Some Quantum Dots Application For DNA Detection And Their Damage Toward DNA

Quantum dots (QDs) have been extensively studied because of their unique size-dependent electronic, magnetic, optical and electrochemical properties. Quantum dots have many potential usages in many fields such as biochemistry, cell biology, immuno-biology etc. Especially, quantum dots can be used as labels for biological systems. However, an existing major argument that may limit their use in medicine and biology is the toxicity of QDs, which has attracted great attention in the past decade. Each individual type of QDs possesses its own unique physicochemical properties, which in turn determine its potential toxicity or nontoxicity. DNA as an important biomolecule of living systems may be oxidatively damaged by a large number of chemical and physical agents. Among them, reactive oxygen species (ROS) are regarded as main DNA oxidative damage reagents. Under UV irradiation, QDs have been reported to produce ROS, which can result in dsDNA breakage.In this paper, the study mainly consists of two aspects. 1: Bismuth sulfide nanoparticle surface-modified with polyvinylpyrrolidone was synthesized under hydrothermal conditions, and used as a marker to label the DNA probe. Target DNA was immobilized covalently on carbon paste electrode modified with gold nanoparicles, and then hybridized with the probe DNA labeled with bismuth sulfide nanoparticle. The hybridization events were monitored by detection of Bi3+ via polarographic complex adsorptive wave. The proposed method showed a good distinguishable ability to one base mismatched or the noncomplementary DNA sequences with the complementary DNA sequences. 2: An electrochemical sensor for the detection of the natural double-stranded DNA (dsDNA) damage induced by different QDs (PbSe QDs, CdSe QDs) under UV irradiation was developed. The biosensing membranes were prepared by successively assembling polycationic poly (diallyldimethyl ammonium) and dsDNA on the surface of the different electrodes. Damage of dsDNA was fulfilled by immersing the sensing membrane electrode in different QDs (PbSe QDs, CdSe QDs) suspension and illuminating it with an UV lamp. Cyclic voltammetry was utilized to detect dsDNA damage with Co(phen)33+ as the electroactive probe. The dsDNA damage induced by PbSe QDs under UV irradiation with CdSe coexisting has been partly investigated. Moreover, the oxidized dsDNA has been repaired simply. This electrochemical sensor provided a simple method for detecting DNA damage, and may be used for investigating the DNA damage induced by other QDs.