Zênis N. da Rocha

Photocytotoxic activity of a nitrosyl phthalocyanine ruthenium complex--a system capable of producing nitric oxide and singlet oxygen.

The synthesis, structural aspects, pharmacological assays, and in vitro photoinduced cytotoxic properties of [Ru(NO)(ONO)(pc)] (pc=phthalocyanine) are described. Its biological effect on the B16F10 cell line was studied in the presence and absence of visible light irradiation. At comparable irradiation levels, [Ru(NO)(ONO)(pc)] was more effective than [Ru(pc)] at inhibiting cell growth, suggesting that occurrence of nitric oxide release following singlet oxygen production upon light irradiation may be an important mechanism by which the nitrosyl ruthenium complex exhibits enhanced biological activity in cells. Following visible light activation, the [Ru(NO)(ONO)(pc)] complex displayed increased potency in B16F10 cells upon modifications to the photoinduced dose; indeed, enhanced potency was detected when the nitrosyl ruthenium complex was encapsulated in a drug delivery system. The liposome containing the [Ru(NO)(ONO)(pc)] complex was over 25% more active than the corresponding ruthenium complex in phosphate buffer solution. The activity of the complex was directly proportional to the ruthenium amount present inside the cell, as determined by inductively coupled plasma mass spectroscopy. Flow cytometry analysis revealed that the photocytotoxic activity was mainly due to apoptosis. Furthermore, the vasorelaxation induced by [Ru(NO)(ONO)(pc)], proposed as NO carrier, was studied in rat isolated aorta. The observed vasodilation was concentration-dependent. Taken together, the present findings demonstrate that the [Ru(NO)(ONO)(pc)] complex induces vascular relaxation and could be a potent anti-tumor agent. Nitric oxide release following singlet oxygen production upon visible light irradiation on a nitrosyl ruthenium complex produces two radicals and may elicit phototoxic responses that may find useful applications in photodynamic therapy.

REDOX PROPERTIES OF RUTHENIUM COMPLEX WITH CATECHOL ARE INVOLVED IN TOXICITY TO GLIAL CELLS

ABSTRACT Since the biological activity of [Ru III (NH 3 ) 4 (catechol)] + has never been tested, its cytotoxicity to glial cells was assayed and correlated with its redox properties. Coordinated catechol oxidizes faster than catechol in the presence of oxygen, but controlled potential electrolysis showed that its oxidation involves only one-electron. However, the oxidation of the free ligand by oxygen involves two electrons, which could generate more reactive oxygen species. Indeed, catechol was more cytotoxic than [Ru III (NH 3 ) 4 (catechol)] + complex to human glioblastoma GL-15 cells and also to rat astrocytes. [Ru III (NH 3 ) 4 (catechol)]-induced cytotoxicity was related to the generation of reactive oxygen species and [Ru II (NH 3 ) 4 (quinone)] 2+ . However, other mechanisms should be involved since antioxidant enzymes and deferoxamine only partially protected GL-15 cells. INTRODUCTION Ruthenium is an element that has industrial, pharmaceutical and medical applications. Ruthenium can be used in the reduction of noxious oxides from industrial emissions

Takovite–Aluminosilicate–Cr Materials Prepared by Adsorption of Cr3+ from Industrial Effluents As Catalysts for Hydrocarbon Oxidation Reactions

The catalytic efficiency of takovite-aluminosilicate-chromium catalysts obtained by adsorption of Cr(3+) ions from aqueous solutions by a takovite-aluminosilicate nanocomposite adsorbent is reported. The adsorbent was synthesized by the coprecipitation method. The catalytic activity of the final Cr-catalysts depended on the amount of adsorbed chromium. (Z)-cyclooctene conversion up to 90% with total selectivity for the epoxide was achieved when the oxidation was carried out with hydrogen peroxide, at room temperature. After five consecutive runs, the catalysts maintained high activity, although after the sixth reuse, the epoxide yields strongly decreased to 35%. The catalysts were also efficient for cyclohexane oxidation, reaching up to 18% conversion, with cyclohexanone/cyclohexanol selectivity close to 1.2. On the whole, their use as catalysts gives a very interesting application for the solids obtained by adsorption of a contaminant cation such as Cr(3+).