| Under the push of the"human genome project", the study of DNA diagnosis and treatment are developed rapidly and various technologies in the fields of disease diagnosis or drug screening have been greatly advanced.Most anti-cancer drugs work through the interactions with DNA in tumor cells. Investigating the interaction mechanism of metal or metal complex with biomolecule, such as DNA, protein and amino acid, provides a starting point for the diagnosis of human disease. Schiff base complexes have been proved to have biological activities in many fields, such as anti-cancer, antibacterial, and interactions with DNA, which causes widespread concern in the scientific community. In recent years, several reports on the interactions of Schiff base complexes with DNA have been published. However, there are rarely reports about the comparison of the interaction mechanism between homologous series of Schiff base complexes and DNA. So to summarize differences of the interactions between homologous series of Schiff base metal complexes and DNA is valuable for drug screening.The recognition and detection of DNA in the human blood, organization or body fluid sample have become more and more important for drug research and development, diseases diagnosis and environmental pollution control. DNA electro chemical sensors hold an enormous potential for the DNA recognition, detection of DNA damage, drug screening or disease diagnosis. It provides an inexpensive, non-pollution, sensitive, easy-to-use and fast response device which therefore stays in the center of interest of many biomedical scientists. At present, many new procedures are under intense investigation in order to improve the function of DNA electrochemical sensors and to meet the new challenges connected to the simple, fast response of low levels DNA in different fields.This dissertation aims to study the interaction mechanism between homologous series of Schiff base complexes and DNA. Moreover, nanomaterials and nucleic acid hybridization technique are introduced to develop two novel DNA electrochemical sensors. The main researches are as follows:(1) The interaction mechanism of [CuL(CH3COO)(H2O)]·H2O and [CoL (CH3COO) (H2O)] with DNA was studied by means of electrochemical methods. Uv-vis spectroscopic methods validated the results. The interaction mode of two Schiff base complexes with deoxyribonucleic acid are intercalation and binding constants are 3.24×104 L·mol-1, 1.36×104 L·mol-1, respectively. Two complexes have the irreversible electrochemical redox reaction process in electrode. The binding functions of Schiff base complexes are positively related to the concentration. The binding functions of Schiff base complexes are stronger than the ligand. The binding constant of [CuL(CH3COO)(H2O)]·H2O is greater than the [CoL(CH3COO)(H2O)]. Meanwhile, experimental results demonstrate that using [CuL(CH3COO)(H2O)]·H2O or [CoL(CH3 COO)(H2O)] as electrochemical probes could detect 2.0×10–5 mol·L-1 1.2×10–4 mol·L-1 or 1.0×10–5 mol·L-19.0×10-5 mol·L-1 DNA in solution, respectively.(2) The interaction mechanism of [CuL1(H2O)3] and [Cu3(L2)2(CH3COO)2 (H2O)]·2H2O with DNA was studied by means of electrochemical methods. Uv-vis spectroscopic methods validated the results. The interaction mode of two Schiff base complexes with deoxyribonucleic acid are electrostatic force and binding constants are 9.6×103 L·mol-1,5.46×103 L·mol-1, respectively. Two complexes have the irreversi ble electrochemical redox reaction process in electrode. The binding functions of Schiff base complexes are positively related to the concentration. The binding functions of Schiff base complexes are stronger than the ligand. The binding ratios are related to the planar area of the complexes. Meanwhile, experimental results demonstrate that using [CuL1(H2O)3] or [[Cu3(L2)2(CH3COO)2(H2O)]·2H2O as electro chemical probes could detect 1.0×10-5 mol·L-19.0×10-5 mol·L-1 or 2.0×10-5 mol·L-1 9.0×10-5 mol·L-1 DNA in solution, respectively.