349 research outputs found
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
An Overview of the Automated and On-Line Systems to Assess the Oxidative Potential of Particulate Matter
Recent years have seen a significant increase in the scientific literature related to various methods for analyzing oxidative potential (OP) of atmospheric particulate matter (PM). The presence of several types of PM, differing chemical and physical properties, released by both anthropogenic and natural sources, leads to numerous health issues in living organisms and represents an attractive target for air quality monitoring. Therefore, several studies have focused on developing rapid and self-operative tests, employing different target molecules to assess OP of atmospheric aerosols as well as unique approaches to overcome some of the most common laboratory-related issues in this kind of analysis. This work provides an overview of online and automated systems, as well as a broad picture of the state-of-art of the various devices and methods developed on this topic over the last two decades. Moreover, representative studies on this subject will be discussed, analyzing the advantages and drawbacks of the developed automated techniques
Modeling the microscopic electrical properties of thrombin binding aptamer (TBA) for label-free biosensors
Aptamers are chemically produced oligonucleotides, able to bind a variety of
targets such as drugs, proteins and pathogens with high sensitivity and
selectivity. Therefore, aptamers are largely employed for producing label-free
biosensors, with significant applications in diagnostics and drug delivery. In
particular, the anti-thrombin aptamers are biomolecules of high interest for
clinical use, because of their ability to recognize and bind the thrombin
enzyme. Among them, the DNA 15-mer thrombin-binding aptamer (TBA), has been
widely explored concerning both its structure, which was resolved with
different techniques, and its function, especially about the possibility of
using it as the active part of biosensors. This paper proposes a microscopic
model of the electrical properties of TBA and the aptamer-thrombin complex,
combining information from both structure and function. The novelty consists in
describing both the aptamer alone and the complex as an impedance network, thus
going deeper inside the issues addressed in an emerging electronics branch
known as proteotronics. The theoretical results are compared and validated with
Electrochemical Impedance Spectroscopy measurements reported in the literature.
Finally, the model suggests resistance measurements as a novel tool for testing
aptamer-target affinity.Comment: 5 figures, 1 tabl
Oxidative potential of fine aerosols from a Portuguese urban-industrial area: preliminary results
Trabalho apresentado em CQ UL 5th Meeting "Forging Bonds", 12-14 julho 2022, Lisboa, PortugalN/
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)
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)
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
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
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