Preparation, Characterization and Cytotoxic Activity of New Oleuropein Microemulsion Against HCT-116 Colon Cancer Cells

The work was aimed to elucidate whether the nanoencapsulation of oleuropein would potentiate its anticancer activity against colon cancer or not. Oleuropein microemulsion was prepared using the water dilution method, in which oleic acid, tween 20, and ethanol were selected as the oily phase, surfactant, and cosurfactant, respectively. The microemulsion was characterized in terms of particle size, zeta potential, polydispersity index, morphology, in vitro drug release, stability, and anticancer activity on HCT-116 colon cancer cells. Results showed that oleuropein microemulsion was successfully prepared with a particle size of 10 nm, polydispersity index of 0.283, and a neutral charge. Moreover, it was able to sustain the release of drug for 24 h with a cumulative percentage release of 99%. Transmission electron microscopic examination of the microemulsion confirmed its small particle size and revealed spherical particle morphology. The as-prepared microemulsion was stable, with no significant changes in particle size, polydispersity or charge observed upon storage. Moreover, the oleuropein microemulsion was 106 times more cytotoxic than oleuropein alone on HCT-116 colon cancer cells. Therefore, it can be concluded that the proposed microemulsion is a promising delivery carrier for oleuropein, which is worthy of further experimentation on animals to examine the drug bioavailability.