Characterization of single fungal aerosol particles in a reactive atmospheric environment using time-resolved optical trapping-Raman spectroscopy (OT-RS)

Abstract

We applied a time-resolved, optical trapping-Raman spectroscopy (OT-RS) technique to characterize single, trapped bioaerosol particles under well-controlled reactive conditions that mimic the native state of particles in the atmosphere. We measured Raman spectra of seven different fungus samples using an OT-RS system, in which single fungal aerosol particles of tens of microns in size are trapped without photo-damage while relative humidity and ozone concentration around the particle are well controlled. We initially obtained Raman spectral fingerprints of seven different single-trapped fungal aerosol particles in air. We then measured time-resolved Raman spectra of the fungal aerosol particles trapped in air over a period of 40 minutes and characterized the temporal behavior of the trapped particles in terms of Raman band structure and intensity. We also measured time-resolved Raman spectra of the fungal aerosol particles exposed to ozone in a controlled concentration and relative humidity and compared the spectral features with those obtained when the single fungal aerosol particles were exposed to air. Results show that we not only observed time variations of the physical and chemical properties of single-trapped particles, but also specified several individual chemical function groups such as lipids and proteins that undergo chemical reactions with ozone. This work demonstrated that OT-RS is a powerful technology for characterization of physical, chemical, and biological properties of single bioaerosol particles in simulated atmospheric conditions and for potential detection of single bioaerosol particles in the atmosphere using Raman spectral fingerprints.