Abstract
Different acellular assays were developed to measure particulate matter’s (PM) oxidative potential (OP), a metric used to predict the ability of PM in generating oxidative stress in living organisms. However, there are still fundamental open issues regarding the complex redox equilibria among the involved species which could include reducing compounds. The aim of this study was the pilot application of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay to PM in order to evaluate the presence of reducing species. The assay, commonly applied to biological matrices, was adapted to PM and showed good analytical performances. It allowed the analysis of conventional 24 h airborne PM samples with suitable sensitivity and good repeatability of the measurements. The assay was applied to seven samples representing possible PM contributes (certified urban dust NIST1648a; brake dust; Saharan dust; coke dust; calcitic soil dust; incinerator dust; and diesel particulate matter certified material NIST1650b) and to PM2.5 field filters. The same samples were also analyzed for elements. Preliminary results indicated that the assay gave a linear response and that detectable amounts of reducing species were present in PM samples. The combined application of DPPH and conventional OP assays could then permit, in the future, to gain more knowledge about the reaction and/or competition between oxidative and reducing processes.
Highlights
Particulate matter (PM) pollution is a serious global problem, especially in urban and industrialized areas [1], threatening both human and environmental health [2]
The aim of this work was to evaluate the applicability of the DPPH assay to PM for measuring reducing potential (RP) due to the presence of antioxidant species which could, in the future, integrate the information about redox properties of PM obtained by oxidative potential (OP) assays
Four DPPH assay experimental procedures with different extraction solutions were compared in terms of limits of detection (LODs), repeatability, and efficiency
Summary
Particulate matter (PM) pollution is a serious global problem, especially in urban and industrialized areas [1], threatening both human and environmental health [2]. A growing number of scientific studies have demonstrated links between exposure to ambient PM and adverse health outcomes in human, especially related to cardio-pulmonary diseases [3] and neurological disorders [4]. Over the last few decades, oxidative stress has been identified as one of the key mechanisms by which PM exerts its negative impacts on cellular systems and, on living organisms [5,6]. Oxidative stress is due to the imbalance between the generation of reactive oxygen species (ROS) alongside reactive nitrogen species (RNS) and the antioxidant defenses [3]. Measurements of particles’ OP are considered a promising and integrative method for assessing health impacts induced by PM [8]
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