940 based gel in various ratios. Mechanical evaluation of the most suitable nanoemulgel (nanoemulsion: carbopol, 1:1 weight ratio) resulted in 94.0±4.62 g of hardness and 4.99±0.057 cm of spreadability. Shear-thinning and pseudoplastic behavior were evidenced in rheological evaluation. Ex vivo skin permeation study on rat skin showed a significant increase in the cumulative amount of drug permeation and steady-state permeation flux compared to the conventional gel. Increasing carbopol concentration showed increased viscosity and reduction in ex vivo drug permeation. The permeation enhancing effect of sunflower oil and Tween 20, nanosize droplets and enhanced retention of the dosage form over skin cumulatively increase the ex vivo drug permeation. Alternately, the potential of raloxifene transdermal delivery by sunflower oil-based nanoemulsion can be established.