Investigation of the structural organization of cationic nanoemulsion/antisense oligonucleotide complexes

Structural organization of antisense oligonucleotide molecules on the oil/water interface of cationic nanoemulsions, as suggested by energy dispersive X-ray diffraction and atomic force microscopy studies. •Cationic nanoemulsions presented dimension of a lamellar structure organization.•Oligonucleotide molecules led to a disorganization of the lipid arrangement.•A flattening phenomenon of emulsion droplets was observed by AFM experiments.•Oligonucleotides molecules on the surface of emulsion droplets prevent their fusion. Atomic force microscopy image analysis and energy dispersive X-ray diffraction experiments were used to investigate the structural organization of cationic nanoemulsion/oligonucleotide complexes. Oligonucleotides targeting topoisomerase II gene were adsorbed on cationic nanoemulsions obtained by means of spontaneous emulsification procedure. Topographical analysis by atomic force microscopy allowed the observation of the nanoemulsion/oligonucleotide complexes through three-dimensional high-resolution images. Flattening of the oil droplets was observed, which was reduced in the complexes obtained at high amount of adsorbed oligonucleotides. In such conditions, complexes exhibit droplet size in the 600nm range. The oligonucleotides molecules were detected on the surface of the droplets, preventing their fusion during aggregation. A lamellar structure organization was identified by energy dispersive X-ray diffraction experiments. The presence of the nucleic acid molecules led to a disorganization of the lipid arrangement and an expansion in the lattice spacing, which was proportional to the amount of oligonucleotides added.