Organic components modulate the morphology of respirable aerovirology-relevant aerosols

Airborne transmission of viruses occurs via aerosol particles, whose morphology provides insights into the microenvironments that viruses experience. Aerosol morphology includes particle size, shape, phase state, and chemical homogeneity, yet systematic studies remain limited. Here, we characterized model bioaerosol morphologies generated from (1) NaCl-organic two-component mixtures, (2) common cell culture media, and (3) artificial respiratory fluids. Particles were collected using a virtual impactor and Andersen cascade impactor and analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Results show that organic components modulate the morphology: dipalmitoylphosphatidylcholine (DPPC) promotes organic-inorganic phase separation while proteins prohibit formation of large crystals and leads to better mixing among components. At 30% RH with a drying period of 10 s, most aerosols appeared desiccated, though NaCl-glucose, DMEM complete media and artificial saliva with mucin remained semi-solid or gel-like. Among all formulations examined, EMEM complete media and artificial saliva (non-mucin) show a size-dependent morphology. Our study demonstrates how chemical composition and size alter surrogate bioaerosol phase (semi-solid or solid) and morphology and provides new insights into the microenvironment of aerosol particles for aerovirology investigations.