Transfection mediated by pH-sensitive sugar-based gemini surfactants; potential for in vivo gene therapy applications

In this study, the in vitro and in vivo transfection capacity of novel pH-sensitive sugar-based gemini surfactants was investigated. In an aqueous environment at physiological pH, these compounds form bilayer vesicles, but they undergo a lamellar-to-micellar phase transition in the endosomal pH range as a consequence of an increased protonation state. In the same way, lipoplexes made with these amphiphiles exhibit a lamellar morphology at physiological pH and a non-lamellar phase at acidic pH. In this study, we confirm that the gemini surfactants are able to form complexes with plasmid DNA at physiological pH and are able to transfect efficiently CHO cells in vitro. Out of the five compounds tested here, two of these amphiphiles, GS1 and GS2, led to 70% of transfected cells with a good cell survival. These two compounds were tested further for in vivo applications. Because of their lamellar organisation, these lipoplexes exhibited a good colloidal stability in salt and in serum at physiological pH compatible with a prolonged stability in vivo. Indeed, when injected intravenously to mice, these stable lipoplexes apparently did not substantially accumulate, as inferred from the observation that transfection of the lungs was not detectable, as examined by in vivo bioluminescence. This potential of avoiding 'preliminary capture' in the lungs may, thus, be further exploited in developing devices for specific targeting of gemini lipoplexes.