Oxidative potential of atmospheric aerosols

Atmospheric particulate matter (PM) is one of the leading health risks worldwide [1,2]. Several epidemiological studies have provided evidence of the association between exposure to PM and the onset of cardiovascular and respiratory diseases [3], as well as cardiopulmonary diseases and other adverse health effects [4]. The exact mechanisms leading to PM toxicity are not fully known, however, several studies suggest that the generation of reactive oxygen species (ROS) could be a major mechanism by which PM leads to both chronic and acute adverse health effects [5,6]. For this reason, in recent years, the oxidative potential (OP) of PM, defined as its ability to generate oxidative stress in biological systems, has been proposed as a relevant metric for addressing PM exposure [7,8]. However, the link between OP and adverse health effects is still uncertain [9–11], and contrasting results have been obtained when PM oxidative potential has been compared with the results of in-vivo and in-vitro toxicological tests or the outcomes of epidemiological studies [12]. The OP can be evaluated through several in vitro assays, but protocols employing chemical (acellular) assays have become common as well. Acellular assays can be useful for investigating the PM properties which are responsible for oxidative stress: ROS compounds can either be carried by components of the aerosol itself (particle-bound ROS) or induced by the catalytic activity exerted by aerosol constituents (PM-induced ROS). The diverse OP assays developed so far have certainly improved our knowledge of the mechanisms underlying PM oxidative stress. At the same time, they pose the issue of comparability between the different assays and protocols, as well as problems surrounding the actual correlation between acellular OP and in vitro (or in vivo) toxicity. Measurements of PM oxidative potential are influenced by the chemical composition of the aerosol, by its size distribution, and by the weight of different natural and anthropogenic sources of PM leading to temporal and spatial variabilities that need investigation in current research. Moreover, recent studies show that photochemical aging increases the oxidative potential of atmospheric aerosols. However, several aspects regarding the specific chemical species, aerosol sources, and atmospheric processes that affect OP are not well established, and further research is needed [13–15]. Another topic that needs extensive research is the characterization of the OP of indoor aerosols. This special issue includes five research papers and two review papers discussing recent advances in the studies of the oxidative potential of atmospheric particulate matter

Nanocellulose/fullerene hybrid films assembled at the air/water interface as promising functional materials for photo-electrocatalysis

Cellulose nanomaterials have been widely investigated in the last decade, unveiling attractive properties for emerging applications. The ability of sulfated cellulose nanocrystals (CNCs) to guide the supramolecular organization of amphiphilic fullerene derivatives at the air/water interface has been recently highlighted. Here, we further investigated the assembly of Langmuir hybrid films that are based on the electrostatic interaction between cationic fulleropyrrolidines deposited at the air/water interface and anionic CNCs dispersed in the subphase, assessing the influence of additional negatively charged species that are dissolved in the water phase. By means of isotherm acquisition and spectroscopic measurements, we demonstrated that a tetra-sulfonated porphyrin, which was introduced in the subphase as anionic competitor, strongly inhibited the binding of CNCs to the floating fullerene layer. Nevertheless, despite the strong inhibition by anionic molecules, the mutual interaction between fulleropyrrolidines at the interface and the CNCs led to the assembly of robust hybrid films, which could be efficiently transferred onto solid substrates. Interestingly, ITO-electrodes that were modified with five-layer hybrid films exhibited enhanced electrical capacitance and produced anodic photocurrents at 0.4 V vs Ag/AgCl, whose intensity (230 nA/cm2) proved to be four times higher than the one that was observed with the sole fullerene derivative (60 nA/cm2)

Oxidative potential of fine aerosols from a Portuguese urban-industrial area

Trabalho apresentado em NInTec Science Days, 6-7 October 2022, Lisboa, PortugalN/

An exploratory study for the implementation of the oxidative potential assessment of particulate matter in Portugal

Particulate matter (PM) is a harmful air pollutant that damages human health by inducing oxidative stress through the excessive generation of reactive oxygen species (ROS). Oxidative Potential (OP) is a proposed metric to measure PM's capacity to generate ROS (Almetwally et al., 2020; Jiang et al., 2019). This study aims to implement the OPDTT assessment methodology at C2TN (Portugal). A set of PM2.5 samples was evaluated using a widely used protocol (Chirizzi et al., 2017), and the results were compared to the values previously obtained at DISTEBA, where the protocol is well established. Moreover, the use of the reference material SRM 1648 (Urban Particulate) as a standard for determining OPDTT was also evaluated. Analyzing a 10 mg.L-1 solution of the reference material, it was possible to conclude that the standard solution presented an average DTT activity (normalized to the mass) value of 27.60 ± 3.79 pmol.min-1.μg-1.info:eu-repo/semantics/publishedVersio

