Amino-ethoxilated fluorinated amphiphile: Synthesis, self-assembling properties and interactions with ssDNA

Fluorinated compounds are not only more hydrophobic than their hydrogenated counterparts but also oleophobic. This makes them interesting for biomedical applications. They form a large variety of supramolecular architectures and, if appropriately designed, they spontaneously form vesicles. Herein we report the synthesis of novel monocatenar fluorinated surfactant, named F9NH(EO)2NH2, its use as ssDNA vector with potential applications in gene delivery or RNA interference. The molecular structure of the amphiphilic compound was designed in three parts: (i) a fluorinated hydrophobic tag responsible of self-assembling, (ii) a flexible and hydrophilic ethylenoxide moiety as polar head and (iii) a protonated at physiological pH primary amine responsible of binding. Surface tension, dynamic light scattering (DLS) measurements, and TEM studies showed that the monocatenar surfactant F9NH(EO)2NH2 spontaneously self-assembles into vesicles. This represents another example in addition to the few existing in the literature and it highlights the unique properties of the fluorinated tail. Interactions between ssDNA and cationic monocharged F9NH(EO)2NH2 were probed by static light scattering (SLS), fluorescence and circular dichroism (CD). F9NH(EO)2NH2 was found to exclude ethidium bromide (EB) from ssDNA/EB complex, and this process was dependent on the ssDNA concentration and on the charge ratio surfactant to ssDNA. CD spectra showed that by increasing the surfactant concentration, ssDNA undergoes a continuous conformational transition from native B-form to a more ordered phase (Z+/Z− ≤ 3) and then to a less ordered phase (Z+/Z− ≥ 4), which confirmed the results obtained by fluorimetry and SLS measurements. Cell viability studies reveled that monocatenar fluorinated surfactant F9NH(EO)2NH2 is not toxic for human cells (MRC-5) below 40 μM.