Detection and quantification of reactive oxygen species (ROS) in indoor air

Abstract

Reactive oxygen species (ROS), such as free radicals and peroxides, are environmental trace pollutants potentially associated with asthma and airways inflammation. These compounds are often not detected in indoor air due to sampling and analytical limitations. This study developed and validated an experimental method to sample, identify and quantify ROS in indoor air using fluorescent probes. Tests were carried out simultaneously using three different probes: 2',7'-dichlorofluorescin (DCFH) to detect a broad range of ROS, Amplex ultra Red® (AuR) to detect peroxides, and terephthalic acid (TPA) to detect hydroxyl radicals (HO(•)). For each test, air samples were collected using two impingers in series kept in an ice bath, containing each 10 mL of 50 mM phosphate buffer at pH 7.2. In tests with TPA, that probe was also added to the buffer prior to sampling; in the other two tests, probes and additional reactants were added immediately after sampling. The concentration of fluorescent byproducts was determined fluorometrically. Calibration curves were developed by reacting DCFH and AuR with known amounts of H2O2, and using known amounts of 2-hydroxyterephthalic acid (HTPA) for TPA. Low detection limits (9-13 nM) and quantification limits (18-22 nM) were determined for all three probes, which presented a linear response in the range 10-500 nM for AuR and TPA, and 100-2000 nM for DCFH. High collection efficiency (CE) and recovery efficiency (RE) were observed for DCFH (CE=RE=100%) and AuR (CE=100%; RE=73%) by sampling from a laboratory-developed gas phase H2O2 generator. Interference of co-occurring ozone was evaluated and quantified for the three probes by sampling from the outlet of an ozone generator. The method was demonstrated by sampling air emitted by two portable air cleaners: a strong ozone generator (AC1) and a plasma generator (AC2). High ozone levels emitted by AC1 did not allow for simultaneous determination of ROS levels due to high background levels associated with ozone decomposition in the buffer. However, emitted ROS were quantified at the outlet of AC2 using two of the three probes. With AuR, the concentration of peroxides in air emitted by the air cleaner was 300 ppt of H2O2 equivalents. With TPA, the HO(•) concentration was 47 ppt. This method is best suited to quantify ROS in the presence of low ozone levels.

The oxidative capacity of indoor source combustion derived particulate matter and resulting respiratory toxicity

“…ROS was determined by the fluorogenic cell-based method using 2′,7′dichlorodihydrofluorescein diacetate (DCFH-DA) as the indicator, which has been commonly used for environmental toxicology (Eruslanov and Kusmartsev, 2010;Montesinos et al, 2015). After 24 hours exposure to PM2.5, DCFH-DA was added to the A549 cells, and cultured for 30 min.…”

Probing Nanoscale Interactions of Antimicrobial Zinc Oxide Quantum Dots on Bacterial and Fungal Cell Surfaces

“…[45,59] Due to the negative charge of the microbial cell wall, negatively charged hydroxyl radicals and superoxides have limited interaction with the surface membrane, [62] while positively charged H 2 O 2 easily interacts through electrostatic forces, and damages lipid molecules, thus easily penetrating the cell walls and membranes and reacting with intracellular contents. [44,45,[63][64][65] In this work, we utilized the fluorogenic probe, 2′,7′-dichlorodihydrofluorescein diacetate (H 2 DCFDA), due to its ability in detecting a broad range of ROS, particularly hydrogen peroxide (H 2 O 2 ) [66] UV-vis spectroscopy was used to determine the rate of release of ROS from ZnO QDs at varied time intervals, and the presence of highly fluorescent oxidized 2′7′-dichlorofluorescein (DCF) was significantly (p < 0.01) increased at 0.5 and 1 h of UV illumination compared to a control containing no ZnO QDs, as shown in Figure 7. ROS species generation was not significantly different between 0.5 and 1 h of UV illumination, due to the equilibrium of H 2 O 2 achieved through elimination when reacting with photogenerated electrons and superoxides.…”

Fabrication and Performance of a Multidischarge Cold-Atmospheric Pressure Plasma Array

“…The production of ultraviolet radiation and reactive oxygen and nitrogen species, such as hydrogen peroxide, ozone, superoxide, and peroxynitrite, are some of the primary mechanisms by which cold atmospheric plasmas exert antimicrobial effects [2], [5], [6], [11]. To begin to examine the production of reactive oxygen species with our system, the formation of hydrogen peroxide was measured using 2',7'-dichlorofluorescin diacetate (DCFH) and horseradish peroxidase [19]. Briefly, the eight-element array was discharged using an Ar/O 2 gas mixture (13 slm Ar/0.5 slm O 2 ) at 1.45 kV, 11.7 mA.…”