Real-time detection of an airborne microorganism using inertial impaction and mini-fluorescent microscopy

Abstract

To achieve successful real-time detection of airborne pathogenic microorganisms, the problem must be considered in terms of their physical size and biological characteristics. We developed an airborne microorganism detection chip to realize the detection of microorganisms, ensuring compactness, sensitivity, cost-efficiency, and portability, using three key components: an inertial impaction system, a cartridgetype impaction plate, and a mini-fluorescent microscope. The inertial impaction system was used to separate microorganisms in terms of their aerodynamic particle size, and was fabricated with three impaction stages. Numerical analysis was performed to design the system; the calculated cutoff diameter at each impaction stage was 2.02 (first stage), 0.88 (second stage), and 0.54 μm (third stage). The measured cutoff diameters were 2.24, 0.91, and 0.49 μm, respectively. A cartridge-type impaction plate was used, composed of molded polydimethylsiloxane (PDMS) and an actual impaction region made of a SYBR green I dye-stained agar plate. A mini-fluorescent microscope was used to distinguish microbes from non-biological particles. Images of the microorganisms deposited at the impaction zone were obtained via mini-fluorescent microscopy, and fluorescent intensities of the images were calculated using in-house image-processing software. The results showed that the developed system successfully identified aerosolized biological particles from non-biological particles in real time.

Integrated micro-optofluidic platform for real-time detection of airborne microorganisms

“…Airborne microorganisms (or bioaerosols), including viruses, bacteria, and fungal spores, are associated with a wide range of health effects and environmental issues 1 . Because of the low settling velocities due to the small size of particles (~20 nm to 100 μm), such bioaerosols may be suspended in the atmosphere for a prolonged period, and can be carried over large distances 2 . Therefore, there is significant potential for inhalation into the human respiratory system, which has health consequences 3 .…”

Development of an automated wet-cyclone system for rapid, continuous and enriched bioaerosol sampling and its application to real-time detection

“…A technique enabling rapid real-time detection of airborne microorganisms would be advantageous for public health research and bioterrorism defense; however, the development of such a system is at an early stage. A major reason for the slow pace of development is the difficulty of determining the concentration and type of bioaerosols in the air stream [11][12][13][14][15][16]. Bioaerosols are typically detected by first collecting them in a liquid or on a surface and analyzing the collected particles using culture-based techniques, biochemical assays (e.g., polymerase chain reaction (PCR)) and/or enzyme-linked immunosorbent assay (ELISA) [14,[17][18][19][20].…”

“…Tan et al developed an automated electrostatic sampler that involves collection of bioaerosols in a liquid reservoir and their delivery to sensing devices [24]. Liu et al and other researchers described an airborne pathogen direct analysis system based on microfluidic enrichment [11][12][13]; however, these systems require prolonged sampling for enrichment. A novel bioaerosol sampling system, the MicroSampler, based on two-phase fluid control in a microchip can be used with a real-time bioaerosol sensor [25]; however, due to the low throughput, adequate sampling is difficult in the presence of bioaerosol concentrations < 500 CFU/m 3 air .…”

Biosensors for Monitoring Airborne Pathogens

“…Kang et al developed an optical lab-on-achip biosensor for the real-time detection of captured aerosolized pathogens using a mini fluorescent microscope and SYBR green intercalating dye. 167 The group reported that the sensor was capable of distinguishing bacterial pathogens (in this case, Staphylococcus epidermidis) from interfering agents collected in aerosols due to the presence of intercalating dye but lacked true specificity (it typically only detected the presence of bacteria). Furthermore, the process, although rapid (total assay time of less than 5 min) and free of sample pretreatment, relies on microscopic techniques.…”