Arantzazu Eiguren-Fernandez

Efficient collection of viable virus aerosol through laminar-flow, water-based condensational particle growth.

State‐of‐the‐art bioaerosol samplers have poor collection efficiencies for ultrafine virus aerosols. This work evaluated the performance of a novel growth tube collector (GTC), which utilizes laminar‐flow water‐based condensation to facilitate particle growth, for the collection of airborne MS2 viruses.

Highly efficient collection of infectious pandemic influenza H1N1 virus (2009) through laminar-flow water based condensation

© 2016 American Association for Aerosol Research

Detection near 1-nm with a laminar-flow, water-based condensation particle counter

ABSTRACT Presented is a laminar-flow, water-based condensation particle counter capable of particle detection near 1 nm. This instrument employs a three-stage, laminar-flow growth tube with a “moderator” stage that reduces the temperature and water content of the output flow without reducing the peak supersaturation, and makes feasible operation at the large temperature differences necessary for achieving high supersaturations. The instrument has an aerosol flow of 0.3 L/min, and does not use a filtered sheath flow. It is referred to as a “versatile” water condensation particle counter, or vWCPC, as operating temperatures can be adjusted in accordance with the cut-point desired. When operated with wall temperatures of ∼2°C, >90°C, and ∼22°C for the three stages, respectively, the vWCPC detects particles generated from a heated nichrome wire with a 50% efficiency cut-point near 1.6 nm mobility diameter. At these operating temperatures, it also detects 10–20% of large molecular ions formed from passing filtered ambient air through a bipolar ion source. Decreasing the temperature difference between the first two stages, with the first and second stages operated at 10 and 90°C, respectively, essentially eliminates the response to charger ions, and raises the 50% efficiency cut-point for the nichrome wire particles to 1.9 nm mobility diameter. The time response, as measured by rapid removal of an inlet filter, yields a characteristic time constant of 195 ms. Copyright

Drifted Influenza A and B Viruses Collected by a Water-Based Condensation Growth Air Sampler in a Student Health Care Center during an Influenza Outbreak

ABSTRACT A viable virus aerosol sampler (VIVAS) effectively collected viable influenza A and B viruses from air inside a student health care center during an influenza outbreak. The viruses had “drifted” genes, showcasing the usefulness of the VIVAS for air sampling and noninvasive surveillance of viruses in circulation.

An online monitor of the oxidative capacity of aerosols (o-MOCA)

The capacity of airborne particulate matter to generate reactive oxygen species (ROS) has been correlated with the generation of oxidative stress both in vitro and in vivo. The cellular damage from oxidative stress, and by implication with ROS, is associated with several common diseases, such as asthma and chronic obstructive pulmonary disease (COPD), and some neurological diseases. Yet currently available chemical and in vitro assays to determine the oxidative capacity of ambient particles require large samples, analyses are typically done offline, and the results are not immediate. Here we report the development of an online monitor of the oxidative capacity of aerosols (o-MOCA) to provide online, time-resolved assessment of the capacity of airborne particles to generate ROS. Our approach combines the Liquid Spot Sampler (LSS), which collects particles directly into small volumes of liquid, and a chemical module optimized for online measurement of the oxidative capacity of aerosol using the dithiothreitol (DTT) assay. The LSS uses a three-stage, laminar-flow water condensation approach to enable the collection of particles as small as 5 nm into liquid. The DTT assay has been improved to allow the online, time-resolved analysis of samples collected with the LSS but could be adapted to other collection methods or offline analysis of liquid extracts. The o-MOCA was optimized and its performance evaluated using the 9,10-phenanthraquinone (PQ) as a standard redox-active compound. Laboratory testing shows minimum interferences or carryover between consecutive samples, low blanks, and a reproducible, linear response between the DTT consumption rate (nmol min−1) and PQ concentration (μM). The calculated limit of detection for o-MOCA was 0.15 nmol min−1. The system was validated with a diesel exhaust particle (DEP) extract, previously characterized and used for the development, improvement, and validation of the standard DTT analysis. The DTT consumption rates (nmol min−1) obtained with the o-MOCA were within experimental uncertainties of those previously reported for these DEP samples. In ambient air testing, the fully automated o-MOCA was run unattended for 3 days with 3 h time resolution and showed a diurnal and daily variability in the measured consumption rates (nmol min−1 m−3).

Water condensation-based nanoparticle charging system: Physical and chemical characterization

Abstract A water condensation-based ion charging system has been developed to enhance both the charging efficiency and the concentration of sub-20 nm particles. This NanoCharger consists of a bipolar ion source followed by a parallel plate water-based condensation system, an embedded ion scavenger, and an aerodynamic focusing stage. Sufficient numbers of ions are transported through the system to attach to the formed droplets. An ion scavenger removes the ions immediately after the droplet formation to minimize multiple charging. A subsequent cold-walled condensation stage removes most of the water vapor, lowering the dew point to below 16 °C, while a set of focusing nozzles concentrates the droplets into ∼10% of the flow. The flow is then slightly heated to evaporate the droplets. The physical enhancement of electrical charging was evaluated in the laboratory using mobility-selected particles, and found to provide ∼40-fold enhancement over bipolar charging for 6–15 nm particles. Chemical artifacts were evaluated through thermal desorption chemical ionization mass spectrometry. Data comparing ion spectra for flow that passed through the NanoCharger to that obtained without it showed nearly equivalent ion spectra, indicating that no significant artifacts were introduced from the condensation–evaporation process. Copyright

