Study On DNA Adsorption And Desorption To Silica/F_e3O₄ Composite Nanospheres

Nucleic acid separation and purification is one of the most important steps of molecular biology and modern medical research. In recent years, Magnetite-SiO2 Beads Adsorption Method became a popular separation and purification method which includes three steps, adsorption, washing and desorption. Thus, in nucleic acid separation and purification process, the study of solid-phase adsorption and desorption performance is extremely important.The methodology of DNA adsorption and desorption to silica nanospheres were studied. Two DNA concentration correction methods, Converted Method and Reference Method, were introduced in this paper. The adsorption of salmon sperm DNA to silica was investigated by these two methods, separately. The results show that Reference Method is more appropriate for adsorption isotherm drawing. According to the influence of Na+, the UV absorbance of high concentration DNA solution is lower than the actual value so that Converted Method is unreasonable. Reference Method is the basic methodology of further study on DNA adsorption and desorption to silica/Fe3O4 composite nanospheres.Then, nine Fe3O4/silica composite nanospheres with different silica thickness were synthesized by sol-gel method. The adsorption and desorption performance of these nanospheres were systematically studied. On one hand, the saturation adsorption capacity of salmon sperm DNA and the initial slope of adsorption isotherms were obtained. On the other hand, elution efficiency was investigated. It is found that by decreasing TEOS addition, the surface area of nanosphere is increased and the saturation adsorption capacity of salmon sperm DNA is enhanced. This provides guidelines of optimizing the surface structure and morphologies of Fe3O4/silica composite nanospheres.In addition, morphology, adsorption and desorption performance of two different mesoporous silica/Fe3O4 composite nanospheres were investigated. Optimizing the adsorption and desorption time, the principle of adsorption was studied. Through the saturation adsorption capacity and the initial slope of adsorption isotherms, it is found that pore volume, pore diameter and surface area of the mesoporous silica/Fe3O4 composite nanospheres have a great influence on DNA adsorption performance.Finally, DNA, with different length, adsorption to these two kinds of silica/Fe3O4 composite nanospheres was studied. The saturation adsorption capacity of salmon sperm DNA, calf thymus DNA andλ-DNA to different nanospheres were compared. Meanwhile, adsorption performance of these three different DNA was learnt. Different models of DNA adsorption on silica/Fe3O4 composite nanospheres were proposed.This study provides guidelines of designing the structure and surface morphology of silica/Fe3O4 composite spheres and builds foundation of systematic research of mesoporous silica/Fe3O4 composite spheres.