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) (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

Phosphate modified screen printed electrodes by lift treatment for glucose detection

The design of new materials as active layers is important for electrochemical sensor and biosensor development. Among the techniques for the modification and functionalization of electrodes, the laser induced forward transfer (LIFT) has emerged as a powerful physisorption method for the deposition of various materials (even labile materials like enzymes) that results in intimate and stable contact with target surface. In this work, Pt, Au, and glassy carbon screen printed electrodes (SPEs) treated by LIFT with phosphate buffer have been characterized by scanning electron microscopy and atomic force microscopy to reveal a flattening effect of all surfaces. The electrochemical characterization by cyclic voltammetry shows significant differences depending on the electrode material. The electroactivity of Au is reduced while that of glassy carbon and Pt is greatly enhanced. In particular, the electrochemical behavior of a phosphate LIFT treated Pt showed a marked enrichment of hydrogen adsorbed layer, suggesting an elevated electrocatalytic activity towards glucose oxidation. When Pt electrodes modified in this way were used as an effective glucose sensor, a 1–10 mM linear response and a 10 µM detection limit were obtained. A possible role of phosphate that was securely immobilized on a Pt surface, as evidenced by XPS analysis, enhancing the glucose electrooxidation is discussed

Assessment of oxidative potential of fine aerosols from different indoor and outdoor environments

Trabalho apresentado em European Aerosol Conference 2023 (EAC2023), September 3−8, 2023, Malaga, SpainN/

Pollution sources affecting oxidative potential of fine aerosols from a Portuguese urban-industrial area

Trabalho apresentado em European Aerosol Conference 2023 (EAC2023), September 3−8, 2023, Malaga, SpainN/

Heavy metals determination by biosensors based on enzyme immobilised by electropolymerisation

The work describes the original application of biosensors based on enzyme immobilised by electropolymerisation to heavy metal determination. An inhibition detection scheme has been employed for detecting Hg2+ by an established glucose biosensor based on glucose oxidase immobilised in poly-o-phenylenediamine. The investigated enzymatic inhibition appears reversible and mixed, in agreement with data for the enzyme in solution. A low response time (<2 min) and a rapid recovery of response by EDTA seem the most interesting characteristics of the proposed biosensor at the present stage of development, along with the well known easy preparation of this kind of biosensors. The occurrence of a high response also for Cu2+ opens the possibility to apply the biosensor in total toxic metal content determination

ANODIC ELECTRODEPOSITION OF CONDUCTING COBALT OXYHYDROXIDE FILMS ON A GOLD SURFACE. XPS STUDY AND ELECTROCHEMICAL BEHAVIOUR IN NEUTRAL AND ALKALINE SOLUTION.

A novel chemically modified electrode prepared by anodic electrodeposition of cobalt (III) film on the gold electrode substrate (Au-Co) was characterised by cyclic voltammetry and XPS techniques in both neutral and alkaline medium. Cobalt oxyhydroxide film was deposited by cycling the potential between 0.0 and 1.1 V versus SCE in 0.1 M sodium acetate solutions containing 10 mM CoCl2. The electrocatalytic properties of the Au-Co electrode were investigated in alkaline medium using glucose as a model compound. A comparative XPS study of bare gold, bare cobalt and Au-Co electrodes after electrochemical treatment in neutral and alkaline solutions has been carried out. A detailed XPS analysis of the Au4f(7.2), Co2p(3.2), O1s and C1s regions was performed to check the chemical composition of the Au-Co electrode upon electrochemical treatments. Film deposition is attributed to growth of conducting and compact CoOOH oxyhydroxide with significant insertion of carbonyl groups within the electrodeposited layer. The prolonged electrochemical treatment in alkaline medium produces a good stabilization of the Co-III oxyhydroxide film, with a dominant O1s feature at about 532.4 eV of BE corresponding to a non-stoichiometric surface oxygen. The absence of CoO species proves good conducting properties of the cobalt film and the absence of any passivation effects on the catalytic performance