Detection of Bioaerosol Based on Single Particle Differential Circular Polarization Scattering

YONG-LE PAN, Aimable Kalume, Jessica Arnold, Chuji Wang, Joshua Santarpia, U.S. Army Research Laboratory

     Abstract Number: 55
     Working Group: Instrumentation and Methods

Abstract
Real-time detection and characterization of bioaerosol has been an important research topic for health and environment sciences. Currently the early warning bioaerosol detection systems are mainly based on fluorescence, elastic scattering etc., optical methods, but they either have a high false alarm rate or are still too expensive. These inconveniences led us to develop new early-warning biosensor with low cost and low false alarm rate.

It was reported that DNA helical structures in biological molecules have non-zero circular intensity differential scattering (CIDS, normalized Mueller scattering-matrix element S14) than that from isotropic particles. So far, CIDS measurements have been only carried out on suspension samples, with a polarization modulator and a rotating detector due to its ultra-weak signals (10^-3-10^-6). Such complex laboratory instrumentation is not readily deployable as a field biosensor.

Here, we report an advanced design for measuring CIDS from single aerosol particles without any moving parts or modulator. The single particle CIDS phase function is obtained using a reflector to project scattering light at different angles onto an ICCD detector instead of a rotating detector. The differential signals were obtained from a particle interacting with two illuminating laser beams with left- and right-circular polarizations, which were produced by fixed optical components without any modulator. This innovative setup, significantly, shortens the measurement times from tens of minutes to tens of micron seconds. Measurements of CIDS phase functions from single aerosol particles of B. subtilis, E. coli spores, MS2 bacteriophage, Yersinia rohdei, DNA-tagged polystyrene (PSL) microsphere, tryptophan, PSL microsphere, atmospheric aerosol particles are carried out using this system. The results showed that DNA contained bioaerosol particles (e.g. B. subtilis spores) have at least three times stronger CIDS signals than non-bioaerosol particles (e.g. PSL microspheres). This newly developed system gives a promise for an innovative early-warning biosensor with low cost and low false alarm rate.

Acknowledgements
Thank DTRA CB10745 support.