Davide Atzei

Quantitative evaluation of oxidative stress, chronic inflammatory indices and leptin in cancer patients: correlation with stage and performance status.

In advanced cancer patients, the oxidative stress could take place either at the onset of disease or as a function of disease progression. To test this hypothesis, the following parameters were investigated: the erythrocyte activity of the enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), the serum activity of glutathione reductase (GR) and the serum total antioxidant status (TAS). The total antioxidant capacity of plasma LMWA was evaluated by the cyclic voltammetry methodology. We further determined the serum levels of proinflammatory cytokines (IL‐6 and TNFα), IL‐2, leptin and C‐reactive protein (CRP). All of these parameters have been correlated with the most important clinical indices of patients such as Stage of disease, ECOG PS and clinical response. Eighty‐two advanced stage cancer patients and 36 healthy individuals used as controls were included in the study. Our findings show that SOD activity was significantly higher in cancer patients than in controls and GPx activity was significantly lower in cancer patients than in controls. Serum values of IL‐6, TNFα and CRP were significantly higher in patients than in controls. Serum leptin values of cancer patients were significantly lower than controls. SOD activity increased significantly from Stage II/ECOG 0‐1 to Stage IV/ECOG 0–1, whereas it decreased significantly in Stage IV/ECOG 3. GPx activity decreased significantly in Stage IV/ECOG 2–3. An inverse correlation between ECOG PS and serum leptin levels was found. Serum levels of IL‐2 decreased from Stage II/ECOG 0–1 to Stage IV/ECOG 2–3. A direct correlation between Stage/ECOG PS and serum levels of both IL‐6 and CRP was observed. Cisplatin administration induced a significant increase of GPx after 24 hr. In conclusion, this is the first study that shows that several “biological” parameters of cancer patients such as antioxidant enzyme activity, cytokines, leptin and CRP strictly correlate with the most important clinical parameters of disease such as Stage and ECOG PS.

Exploiting XPS for the identification of sulfides and polysulfides

The identification of surface sulfide and polysulfide species based on the curve fitting of S2p photoelectron spectra and, for the first time, of X-ray excited S KLL Auger spectra has been performed. The different sulfur chemical states present on the surface (sulfide S2−, central S and terminal S in polysulfide chains) could be unambiguously assigned in the chemical state plot. Sulfur atoms in the central or terminal position, respectively, are found on a line with slope ca. −3 irrespective of the cation indicating similar initial state effects. On the other hand, for a given polysulfide, e.g. K2Sn, sulfur atoms both in central or terminal positions are found on the same line with slope −1 indicating similar final state effects. This behavior can be rationalized with the fact that the negative charge in polysulfide chains is located mainly on sulfur atoms in the terminal position; indeed, sulfur present as central S shows a binding energy shift of −0.6 eV with respect to elemental sulfur (S8), and sulfur in terminal S a shift of −2.4 eV. An application of this approach tested on commercial alkali polysulfides is provided for the curve fitting of SKLL signals and sulfur speciation of three different sulfide minerals enargite (Cu3AsS4), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). Also for the surface of mineral sulfides, terminal S atoms and central S atoms in the polysulfide chains can successfully be identified.

Combined use of X-ray photoelectron and Mössbauer spectroscopic techniques in the analytical characterization of iron oxidation state in amphibole asbestos

Asbestos fibers are an important cause of serious health problems and respiratory diseases. The presence, structural coordination, and oxidation state of iron at the fiber surface are potentially important for the biological effects of asbestos because iron can catalyze the Haber–Weiss reaction, generating the reactive oxygen species ⋅OH. Literature results indicate that the surface concentration of Fe(III) may play an important role in fiber-related radical formation. Amphibole asbestos were analyzed by X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy, with the aim of determining the surface vs. bulk Fe(III)/Fetot ratios. A standard reference asbestos (Union Internationale Contre le Cancer crocidolite from South Africa) and three fibrous tremolite samples (from Italy and USA) were investigated. In addition to the Mössbauer spectroscopy study of bulk Fe(III)/Fetot ratios, much work was dedicated to the interpretation of the XPS Fe2p signal and to the quantification of surface Fe(III)/Fetot ratios. Results confirmed the importance of surface properties because this showed that fiber surfaces are always more oxidized than the bulk and that Fe(III) is present as oxide and oxyhydroxide species. Notably, the highest difference of surface/bulk Fe oxidation was found for San Mango tremolite—the sample that in preliminary cytotoxicity tests (MTT assay) had revealed a cell mortality delayed with respect to the other samples.

