Gibbons Angel M, Boadu Michael, Ohno Paul E
Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States.
Anal Chem. 2024 Dec 17;96(50):19947-19954. doi: 10.1021/acs.analchem.4c04291. Epub 2024 Dec 4.
The physicochemical properties of aerosols, including hygroscopicity, phase state, pH, and viscosity, influence important processes ranging from virus transmission and pulmonary drug delivery to atmospheric light scattering and chemical reactivity. Despite their importance, measurements of these key properties in aerosols remain experimentally challenging due to small particle sizes and low mass densities in air. Fluorescence probe spectroscopy is one of the only analytical techniques that is capable of experimentally determining these properties in situ in a nondestructive and minimally perturbative manner. However, the application of fluorescence probe spectroscopy to important classes of aerosols including exhaled respiratory and ambient atmospheric aerosols has been limited due to a typical reliance on premixing the probe molecule with particle constituents prior to particle generation, which is not always possible. Here, a method for aerosol fluorescent labeling based on probe molecule volatilization is developed. The method is first applied to label model polyethylene glycol (PEG) aerosols with two different polarity-sensitive probes, Nile red and Prodan. The similarity of the relative humidity-dependent fluorescent emission of each probe between prelabeled and volatilized-probe PEG particles validated the methodology. A preliminary application of the technique to indicate the hygroscopicity of artificial saliva respiratory particles and model atmospheric secondary organic aerosol particles is demonstrated. The methodology developed here paves the way for future studies applying powerful fluorescent probe-based analytical techniques to study exhaled or natural aerosols for which fluorescent prelabeling is not possible.
气溶胶的物理化学性质，包括吸湿性、相态、pH值和粘度，影响着从病毒传播、肺部药物递送，到大气光散射和化学反应性等重要过程。尽管这些性质很重要，但由于气溶胶颗粒尺寸小且在空气中质量密度低，对其关键性质的测量在实验上仍然具有挑战性。荧光探针光谱法是仅有的能够以无损且最小扰动的方式原位实验测定这些性质的分析技术之一。然而，由于通常依赖于在颗粒生成之前将探针分子与颗粒成分预混合，而这并非总是可行的，荧光探针光谱法在包括呼出的呼吸道气溶胶和环境大气气溶胶等重要类型气溶胶中的应用受到了限制。在此，开发了一种基于探针分子挥发的气溶胶荧光标记方法。该方法首先应用两种不同的极性敏感探针尼罗红和普罗丹对模型聚乙二醇（PEG）气溶胶进行标记。预标记的PEG颗粒和挥发探针的PEG颗粒之间每种探针的相对湿度依赖性荧光发射的相似性验证了该方法。展示了该技术在指示人工唾液呼吸颗粒和模型大气二次有机气溶胶颗粒吸湿性方面的初步应用。这里开发的方法为未来应用强大的基于荧光探针的分析技术研究无法进行荧光预标记的呼出或天然气溶胶的研究铺平了道路。
