Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
J Hazard Mater. 2023 Aug 15;456:131693. doi: 10.1016/j.jhazmat.2023.131693. Epub 2023 May 24.
Metals in particulate matter (PM) are hypothesized to have enhanced toxicity based on their ability to catalyze reactive oxygen species (ROS) formation. Acellular assays are used to measure the oxidative potential (OP) of PM and its individual components. Many OP assays, including the dithiothreitol (DTT) assay, use a phosphate buffer matrix to simulate biological conditions (pH 7.4 and 37 °C). Prior work from our group observed transition metal precipitation in the DTT assay, consistent with thermodynamic equilibria. In this study, we characterized the effects of metal precipitation on OP measured by the DTT assay. Metal precipitation was affected by aqueous metal concentrations, ionic strength, and phosphate concentrations in ambient PM sampled in Baltimore, MD and a standard PM sample (NIST SRM-1648a, Urban Particulate Matter). Critically, differences in metal precipitation induced differing OP responses of the DTT assay as a function of phosphate concentration in all PM samples analyzed. These results indicate that comparison of DTT assay results obtained at differing phosphate buffer concentrations is highly problematic. Further, these results have implications for other chemical and biological assays that use phosphate buffer for pH control and their use to infer PM toxicity.
颗粒物（PM）中的金属被假设具有增强的毒性，这基于它们催化活性氧（ROS）形成的能力。无细胞测定法用于测量 PM 及其各个成分的氧化潜力（OP）。许多 OP 测定法，包括二硫苏糖醇（DTT）测定法，使用磷酸盐缓冲基质来模拟生物条件（pH7.4 和 37°C）。我们小组之前的工作观察到 DTT 测定法中过渡金属的沉淀，这与热力学平衡一致。在这项研究中，我们研究了金属沉淀对 DTT 测定法测量的 OP 的影响。金属沉淀受水相金属浓度、离子强度和巴尔的摩市（马里兰州）和标准 PM 样品（NIST SRM-1648a，城市颗粒物）中环境 PM 中的磷酸盐浓度的影响。关键的是，在所有分析的 PM 样品中，金属沉淀引起的 DTT 测定法的 OP 响应差异随磷酸盐浓度的不同而不同。这些结果表明，在不同磷酸盐缓冲浓度下获得的 DTT 测定法结果的比较存在很大问题。此外，这些结果对其他使用磷酸盐缓冲液进行 pH 控制的化学和生物学测定法及其用于推断 PM 毒性的应用具有影响。
