As part of the U.S. Department of Homeland Security Detect-to-Protect program, a multilab [Sandia National
Laboratories (SNL), Lawrence Livermore National Laboratories (LLNL), Pacific Northwest National Laboratory
(PNNL), Oak Ridge National Laboratory (ORNL), and Los Alamos National Laboratory (LANL)] effort is addressing
the need for useable detect-to-warn bioaerosol sensors for public facility protection. Towards this end, the SNL team is
employing rapid fluorogenic staining to infer the protein content of bioaerosols. This is being implemented in a flow
cytometry platform wherein each particle detected generates coincident signals of forward scatter, side scatter, and
fluorescence. Several thousand such coincident signal sets are typically collected to generate a probability distribution
over the scattering and fluorescence values. A linear unmixing analysis is performed to differentiate components in the
mixture. After forming a library of pure component distributions from measured pure material samples, the distribution
of an unknown mixture of particles is treated as a linear combination of the pure component distributions. The
scattering/fluorescence probability distribution data vector a is considered the product of two vectors, the fractional
profile f and the scattering/fluorescence distributions from pure components P. A least squares procedure minimizes the
magnitude of the residual vector e in the expression a = fPT + e. The profile f designates a weighting fraction for each
particle type included in the set of pure components, providing the composition of the unknown mixture. We discuss
testing of this analysis approach and steps we have taken to evaluate the effect of interferents, both known and unknown.
As part of the U.S. Department of Homeland Security Detect-to-Protect (DTP) program, a multilab [Sandia National
Laboratories (SNL), Lawrence Livermore National Laboratories (LLNL), Pacific Northwest National Laboratory
(PNNL), Oak Ridge National Laboratory (ORNL), and Los Alamos National Laboratory (LANL)] effort is addressing
the need for useable detect-to-warn bioaerosol sensors for public facility protection. Towards this end, the SNL team is
investigating the use of rapid fluorogenic staining to infer the protein content of bioaerosols. This is being implemented
in a flow cytometer wherein each particle detected generates coincident signals of correlated forward scatter, side
scatter, and fluorescence. Several thousand such coincident signal sets are typically collected to generate a distribution
describing the probability of observing a particle with certain scattering and fluorescence values. These data are
collected for sample particles in both a stained and unstained state. A linear unmixing analysis is performed to
differentiate components in the mixture. In this paper, we discuss the implementation of the staining process and the
cytometric measurement, the results of their application to the analysis of known and blind samples, and a potential
instrumental implementations that would use staining.
We are developing a variety of microsystems for the separation and detection of biological samples. At the heart of these systems, inexpensive polymer microfluidic chips carry out sample preparation and analysis. Fabrication of polymer microfluidic chips involves the creation of a master in etched silicon or glass; plating of the master to produce a nickel stamp; large lot chip replication by injection molding; precision chip sealing; and chemical modification of channel surfaces. Separation chips rely on insulator-based dielectrophoresis for the separation of biological particles. Detection chips carry out capillary electrophoresis to detect fluorescent tags that identify specific biological samples. Since the performance and reliability of these microfluidic chips are very sensitive to fluidic impedance, electromagnetic flux, and zeta potential, the microchannel dimensions, shape, and surface chemistry have to be tightly controlled during chip fabrication and use. This paper will present an overview of chip design, fabrication, and testing. Dimensional metrology data, surface chemistry characterization, and chip performance data will be discussed in detail.
Sandia and Lawrence Livermore National Laboratories are developing a briefcase-sized, broad-spectrum bioagent detection system. This autonomous instrument, the BioBriefcase, will monitor the environment and warn against bacterium, virus, and toxin based biological attacks. At the heart of this device, inexpensive polymer microfluidic chips will carry out sample preparation and analysis. Fabrication of polymer microfluidic chips involves the creation of a master in etched glass; plating of the master to produce a nickel stamp; large lot chip replication by injection molding; and thermal chip sealing. Since the performance and reliability of microfluidic chips are very sensitive to fluidic impedance and to electromagnetic fluxes, the microchannel dimensions and shape have to be tightly controlled during chip fabrication. In this talk, we will present an overview of chip design and fabrication. Metrology data collected at different fabrication steps and the dimensional deviations of the polymer chip from the original design will be discussed.
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