Functionalized SiO 2 Nanoparticles Interact With DNA And Hg 2+ And Pb 2+ Electrochemiluminescence Analysis

Heavy metal pollution has become an important global issue for years arising from a variety of natural processes and human activities. Accumulation of heavy metal in the bodies of humans and animals can lead to serious illnesses. Therefore, the development of a sensitive, low-cost and environmentally friendly method for the determination of heavy metal ions has become an urgent need. Most of previously reported metal ion detection methods required a procedure of complex labeling, immobilization or surface functionalization chemistry. In this case, it was time-consuming and high-cost. Therefore, the development of metal ion detection methods that are label-free, immobilization-free approach is of great significance.Electrochemiluminescence detection method can widely be applied due to its the simple equipment, high detection sensitivity and ease of control. Nanomaterials possess unique optical, electronic, magnetic, and catalytic properties, which make them ideal candidates for signal generation and transduction in developing novel sensing platforms. This thesis combined nanoparticles, ECL analytical method and DNA probe together to realize a label-free, immobilization-free detection for metal ion.This paper mainly consists of two parts.The first part is the review section which briefly described DNA probe and focused on the metal ion detection method using DNA as the probe.The second part is research report section which mainly consists of the following two parts:1. The interaction of Silica/Ru?bpy?₃²⁺/Chitosan nanoparticles with DNA and ECL analysis study of Hg2+The electroactive Silica/Ru?bpy?₃²⁺/Chitosan nanoparticles ?SRCNPs? presented the large differential affinty ability for single-stranded DNA ?ssDNA? probe and ssDNA/target complex. By taking advantage of this differential effect and the T-rich DNA probe recognition Hg+ as the model system, we put forward a sensitive, label-free and immobilization-free ECL sensing scheme for detecting Hg2+. In the absence of Hg2+, ssDNA probes were strongly adsorbed on the surface of SRCNPs and formed the SRCNPs/DNA nanocomposites. Because the SRCNPs/DNA nanocomposites charged negatively, the electrostatic repulsive force between Nafion film and SRCNPs/DNA nanocomposites reduced the adsorption of nanocomposites onto the surface of Nafion/CNT modified electrode and produced the weak ECL signal. In the presence of Hg2+, they reacted with ssDNA probes to form the ssDNA/Hg complexes by T-Hg-T coordination chemistry. This double-stranded structure of ssDNA/Hg complexes were not easy to be adsorbed on SRCNPs, so SRCNPs existed in their free-state. In this case, the free-state SRCNPs could be effectively assembled on Nafion/CNT electrode and produced stronger ECL signal. Based on this ECL signal difference, a 0.3 pM detection limit for Hg2+ was achieved with the proposed ECL sensing scheme. Compared with the previously reported ECL methods for Hg???, the proposed ECL method has a higher sensitivity for Hg???.2. The interaction of Silica/Ru?bpy?₃²⁺/PVP nanoparticles with DNAzymes and its application for ECL detecting Pb²⁺.The Silica/Ru?bpy?₃²⁺/PVP nanoparticles ?SRPNPs? were synthesized by reverse microemulsion method. The morphology and optical characteristics of the synthesized SRCNPs were characterized by TEM, UV-vis and fluorescence spectra methods. Furthermore, based on the large differential affinity ability of SRPNPs towards the DNAzymes and single-stranded DNA fragments from Pb??? inducing DNAzyme reaction, a label-free, immobilization-free ECL method for Pb²⁺ was developed.