In vitro cytotoxicity of a thermoresponsive gel system combining ethyl(hydroxyethyl) cellulose and lysine-based surfactants.

The cytotoxicity of three lysine-derived surfactants with a gemini-like structure was evaluated on HeLa cells. The half maximal effective concentration (EC(50)) was estimated from the dose-response curves and the values indicated an increase in toxicity with the increase in alkyl chain length. The shorter chain length surfactant (C(6)) was shown to be less cytotoxic than sodium dodecyl sulfate (SDS), and all the lysine-derived surfactants were less toxic than the cationic cetyl trimethylammonium bromide (CTAB). The presence of ethyl (hydroxyethyl) cellulose (EHEC), shown previously to form thermoresponsive gels in combination with these surfactants, was found to contribute to a lower toxicity on HeLa cells. The conjecture is that the polymer-surfactant interactions in forming mixed micelles are the key contributors to the enhanced biocompatibility of the hydrogels. The most promising results were obtained in the presence of either the most hydrophilic surfactant or in the presence of the longest chain-length surfactant. For the latter, very low concentrations are needed to induce a sol-gel transition of EHEC semi-dilute solutions.