Chemical Composition Dependent Morphology of Model Bioaerosols Generated in Aerovirological Studies

DEEPAK SAPKOTA, Yuhui Guo, Zhenpeng Qin, Hui Ouyang, The University of Texas at Dallas

     Abstract Number: 377
     Working Group: Aerosol Physics

Abstract
Virus-laden particles are bioaerosols generated through respiratory activities or aerosol generators in aerovirological experiments. Bioaerosol morphology, which encompasses characteristics such as shape, phase state, and chemical homogeneity, is a critical property for the mechanistic understanding of virus transmission in indoor environments. Currently, aerovirological experiments often utilize different aerosolization media, each with distinct physical properties and chemical compositions. We hypothesize that these varying compositions result in different morphologies, which in turn might contribute to inconsistencies in study outcomes. In this study, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) imaging were used to examine the morphology and chemical composition distribution of model bioaerosols equilibrated at a controlled relative humidity (RH) of 30%. Our results show that bioaerosol morphology is strongly influenced by chemical composition. In two-component systems with a 1:1 organic-to-inorganic mass ratio, aerosols containing NaCl with mucin or bovine serum albumin (BSA) appeared well-mixed, whereas NaCl with glucose or dipalmitoylphosphatidylcholine (DPPC) exhibited phase separation, with the inorganic salt crystallized and forming a clear boundary from the organic contents. Among cell culture media, Dulbecco’s Modified Eagle Medium (DMEM), with or without fetal bovine serum (FBS) and penicillin, formed core-shell phase-separated structures, whereas Eagle’s Minimum Essential Medium (EMEM) displayed a well-mixed distribution. Artificial saliva prepared following Woo’s formulation showed homogeneous chemical distribution. In contrast, Artificial Saliva (AS) and Artificial Lung Fluid (ALF), purchased and used without modifications from Pickering Laboratories, both exhibited phase-separated morphologies, with AS forming a core-shell structure. Interestingly, even at 30% RH, several organic-rich bioaerosols, such as NaCl with glucose, DMEM formulations, and AS from Pickering Lab exhibited semi-solid states. If virions are localized with organics, the spatial distribution of these organics may influence their microenvironmental conditions and survival mechanisms. Therefore, when possible, bioaerosol morphology should be reported in laboratory-based aerovirology studies to improve reproducibility and understanding of transmission dynamics.