Arsenopyrite and pyrite bioleaching: evidence from XPS, XRD and ICP techniques

In this work, a multi-technical bulk and surface analytical approach was used to investigate the bioleaching of a pyrite and arsenopyrite flotation concentrate with a mixed microflora mainly consisting of Acidithiobacillus ferrooxidans. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and X-ray-induced Auger electron spectroscopy mineral surfaces investigations, along with inductively coupled plasma-atomic emission spectroscopy and carbon, hydrogen, nitrogen and sulphur determination (CHNS) analyses, were carried out prior and after bioleaching. The flotation concentrate was a mixture of pyrite (FeS2) and arsenopyrite (FeAsS); after bioleaching, 95% of the initial content of pyrite and 85% of arsenopyrite were dissolved. The chemical state of the main elements (Fe, As and S) at the surface of the bioreactor feed particles and of the residue after bioleaching was investigated by X-ray photoelectron and X-ray excited Auger electron spectroscopy. After bioleaching, no signals of iron, arsenic and sulphur originating from pyrite and arsenopyrite were detected, confirming a strong oxidation and the dissolution of the particles. On the surfaces of the mineral residue particles, elemental sulphur as reaction intermediate of the leaching process and precipitated secondary phases (Fe–OOH and jarosite), together with adsorbed arsenates, was detected. Evidence of microbial cells adhesion at mineral surfaces was also produced: carbon and nitrogen were revealed by CHNS, and nitrogen was also detected on the bioleached surfaces by XPS. This was attributed to the deposition, on the mineral surfaces, of the remnants of a bio-film consisting of an extra-cellular polymer layer that had favoured the bacterial action.

XPS and LAXS study of 1,3-thiazolidine-2-thione and its complexes with Co(II) and Zn(II)

Abstract Metal complexes of general formula M(ttz) 2 X 2 (with M = Zn(II) or Co(II); X = Cl or Br; ttz = 1,3-thiazolidine-2-thione) have been synthetized as crystalline (Br and Cl) and amorphous (chloride derivative only) compounds. LAXS (Large Angle X-ray Scattering) investigations reveal that the ttz ligand is bonded to the zinc or cobalt ion through one of the two sulphur atoms and no metal-nitrogen bonds are present. Detailed XPS (X-ray Photoelectron Spectroscopy) studies show that ttz is bonded to the metal through the thioketonic sulphur atom and that electronic charge redistribution in the ligand takes place after complexation.

Synthesis and characterization of a cobalt(III) complex with 1-(d-3-mercapto-2-methylpropionyl)-l-proline

The reaction of CoCl2 with 1-(D-3-mercapto-2-methylpropionyl)-L-proline (L or captopril) yields a new nanocrystalline complex with general formula [CoL2(OH)]2. The complex has been characterised with infrared (IR) and ultra-violet visible (UV-vis) spectroscopies, magnetic measurements, X-ray photoelectron spectroscopy (XPS), and wide angle X-ray scattering (WAXS). XPS analyses is a valuable tool for studying the chemical composition and the chemical state of elements at the surface of solids whereas WAXS provides information on the short range order. A model is proposed for the binding of the complex and its structure: the Co(III) ion is bonded with a pseudo-octahedral configuration. Captopril molecules are coordinated via mercapto group and amidic C=O group to Co(III) ions: two S atoms are bridging bonded between two Co(III) ions. The OH- ion completes the coordination around the Co(III).

X-ray photoelectron spectra of complexes with 1-(D-3-mercapto-2-methylpropionyl)-L-proline and Ni(II), Cd(II) and Cu(I): synthesis and LAXS study of Cu(I) derivative.

Metal complexes of general formula Na2M(CAP)2xH2O (with M = Cd(II) or Ni(II), x = 7 and 4, respectively, CAP = 1-(D-3-mercapto-2-methylpropionyl)-L-proline) and NaCuCAPx3H2O have been synthesized as amorphous compounds and studied by means of X-ray photoelectron spectroscopy (XPS). Cu(I) derivative has been studied by IR, XPS and large-angle X-ray scattering (LAXS). IR data and the chemical shift of core level signals suggest that CAP is bonded to the metal via the sulphur atom and the carbonylic oxygen. LAXS data confirm this finding and are consistent with a tetrahedral configuration around the copper ion. The CAP molecule is bonded through the sulphur and the carbonylic oxygen and two water molecules complete the coordination around the metal. The sodium ion exhibits a tetrahedral configuration and interacts with the carboxylic group and two water molecules. One of these is bridging bonded between copper and sodium. No metal-nitrogen bonds are present.

