Optimization of stearylamine-based nanoemulsions obtained by spontaneous emulsification process as nucleic acids delivery systems

This study describes the optimization of stearylamine-based nanoemulsions obtained by means of a spontaneous emulsification process used as a delivery system for nucleic acids. First, the effect of both emulsification conditions and stearylamine content on the properties of nanoemulsions was optimized. Single-or double-strand nucleic acids were efficiently complexed with nanoemulsions. No marked differences were detected in the physicochemicalproperties or morphology of the oil droplets examined through TEM for complexes obtained at a charge ratio of + 2/-. The toxicity of formulations on HepG2 cells was evaluated through MTT assay. Progressive toxicity with a similar increasing addition of both nanoemulsions and complexes could be detected. However, the cytotoxicity of complexes was lower than that observed for nanoemulsions, suggesting that nucleic acids can indeed cover part of the positively-charged interface of nanoemulsions by neutralizing stearylamine molecules. Such results open interesting perspectives on the use of these nanoemulsions as a nucleic acid delivery system for Hep G2 cells.