Preparation And Application Research Of IDA-APS Modified Silica Particles

Extraction of DNA is a routine work for their biological andmedical applications. In the majority of reported methods, DNA extraction wasmainly based on electrostatic or coordination interaction. Modification of silicasurface with cationic groups was a common approach to DNA extraction byelectrostatic interaction, as DNA molecule behaves a negatively chargedpolyelectrolyte under physiological conditions. If molecules with negative groups wasintroduced on the silica surface at the same time, DNA could be desorbed from theparticles with electrostatic repulsion. The method based on electrostatic interactionhas the advantage of high extraction efficiency, but the characteristic of non-specificadsorption lead to a low purity of the extracted DNA. On the other hand, DNA can beextracted selectively by immobilization of metal ions on the surface of the silicaparticles via coordination interaction between metal ions and phosphate groups ofDNA molecules. The method based on coordination interaction shows specificadsorption, while the desorption of DNA become very difficult as the coordinationinteraction is too strong. As a result, we designed a kind of particles, combining theelectrostatic with coordination interaction, to achieve DNA extraction with highefficiency and specificity. The main content of the thesis as following: 1.200nm silica particles were co-modified with iminodiacetic acid (IDA) andaminopropyltrimethoxy silane (APS), which provided charge reversible surfacedue to carboxyl and amine groups. At pH lower than the IEP, DNA could beabsorbed effectively on the particle surface via direct electrostatic interactions.While at pH higher than the IEP, the absorbed DNA could be desorbed almostcompletely driven by the electrostatic repulsion between DNA and the particlesurface. High DNA adsorption (100%) and desorption efficiency (80%) could beachieved by tuning IDA/APS concentration modified on the particles.2. Fe3+was immobilized on the IDA/APS co-modified silica particles to form theFe3+-IDA-APS-SiO2particles. DNA could be absorbed efficiently (～100%) onthe Fe3+-IDA-APS-SiO2particles surface at pH3.0and desorbed efficiently (～85%) at pH10.0. The DNA extraction were related to the kinds of metal ions,and the ferric ions showed stronger affinity than other metal ions investigated,such as zinc ions, copper ions. Furthermore, the particles could selectivelyextract DNA from the mixture of bovine hemoglobin (BHb) and DNA.Compared to the DNA extraction approaches relying solely on the electrostaticinteraction or coordination, the novel particles showed the advantages of highefficiency and high specificity, which should be attributed to the cooperativityfrom electrostatic and coordination interactions.