Oligonucleotide Generated Single-chain Cationic Surfactant Vesicles Induced

By using conductivity meter, UV-vis spectrometer, transmission electron microscopy, circular dichroism spectrometer, fluorescence microscopy and dynamic light scattering instrument, the interactions between oligonucleotides and single-chained cationic surfactants were investigated. The results showed that all the oligonucleotides in this paper other than oligo d(T)n can induce single-chained cationic surfactants to organize into vesicles when their concentrations are higher than a critical value, accompanying by the decrease of the base stacking in oligonucleotide. Hydrophobic and electrostatic interactions between oligonucleotide and surfactants are the main force for vesicle formation and the oligonucleotide is located in the bilayer of vesicles. The ability of oligonucleotide in inducing single-chained cationic surfactant to assembly into vesicles depends on the size and sequence of oligonucleotide; the facilitation efficiency of oligonucleotide with hairpin structure or larger size is higher. Moreover, it is easier for surfactants with smaller head group or shorter hydrophobic chain to assemble into vesicles in the presence of oligonucleotide.pH value, temperature and salt concentration also have effects on the formation of single-chained cationic surfactant/oligonucleotide vesicles. The inducibility of oligonucleotide on vesicle formation in acidic solution is almost the same as that under neutral condition. However, it is decreased under basic condition. Kinetic studies showed that vesicle formation is a consecutive reaction consisting of two first order reaction, and the intermediate shows rod-like structure.Further studies illustrated that when the salt concentration in the cationic surfactant/oligonucleotide mixed solution is higher than a critical value, an appropriate content of salt favors the vesicle formation. Furthermore, in the absence of salt, vesicles only fuse with increasing temperatures and this process is irreversible, whereas in the presence of salt, the increase of temperature could induce the fusion of vesicles first, followed by breakage to micelles and this process is reversible. Moreover, the effect of temperature on cationic surfactant/oligonucleotide/NaCl aggregation becomes obvious with the increase of salt concentration.