Coumarin-based fluorescent probes for dual recognition of copper(II) and iron(III) ions and their application in bio-imaging.

Two new coumarin-based "turn-off" fluorescent probes, (E)-3-((3,4-dihydroxybenzylidene)amino)-7-hydroxy-2H-chromen-2-one (BS1) and (E)-3-((2,4-dihydroxybenzylidene)amino)-7-hydroxy-2H-chromen-2-one (BS2), were synthesized and their detection of copper(II) and iron(III) ions was studied. Results show that both compounds are highly selective for Cu²âº and Fe³âº ions over other metal ions. However, BS2 is detected directly, while detection of BS1 involves a hydrolysis reaction to regenerate 3-amino-7-hydroxycoumarin (3) and 3,4-dihydroxybenzaldehyde, of which 3 is able to react with copper(II) or iron(III) ions. The interaction between the tested compounds and copper or iron ions is associated with a large fluorescence decrease, showing detection limits of ca. 10⁻5 M. Preliminary studies employing epifluorescence microscopy demonstrate that Cu²âº and Fe³âº ions can be imaged in human neuroblastoma SH-SY5Y cells treated with the tested probes.

Oxidative DNA damage and ß-catenin expression in colorectal cancer evolution.

PURPOSE: Oxidative DNA damage is one of the mechanisms associated to initial colorectal carcinogenesis, but how it interacts with ß-catenin, an adherence protein related to cancer evolution, is not clear. This study investigates the relationship between oxidative DNA damage and ß-catenin expression in normal mucosa and colon tumor tissue (adenoma and adenocarcinoma) in colorectal adenocarcinoma evolution. METHOD: One hundred and 13 samples were studied. Hematoxylin-eosin determined histological grade. ß-Catenin expression was analyzed by immunohistochemistry. The oxidative DNA damage was evaluated using comet assay technique. The coefficient for rejection of the nullity hypothesis was taken to 5 %. Kruskal-Wallis, Spearman test, and partial correlation were used to analyze the data. RESULTS: There was oxidative DNA damage increase in colorectal cancer evolution (p < 0.01). Histological grade was correlated with oxidative DNA damage (p < 0.01). There were differences in ß-catenin expression among normal, adenoma, and adenocarcinoma tissue with progressive increase of ß-catenin expression (p < 0.00). Histological grade was correlated to ß-catenin expression (p < 0.00). There was a relationship (p < 0.00) between ß-catenin and histological grade while controlling for the effect of oxidative DNA damage. CONCLUSION: The findings of this study make it possible to establish a relationship between oxidative DNA damage and ß-catenin expression in normal mucosa and colorectal tumor tissue. Additionally, they show a causal relationship between variations of ß-catenin in different tissues analyzed while controlling for the effect of oxidative DNA damage.

Exploring the Effect of the Irradiation Time on Photosensitized Dendrimer-Based Nanoaggregates for Potential Applications in Light-Driven Water Photoreduction.

Fourth generation polyamidoamine dendrimer (PAMAM, G4) modified with fluorescein units (F) at the periphery and Pt nanoparticles stabilized by L-ascorbate were prepared. These dendrimers modified with hydrophobic fluorescein were used to achieve self-assembling structures, giving rise to the formation of nanoaggregates in water. The photoactive fluorescein units were mainly used as photosensitizer units in the process of the catalytic photoreduction of water propitiated by light. Complementarily, Pt-ascorbate nanoparticles acted as the active sites to generate H2. Importantly, the study of the functional, optical, surface potential and morphological properties of the photosensitized dendrimer aggregates at different irradiation times allowed for insights to be gained into the behavior of these systems. Thus, the resultant photosensitized PAMAM-fluorescein (G4-F) nanoaggregates (NG) were conveniently applied to light-driven water photoreduction along with sodium L-ascorbate and methyl viologen as the sacrificial reagent and electron relay agent, respectively. Notably, these aggregates exhibited appropriate stability and catalytic activity over time for hydrogen production. Additionally, in order to propose a potential use of these types of systems, the in situ generated H2 was able to reduce a certain amount of methylene blue (MB). Finally, theoretical electronic analyses provided insights into the possible excited states of the fluorescein molecules that could intervene in the global mechanism of H2 generation.

Effects of non-covalent interactions on the electronic and electrochemical properties of Cu(i) biquinoline complexes.

A Cu(i) complex {[CuI(biq)2]ClO4-biq} with biq = 2,2'-biquinoline was prepared, fully characterized and its properties compared with those of the well-known [CuI(biq)2]ClO4 complex. The crystal structures were obtained for both complexes (crystal structure for [CuI(biq)2]ClO4 has not been previously reported). Complex [CuI(biq)2]ClO4 crystallizes as a racemate where each enantiomer has a different τ4 value while compound {[CuI(biq)2]ClO4-biq} crystallizes as a non-chiral supramolecular aggregate with an uncoordinated biq molecule forming a π-π stacking interaction with a coordinated biq. 1H-NMR spectroscopy in non-coordinating solvents reveals that structures in solution are similar to those in the solid phase, confirming the presence of a supramolecular arrangement for compound {[CuI(biq)2]ClO4-biq}. The stability of the non-covalent aggregate in solution of {[CuI(biq)2]ClO4-biq} causes significant differences between the spectroscopic and electrochemical properties of {[CuI(biq)2]ClO4-biq} and [CuI(biq)2]ClO4.