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Lung toxicity of carbon nanotubes (CNTs) is matter of concern since very long time. However, their mechanism of toxicity is still not yet well defined. In this work, the role of structural defects as organic stressors of CNTs able to trigger their potential toxicity is investigated. Four commercial CNTs, with different carbon purity grade, are morphologically characterized by transmission electron microscopy (TEM) and the relative amount of structural defects are estimated through Raman spectroscopy, by measuring the intensity ratio D/G (ID/IG). The oxidative potential of CNTs is evaluated with cytochrome-C assay and reactive oxygen species (ROS) detection. Data show that CNTs with larger amounts of structural defects (higher ID/IG ratio) induce an increased ROS generation and consequent cytotoxicity and cellular damage, shown by TEM images of CNTs-cells interaction. Raman analyses of cells exposed to CNTs point out that the spectra of the CNTs inside the cells show no differences with respect of the signal recorded for cell-free CNTs, evidencing their biopersistence in lung cells. Raman spectra cannot provide direct indication of the existence of metals as impurity. It follows that the intensity ratio ID/IG can be taken as a predictive marker of the toxicity of a given CNT.

It is commonly accepted that the toxicity of carbonaceous particulate matter (PM) is due to the production of reactive oxygen species (ROS) which induce biological damage in the exposed cells. It is also known that PM produced during the combustion processes consists of a carbonaceous core "dressed" with other organic and/or inorganic materials. In spite of this knowledge, the role of these materials in the production of ROS has not yet been clear. This work aims at understanding whether "naked" carbonaceous particles are capable of forming ROS either in cell-free or in-cell systems. The problem has been treated based on the data collected from pure graphite samples of different sizes obtained by ball-milling pure graphite for various lengths of time. The experimental approach considered Raman, ESR (spin trapping), cell viability and fluorescence spectroscopy measurements. These techniques allowed us to carry out measurements both in cell and cell-free systems and the results consistently indicate that also pure naked carbonaceous particles can catalyze the electron transfer that produces superoxide ions. The process depends on the particle size and enlightens the role of the edges of the graphitic platelets. Evidence has been collected that even "naked" graphitic nanoparticles are capable of producing ROS and decreasing the cell viability thus representing a potential danger to human health.

Air pollution mostly originating from car exhaust and industrial emissions is seriously endangering human health. The study of toxic effects of particulate matter (PM) is a subject of very active research that covers a broad field from biology to chemistry and technology. The main issue of these works is the understanding of the oxidative properties of PM. In this paper, we present a quantitative analytical method based on the resonance Raman spectroscopy of cytocrome c that can be used to monitor the oxidative reactions that may take place between biological samples and PM., Air pollution mostly originating from car exhaust and industrial emissions is seriously endangering human health. The study of toxic effects of particulate matter (PM) is a subject of very active research that covers a broad field from biology to chemistry and technology. The main issue of these works is the understanding of the oxidative properties of PM. In this paper, we present a quantitative analytical method based on the resonance Raman spectroscopy of cytocrome c that can be used to monitor the oxidative reactions that may take place between biological samples and PM.

Calcium oxalate is found in nature in three different crystalline states determined by the number of H2O in the unit formula (whewellite CaC2O4·H2O, COM; weddellite CaC2O4·(2 + x)H2O, COD and caoxite CaC2O4·3H2O, COT). The properties of these materials are relevant in the field of biomedicine, cultural heritage and mineralogy. In two previous papers, we have used X-ray diffraction and vibrational spectroscopy (infrared and Raman) to derive information on crystal and molecular structures of COM and COD. In this paper, we complete the synthesis and analysis on the third form, COT, and present a comparative study of the data collected from the three crystalline states. The experiments clearly highlight the role played by the H2O molecules linked within the structure by different kinds of hydrogen bonds. The vibrational assignment of the infrared and Raman bands are critically proposed. The fact relevant for the work in biomedicine, cultural heritage and crystallography is that a simple examination of the spectra allows quickly to determine the chemical nature of the material in an unknown sample even in a minute quantity or in awkward experimental conditions.

New data on vibrational properties of calcium oxalates and their controversial transformation mechanism are presented. We have focused on whewellite (CaC2O4·H2O) and weddellite [CaC2O4·(2 + x) H2O], the most common phases of calcium oxalate; these compounds occur in many organisms, in kidney stones and in particular kinds of films found on the surface of many works of art. Low temperature experiments carried out by Fourier transform infrared spectroscopy have highlighted both the high structural order in the crystalline state of whewellite and the disordered distribution of the zeolitic water molecules in weddellite. The synthesised nanocrystals of weddellite have been kept under different hygrometric conditions in order to study, by X-ray powder diffraction, the role of "external" water molecules on their stability. Moreover, in order to identify the different kinds of water molecules, a re-investigation, supported by quantum chemical calculations, of the observed vibrational spectra (IR and Raman) of whewellite has been conducted. © 2014 Published by Elsevier B.V.