The Synthesis Of Several Metal Complexes That Recognize SS- And DS- DNA And The Application In GMP Biosensor

Deoxyribonucleic acid (DNA) is the carriers of hereditary information and thebasic substance of gene expression, and plays key roles in the growth, developmentand breeding of lives. So, the probing on the structure and properties of DNA viainvestigating the interaction of metal complexes and DNA is an important branch andhot point in the field of bioinorganic chemistry, which will help to realize the actionmechanism of drugs and toxic reagents, and to develop novel anti-cancer drug andnew biological technologies. Meanwhile, the metal complexes that can recognize thestructure and special site of DNA have outstanding theory studies and practicalapplication values in much more fields.Genetically modified plants (GMP) are the products of the rapid development ofgenetic engineering technology, which benefits the people as well as also arise thepotential risks of environment and health. So, it is very necessary to establish andstrengthen the rapid and accurate detection technologies for the safety evaluation ofGMP. Electrochemical DNA biosensor, a kind of technology that involves severalfields, such as biological chemistry, electrochemistry, medical science, and electronicscience, et al., can satisfy the acquirement of GMP detection. This technology has theadvantages of simplicity, accuracy, inexpensiveness, sensitivity and well-selectivity,and also can be compatible with DNA chips technology. The design, choose and use ofperfect hybridization indicators are one of the valuable work in DNA biosensor. Metalcomplex-based indicators are a series of promising indicatofs, which have thecharacteristics of easy synthesis process, abundant kinds, sensitive optical andelectrochemical signals and controllable function modification, et al. The metal complex-based indicators have been widely used in DNA electrochemical biosensors.In this paper, several transitional metal complexes were synthesized andcharacterized. The different binding actions of these complexes to single-strandedDNA (ssDNA) and double-stranded DNA (dsDNA) were investigated by spectral andelectrochemical methods, and the binding modes and mechanism were discussed andproposed. Several electrochemical DNA biosensors were manufactured by differentprotocols and the gene probes were successfully deposited at the electrode surface.Some of synthesized metal complexes were used as indicators to detect the targetsequences related to GMP.(1) The complexes, such as binuclear iron complex, {[Fe(phen)(H₂O)₃]₂O}⁴⁺;mixed-ligands copper complexes containing polypridyl moiety,Cu(phendione)(DAP)]²⁺ (phendione=1, 10-phenanthroline-5, 6-dione, DAP=2, 3-diaminophenazine) and Cu(bpy)(MBZ)₂ (MBZ=p-methylbenzoate); electron-neutralcharge cobalt comlex, Co(Eim)₄(NCS)₂ (Eim=1-ethylimidazole); and low molecularweight and water-soluble chitosan copper and cadmium complexes, were synthesized.The molecular structures and physicochemical properties of these complexes werecharacterized by X-ray diffraction analysis, elemental analysis, spectral analysis andelectrochemistry, et al.(2) The electrochemical properties and mechanism of the metal complexesthemselves were obtained by several electrochemical methods, such as cyclicvoltammetry, differential pulse voltammetry, chronocoulometry and electrolysis, et al.The conditions of the electrochemical reaction were optimized.(3) The interactions of each metal complex with DNA in solution were studied viaspectral methods (electronic absorption spectra and emission spectra) and differentelectrochemical methods. The recognition mechanism of each complex to the structuredifference of dsDNA and ssDNA was proposed by analyzing the varies of spectral andelectrochemical signals of the complexes after interaction with DNA. The bindingconstant, binding site, and electrochemical parameters such as electron transfercoefficient and electron transfer rate constant were also obtained by electrochemicalassays.(4) The dsDNA and ssDNA modified electrodes were prepared by directadsorption method, and were used to study the interactions with metal complexes atthe electrode surface. The binding mechanism, binding parameters and electrochemicaldata were also obtained by this micromethod. (5) The gene probes, such as CaMV35S (35S promoter from cauliflower mosaicvirus), PAT (phosphinothficin N-acetyltransferase gene) related to GMP, wereimmobilized at the transducer by covalent binding or electrostatic interaction, resultingin DNA electrochemical biosesors. [Cu(phendione)(DAP)]²⁺, Co(Eim)₄(NCS)₂,Cu(bpy)(MBZ)₂ and CHTCd were used as electroactive hybridization indicators todetect the target sequences, and obtained good selectivity and linear range, showingthat the electrochemical biosensors can be used for the qualitative and quantitativedetection of GMP.