Study Of The Interaction Between Surfactants And DNA

Interaction between DNA and cationic surfactant has been paid much attention due to its implications for gene therapy, a conceptually new approach for the treatment of human disease. Although the interaction of DNA/cationic surfactant system has been fully studied, many studies are focused on the behaviors in bulk solution. Adsorption at air/water interface of complexes formed by DNA and surfactant complex, which are likely to interact between DNA /surfactant complex and cell membrane. By making clear the interfacial structure, we can control the interfacial adsorption of surfactant and therefore adjust the interfacial activity. However, because of less efficient techniques, the interfacial behavior of DNA/surfactant complexes has received relatively little attention both theoretically and experimentally. Meantime, the surfactants, which used in study between surfactants and DNA, are relatively singularity. Cetyltrimethylammonium bromide (CTAB) is the most often used one.Based on previous research results on the interaction between DNA and cationic surfactant, in this dissertation with aid of neutron reflection technique we put the emphasis on the study at the air/water interface. By making clear the interfacial interactions between DNA and Cetyltrimethylammonium bromide (CTAB), we furthermore design and synthesize some new type of gemini-cationic surfactants as well as a non-toxic sugar-based nonionicsurfactant alkyl polyglucoside (APG). For the first time, we use neutron reflection technique to study the adsorption of the above surfactant samples in the presence of DNA, in order to get an insight into the molecular-level interaction between DNA and surfactants and make clear the mechanism lying behind.This dissertation contains six parts: 1. Research progress on the interaction between DNA and surfactant; 2. Adsorption at air/water interface of complexes formed by DNA and dodecyl trimethyl bromide; 3. The influence of quaternary ammonium surfactant with various head group and alkyl chain structure on the formed DNA/surfactant complex; 4. Adsorption at air/water interface of complexes formed by DNA and Gemini quaternary ammonium with different counter ions; 5. Study on the interaction between DNA and sugar-based nonionic surfactant and 6. Study on the synthesis differences between alkyl polyglucosides of natural alcohol and oxo-alcohol. Research results are as follows:For the first time, neutron reflection technique combined with surface pressure and surface tension measurements, the interactions between dodecyl trimethyl bromide(CTAB) and salmon testes DNA(300 base pair) and calf thymus DNA(50,000 base pair) were studied. Adsorption data and the structural information of DNA/CTAB complex at air/water interface were obtained. Binding of CTAB on DNA at air/water interface can be divided into two stages. It can be deduced that strongly absorbed between DNAs and C!2TAB impose a new packing arrangement of the monolayer at the first stages through surface pressure measurement. At the second stage accompany with the surfactant concentration increase, DNA/ CTAB complex interface layer become thicker, indicating the condensation of DNA molecules.The influences of quaternary ammonium surfactant with various head andtails group on the formed DNA/surfactant complex were studied. The structure of complexes formed by these three samples, single-headgroup, single alkyl chain CTAB, single-headgroup, double-alkyl chain didodecyl dimethylammonium bromide DDAB and double-headgroup, double-alkyl chain didodecyl dimethyldiamonium bromide Ci2-C6-Ci2 and DNA at air/water interface as well as bulk phase is examined by neutron reflection and small angle neutron scattering. Obtained conclusions are that gemini surfactant is the most efficient compacting agent for DNA whether at air/water interface or in bulk phase and is a promising candidate for gene delivery.Adsorption at air/water interface of complexes formed by DNA and Gemini quaternary ammonium with different counter ions i.e., didodecyl diquaternaryammonium bromide, didodecyl diquaternaryammonium fluoride and didodecyl diquaternaryammonium sulfate are studied. Neutron reflection results have a good agreement with surface tension data in that the interaction between DNA and sulfate Gemini surfactant is stronger than the interaction between DNA and fluoride and bromide Gemini surfactants.As the gene delivery carrier, safety is one of the most important factors. Therefore we synthesize the non-toxic sugar surfactant alkyl polyglucoside and studies on the synthesis procedures. The interaction between non-toxic sugar surfactant alkyl polyglucoside and DNA was studied. Experimental results show that alkyl polyglucoside can interact with DNA, much stronger than other nonionic surfactants. This makes a potential breakthrough for choosing the mixed cationic/nonionic surfactant system as gene delivery carrier.