Complexes of polycations and DNA, also known as polyplexes, have been extensively studied in the last decades, as potential gene delivery systems. Their stability depends strongly on the characteristics of the polycations, as well as the nature of the added salt. We present here a study of the DNA ionene complexation in which we used UV and CD spectroscopy, combined with the molecular dynamics computer simuations, to systematically examine the influence of the polycation charge density, as well as the influence of the nature of the counterion, on the stability of these systems. Ionenes as polycations have previously been found to posses low cytotoxicity, and are therefore particularly interesting as potential gene delivery agents. The results show that the DNA solutions in the presence of the polycation are more stable in the case of very large or very small ionene charge density, suggesting different mechanism of complexation. The computer simulations show that the ionenes with high charge density bind to the minor groove of the DNA molecules, while the ionenes with lower charge density bind to the major groove of the DNA. The nature of the counterions play only a minor role: precipitation of the DNA molecules occurs at slightly lower ionene concetration when fluoride counterions are present, compared to the bromide counterions.

Role of ion-specific effects in DNA/ionene complexation

253rd National Meeting (2017)

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