New serine-derived gemini surfactants as gene delivery systems

• Complexes of serine-derived gemini surfactants efficiently transfect cells.
• The most efficient DNA complexes were those containing (12Ser)2COO5 and DOPE:Chol.
• The size of the most efficient complexes is compatible with i.v. administration.
• Serum does not inhibit transfection mediated by (12Ser)2COO5-based complexes.

Gemini surfactants have been extensively used for in vitro gene delivery. Amino acid-derived gemini surfactants combine the special aggregation properties characteristic of the gemini surfactants with high biocompatibility and biodegradability. In this work, novel serine-derived gemini surfactants, differing in alkyl chain lengths and in the linker group bridging the spacer to the headgroups (amine, amide and ester), were evaluated for their ability to mediate gene delivery either per se or in combination with helper lipids. Gemini surfactant-based DNA complexes were characterized in terms of hydrodynamic diameter, surface charge, stability in aqueous buffer and ability to protect DNA. Efficient formulations, able to transfect up to 50% of the cells without causing toxicity, were found at very low surfactant/DNA charge ratios (1/1–2/1). The most efficient complexes presented sizes suitable for intravenous administration and negative surface charge, a feature known to preclude potentially adverse interactions with serum components. This work brings forward a new family of gemini surfactants with great potential as gene delivery systems.

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