Nanoemulsion and Solid Nanoemulsion for Improving Oral Delivery of a Breast Cancer Drug: Formulation, Evaluation, and a Comparison Study.

Letrozole (LZ) is an aromatase inhibitor, which inhibits the formation of estrogens from androgens. Nanoemulsion is a liquid emulsion formulation utilized to increase solubility, bioavailability, and drug delivery to cancer cells. This study aims to improve LZ oral delivery through formulating solid nanoemulsion (SNE). Peppermint oil, tween 80, and transcutol P were used as an oil, surfactant, and co-surfactant, respectively. The optimized nanoemulsion (NE-3) was then incorporated into solid polyethylene glycol (PEG) to formulate (SNE). The optimized (NE-3), SNE-2, and the available marketed tablet have been compared. The optimized (NE-3) was selected according to specific parameters of optimum small nano-size 80 nm, PDI of 0.181, the zeta potential of-98.2, high transmittance (99.78%), optimum pH (5.6), a high percent of LZ content (99.03 ± 1.90), the relatively low viscosity of 60.2 mPa.s, and a rapid release of LZ within 30 min. NE-3 was selected to be formulated as SNE. LZ's best release rate was 80% in 5 min with a content homogeneity of 99.85 ± 0.04 for SNE-2. Zero-order kinetics is determined to have the greatest R values. Field emission scanning electron microscopy (FE-SEM) detected that SNE-2 was (36.75-96.64 nm) with a spherical form and no adhesion or aggregation. FT-IR showed no significant variations in position and shape of the absorption peaks between the pure drug and optimal formulation diagrams. This novel nanoemulsion technology aids in improving the solubility of poorly water-soluble drugs, particularly the SNE delivery method, which has a higher in-vitro release rate and expiration date of LZ than others.