Light and host-guest inclusion mediated salmon sperm DNA/surfactant interactions

DNA/cationic surfactant interaction is relevant from the viewpoint of gene therapy, where the complexation and resulting compaction are essential to protect DNA from nuclease, and to allow entry of DNA into cells. In this work, light input and host-guest inclusion controlled DNA complexation by a novel cationic surfactant 1-[6-(4-phenylazo-phenoxy)-hexyl]-3-methylimidazolium bromide (AzoC6Mim) is reported. The surfactant is covalently attached with an azobenzene group, which undergoes reversible photoisomerizations by changing light input. Under visible light, trans-AzoC6Mim can bind to salmon sperm DNA through electrostatic attraction and hydrophobic interaction, resulting into DNA compaction. Under UV light, although cis-AzoC6Mim still binds to DNA chain, DNA/surfactant complex is decompacted owing to the decrease of surfactant hydrophobicity. On the other hand, azobenzene group can form an inclusion complex with α-CD through host-guest interaction, which removes AzoC6Mim from DNA chain and decompacts the DNA/surfactant complex.