A new method for the real-time quantification of airborne biological particles using a coupled inertial aerosol system with in situ fluorescence imaging

Abstract

We describe the integration of an aerosol inertial impactor with in situ fluorescence imaging for the real-time detection and monitoring of airborne biological particles. Airborne particles were continuously collected on a fluorescent dye-containing agarose gel, and a mini-fluorescence microscope was used to produce in situ fluorescence particle images. Concentrations of size-segregated and dye-stained particles were then measured in real time upon deposition of airborne biological particles on the agarose gel substrate. To evaluate system performance, airborne bacterial particles from Escherichia coli were introduced onto the impactor (termed Bio-impactor) at various air flow rates and collection times. The particle cut-off diameter (d(50)) was controlled by adjusting sample flow rate so that a sample flow rate of 10 L/min produced a d(50) of similar to 0.84 mu m, which efficiently collected airborne E. coli particles. Our Bio-impactor system allows for the automated fluorescence imaging of collected particles, providing in situ information about fluorescence intensity at regular time intervals. We compared results from our system with those obtained using a colony counting method; our results demonstrated a clear correlation (R-2 = 0.9536) between system response and expected particle counts. Our novel impactor system could provide an inexpensive, simple, and portable method of real-time bioaerosol quantification. (C) 2017 Elsevier B.V. All rights reserved.