Evaluation of Cytotoxicity of Self-Emulsifying Formulations Containing Long-Chain Lipids Using Caco-2 Cell Model: Superior Safety Profile Compared to Medium-Chain Lipids.

Medium-chain (MC) and long-chain (LC) lipids are used for development of self-emulsifying drug delivery systems (SEDDS). MC lipids are often preferred because of their ability to form stable microemulsions with relatively high drug solubilization capacity. On the other hand, LC lipids could be more biocompatible as most endogenous and dietary lipids are LC glycerides. They also maintain high drug solubilization capacity after digestion. The present study was undertaken to determine the cytotoxicity of LC lipids and their formulations on Caco-2 cells of 1-day, 5-day, and 21-day maturity. The results were compared with the cytotoxicity profiles of MC lipids reported previously from our laboratory. The cell viability and cell membrane integrity were, respectively, determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the lactate dehydrogenase assay. The cytotoxicity was partially due to lipid surfactant-induced membrane rupture, and it was influenced by cell maturity and formulation composition. The lipid-surfactant combinations showed greater tolerance than surfactants alone, and LC-SEDDS were well-tolerated at almost 10-fold higher concentration than corresponding MC-SEDDS. Furthermore, the cytotoxicity of digestion end products of both LC and MC triglycerides in the presence of 3 mM sodium taurocholate was compared on 21-day Caco-2 cultures by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The LC lipid formulations showed better tolerance than MC lipid formulations after digestion. Thus, although MC and LC lipids are well-tolerated at doses normally administered to humans, LC lipids show much better safety than MC lipids in a cell-culture model.