s Self-emulsifying System Co-loaded with Paclitaxel and Coix Seed Oil Deeply Penetrated to Enhance Efficacy in Cervical Cancer

Background: Paclitaxel (PTX), voted as the promising natural medicine molecule, is widely used in the treatment of cancers. Nevertheless, its clinical application is strictly limited by its poor water solubility. Objective: CP-MEs (Paclitaxel-coix seed oil coloaded microemulsion), a small-sized self-emulsifying nanoemulsion formed from a combination of PTX and coix seed oil (CSO), was developed in order to improve the solubility of paclitaxel and enhance anti-cervical cancer efficacy in vitro. CSO was selected as the oil phase to replace conventional organic solvents and achieve a synergistic anti-tumor effect with paclitaxel. Methods: Pseudoternary phase diagram was applied to the study of CP-MEs formulation. CP-MEs were prepared and characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The encapsulation efficiency and drug loading efficiency (EE and LE) were detected by HPLC. MTT was adopted to evaluate the cytotoxicity of CP-MEs against HeLa cells. The cellular uptake and apoptotic ratio of CP-MEs were evaluated by flow cytometry. Notably, HeLa 3D tumor spheroid was adopted to evaluate tumor permeability of different size microemulsions as the model. Results: The best self-emulsifying ability was exhibited by HS 15: PEG 400 combination. The appearance of CP-MEs was clear and transparent, which exhibited a small size (30.28 ± 0.36) and a slight negative surface charge (-4.40 ± 1.13) mV. The EE and LE of CP-MEs were 98.80% and 0.978%, respectively. The cumulative release rate within 48 h of the CP-MEs was 80.21%. In cellular studies, the uptake of fluorescein isothiocyanate (FITC) labeled CP-MEs (FITC/C-MEs) was 17.86-fold higher than the free FITC group, leading to significant synergistic anticancer activity in terms of cytotoxicity and apoptosis induction in vitro. The apoptotic rate of CP-MEs treated was 1.70-fold higher than PTXtreated. Notably, the penetration of CP-MEs in the HeLa 3D tumor sphere model was enhanced, which was related to deeply penetrated microemulsion of small size mediated at the tumor site. Conclusion: With the advantage of the small-sized self-emulsifying system, CP-MEs hold great potential to become an efficient nano drug delivery system for cervical cancer treatment in the clinic.