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

 描述（由申请方提供）：空气中颗粒物的氧化能力与体外和体内氧化应激的产生相关。近年来，流行病学研究发现，细胞氧化应激损伤与哮喘、慢性阻塞性肺疾病（COPD）、阿尔茨海默病（Alzheimer's disease）等神经系统疾病有关。然而，这些研究是基于每日暴露和平均氧化能力的环境颗粒物。颗粒的氧化电位在很大程度上取决于它们的化学组成，更具体地说，取决于它们的氧化还原活性化合物，如过渡金属和醌。众所周知，环境颗粒物的物理化学性质随排放源和光化学老化程度而变化。因此，我们预计颗粒物产生活性氧和产生氧化损伤的能力会出现昼夜变化。 目前，有几种化学和体外试验来确定周围颗粒的氧化能力。然而，需要大量的样品来获得可量化的响应。使用普通的采集设备，需要较长的采样周期，通常为24至48小时。由于收集时间较长，颗粒的化学性质可能会改变，峰值暴露可能会被隐藏。最近关于空气中颗粒物暴露与不良健康影响之间关系的研究表明，颗粒物暴露的短期峰值是健康威胁的重要因素，特别是肺部疾病。流行病学研究 短期暴露于颗粒物浓度峰值的影响发现，与24小时平均PM10暴露相比，哮喘症状与1小时和8小时最大PM10（直径<10µm的颗粒）暴露的相关性更高。根据这些结果，开发能够测量健康压力源峰值浓度的仪器至关重要。在这个项目中，我们提出了一种新的方法，在线监测的氧化能力的气溶胶（莫卡）。其主要目标是开发一个现场部署的系统，允许在现场，时间分辨评估的能力，空气中的颗粒产生活性氧。我们的方法利用了我们公司的新颗粒生长技术，该技术能够将颗粒直接沉积到液体中，获得浓缩的悬浮液，可用于化学和体外分析。气溶胶收集器采用水冷凝生长技术，可将小至10 nm的颗粒收集到浓缩的水悬浮液中，效率> 90%。将使用通常称为DTT试验（二硫苏糖醇试验）的化学试验测量收集颗粒的氧化电位。 与现有的实验室和在线系统相比，o-MOCA方法有几个优点：i）它可以有效地将PM2.5直接收集到小体积的空气中， 水，增加了颗粒浓度，从而减少了收集所需的时间; ii）直接收集避免了与其他颗粒收集系统相关的最常见的人为因素; iii）它允许时间分辨的收集和现场直接分析，允许PM氧化能力的更令人满意的日常表征。以时间分辨方式表征气溶胶氧化潜力的能力将在评估PM暴露导致的氧化应激反应相关的可能不良结果时提供更准确的结果。 我们的目标将通过完成以下具体目标来实现：i）化学分析模块的设计、构造和离线优化; ii）化学模块与液体收集器的接口; iii）进行实验室控制研究以评估是否使用该方法允许对环境PM的氧化能力进行近实时测量。

 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), Alzheimer'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 24 to 48 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 1-h and 8-h maximum PM10 (particles with diameter <10µm) exposures than with 24-h mean PM10 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 firm'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 10 nm into concentrated water suspensions with efficiencies >90%. 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 PM2.5 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.