ORIGINAL PAPER Synthesis, cytotoxicity and spectroscopy studies of a new copper (II) complex: calf thymus DNA and T47D as targets H. Derakhshankhah • A. A. Saboury • R. Bazl • H. A. Tajmir-Riahi • M. Falahati • D. Ajloo • H. Mansoori-Torshizi • A. Divsalar • A. Hekmat • A. A. Moosavi-Movahedi Received: 13 September 2011 / Accepted: 15 February 2012 / Published online: 27 April 2012 Ó Iranian Chemical Society 2012 Abstract A water-soluble Cu (II) complex [(dien)Cu (l-1,6-DAH)Cu(dien) (NO 3 ) 2 ](NO 3 ) 2 has been synthesized and its effect on the carrier model DNA structure and cancer cell line proliferation was investigated. In this regard, calf thymus DNA (CT-DNA) and human breast cancer cell line, T47D, were the targets. The effect of the complex on DNA structure was investigated by means of UV/vis, fluorescence and circular dichroism (CD) spectroscopic techniques as well as dynamic light scattering (DLS), zeta potential anal- ysis and docking assay for more analysis. The UV–vis absorption spectra of complex with DNA showed a slight red shift and hypochromic effect, which indicated the interca- lation and electrostatic effect of complex with CT-DNA. Using ethidium bromide (EB) as a probe in fluorescence studies revealed that complex can quench the EB–DNA fluorescence emission at different temperatures. Besides, the far UV–CD studies displayed that the complex induces changes in the secondary structure of CT-DNA and can increase the melting temperature of DNA up to 14 °C. The DLS and zeta potential measurements confirmed the elec- trostatic interaction of complex with the negatively charged DNA and subsequent DNA condensation. Besides, compu- tational studies reflect that major and minor groove binding are two modes of interaction between complex and DNA. On the other hand, growth inhibition of the complex toward T47D cell line was measured using 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide assay, which showed no cytotoxic properties. Keywords DNA–complex  Fluorescence  Intercalation  Electrostatic interaction Introduction It has been reported that a wide range of agents including pigments [1], natural products [2], anionic lipids, polymers, dendrimers, polypeptides and nanoparticles are able to induce the condensation of DNA [3–6]. For example, cat- ionic alkylammonium ligands displace Na ? cations, bind to DNA and condense the lipid–DNA complex [7]. The size of DNA aggregates can be affected appreciably by polymers rather than monomers [8] since it is found that the structures and dimensions of cationic polymers/DNA complexes are sensitively dependent on the condensing agents. In another study, it is reported that the DNA in the presence of 5-pol- yamidoamine (G5 PAMAM) cationic dendrimer particles is condensed to a much higher degree than in its absence. Moreover, high degree of cooperativity in dendrimer-induced H. Derakhshankhah  A. A. Saboury (&)  M. Falahati  A. Hekmat  A. A. Moosavi-Movahedi Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran e-mail: saboury@ut.ac.ir R. Bazl Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran, Iran H. A. Tajmir-Riahi Department of Chemistry-Biology, Universite ´ du Que ´bec, Trois-Rivie `res, Canada D. Ajloo School of Chemistry, Damghan University, Damghan, Iran H. Mansoori-Torshizi Department of Chemistry, University of Sistan and Bluchestan, Zahedan, Iran A. Divsalar Department of Biological Sciences, Kharazmi University, Tehran, Iran 123 J IRAN CHEM SOC (2012) 9:737–746 DOI 10.1007/s13738-012-0086-3