Formulation Development and Toxicity Assessment of Triacetin Mediated Nanoemulsions as Novel Delivery Systems for Rapamycin

The aim of this investigation was to design and develop nanoemulsions (NEs) as novel delivery systems for rapamycin. Phase behavior of quaternary systems composed of Traicetin (as oil), various surfactants and co-surfactants and water at different surfactant/co-surfactant weight ratios was investigated by the construction of phase diagrams. Formulations were taken from the o/w NE region of the phase diagrams, depending upon the extent of NE domain. The spontaneous emulsification method was used to prepare various formulations containing 1 mg/mL of the drug. The NEs were characterized and subjected to stability tests at various temperatures over 9-12 months. Cumulative drug release from the selected formulations was determined for a period of 48 h using a dialysis sac. The assay of rapamycin was carried out using an HPLC technique. The effect of NEs on the viability of SKBR-3 cells was evaluated by MTT assay. The integrity of Caco-2 cell monolayers was measured by Transepithelial Electrical Resistance (TEER) and the transport of rapamycin-loaded NEs across Caco-2 cell monolayers was then assessed. The uptake of NEs by SKBR-3 cells was also investigated using florescence microscopy. Maximum drug release was observed in case of 4 formulations prepared with Tween 80 and Tween 20. MTT test results revealed different toxicity of NEs for SKBR-3 cell line and TEER demonstrated that formulations containing Tween 20 caused a more considerable decrease in cell integrity in comparison with those prepared with Tween 80. The results obtained from cellular uptake experiments were in consistent with those obtained from TEER and cytotoxicity experiments.