(3) The interaction mechanism of [C19H11NO5Cu]n·n CH3CH2OH, [C16H10O6NCu]n·2nH2O and [C15H9NO5Cu]n·n(CH3CH2OH)(H2O) with DNA was studied by means of electrochemical methods. Uv-vis spectroscopic methods validated the results. The interaction mode of three Schiff base coordination polymers with deoxyribonucleic acid are intercalation. Three coordination polymers have the irreversible electro chemical redox reaction process in electrode. The binding functions of Schiff base coordination polymers are positively related to the concentration. The binding functions of Schiff base coordination polymers are stronger than the ligand. The binding constant of [CuL(CH3COO)(H2O)]·H2O is greater than the [CoL(CH3COO) (H2O)]. No matter whether there are some flat areas like naphthalene molecular in the structure, all the coordination polymers showed intercalation with DNA. It is speculated that this might be caused by the special structure of coordination polymer. Meanwhile, experimental results demonstrate that using [C19H11NO5Cu]n·nCH3 CH2OH, [C16H10O6NCu]n·2nH2O or [C15H9NO5Cu]n·n(CH3CH2OH)(H2O) as electro chemical probes could detect 0.4×10-5 mol·L-14.0×10-5 mol·L-1, 1.0×10-5 mol·L-1 1.2×10-4 mol·L-1 and 1.0×10-5 mol·L-1 1.2×10-4 mol·L-1 DNA in solution, resp ectively.(4) An novel electrochemical DNA detection method was developed based on the Nanoporous Gold Electrode (NPG) and singal multiple amplification with two different diameters of DNA-Au bio-barcodes. The target DNA signal amplification assay used here was fabricated by immobilizing probe DNA on the NPG electrode and then being hybridized with one end of target DNA. The other end of target DNA was further hybridized with the linker DNA loaded on the carboxyl group modified Au NPs of 30 nm. To further amplify the target DNA signals, the immobilized 30 nm Au NPs was also modified with 13 nm DNA-Au bio-barcodes which were labelled many reporter DNA. In this means, one target signal could be transformed into multiple signals of the markers since a single 30 nm Au NP could be loaded with dozens of 13 nm Au NPs, and an 13 nm Au NPs could be loaded with thousands of signal DNA. Electrochemical signals of [Ru(NH3)6]3+ bound to the signal DNA via electrostatic interactions were measured by chronocoulometry (CC). Using NPG electrode as the platform for fixing DNA probes has two advantages, one is because NPG electrode has larger surface area than the gold electrodes which makes it fixed more DNA probes. In addition, NPG electrode has high conductivity which further enhances the sensor sensitivity. Combining the two advantages of DNA-Au bio-barcodes and the NPG electrode, this assay could detect as low as amol·L-1 target DNA and exhibited excellent selectivity against one-base mismatched DNA. This DNA biosensor could detect DNA target quantitatively in the range of 8.0×10-16 mol·L-1 to 5.0×10-17 mol·L-1, with the detection limit of 2.0×10–17 mol·L-1 and exhi bited excellent selectivity even for single-mismatched DNA detection.(5) An ultrasensitive electrochemical DNA detection method was developed based on multiple amplification of Nanoporous Gold Electrode, DNA-Au bio-barcodes and dithiothreitol-induced oligonucleotide releasing from bio-barcodes. Its innovations has two aspects: first, using carboxyl modified nanoscale magnetic beads as the carrier of probe DNA in order to capture more target DNA. The probe DNA which was immobilized in the magnetic beads captured the specific target DNA and then assembled layer-by-layer with the two different diameters of modified Au NPs. And the detection of target DNA is transformed into directly measure the amplified amount of reporter DNA, which greatly improve the detection sensitivity. Second, this assay relied on the ability to liberate the adsorbed thiolated oligonucleotides from the gold nanoparticle surface with dithiothreitol (DTT). DTT was added to break up disulfide bonds and remove the reporter DNA from the surface of the layer-by-layer assembly magnetic beads. After magnetic separation, DTT-released reporter DNA were subsequently detected using the"sandwich-type"NPG-DNA assay by chronocou lometry (CC) analysis. The"sandwich-type"NPG-DNA assay was fabricated by immobilizing probe DNA on the NPG electrode and being hybridized with DTT-released reporter DNA which further hybridized with the barcode DNA loaded on the Au NPs. Electrochemical signals of [Ru(NH3)6]3+ bound to the reporter DNA via electrostatic interactions were measured by chronocoulometry (CC). Under the optimum conditions, this assay could detect as low as 0.12 amol·L-1 target DNA and exhibited excellent selectivity against one-base mismatched DNA.
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