Spectrally-resolved fluorescence cross sections of aerosolized biological live agents and simulants using five excitation wavelengths in a BSL-3 laboratory

Abstract

A system for measuring spectrally-resolved fluorescence cross sections of single bioaerosol particles has been developed and employed in a biological safety level 3 (BSL-3) facility at Edgewood Chemical and Biological Center (ECBC). It is used to aerosolize the slurry or solution of live agents and surrogates into dried micron-size particles, and to measure the fluorescence spectra and sizes of the particles one at a time. Spectrally-resolved fluorescence cross sections were measured for (1) bacterial spores: Bacillus anthracis Ames (BaA), B. atrophaeus var. globigii (BG) (formerly known as Bacillus globigii), B. thuringiensis israelensis (Bti), B. thuringiensis kurstaki (Btk), B. anthracis Sterne (BaS); (2) vegetative bacteria: Escherichia coli (E. coli), Pantoea agglomerans (Eh) (formerly known as Erwinia herbicola), Yersinia rohdei (Yr), Yersinia pestis CO92 (Yp); and (3) virus preparations: Venezuelan equine encephalitis TC83 (VEE) and the bacteriophage MS2. The excitation wavelengths were 266 nm, 273 nm, 280 nm, 365 nm and 405 nm.

Airborne observations of regional variation in fluorescent aerosol across the United States

“…Less is known about the ability of the WIBS to detect bacteria, which are predicted to be another important source of PBAP with global emissions estimated to be between 0.74 and 28.1 Tg/yr [Burrows et al, 2009a;Hoose et al, 2010a;Jacobson and Streets, 2009]. Emission spectra of several kinds of bacteria have been measured at a variety of excitation wavelengths [Hill et al, 2009;Pan et al, 2014b], as a function of particle size, illumination intensity, and fluorophore concentration [Hill et al, 2001] and as a function of oxidation and humidity [Pan et al, 2014a]. Bacteria typically have strong absorption features around 280 nm with emission occurring between 310 and 400 nm.…”

Detection and characterization of biological and other organic-carbon aerosol particles in atmosphere using fluorescence

“…Fig. 4 shows the averaged UV-LIF spectra of 1000 individual aerosol particles for different measured samples excited at 266, 273, 280, 365 and 405 nm [74]. As the live bioagents measured are very dangerous, all the measurements were required to carry out in a biological safety level 3 (BSL3) laboratory.…”

“…However, the spectra excited by 365 and 405 nm had not been adjusted, other than subtracting the background and applying the spectral response calibration, because the fluorescence from some samples (e.g., BtK) is too weak and too noisy to be adjusted for comparisons of the spectral shapes. Table 1 Averaged total and peak fluorescence cross sections from about 2000 (range 1000-3000) particles of various aerosolized live agents and surrogates excited at 5 different wavelengths [74].…”

“…Even slightly different aerosol generation conditions may result in different fluorescence cross sections. For bacterial spores (prepared under the conditions as stated in the reference by [74]), Btk has optical properties similar to BaA, based on particle size and total fluorescence intensity via 266-, 273-or 280-nm excitation. But BG, Bti or Btk are not good simulants for BaA if the system is using particle size and total fluorescence by 355-, 365-or 405-nm excitation.…”

“…The spectra excited by 266, 273 and 280 nm are normalized to the same peak intensities at about 330 nm for easy comparisons of spectral profiles. The spectra excited at 365 and 405 nm have not been normalized[74].…”