Oligonucleotide Adsorption Affects Phase Transition but Not Interdigitation of diC14-Amidine Bilayers

Abstract

In this work, we investigate the effect of a small singlestranded oligonucleotide (ODN) on the colloid stability and structure of cationic diC14-amidine liposomes. Dynamic light scattering (DLS) shows that small, stable, anionic assemblies are formed in presence of excess ODN negative charge. This charge overcompensation condition was further characterized. A less cooperative bilayer phase transition is observed by differential scanning calorimetry (DSC). Electron spin resonance (ESR) spectra of probes at different bilayer depths show that ODN electrostatic adsorption increases the rigidity of both interdigitated gel and lamellar fluid phases. The increase in gel phase rigidity could be explained by the transformation of an adjacent to an interpenetrated interdigitation. Interdigitated fusogenic bilayers may find interesting applications in delivery of therapeutic oligonucleotides.

The effect of an oligonucleotide on the structure of cationic DODAB vesicles

“…The absence of interdigitation might explain why ODN adsorption increases the phase transition temperature for DODAB (Fig. 2) but decreases for diC14-amidine, 58 as previously noted.…”

“…However, electrostatic shielding is not the only driving force behind thermotropic behavior changes upon polyelectrolyte adsorption, since ODN was shown to decrease the phase transition temperature of interdigitated cationic diC14-amidine bilayers. 58 In fact, ODN adsorption onto DODAB vesicles simultaneously induces an increase in transition temperature and a decrease in transition cooperativity (Fig. 2).…”

Structural insights on biologically relevant cationic membranes by ESR spectroscopy

“…13 Scheme of adjacent (a) and interpenetrated (b) interdigitated gel phases of diC14-amidine bilayers. (Adapted from Rozenfeld et al 2013, copyright 2013 headgroups increased the rigidity of both the gel and fluid phases (Rozenfeld et al 2013). As previously described, gel phase diC14-amidine bilayers display an interdigitated gel phase in which molecules are packed side by side and flipped horizontally from one to the other (Oliveira et al 2012;Pabst et al 2012).…”

Phase behavior of selected artificial lipids

“…In the case of diC14-amidine one extra CH 2 atom in the backbone is thought to space the tails apart a bit more than natural, leading to an ease of chain interdigitation [27].…”