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In this work, several normal, oil-in-water (o/w) microemulsions (MEs) were prepared using peppermint essential oil, jojoba oil, trans-anethole, and vitamin E as oil phases to test their capacity to load paclitaxel (PTX). Initially, pseudo-ternary partial phase diagrams were constructed in order to find the normal microemulsion region using d-α-tocopherol polyethylene glycol 1000 succinate (TPGS-1000) as surfactant and isobutanol (iso-BuOH) as co-surfactant. Selected ME formulations were loaded with PTX reaching concentrations of 0.6 mg mL -1 for the peppermint oil and trans-anethole MEs, while for the vitamin E and jojoba oil MEs, the maximum concentration was 0.3 mg mL -1 . The PTX-loaded MEs were stable according to the results of heating-cooling cycles and mechanical force (centrifugation) test. Particularly, drug release profile for the PTX-loaded peppermint oil ME (MEPP) showed that ∼ 90% of drug was released in the first 48 h. Also, MEPP formulation showed 70% and 90% viability reduction on human cervical cancer (HeLa) cells after 24 and 48 h of exposure, respectively. In addition, HeLa cell apoptosis was confirmed by measuring caspase activity and DNA fragmentation. Results showed that the MEPP sample presented a major pro-apoptotic capability by comparing with the unloaded PTX ME sample.

The preparation of biocompatible normal (oil-in-water, o/w) microemulsions (ME) with different oil phases (peppermint oil, trans-anethole, vitamin E, jojoba oil) and stabilized with d-α polyethylene glycol succinate (TPGS-1000) and isobutanol ( iso-BuOH) is presented. Results of average particle diameter determination, Dp, indicated 6.35 ≤ Dp ≤ 10.24 nm. These ME showed excellent colloidal stability (−40 and +40 °C) and, without any drug loaded, decreased dramatically the viability of leukemia cells (K562), 60-90 %, in 24 hours. Besides, this behavior was potentiated when paclitaxel (PTX, an anticancer drug) was loaded in the transanethole microemulsion, where the cell viability decreased until 2 % at 0.5 μg/mL of PTX. These MEs are precursors to synthetize polymeric nanocapsules when coated with a thermo or pH - sensible polymer with potential for cancer treatment. [ABSTRACT FROM AUTHOR]