Electronic properties of TiO2-based materials characterized by high Ti3+ self-doping and low recombination rate of electron–hole pairs

Factors tuning the functional performances of the various TiO2-based materials in the wide range of their possible applications are poorly understood. Here the electronic structure of TiO2-based materials characterized by Ti3+ self-doping, obtained by a sol–gel route wholly performed in air at room temperature, is reported. In the amorphous hybrid TiO2–acetylacetonate (HSGT) material the formation of the Ti(IV)–acac complex makes it photoresponsive to visible light and allows us to obtain by means of a simple annealing in air at 400 °C a very stable black Ti3+ self-doped anatase TiO2 nanomaterial (HSGT-400), characterized by an extraordinary high concentration of Ti atoms with oxidation states lower than IV (about 26%), which absorbs light in the entire visible range. The very high stability of HSGT-400 is mainly related to the process, which does not require the use of harsh conditions nor external reducing agents. The electronic structure of HSGT, owing to the presence of the Ti(IV)–acac complex, allows the stabilization of superoxide anion radicals on its surface for a very long time (months) at room temperature. The extraordinary low recombination rate of electron–hole pairs gives to HSGT unusual catalytic performances at room temperature allowing the complete removal of 2,4-dichlorophenol from water in about one hour without any light irradiation. Our results clearly highlight the connection among the production process of TiO2-based materials, their electronic structure and, finally, their functional behaviour.

Nanosized surface films on brass alloys by XPS and XAES

Chemical state identification and quantification based on photoelectron spectra is challenging in the case of copper and zinc and their alloys. In this work an analytical strategy for simultaneous chemical state identification and quantification of copper and zinc chemical states in complex layered systems is presented. This approach is based on the curve fitting of the multicomponent X-ray excited Auger spectra, CuL3M4.5M4.5 and ZnL3M4.5M4.5, that clearly distinguish metallic and oxide components and result in separated ILMM,met and ILMM,ox peak areas. On reference copper and zinc compounds, showing only a single chemical state, the intensity ratio R between photoelectron I2p and Auger intensity ILMM was determined. Rmet was obtained using pure metals and a sputtered brass alloy Cu37Zn. Rox was calculated using the pure oxides. Based on these experimental intensity ratios, R, a quantification factor, k = Rox/Rmet, is calculated for both copper and zinc. This quantification factor k is independent of the instrument employed for the analysis, as proved here by using different spectrometers. The factor k is then used to transfer the experimental Auger intensity ratio (ILMM,met/ILMM,ox) into the I2p,met/I2p,ox intensity ratio, which is required for the quantitative analysis by XPS. The potential of this approach based on XPS and XAES for the patina studies on copper alloys, relevant in various fields including corrosion and cultural heritage, is presented for Cu37Zn model brass alloy after different surface pre-treatments. This approach has proven to be successful.

Electrochemical and XPS surface analytical studies on the reactivity of enargite

Enargite, a copper arsenic sulfide having the formula Cu 3 AsS 4 , is a source of arsenic and may cause environmental problems owing to the release of toxic elements upon oxidation, especially in acid mine effluents. In this work the oxidative dissolution of enargite has been studied on freshly cleaved samples exposed to distilled water, sulfuric acid solution at pH 4 and acidic FeCl 3 or Fe 2 (SO 4 ) 3 solutions at pH ca . 2 with 0.025 M Fe 3+ simulating abiotic acid mine drainage environments. The open circuit potential of the acidic solutions with ferric ions achieved stabilization at + 0.72 ± 0.02 V NHE thus, according to the mixed potential theory, the redox couple Fe 3+ /Fe 2+ strongly polarizes the enargite surface towards positive potentials. Solution analyses showed that in these conditions about 10–14 μg copper are released every 24 h into solution from approximately 0.5 cm 2 enargite surface. Based on the amount of dissolved copper, the thickness of the dissolved enargite has been calculated to be about 60–130 nm. XPS analyses of the reacted enargite surfaces revealed no changes in the binding energy of copper Cu2p3/2 found at 932.4 ± 0.2 eV, arsenic As3d5/2 found at 43.3 ± 0.2 eV and of sulfur, S2p3/2 at 161.9 ± 0.2 eV compared to the pristine surface, whereas a prominent sulfur signal appeared at ca. 163.5 ±0.2 eV, assigned to sulfur in a copper-deficient layer. The XPS quantitative analysis performed by applying a three-layer model revealed the presence of a metal-deficient layer of ca. 0.7 nm thickness on the enargite surface. The interface beneath this layer (estimated thickness 5–10 nm) was slightly enriched in sulfur and depleted in copper. Based on these complementary data from solution analysis and XPS surface analysis, a model similar to the dissolution of binary metallic alloys is here proposed for enargite dissolution under oxidizing conditions.