A MAGIC Concept for Self-Sustained, Water based, Ultrafine Particle Counting

Abstract A self-sustaining, motion-tolerant, water-based condensation particle counter (CPC) has been designed, fabricated, and tested. Referred to as “MAGIC” for moderated aerosol growth with internal water cycling, the particle size response is similar to the 5-nm cut-point commercial CPCs. MAGIC is a laminar-flow instrument with three temperature stages: cool, warm, and cool. The middle warm-walled stage initiates the condensational growth and the final cool-walled stage maintains supersaturated conditions while recovering water vapor. By using a continuous wick throughout all three stages, the system recharges itself through a combination of water condensate from the sampled airstream and recovery of water vapor from the peak supersaturation region. A reservoir-less prototype system based on this concept was built and tested. Experiments show equal performance in any orientation, upright or inverted, and tolerance to tipping, shaking and vibrational shocks up to 5 g. Under mild ambient conditions, it provided multi-week operation without replenishing the wick. Copyright

Collection of airborne bacteria and yeast through water-based condensational growth

One limitation in air sampling of airborne microorganisms is their inactivation by forceful impaction and/or dehydration during the collection process. Proper inhalation risk assessments require proof of viability, as non-viable microorganisms cannot cause infectious diseases. In this study, laboratory-generated aerosols of a vegetative bacterium (E. coli) or yeast (S. kudriavzevii) were collected by a laminar-flow water-based condensational “growth tube collector (GTC),” and the GTC’s collection efficiencies were compared with those using an industry standard BioSampler. Collection efficiencies resulting from two types of collection media, phosphate-buffered saline (PBS) and nutrient media (Nutrient Broth, NB, for E. coli, and Yeast Tryptone Glucose Broth, YTGB, for S. kudriavzevii) were also assessed. Both the GTC and the BioSampler performed equally when PBS was used as the collection medium for E. coli, whereas more viable E. coli cells were collected in the GTC than the BioSampler with NB. For S. kudriavzevii, the GTC outperformed the BioSampler using either PBS or YTGB. This is likely because aerosolized E. coli cells can better survive impaction than S. kudriavzevii under the conditions used, and the BioSampler has a much higher collection efficiency for particles in the size range of single-celled E. coli than S. kudriavzevii. Moreover, the GTC had a detection limit one order of magnitude lower for yeast aerosols compared with that of the BioSampler. These results indicate that the GTC is a promising device for sampling viable aerosolized gram-negative bacteria and yeast, as it is less damaging to these types of microorganisms during the collection process.

Collection of Viable Aerosolized Influenza Virus and Other Respiratory Viruses in a Student Health Care Center through Water-Based Condensation Growth

The significance of virus aerosols in the natural transmission of respiratory diseases has been a contentious issue, primarily because it is difficult to collect or sample virus aerosols using currently available air sampling devices. We tested a new air sampler based on water vapor condensation for efficient sampling of viable airborne respiratory viruses in a student health care center as a model of a real world environment. The new sampler outperformed the industry standard device (the SKC BioSampler) in the collection of natural virus aerosols and in maintaining virus viability. These results using the VIVAS indicate that respiratory virus aerosols are more prevalent and potentially pose a greater inhalation biohazard than previously thought. The VIVAS thus appears to be a useful apparatus for microbiology air quality tests related to the detection of viable airborne viruses. ABSTRACT The dynamics and significance of aerosol transmission of respiratory viruses are still controversial, for the major reasons that virus aerosols are inefficiently collected by commonly used air samplers and that the collected viruses are inactivated by the collection method. Without knowledge of virus viability, infection risk analyses lack accuracy. This pilot study was performed to (i) determine whether infectious (viable) respiratory viruses in aerosols could be collected from air in a real world environment by the viable virus aerosol sampler (VIVAS), (ii) compare and contrast the efficacy of the standard bioaerosol sampler, the BioSampler, with that of the VIVAS for the collection of airborne viruses in a real world environment, and (iii) gain insights for the use of the VIVAS for respiratory virus sampling. The VIVAS operates via a water vapor condensation process to enlarge aerosolized virus particles to facilitate their capture. A variety of viable human respiratory viruses, including influenza A H1N1 and H3N2 viruses and influenza B viruses, were collected by the VIVAS located at least 2 m from seated patients, during a late-onset 2016 influenza virus outbreak. Whereas the BioSampler when operated following our optimized parameters also collected virus aerosols, it was nevertheless overall less successful based on a lower frequency of virus isolation in most cases. This side-by-side comparison highlights some limitations of past studies based on impingement-based sampling, which may have generated false-negative results due to either poor collection efficiency and/or virus inactivation due to the collection process. IMPORTANCE The significance of virus aerosols in the natural transmission of respiratory diseases has been a contentious issue, primarily because it is difficult to collect or sample virus aerosols using currently available air sampling devices. We tested a new air sampler based on water vapor condensation for efficient sampling of viable airborne respiratory viruses in a student health care center as a model of a real world environment. The new sampler outperformed the industry standard device (the SKC BioSampler) in the collection of natural virus aerosols and in maintaining virus viability. These results using the VIVAS indicate that respiratory virus aerosols are more prevalent and potentially pose a greater inhalation biohazard than previously thought. The VIVAS thus appears to be a useful apparatus for microbiology air quality tests related to the detection of viable airborne viruses.