The Aggregation Behavior,Aggregation Structures And Properties Of DNA And Catanionic Surfactants

DNA,the natural functional biomacromolecule,has expanded beyond its gene carrier role to applications in nanotechnology,material science,biomedicine and other fields in recent years.DNA molecules are considered the most promising molecular building blocks due to their unique molecular recognition,accurate structural design,and excellent biocompatibility.The phosphate groups in DNA can self-assemble with the polar groups of cationic surfactants to construct multifunctional DNA complex materials by electrostatic interaction.The self-assembly behaviors of DNA and catanionic surfactants were studied in the aqueous and solvent-free environment.We studied the phase behaviors of DNA/surfactant systems,the basic physical and chemical properties of the DNA complexes,and the effect of stimuli-responsive surfactants on the structures and properties of DNA self-assembly materials in detail.The contents of the dissertation are as follows:Chapter ?:Introduction.The concepts of self-assembly,DNA molecular structures,DNA self-assembly modes driven by multiple interactions,basic structures and properties of surfactants were introduced.The structures,properties and formation mechanisms of the catanionic surfactant vesicles were discussed in detail.The process and mechanisms of ionic self-assembly of DNA and surfactants were discussed,and the influences of the driving force,DNA and surfactant molecular structures,solvent environment on the DNA self-assembly process were analyzed.The functional applications of DNA/surfactant complex materials were summarized.Finally,the purpose,research contents and significance of the dissertation are summarized.Chapter ?:We studied the vesicle transition of catanionic redox-switchable surfactants regulated by DNA with different chain lengths.The redox-responsive cationic surfactant,(11-ferrocenylundecyl)-trimethylammonium hydroxide(FTMOH)was synthesized.FTMOH self-assembled with lauric acid(LA)to form catanionic salt-free vesicles(FTMOH+LA? FTML+H2O),in which the concentration of FTMOH was in excess to ensure that the FTML vesicles are positively charged.The positively charged FTML vesicles self-assembled with DNA by electrostatic interaction,the structures of DNA/FTML complexes could be controlled by DNA with different chain lengths.Cryo-TEM images revealed that short-chain DNA with 50 bp could act as anionic glue in the construction of catanionic bilayer vesicles to form tubular vesicles Medium-long DNA of 250 bp adsorbed onto FTML vesicles via electrostatic interactions to produce slightly thickened DNA vesicles.Long-chain DNA with 2000 bp could fabricate super-wall thickened DNA vesicles with an average wall thickness of 14.0 nm.The rigid skeletons of FTML vesicles,the greater number of charges and more flexible of long-chain DNA may account for the construction of the super-wall thickened DNA vesicles.Besides,the super-wall thickened DNA vesicles can even undergo structural rearrangement to generate over-sized bilayer vesicles by redox stimulation.This facile noncovalent self-assembly may inspire the innovative use of DNA as the structural motif to construct DNA/surfactant nanomaterials,and our observations may prove useful in constructing nano-vehicles and soft-template capsules.Chapter ?:The preparation and properties of long-range ordered DNA thermotropic liquid crystals are studied based on the electrostatic self-assembly of surfactant vesicles and single-strand DNA(ssDNA).The single-chain cationic surfactant,dodecyltrimethylammonium bromide(DTABr),cannot form thermotropic liquid crystals with ssDNA.DTABr was mixed with anionic sodium laurate(NaL)to form positively charged catanionic bilayer vesicles(DTABr+NaL?DTAL+NaBr).The DTAL vesicles exhibit an ability to interact with phosphate groups of ssDNA due to electrostatic force for forming long-range ordered DNA/surfactant lamellar structures through freeze-drying DNA/vesicle complexes.The physicochemical properties(phase transition temperature,rheological properties,layer spacing)of DNA thermotropic liquid crystals could be manipulated by DNA concentration.We believe that the method of building DNA thermotropic liquid crystals based on ssDNA and catanionic vesicles will greatly expand the selection range of surfactants and bring novel inspiration for researchers to prepare biomacromolecular solvent-free liquid crystals.Chapter ?:The DNA solvent-free liquid crystals were constructed of ssDNA and positively charged bilayer vesicles that were prepared by NaL and cationic surfactants with different structures.The effects of surfactant structures(hydrophobic chains,polar groups)on DNA solvent-free liquid crystal were explored.The cationic surfactants,(11-ferrocenylundecyl)-trimethylammonium bromide(FTMBr)and 1-dodecylpyridinium bromide(DPBr)constructed with NaL,respectively,for forming FTML and DPBL bilayer vesicles in solution.Both of the FTML and DPBL bilayer vesicles could successfully prepared DNA/surfactant thermotropic liquid crystals with ssDNA,indicating that the tactic of DNA thermotropic liquid crystals constructed by catanionic vesicles and DNA has a universality which can eliminate the influence of surfactant structures.The properties of DNA thermotropic liquid crystals were found to be manipulated by both the chemical structures of cationic and anionic surfactants and the DNA amount.By introducing responsive motifs into catanionic vesicles,versatile anhydrous DNA thermotropic liquid crystals could be constructed,which should expand many technological applications of DNA liquid crystals.