The Study Of DNA Aggregation And DNA/Chitosan Complex

As two kinds of important biological materials, DNA and chitosan (CS) werewidely used in various fields in recent years. In1995scientists found that chitosanand DNA could bind to each other through electrostatic interaction and since thenchitosan was frequently used as gene vector. This novel vector was harmless to livingorganisms and had good biocompatibility thus replaced the original viral vector.Based on these findings this study evaluated the factors that affect DNA aggregationwith CS, and used the formed DNA/CS complex to embed fat-soluble carotenoids(Car): β-carotenoids and astaxanthin. In order to improve the water-soluble capacityand stability of carotenoids, a variety of methods were employed for DNA/CS/Carnano-complex system microstructure characterization and stability determination, andthis study also helped to broaden the applications of carotenoids to be used in thepharmaceutical, food and other fields.The contents of this study can be mainly divided into three parts:(I) explore theinfluence of experimental conditions on DNA aggregation, including the solution pHvalue, temperature, ionic strength on various concentrations and molar weights ofDNA. The results show that under pH1.5, the aggregation of DNA is independentwith concentration, molar weight, solution ionic strength and temperature. Meanwhile,the aggregation of DNA is a reversible reaction-about74%of the aggregated DNAcan be redissolved by adding neutral buffer or ddH2O;(II) based on the work of part I,this study further investigate the influence of cationic compounds (glucosamine,chitosan oligosaccharide and chitosan) to the aggregation of DNA. Under acidicconditions (pH1.5-7.0), the addition of chitosan oligosaccharide and chitosan cangreatly accelerate the aggregation of DNA to form DNA/CS complex, the DNA canbe aggregated even under pH7.0when the amino/phosphate ratio is1:1. However, theglucosamine has no significant effect on the aggregation of the DNA;(III) dependingon the self-assembly between DNA and CS by non-covalent interactions, this studyemployed salmon sperm DNA and CS as wall materials to assembly DNA/CS complex to embed β-carotenoids and astaxanthin. The diameters of formedcarotenoids colloid were ranged from100to500nanometers approximately, and thehighest embedding ratio achieved70%. The relative stable carotenoids colloid couldbe stored under low temperature for long periods thus effectively avoid theastaxanthin or β-carotenoids loss.In conclusion, this study evaluated the comprehensive impacts of pH,temperature, ionic strength, DNA concentration, molecular weight and cationiccompounds on DNA state presented in solution and could provide some reference forfurther research. Successful realized the embedding of fat-soluble carotenoids withDNA/CS complex to form stable colloid to dissolve in water. The newly formedwater-soluble and stable nano-complex has broad application aspects in food andmedicine fields.