Performance Evaluation of the UVAPS in Measuring Biological Aerosols: Fluorescence Spectra from NAD(P)H Coenzymes and Riboflavin

Abstract

This article presents the results of the performance evaluation of the Ultraviolet Aerodynamic Particle Sizer (UVAPS, model 3312, TSI Inc., St. Paul, MN, USA), the novel instrument for real-time monitoring of biological aerosols. The main objective of the study was to compare the UVAPS response in measuring aerosols containing NADH, NADPH, or riboflavin particles. At the excitation and emission wavelengths at which the UVAPS operates, these compounds are the primary intrinsic fluorophores specific to biological particles. In addition, the study was focused on determining the detection limits of the UVAPS for these fluorophores. This information is important for the interpretation of UVAPS data while measuring bacterial aerosols. Fluorescence measurements were initially taken with a Varian Cary Eclipse Fluorescence Spectrophotometer for all three fluorophores. The samples were then aerosolized with the 6-jet Collison nebulizer. Riboflavin was found to be a stronger fluorophore than both NAD(P)H coenzymes. The fluorescence signals were considerably weaker for the NADPH samples compared to the NADH samples. The sensitivity of the UVAPS was found to be sufficiently high to detect the NADH and riboflavin at the concentrations characteristic of bacterial cells. The results of this study are discussed in a context of the results previously reported for the bacterial aerosols. It can be concluded that the amount of fluorophores detectable in uniformly mixed particles is equal to or less than the fluorophores expected to be present in the individual bacterial particles.

Systematic characterization and fluorescence threshold strategies for the wideband integrated bioaerosol sensor (WIBS) using size-resolved biological and interfering particles

“…The results presented here and from other studies using WIBS instruments, in contrast to reports using other UV-LIF instruments, suggest that the WIBS-4A is highly sensitive to the detection of bacteria using 280 nm excitation (only FL1 emission), but less so using the 370 nm excitation (FL3 emission) (e.g., Perring et al, 2015;Hernandez et al, 2016). A study by Agranovski et al (2003) also demonstrated that the UV-APS was limited in its ability to detect endospores (reproductive bacterial cells from sporeforming species with little or no metabolic activity and thus low NAD(P)H concentration). The lack of FL3 emission observed from bacteria in the WIBS may also suggest a weaker excitation intensity in Xe2 with respect to Xe1, manifesting in lower overall FL3 emission intensity (Könemann et al, 2017).…”

“…The FL3 channel in the WIBS-4A has an excitation of 370 nm and emission band of 420-650 nm, similar to that of the UV-APS with an excitation of 355 nm and emission band of 420-575 nm. Previous studies have suggested that viable microorganisms (i.e., bacteria) show fluorescence characteristics in the UV-APS due to the excitation source of 355 nm that was originally designed to excite NAD(P)H and riboflavin molecules present in actively metabolizing organisms (Agranovski et al, 2004;Hairston et al, 1997;Ho et al, 1999;Pöhlker et al, 2012). Previous studies with the UV-APS and other UV-LIF instruments using approximately similar excitation wavelengths have shown a strong sensitivity to the detection of "viable" bacteria Pan et al, 1999;Hairston et al, 1997;Brosseau et al, 2000).…”

“…For example, Kanaani et al (2007Kanaani et al ( , 2008Kanaani et al ( , 2009) and Agranovski et al (2003Agranovski et al ( , 2004Agranovski et al ( , 2005 presented several examples of UV-APS operation with respect to biofluorophores and biological particles. Healy et al (2012) provided an overview of 15 spore and pollen species analyzed by the WIBS, and Toprak and Schnaiter (2013) discussed the separation of dust from ambient fluorescent aerosol by applying a simple screen of any particles that exhibited fluorescence in one specific fluorescent channel.…”

“…The majority of bioaerosol analysis historically utilized microscopy or cultivation-based techniques. Both are time-consuming, relatively costly, and cannot be utilized for real-time analysis (Griffiths and Decosemo, 1994;Agranovski et al, 2004). Cultivation techniques can provide information about properties of the culturable fraction of the aerosol (e.g., bacterial and fungal spores) but can greatly underestimate the diversity and abundance of bioaerosols because the vast majority of microorganism species are not culturable (Amann et al, 1995;Chi and Li, 2007;Heidelberg et al, 1997).…”

Factors Influencing Rapid Detection of Bioaerosols by Surface Plasmon Resonance-Based Technique

“…As the result, a number of techniques for nearly real-time continuous detection and quantification of biological airborne particles have been developed, including ultraviolet aerodynamic particle sizer spectrometer (UVAPS), bioaerosol mass spectrometer (BAMS), ATP bioluminescence-based method and NanoPCR technique (Agranovski et al 2004c;Russell et al 2005;Xu and Yao 2013;Park et al 2014).…”