Determination of pH and Other Physicochemical Properties of Respiratory Aerosols via Fluorescence Probe Spectroscopy

ANGEL GIBBONS, Victoria Cover, Paul Ohno, Auburn University

     Abstract Number: 50
     Working Group: Bioaerosols

Abstract
Understanding the viability of viruses contained in respiratory particles and the connections between this viability and the relative humidity (RH)- and temperature-mediated physicochemical properties of the particles themselves is critical to mitigate respiratory disease transmission. Here, we present the use of fluorescence probe spectroscopy to investigate the pH of submicron model respiratory aerosols. pH-sensitive fluorescent molecules were incorporated into the particles of interest and their ratiometric fluorescent response was used to determine particle pH. The pH of the particles trended towards more acidic pH values than that of bulk solution from which the particles were generated. Furthermore, we demonstrate that volatilization of probe molecules and subsequent condensation into particles of interest is a viable method of aerosol fluorescent labeling. This technique enables the study of real exhaled respiratory particles using fluorescence probe spectroscopy. Finally, we discuss the outlook for fluorescence probe spectroscopy in the field, including its use to investigate viscosity as well as its application to more chemically-complex systems.