Rapamycin-Loaded, Capryol(TM) 90 and Oleic Acid Mediated Nanoemulsions: Formulation Development, Characterization and Toxicity Assessment

This study was planned to explore the capability of nanoemulsions (NEs) consisting of Capryol(TM )90 and oleic acid for the delivery of rapamycin (RAP). Permeability and cytotoxicity of RAP-loaded NEs were also inspected. Pseudo-ternary phase diagrams were created with oleic acid and Capryol(TM )90 (as oil phase) and four surfactants and co-surfactants at various weight ratios (R(sm)). Selected NEs from O/W region on the phase diagrams with the drug concentration of 1 mg/mL, were prepared via the spontaneous emulsification technique, characterized for particle size and subjected to stability tests at various temperatures over 9-12 months. Cumulative drug release was determined for a period of 48 h using a dialysis sac. The assay of RAP was determined using HPLC technique. Cytotoxicity of NEs was evaluated by MTT assay on breast cancer cell line, namely SKBR-3. The permeability of RAP-loaded NEs across Caco-2 monolayers was assessed by measurement of TEER (transepithelial electrical resistance) value. The intracellular uptake of coumarin 6-loaded NEs by SKBR-3 cells was also investigated using florescence microscopy. NEs containing oleic acid/Tween 20/propylene glycol, Capryol(TM) 90/Tween 20/iso-propanol, and Capryol(TM) 90/Cremophor(®) RH40/Transcutol(® )P showed more cytotoxicity and permeability compared with the RAP methanolic solution. The minimum toxic concentration of RAP in NE formulations was found to be 7.5 µg/mL. The highest intracellular uptake was observed for the NE composed of Capryol(TM) 90/Tween 20/iso-propanol which was in consistent with the results obtained from cytotoxicity and permeability tests. The overall results implicated that this novel carrier was effective for enhancing RAP permeation in Caco-2 cell membrane along with enhancement of cytotoxicity.