Characterization, in vitro cytotoxicity and cellular accumulation of paclitaxel-loaded lipid nano-emulsions

Lipid nano-emulsions (LNEs) having a mean droplet size of ∼50 nm were investigated as drug carriers for paclitaxel (TXL) to achieve its satisfactory loadings and to develop a pharmaceutically acceptable alternative to the current formulation, Taxol®. TXL was incorporated into the LNEs at 2.0 mg/ml without changes in particle size or drug precipitation. In the cytotoxicity study, TXL-loaded LNEs had cytotoxicity to HeLa cells equivalent to that of TXL alone; the 50% growth inhibitory concentrations (IC50) of TXL-loaded LNEs and TXL alone were 1.53 ± 0.23 nM and 1.76 ± 0.08 nM, respectively. However, a cellular accumulation study using 1,6-diphenyl-1,3,5-hexatriene (DPH) as a fluorescent probe showed that the accumulation of DPH-loaded LNEs in HeLa cells was remarkably lower than that of DPH alone. These results indicated that LNEs were a useful vehicle for TXL, even though LNEs themselves could not be efficiently accumulated in HeLa cells.