Size-Resolved Redox Activity and Cytotoxicity of Water-Soluble Urban Atmospheric Particulate Matter: Assessing Contributions from Chemical Components.

Throughout the cold and the warm periods of 2020, chemical and toxicological characterization of the water-soluble fraction of size segregated particulate matter (PM) (<0.49, 0.49−0.95, 0.95−1.5, 1.5−3.0, 3.0−7.2 and >7.2 µm) was conducted in the urban agglomeration of Thessaloniki, northern Greece. Chemical analysis of the water-soluble PM fraction included water-soluble organic carbon (WSOC), humic-like substances (HULIS), and trace elements (V, Cr, Mn, Fe, Ni, Cu, Zn, As, Cd and Pb). The bulk (sum of all size fractions) concentrations of HULIS were 2.5 ± 0.5 and 1.2 ± 0.3 µg m−3, for the cold and warm sampling periods, respectively with highest values in the <0.49 µm particle size fraction. The total HULIS-C/WSOC ratio ranged from 17 to 26% for all sampling periods, confirming that HULIS are a significant part of WSOC. The most abundant water-soluble metals were Fe, Zn, Cu, and Mn. The oxidative PM activity was measured abiotically using the dithiothreitol (DTT) assay. In vitro cytotoxic responses were investigated using mitochondrial dehydrogenase (MTT). A significant positive correlation was found between OPmDTT, WSOC, HULIS and the MTT cytotoxicity of PM. Multiple Linear Regression (MLR) showed a good relationship between OPMDTT, HULIS and Cu.

Characterisation of the correlations between oxidative potential and in vitro biological effects of PM10 at three sites in the central Mediterranean.

Atmospheric particulate matter (PM) is one of the major risks for global health. The exact mechanisms of toxicity are still not completely understood leading to contrasting results when different toxicity metrics are compared. In this work, PM10 was collected at three sites for the determination of acellular oxidative potential (OP), intracellular oxidative stress (OSGC), cytotoxicity (MTT assay), and genotoxicity (Comet assay). The in vitro tests were done on the A549 cell line. The objective was to investigate the correlations among acellular and intracellular toxicity indicators, the variability among the sites, and how these correlations were influenced by the main sources by using PMF receptor model coupled with MLR. The OPDTTV, OSGCV, and cytotoxicity were strongly influenced by combustion sources. Advection of African dust led to lower-than-average intrinsic toxicity indicators. OPDTTV and OSGCV showed site-dependent correlations suggesting that acellular OP may not be fully representative of the intracellular oxidative stress at all sites and conditions. Cytotoxicity correlated with both OPDTTV and OSGCV at two sites out of three and the strength of the correlation was larger with OSGCV. Genotoxicity was correlated with cytotoxicity at all sites and correlated with both, OPDTTV and OSGCV, at two sites out of three. Results suggest that several toxicity indicators are useful to gain a global picture of the potential health effects of PM.

Development and characterization of a gold nanoparticles glassy carbon modified electrode for dithiotreitol (DTT) detection suitable to be applied for determination of atmospheric particulate oxidative potential.

A gold nanostructured electrochemical sensor based on modified GC electrode for thiols' detection is described and characterized. This sensor is a suitable device for the measurement of the oxidative potential (OP) of the atmospheric particulate matter (PM), considered a global indicator of adverse health effects of PM, as an alternative to the classic spectrophotometric methods. The operating principle is the determination of the OP, through the measurement of the consumption of DTT content. The DTT-based chemical reactivity is indeed a quantitative acellular probe for assessment of the capacity of the atmospheric PM to catalyze reactive oxygen species generation which contributes to the induction of oxidative stress in living organisms and in turn to the outcome of adverse health effects. To make the sensors, glassy carbon electrodes, traditional (GC) and screen printed (SPE) electrodes, have been electrochemically modified with well-shaped rounded gold nanoparticles (AuNPs) by using a deposition method that allows obtaining a stable and efficient modified surface in a very simple and reproducible modality. The chemical and morphological characterization of the nano-hybrid material has been performed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy coupled with electron dispersive spectroscopy analysis (SEM/EDS). The electrochemical properties have been evaluated by cyclic voltammetry (CV) and chrono-amperometry (CA) in phosphate buffer at neutral pH as requested in DTT assay for OP measurements. The electroanalytical performances of the sensor in DTT detection are strongly encouraging showing low LODs (0.750 µM and 1.5 µM), high sensitivity (0.0622 µA cm-2 µM-1 and 0.0281 µA cm-2 µM-1), wide linear and dynamic ranges extending over 2-4 orders of magnitude and high selectivity. FIA preliminary results obtained on measuring the DTT rate consumption in six PM aqueous extracts samples showed a good correlation with measurements obtained in parallel on the same set of samples by using the classic spectrophotometric method based on the Ellman's reactive use. These results confirm the high selectivity of the method and its suitability for application to be applied in PM oxidative potential measurements.