In-situ Measurement of the Capacity of Airborne Particulate Matter to Generate Reactive Oxygen Species

DESCRIPTION provided by applicant The oxidative capacity of airborne particulate matter has been correlated with the generation of oxidative stress both in vitro and in vivo In recent years epidemiological studies have associated damaged caused by cellular oxidative stress with several common diseases such as asthma chronic obstructive pulmonary disease COPD Alzheimerandapos s and other neurological diseases However these studies are based on daily exposure and averaged oxidative capacity of ambient particulate matter Oxidative potential of the particles depends considerably on their chemical composition more specifically on their redox active compounds such as transition metals and quinones It is well known that physical chemical properties of ambient particles vary with emission sources and the extent of photochemical aging Thus we expect diurnal variations in the ability of particulate matter to generate reactive oxygen species and exert oxidative damage are expected Currently there are several chemical and in vitro assays to determine the oxidative capacity of ambient particles However significant amounts of sample are needed to obtain a quantifiable response Using the common collection devices long sampling periods are needed usually to hours With these long collection periods chemical properties of the particles may be altered and peak exposures hidden Recent studies on the association between airborne particle exposures and adverse health effects identify short term peaks in particulate matter exposures as important factors in health threat especially in lung diseases An epidemiological study of the effect of short term exposure to peaks in particulate matter concentrations found that asthma symptoms were more highly associated with h and h maximum PM particles with diameter andlt m exposures than with h mean PM exposures Based on these results the development of instruments capable of measuring exposure to peak concentrations of health stressors is of vital importance In this project we propose a new approach for an on line monitor of the oxidative capacity of aerosols o MOCA The main objective is to develop a field deployable system that allows in situ time resolved assessment of the capacity of airborne particles to generate ROS Our approach capitalizes on our firmandapos s new particle growth technology that enables direct particle deposition into liquids obtaining concentrated suspensions ready for chemical and in vitro assays The aerosol collector uses the water condensational growth technology which allows the collection of particles as small as nm into concentrated water suspensions with efficiencies andgt The oxidative potential of the collected particles will be measured using the chemical assays commonly known as the DTT assay dithiothreitol assay The o MOCA approach has several advantages over the existing laboratory and on line systems i it can efficiently collect PM directly into a small volume of water increasing the particle concentration and thus reducing the time needed for collection ii with direct collection it avoids the most common artifacts associated with other particle collectio systems iii it allows for time resolved collection and in field direct analysis allowing for a mre satisfactory daily characterization of the PM oxidative capacity The ability to characterize the oxidative potential of aerosols in a time resolved manner will provide more accurate results when assessing possible adverse outcomes related to oxidative stress responses resulting from PM exposure Our goal will be achieved by completing the following specific aims i design construction and off line optimization of the chemical assay module ii interface the chemical module with the liquid collector iii conduct laboratory controlled studies to evaluate whether ou approach allows for near real time measurements of the oxidative capacity of ambient PM PUBLIC HEALTH RELEVANCE Exposure to fine particulate matter is associated with a number of adverse health effects However the mechanisms by which airborne particles exert toxicity are not well understood A leading hypothesis states that inhaled airborne particles induce injury by generating reactive oxygen species ROS In this project we proposed a new approach to measure the ability of particles to produce ROS by developing an on line monitor of the oxidative capacity of aerosols o MOCA The proposed system allows direct deposition of airborne particles into liquid capturing both soluble and insoluble components and minimizing changes in particle properties involved in their oxidative potential The oxidative capacity of the particles in suspension is measured on line using the dithiothreitol DTT assay The o MOCA provides the means for in situ real time assessment of the ability of airborne particles to generate ROS allowing a better understanding of the impact that exposure to aerosol may have on human health