Studies On Interaction Mechanism Of Zn(Ⅱ), Cd(Ⅱ) And Co(Ⅱ) Of Morin Complexes With Deoxyribonucleic Acid And DNA Electrochemical Biosensor

In this article, three complexes of Morin with transitional metals were synthesized and characterized using IR and EA methods. Electrochemical techniques were used to study the interaction between these complexes and salmon sperm DNA to optimize conditions. Using electroactive Morin-Cd and Morin-Co as the novel hybridization indicators, the novel electrochemical DNA biosensors were developed respectively. These sensors were prepared through covalently immobilizing single-stranded DNA probes on different modified electrodes and using electroactive indicators to measure the hybridization events between the DNA probes and their complementary DNA fragments. The biosensors with good selectivity and sensitivity can be use for the really detection. There are three sections as follow.(1) With Morin as ligand, the complex Zn(C₁₅H₉O₇)₂-3H2O [abbreviated by ZnL2], was synthesized and characterized by means of IR and EA respectively. The interaction between the ZnL2 and double-stranded salmon sperm DNA was investigated by electrochemical methods in 0.2 mol·L-1 HAc-NaAc buffer solution (pH 5.0). The results showed that the interaction mode between ZnL2 and DNA was intercalation, the binding stoichiometry and the binding constant were calculated to be 0.5 and 4.15×104 L-0.5-mor-0.5, respectively. Optimizing the reaction conditions, the value of variational peak current is linear proportion to the concentration of DNA in the range of 2.27×10-5 1.73×10-4 mol·L-1, and a detection limit of 6.15×l0-7 mol·L-1 (s/n=3).(2) The cadmium(II) complex of Morin, Cd(C₁₅H₉O₇)₂·2H2O [abbreviated by CdL2], was synthesized and characterized by means of IR and EA. Its interaction with double-stranded salmon sperm DNA was studied by electrochemical methods in 0.2 mol-L-1 Tris-HCl buffer solution (pH5.8). It shows that CdL2 with high electrochemical activity can intercalate into the double-helix DNA, the binding stoichiometry and binding constant were calculated to be 1.761(m 2) and 1.2×108 L2·mol-2 , respectively. Using CdL2 as a novel hybridization indicator, a novel DNA electrochemical biosensor for the detection of the specific coliform DNA fragment was constructed by covalently method. The complementary target ssDNA could be quantified over the range from 2.69×10-8 mol-L-1 to 9.16×10-7 mol-L-1 with a detection limit of 9.30×10-9 mol-L-1 (s/n=3).(3) The coblat(II) complex of Morin, Co(C₁₅H₉O₇)₂·3H2O [abbreviated by CoL2], was synthesized and characterized by means of IR and EA. The interaction between the CoL2 and double-stranded salmon sperm DNA was studied by electrochemical methods in 0.2 mol-L-1 PBS buffer solution (pH 6.0). The results showed that the interaction mode between C0L2 and DNA was intercalation, the binding stoichiometry and the binding constant were calculated to be 2.12(m≈2) and 3.59×109 L2·mol-2, respectively. Using C0L2 as electroactive intercalator, a sensitive and novel DNA electrochemical biosensor for the detection of the specific target DNA fragment was presented. The sensor wasbased on multi-walled carbon nanotubes functionalized with a carboxylic acid group (MWCNTs-COOH) as the signal hybridization detection enhancement element. Oligonucleotides with the 5'-amino group were covalently bonded to the carboxyl group of carbon nanotubes. The specific coliform DNA fragment was detected by this DNA electrochemical sensor. The dynamic detection range of this sensor was from l.0×l0-10 mol-L"1 to l.0×l0-9 mol-L-1 with a detection limit of 3.1×10-11 mol·L-1 (s/n=3). Compared with those methods based on covalent immobilization of DNA probes, this present work was found to be more sensitive and lower detection limit.