Biocascade inlet - Project Summary
Respiratory infections are the most common reason for doctor visits and the third leading cause
of deaths. Viruses are the causative agents of most respiratory tract infections. Knowledge of
the transmission modes for pathogenic respiratory viruses is critical for improving mitigation
strategies that safeguard public health, but understanding their transmission mechanisms is
hampered by existing sampling methods. So far, no method has been recommended by the
public health organizations for the collection and detection of airborne viruses. The lack of
standard protocols results from the fact that no sampling procedure is appropriate for sampling
of all bioaerosols. During sampling, it is necessary to minimize inactivation of microbes, such as
incapacitating desiccation and destructive impaction upon collection onto a collection surface.
When collecting samples for detection of viral genomic RNA or DNA, maintaining the viability of
the virus is not necessary, but maintaining nucleic acid integrity is essential, especially for RNA,
which is rapidly degraded upon exposure to the environment. For assessing infectivity, the
pathogen needs to be viable. In both cases, gentle collection methods are required.
Although previous efforts have tried to separate virus-containing particles by aerodynamic
size, maintaining their infectivity during sampling remains challenging. Here, we aim to develop
a novel sampling system, the BioCascade, that will allow the collection of airborne viruses within
four different bioaerosol particle size-fractions: >10 um, PM4-10, PM1.5-4 and PM1.5 into liquid
medium, while maintaining infectivity of the viruses that are collected. In Phase I, we built a
BioCascade prototype. Its particle size-range cut-off and the collection efficiency of each stage
were modeled and designed by numerical simulations followed by validation through laboratory
experiments using National Institutes of Science and Technology (NIST)-certified standard-
sized particles. Its ability to collect and maintain the infectivity of bioaerosol was then assessed
using microorganisms that were representative of the size ranges that would be encountered in
bioaerosols. All Phase-I aims were successfully achieved. In Phase II, we aim to improve our
prototype by expanding its capabilities, such as a cold collection chamber for providing a better
environment for the collected pathogens, and a control system to maintain the liquid level that
enables increased sampling time to several hours. By providing size-fractionated air samples
that contain infectious pathogens, the Biocascade is envisioned as a powerful tool, not available
before, that can transform our current disease-control paradigm from a reactive approach (to an
outbreak after its fact) to a proactive approach (inform us the forthcoming viruses).
