DNA and cationic surfactants at solid surfaces

The behavior of DNA at different types of interfaces and how the formed structures DNA at an interface could be affected by cationic surfactant has been studied. Particular attention was paid to how the type of cationic surfactant and DNA (single or double stranded and length) affects the compaction/decompaction of DNA. Adsorption of DNA–cationic surfactant complexes is determined by a delicate balance of DNA–surface, cationic surfactant–surface, and cationic surfactant–DNA interactions. DNA do not adsorb on hydrophilic negatively charged surfaces due to effective electrostatic repulsion between DNA and the surfacs. However, the interaction between DNA cationic surfactant ions leads to a substantial adsorption of the formed DNA–cationic surfactant complex once the charge density of both the DNA macromolecule and the surface is sufficiently decreased. On hydrophobic surfaces, where both DNA and cationic surfactant interact with the surface, the presence of the cationic surfactant leads to a considerable increase in adsorbed amount and a significant layer compaction of DNA. The stability of the mixed adsorbed layer largely depends on the strength of the interactions between DNA and the cationic surfactant, as well as between the surface and the cationic surfactant. DNA interacts with small latex particles in a similar way as to the macroscopic hydrophobic flat surfaces.