The Design, Syntheses And The Investigations On Activities Of Biological Functional Complexes Containing Copper,Platinum And Nickel

DNA is essential for life because it contains the genetic information. So the investigation on the interaction between small molecules and DNA is valuable in understanding the essence of life. It also plays its role in the theory research and practical application. The researches on metallonucleases, anti-cancer metal complexes and artificial vectors were attractive owing to the biological function accessible and rich structures of transition metal complexes. Development of artificial nucleases with improved efficiency and selectivity is highly demanded. In practical application, the high selectivity is more important than the cleavage efficiency. It is a new strategy to conjugate a site specific group with DNA scission moiety may enhance the regional selectivity and cleavage efficiency of an artificial nuclease. DNA condensing agents play a critical role in gene therapy. Viral vectors usually display high efficiency in transfection; however, some disadvantages such as host exhibit significant cytotoxicity and immunogenicity. Transition metal complexes are beginning to emerge as a new class of nonviral vectors which have displayed remarkable ability to induce DNA condensation. It is important in constructing polynuclear complex bearing the highly positive charge as new nonviral vectors. The wider application of cisplatin has been largely hampered by the fact that tumors become resistant after prolonged expose to the drug. Great efforts have been devoted to the design of new platinum complexes carrying polyamino, multinuclear and low activity towards GSH. They are anticipated to have high efficiency, reduced toxicity, a wide spectrum of activity, lack of tumor cell resistance and present promising perspective as antitumor drugs.Firstly, two copper(Ⅱ) complexes, [CuL1Cl2](1) and [CuL2Cl2] (2), and two copper(Ⅱ)-platinum(Ⅱ) heteronuclear complexes, [CuPtL1(DMSO)Cl4] (3) and [CuPtL2(DMSO)Cl4] (4), were synthesized using two bifunctional ligands, N-(4-(2-pyridylmethoxy)benzyl)-N,N-bis(2-pyridylmethyl)amine (L1) and N-(3-(2-pyridylmethoxy)benzyl)-N,N-bis(2-pyridylmethyl)amine (L2). These complexes have been characterized by elemental analysis, electrospray ionization mass spectrometry, infrared spectroscopy, and ultraviolet-visible spectroscopy. The DNA binding ability of these complexes follows an order of 1<2<3<4 as revealed by the results of spectroscopy and agarose gel electrophoresis studies. Their cleavage activity toward supercoiled pUC19 plasmid DNA is prominent at micromolar concentration levels in the presence of ascorbic acid. Complexes seem to follow some similar pathways in the cleavage process, in which hydroxyl radicals, hydrogen peroxide and singlet oxygen are crucial ROS for the cleavage reactions. The introduction of a platinum(Ⅱ) center to the copper(Ⅱ) complexes induces a significant enhancement in cleavage activity as compared with copper(Ⅱ) complexes alone. These results show that the presence of a platinum(Ⅱ) center in copper(Ⅱ) complexes strengthens both their DNA binding ability and DNA cleavage efficiency.A tetranuclear nickel(Ⅱ) complex, [Ni4Ⅱ(L-2H)(H2O)6(CH3CH2OH)2]·6NO3{L3= 3,3',5,5'-tetrakis[((2-hydroxyethyl)(pyridin-2-ylmethyl)amino)methyl)]biphen-yl-4,4'-diol}, has been fully characterized by X-ray crystallography, it bears six positive charges. UV-Vis spectroscopy, fluorescence spectroscopy displays the complex interacts strongly with DNA through electrostatic attraction. The AFM images clearly indicate that complex can induce the condensation of DNA into globular nanoparticles at concentrations less than 10μM. The results of the DLS measurements shows the hydrodynamic diameter of the condensed DNA particles are about 200 and 1000 nm, respectively. EDTA can unpack the compact DNA induced by complex 5, and the amount of relaxed DNA increases with the increment of EDTA examined by CD spectroscopy. Form ESI-MS, we suggest that EDTA could grab nickel(Ⅱ) ion from complex 5 mingled with compact DNA. In the presence of ascorbic acid this octahedral nickel(Ⅱ) complex has no cleavage activity towards DNA. The cytotoxic profiles of complex 5 was thus tested in vitro against the human hepatocarcinoma cell line HepG2, the human non-small-cell lung cancer cell line A549, the human renal epithelial cell line 293T, the rat pheochromocytoma cell line PC12, and the human breast cancer cell lines MCF-7. Even when the concentration of complex 5 goes up to 100μM, the viability of all the cells is still above 65%. The results indicate that the cytotoxicity of complex 5 is considerably low. These results show its promising perspective as a vector.In the search for a new Pt(Ⅱ) complexes with high efficiency, reduced toxicity, a wide spectrum of activity, lack of tumor cell resistance.In this work, L4=4,4'-bis(pyridin-2-ylmethoxy)biphenyl, L5= 2,2'-(4,4'-(propane-2,2-diyl)bis(4,1-phenylene))bis(oxy) bis(methylene)dipyridine and two new binuclear complexes 6,7 of mono-functional chelated platinum centers was constructed and characerized. CD spectra and agarose gel electrophoresis demonstrate the complexes can induce the unwinding of the DNA superhelix. The remarkable differences between 6,7 and cisplatin in DNA binding and cross-linking provide mechanistic insights into their different cytotoxicity against the tumor cell lines. ESI-MS spectra shows both the Pt(Ⅱ) complexes could react with 5'-GMP quickly. The presence of bulky groups in complexes could slow down its reaction with GSH; the complexes reacted with glutathione(GSH) give its mono-substituted or bi-substituted products, yet the multinuclear skeleton remain intact for long time. The result suggests that the complex should have the improved biostability and bioavailabilty. In the cytotoxity assay against the human hepatocarcinoma cell line HepG2 and Ovarian cancer cell line COC1, the complexes are less cytotoxic than ciplatin. The monofunction-Pt(II) complex 6 demonstrated much higher potency against human hepatocarcinoma cell line (BEL-7402) and human B lymphoma cell line(Raji) than cisplatin, exhibiting great potentials to circumvent cisplatin resistance. The character of the complex 6 make it a kind of excellent platinum compound for further entering clinical trials for the treatment of the cancer as a potential antitumour agents.