Rosa F. Brissos

Luminescent zinc salophen derivatives: cytotoxicity assessment and action mechanism studies

The biological activity of two fluorescent Zn(II)–salophen derivatives has been evaluated. In vitro studies (AFM, emission and UV-vis titration with ethidium bromide and cell growth inhibition) show different mechanisms of interaction with DNA. It has been observed that these compounds enter the cells. Comet assays (with cultured fibroblast cells) have revealed that cellular uptake occurs without damaging the DNA strands. Preliminary studies carried out with living cells have shown IC50 values in a millimolar range, indicative of a non-cytotoxic behaviour. This fact could be understood by confocal microscopy co-localization studies with living cell internalization that have shown that, in fact, the compounds seem to enter the cells but not the nucleus under in vivo conditions.

DNA-interacting and biological properties of copper(II) complexes from amidino-O-methylurea

The interaction of two copper(II) complexes, namely [Cu(L1)Cl2]2 (1) and [Cu(L2)Cl2]2 (2), where L1 = 1-amidino-O-methylurea and L2 = N-(benzyl)-amidino-O-methylurea, with DNA has been thoroughly investigated using different characterization techniques, including electronic absorption spectroscopy, viscosity measurements, fluorescence spectroscopy, circular dichroism spectroscopy, thermal denaturation, stoichiometric determination, gel electrophoresis and atomic-force microscopy. The coordination compounds exhibit DNA binding potential by non-intercalation and DNA-cleaving ability through the oxidative pathway. Indeed, both complexes display antibacterial properties (against three bacteria involved in human-food poisoning, i.e. Salmonella, E. coli and Campylobacter). Furthermore, their cytotoxicity has been tested against three cancer cell lines, which are the small cell lung carcinoma (NCI-H187), the oral cavity carcinoma (KB) and the breast adenocarcinoma (MCF-7) and it was revealed that they are more cytotoxic than cisplatin against the NCI-H187 cancer cell line.

BIO-RELATED COPPER-MEDIATED OXIDATIVE PROCESSES

The present minireview deals with the use of the oxidative properties of copper(II/I) coordination compounds for valuable applications, namely the selective conversion of alcohols into aldehydes (or ketones), the cleavage of DNA strands (anti-cancer drugs), and the prevention of the formation of copper/amyloid plaques in Alzheimers disease (AD). The concise report is therefore organized in three clearly defined parts: i) the design and preparation of simple copper(II) (and copper(I)) coordination compounds, mimicking the enzymatic activity of galactose oxidase, to mediate the selective oxidation of alcoholic substrates; ii) the generation of copper-containing chemical nucleases for the development of effective anti-cancer agents; iii) the current state of the art regarding the elucidation of the copper-based biological mechanisms (involving β-amyloid) that govern neural degeneration in AD.

Custom-Fit Ruthenium(II) Metallopeptides: A New Twist to DNA Binding With Coordination Compounds

A new bipyridine building block has been used for the solid-phase synthesis of dinuclear DNA-binding ruthenium(II) metallopeptides. Detailed spectroscopic studies suggest that these compounds bind to the DNA by insertion into the DNA minor groove. Moreover, the potential of the solid-phase peptide synthesis approach is demonstrated by the straightforward synthesis of an octaarginine derivative that shows effective cellular internalization and cytotoxicity linked with strong DNA interaction, as evidenced by steady-state fluorescence spectroscopy and AFM studies.

Effects of N,N-heterocyclic ligands on the in vitro cytotoxicity and DNA interactions of copper(II) chloride complexes from amidino-O-methylurea ligands

Copper(II) complexes based on guanidine derivatives have been synthesized by the addition of N,N-heterocyclic ligands, yielding four new compounds, [Cu(L1)(bipy)]Cl2 (1), [Cu(L1)(phen)]Cl2 (2), [Cu(L2)(bipy)Cl2] (3) and [Cu(L2)(phen)]Cl2 (4) (L1 = amidino-O-methylurea, L2 = N-(benzyl)-amidino-O-methylurea, bipy = 2,2′-bipyridine and phen = 1,10-phenanthroline), and their biological activities have been studied. All complexes were characterized by elemental analysis and various spectroscopic methods (FT-IR, mass, diffuse reflectance, UV-Vis and EPR). Their structures were proposed to be square planar (for 1, 2 and 4) and distorted octahedral (for 3). Their interactions with calf thymus (CT) DNA were examined by electronic absorption titration, viscosity measurements, circular dichroism spectroscopy, DNA-melting analysis, fluorescence spectroscopy and determination of the stoichiometry. Two possible DNA-binding modes of the complexes are proposed to be non-intercalation at low [complex]/[DNA] ratios and intercalation at high [complex]/[DNA] ratios. Their nuclease activities, investigated by gel-electrophoresis and atomic-force microscopy (AFM), show that the complexes can cleave plasmid pBR322 DNA, probably through oxidative pathways. Moreover, their in vitro cytotoxic activities against three human tumor cell lines (small cell lung carcinoma (NCI-H187), oral cavity carcinoma (KB) and breast adenocarcinoma (MCF-7)) and their antibacterial activities toward three Gram negative bacteria (E. coli, Salmonella and Campylobacter) were determined. The complexes in this system exhibit a more potent anticancer effect against the NCI-H187 cell line. Complex 2 had the best inhibition efficiency, particularly against Campylobacter. Indeed, the biological activities of the complexes follow the trend of 2 > 4 > 1 > 3.

Dual role of Cu2+ ions on the aggregation and degradation of soluble Aβ oligomers and protofibrils investigated by fluorescence spectroscopy and AFM

The neuropathological character of copper(II) ions (Cu(2+)) upon interaction with soluble human amyloid-β(1-42) that subsequently generates senile plaques and/or reactive oxygen species (ROS) is considered as one of the very important features of Alzheimers disease. The present study carried out by using fluorescence spectroscopy and atomic-force microscopy (AFM) indeed confirms the dual role played by Cu(2+), namely as mediator of protein aggregation and as generator of ROS leading to irreversible protein alteration, which most likely involve two distinct copper-binding sites. The AFM investigations clearly evidence the copper-induced aggregation of Aβ oligomers and protofibrils, while comparative fluorescence measurements with copper and zinc reveals the crucial involvement of redox-active copper in the generation of Aβ-cross-linked structures.